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The coolant lines are coated on the inside with dried out something. Probably algae. Replacing the tubing in the umbilical would be a nightmare. I've been circulating water through it in an effort to dissolve things. Adding bubbles to the water with an aquarium pump improves the scrubbing, without being chemical or abrasive. Just don't add too many, or the pump stalls.
All the micrometers and adjustment screws for the optics were goo-ed. The lubricant was all dried up and nearly frozen. I got all but the lower screw on the output coupler un-wedged, soaking everything with WD40 and then wiping out all the threads with q-tips. Hopefully WD40 will get the last screw un-frozen.
Minor q-switch enlightenment: it could be going from negative 3.2k to 0, to positive 3.2k. That makes the "balance" control on the original q-switch driver a little more logical as well. It adjusts the voltage the first SCR stack switches.
2N2647 unijunction transistor 2N6027? (30V 300mw SCR) there are /no/ SMT unijunction transistors BC107/BC109 NPN small signal for general purpose amp 107 is slightly higher voltage rating than 109 BC546 is modern part (more or less) and should work for both (No SMT) 2PD601ASL,215 is SMT. There is weirdness with the hfe. 1N4148 100V 200ma rectifier currently available Yes SMT 2N4402 bipolar small signal PNP available but getting obscure No SMT 771-PZT2907A-T/R SMT BSR16 MMBT4403 3.9V zener 5.6V zener 741 opamp 324? I2C controlled POT? DAC7571IDBVTG4 0 to 5V I2C DAC 12 bit DAC8571IDGKR 0 to 5V I2C DAC 16 bit These will need an opamp to negate and get to 15V for the existing circuit 4093: quad 2 input NAND Schmitt triggers high voltage (20V).Also disconnected the pump chambers from the coolant loop, and put some cascade in to try and clean out the algae. With the aquarium pump, it made some pretty impressive foam.
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Assembled the cooler.
The first plan was to put the de-ionizing cartridge in line with the laser. That didn't work, the pump couldn't get enough water through the cartridge. So, put the cartridge in parallel with the laser. That worked better, but the pump was not able to reliably trip the pressure switch for the laser's interlock. Except that then it started being reliable. (and problems which go away on their own, come back on their own.)
The laser should really have a flow sensor, not a pressure sensor. And the fitting at the bottom of the tank (Home Despot bucket) is leaking. Epoxy is apparently compatible with de-ionized water.
See http://www.coleparmer.com/techinfo/chemcomp.asp
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The YAG controller, while mechanically compatible, IS NOT electrically compatible. V.35 connectors are lettered, not numbered, so the schematics are useless for determining pin-outs. From continuity probing, the various 220V hot and neutrals would have been more or less shuffled, and probably dead-shorted.
An adaptor would have to be built, involving two V.35 connectors at $22 each. MEH. So the question is whether to press on with testing with existing hardware, or go straight for the re-engineered one.
The cooler is no longer leaking, and still does not reliably trip the pressure sensor. The current plan is to reverse supply and return, so the pressure sensor is further up-stream, and sees more pressure. The ideal plan would be to replace it with a flow sensor.
M.34 connectors are obscenely expensive. The pins are $2 each. But replacing the connectors on the capacitor cabinet would suck even more. This does mean I've bailed on buying a female connector to do an adaptor for the YAG controller. I'll attempt to rearrange its pins instead. That will allow me to observe what the original circuitry does.
Unijunction transistors are also surprisingly expensive, though mostly because the minimum order is 500 of them. Its an archaic component, used for simple oscillators. I think I'll replace it with a 555. They are also archaic, but are currently available.
After much poring over schematics, I've convinced myself that the YAG controller is in-fact electrically compatible. All the pins line up, and all the signal lines (SCR, PD2000) go to the right places. All the shields being tied together with frame GND threw me off.
So, I applied power. The interlock was not closed. After some debugging it was determined that the interlock override switch is defective. That is not a part I would expect to fail. On attempt number 2, there was the usual explosions flames and smoke.
C3 on the power card exploded. It was an old tantalum so that may not be surprising. It went from the +15V rail to GND, after the regulator.
R22 on the energy control card also smoked. It went from the +15V rail to R19, R31, and C10, on the top of TR2, which then drives the shunt SCR. The SCR is driven through a transformer, so I'm hoping the SCR is undamaged. The transformer's coil is 3.7 ohms, which matches the other SCR's transformer.
I should have replaced caps before proceeding. I suspect C10 is shorted. Dan suggests that TR2 might also be dead.
More substitute components:
2N4402: BSR16 MMBT4403
Based on measuring image 20110118/dscn6938.jpg Rods are 13mm diameter. Bottom two are 118 mm apart (center to center) Side two are 87mm apart (center to center) Or in imperial units: Rods are 0.5 inches diameter Bottom two are 4 5/8 apart (center to center) Side two are 3.4111261794 or 3 and 6 or 7 16'ths Neither of these measurements really make me confident. Re-measure with a pair of calipers... Rods are 0.5 inches diameter Bottom two are 4 9/16 apart (center to center) Side two are 3 11/32 apart (center to center)
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Fabricated the alignment laser mount. Ordered a whole horde o' hardware from Mcmaster-carr, since the alignment laser needed longer #4 screws.
The circuit breakers (for controller) and transistor sockets (for q-switch) are much cheaper via ebay. The question is how many transistor sockets to get, given the active-low requirement. The qswitch's use of a TNC connector also complicates things, can't float both ends above GND.
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Beam height is 2 5/16. maybe...
Got the alignment laser assembled, with external batteries, and rough-aligned through all the optics. Need to determine the actual beam height, make an alignment card, put a pin hole on the alignment laser, and then actually align it.
I've decided to get 30 transistor sockets. Which will probably mean I need more.
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Noticed a bunch of damage on the pulse generator card. pin 4, which is the +15 rail, vaporized a bunch of traces, and some components. I suspect the +15 rail had more of a voltage excursion than I thought...
The power card is acting like a dead short. Bad 7815? The 3A version is unavailable from mouser or digikey.
When you plug in the cabinet, something clicks quietly. (I believe its the OV card) When you close the circuit breaker, +48V is turned on (from T3). When you turn the key, and the interlock is closed, the +48V is used to close R1 on the charger chassis. Its loud... That applies 220VAC to T2, through Fuse 1 (which may be a self-resetting circuit breaker). Which applies 18VAC to the power supply card in the controller, and 480V to the trigger card.
Circuit breakers: mouser 691-BA2B034615221D ( manufacturer BA2-B0-34-615-221-D) momentary key switch: mouser 642-JD-7510A ($13) or 642-A018302 ($30, 10x lifetime) momentary button, want LEDs? MP0042/1
I moved the taps on T3 and T2 from the 200 to the 240V pins. The 48V rail is now 50V, instead of 60, the 18V rail is 19VAC, and the 435V rail is about 440V. That may have caused the excursion on the 15VDC rail, but I thought that a 7815 was rated for more like 35V input.
The voltage taps on T1, the big charging transformer, are not labeled.
I've also gotten the alignment laser more or less aligned down the middle of the resonator. It still needs a pinhole. The beam height is 2 3/8 inches above the rail.
The 7815 regulator is fried. The rectifier, filter caps, and 7915 are OK though. I believe that the problem was that the YAG laser used low voltage dump relays, while this ruby uses 220VAC dump relays. So the 220V got into the 15V rail, and Bad Things Happened.
Lots more reverse-engineering. I believe I can now get power all the way to the energy control card, after fixing the 7815 problem. Bypass the 220VAC dump relay circuit through the controller. I've ordered some circuit breakers. Need to order some buttons and a key switch. Should the buttons be 220VAC, like the original circuitry, or more 48VAC relay stuff?
The next question is what frequency is used to couple through the transformers to drive the SCRs, and what the horde o' weird transistor circuitry is supposed to be doing.
Then, on to re-engineering the energy control card with i2c stuff pondered above.
Then, there is the pulse generator card. What sort of pulse does the trigger card need? I'd rather replace the pulse generator card with an MSP430 doing the same timer trick as was done on the q-switch driver.
And then there is the q-switch driver question. Plan A is to find a 1/4 wave plate, to reverse the sense of the q-switch. Plan B is to make a much more annoying waveform. Blea.
*** Disconnected wire 66 from TB1/L, moved wire 32 from TB1/K to TB1/L *** That forces the dump relays closed, and removes the 240VAC stuff from the YAG controller's low voltage dump relay circuitry. I only did that on the OSC, not the AMP.
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I moved the taps on the big transformer (T1) from the 220 to the 240V pin.
The schematics I have are for a more recent version of the energy control card and pulse generator card. The actual hardware uses MHTL logic. Motorola's MHTL logic family: Motorola High Threshold Logic. Allegedly very high noise immunity.
An MC672 is a 2 input NAND. An MC667 is a dual mono-stable multivibrator. http://html.alldatasheet.com/html-pdf/107787/ETC/MC672/110/2/MC672.html Those data sheet aggregator web sites suck...
The pin-out from MC672 to 4093 is slightly different, but may be adapted.
The energy control card almost works... The voltage comparator works, but its sense is strange. Is the voltage from the PD2000 card negative? (It is.) The NAND chip makes sense. The transistors driving the series SCR make sense on the schematic, but their behavior does not. I've replaced everything that was on the 15V rail, but not T5 and T6, since they are on the switched 15V rail, and T5 is irreplaceable.
Shopping list:
momentary buttons digikey 708-1434-ND manufacturer MP0045/3D0NN000 rotary switch digikey EG1954-ND thin 50 ohm coax digikey A307-100-ND RG174 50 ohm 0.1" diameter 100' $72 panel mount D9? (Stock) panel mount stereo 1/8 inch? (Stock) jack screws 201414-4 201413-4 M34 pin tool tyco number 305183 digikey A1329-ND 240V to 6V transformer, for powering CPU digikey MT3102-ND SMT optocouplers, for checking 48V stuff, and inputs NO: socket the optocouplers digikey 751-1263-5-ND $1.43 each 8 pin DIP sockets (or 6?) ED3308-ND gold plated machined pin $0.84 each watch crystals digikey 300-8303-ND 1K, 1.5K through hole resistors flow sensor digikey 725-1070-ND 4081 quad AND, for generating SCR clock from disable
Q-switch is controlled by a separate CPU in the head. (existing q-switch trigger) Second serial port of controller CPU is connected to the q-switch controller.
How to control power? By varying the voltage of course... But what should the user interface be? Current opinion is that there will be multiple configurations setup via the serial port, and selected with a rotary switch.
safe-light switch: disables LEDs
Serial port has all the voltages reported and controllable.
Socket the optocouplers.
voltage from the PD2000 card is /negative/. Why?
Gave up on the transistor magic of the energy control card... Assembled a 555 timer, NANDed that with the output from the comparator, and injected that into the base of TR6 (through the existing resistor). That got voltage into the caps, for the first time. Went up to 400V, and chickened out. I am currently ignoring the shunt SCR, but my current belief is that it is activated when the desired voltage is reached.
I still don't know the optimal frequency for getting a signal through the pulse transformer. 30 kHz makes strange noises in the charging chassis. I'm not sure /what/ is moving, its supposed to be solid state...
panel mount fuse holders door latches (mcmaster-carr) 10335A75 6-32 flat head machine screw 1/4" #6 flat head wood screw 1/2"
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Spent most of the day fabricating a box for the controller. 1/8" aluminum and some nice hard wood left over from my microwave cart. The aluminum is a bit thick, but it was in stock (Kody gave it to me.). It came out extremely well.
2x M34 on the back, and a D9 for the head electronics. The head will need RS-232, trigger, and some power. The power can't just be low voltage due to the q-switch power supply requirements. Might include low voltage anyway so the CPU comes up at the same time as the controller CPU.
D9, 2x BNC, 1/8" stereo on the front, for RS-232, gate, trigger (TTL), trigger (dry relay).
I of course don't have the right screws to mount the circuit breakers, and no panel mount fuse holders.
I then validated some opamp circuitry. The inverting buffer between the DAC and the comparator correctly inverts. So the other inverting buffer between the PD2000 and the ADC should be fine. The voltage comparator was cargo-culted so it should be fine.
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The 5/8" drill bit I ordered did not fit in my drill press's chuck. Blea... So I ended up using a 9/16'ths to get close, and a round file to finish it. The less than round hole is covered by bezel of the button.
I then took the panel artwork to Kinko's, and laminated it. I got two, just in case I screwed up the first one. Which meant I didn't. I then cut all the control's holes in the artwork, and epoxied the artwork to the aluminum panel. I had to put the circuit breakers on first, since the artwork covers the mounting screws (so replacing them will be a nightmare...). There was a bit of debate regarding which glue to use, it needs to adhere to aluminum and plastic, which IMHO eliminates standard elmer's glue. Super glue is a pain, and tends to fog stuff anyway. I have no experience with contact cement. So epoxy it was.
Spray adhesive is extremely non-archival. It turns yellow and starts peeling after a couple of years. My 315M control panel is not looking particularly happy.
After sticking the artwork on, I cut the overhanging paper/plastic flush with the edge of the aluminum and then mounted all the controls. I then put a bead of epoxy around the edge to seal the now exposed edge of the artwork. If it gets wet, or perhaps someone is removing drooling epoxy with Windex, water will wick in, and make a mess.
And then I started doing the point to point stuff for the LEDs and buttons. Electrical work has started, Yay. I figure finish all the low voltage stuff, cable tie it into submission, and then do the 48V and 240V stuff, separately bundled. I'll probably route everything to one side, so it can hinge open.
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Found a whole bunch of not-quite-right footprints, and corrected them. Missed the 1uf filter cap footprint being a bit small. I then etched the board, and am now populating. The 3.3V power supply functions. To register the two sides of the board, I lined up the two pieces of blue stuff, and then taped three of the edges together with laser printer labels. I then inserted the copper-clad board into the "envelope", and ran it through the laminator. The two layers lined up remarkably precisely. I might be able to consider my tool chain to be two layer now. (Perhaps when the feat is duplicated...)
I mounted the board and transformer for the 3.3V supply on the back of the box. Had the PCB upside down the first time, so there are a bunch of extra holes in the back. :-P
I don't want to put connectors on everything, its just too many points of failure. But that complicates testing, I don't want to assemble the second energy control part until the first one demonstrates functionality.
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The power supply is functioning. I assembled a testing power supply to avoid having to deal with the rest of the chassis for now. There is some weirdness trying to run both the 3.3V and +-15V rectify/regulators off the same transformer, the 3.3V filter cap gets reversed and very hot. I need to tie the regulator inputs together directly.
The CPU is installed and running, talking to it with both JTAG and RS-232. The RS-232 line driver is also installed and happy.
So next up is straightening out the power supplies so they both operate at the same time, and then getting the DAC chips installed and functional. Once that works, on to the opamp, to make sure the inverting buffer inverts. Then 555 and and gates...
The theory is to assemble the OSC energy control subassembly completely, and test at least charging, if not all the way to firing. Then do the AMP sub assembly after the design is validated, so as to avoid installing expensive voltage reference and DAC chips pointlessly. However that makes the order of assembly very non-optimal.
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The GND plane was not complete, it ran off the edge of the board, so the big filter cap for the 3.3V supply was not properly connected. Until it arced. Which incinerated the MSP430... So I got to replace it... no more spares.
I then placed the REF02, and the DAC. So now I need to get the i2c code working, to test the DAC.
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The 555 timer runs warm. Absolute max Vcc is 16V, and we're running at 15.5 or so. I suspect its marginal. I can get 18V 555's.
10K SMT (lots) 180 SMT, TH 820 SMT, TH MSP430s 470 pf SMT 805 gnd loop xfrmers for car stereo
I suspect that P1.3 is fried, had issues with damaged 15V CMOS. Bridged with P1.4.
3.3V is not sufficient to drive the 15V CMOS. Need level conversion transistors. So I did the components floating in the air thing, and got an NPN with some 10K resistors between the MSP430 and the AND gate. It reversed the sense of the enable bit (not a problem, its software) but that is a bit less optimal, in that it is enabled if the CPU is not up, and thus does not fail safe.
So now, the series SCR driver is populated, the opamps are opamping, the ready LED driver is populated and LEDing (but needs a GND connection, the trace was severed by the board cropping), the ADC is happily reporting millivolts on the voltage monitor pin (but the buffer opamp is not calibrated), the DAC is driving the reference for the opamp, its buffer opamp is also not calibrated, and last but not least the charge/done opamp is generating the correct signals.
Then I assembled the back of the panel, with lots of indistinguishable wires. There are separate bundles for the LEDs, the controls, the OSC, the AMP, and the 48V interlock stuff. I have some doubts about exactly which pins do the latching R1 closed thing on the 48V stuff.
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Finished assembling the 240V and 48V wiring (except for the connection to the micro-controller for observing interlock). I then went over it again with a continuity tester and re-verified everything. Found an error too, pin P ended up in pin L.
Then I Applied Power. The 240V wiring is correct, the 48V wiring is also correct, the key switch properly closes R1, the dump switch properly opens R1. The little transformer for the 3.3V supply works, but there is no integration with the PC-board or amplifier chassis yet.
Now I'm assembling coax cable assemblies for going between the M35 connectors and the PCB. Lots of gratuitous heat-shrink.
Note that there are two pin numbering schemes for M35 connectors. The old style has lower case letters, the newer style has double uppercase letters, AND THEY ARE DIFFERENT.
The next step is testing the entire energy control circuit, which will be scary.
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Spent the last few week days assembling laborious but non-difficult cable assemblies for the 6VAC power, 18VAC power, and coaxial lines for SCR drivers and triggers.
Filled out the firmware some more as well. Rearranged the lamps code to generate the lamp timing instead of qswitch timing. Added read-back to the i2c code, since if that value is written to the DAC wrong very bad things may happen.
Assuming I don't find anything catastrophic, the caps should charge on Saturday, and possibly even fire the lamps. If the design is validated, then populate all the AMP sub-assemblies and do it again.
The i2c read-back code works... All the front panel LEDs are in backwards (need to be common positive, not common negative).
Short answer: no joy. No smoke either, but things seem to run warm. (1/8 watt components may be a problem.)
The original energy control card puts a square wave across the pulse transformer which is 7.5V peak to peak, with the low being maybe 1V under GND. Mine is much less amplitude. Is the transistor in backwards?
The original transistor is 100 ohms from +15V, mine is 400 ohms from +15V, or 150 and 37 ma respectively.
Replaced 390 ohm with 82 ohm, resulting in being 92 ohms from +15V, or 163 ma. The amplitude is 3V peak to peak, with low being 1.2V under GND. The cap is now charging, with no voltage calibration. It overshoots though. Set it to n volts, and you get n+m volts.
NAND is running hot, and amplitude of square wave going to SCR is still low.
The over-voltage card has been empirically observed to function... and opens at about 3 kv. Lamp min voltage is 800 V, and max voltage is about 4 kv, according to the usual flash lamp sources. (8 inch arc length, assume 5 mm bore.)
The trigger circuit is completely wrong. It just needs an NPN from +15V, to generate an active high signal. See energy monitor/delay card schematic, for the thing driving OSC sync or AMP sync.
ready signal doesn't reset properly...
After correcting the trigger circuit, it charged the cap, and the lamps have fired. Yay, photons!
Now I'm poking at the AMP 48VAC stuff. Its being annoying.
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Dan suggested that the 555 was being torn up by charge current, and to use a smaller cap. So I substituted a 10 nf cap, and replaced the resistors with larger values, 12K and 1.5K for the 1.5 and 270 respectively. The 555 is now Much Happier. The resulting frequency was 5 kHz, and it drove the SCRs fine.
Got the AMP interlock figured out... Finally... So the AMPs 240VAC and 48VAC stuff is now working. Its energy control section is still unpopulated.
Got the OSC to observe the interlock, but only across the key switch, so it can't be observed when the laser is on. Which is abnormal, but matches the original controller's behavior, the light would go out when the key was turned.
Corrected the polarity of the panel LEDs, and hooked up the supply and OSC ready for testing. (worked)
Attempted to switch to on board power. There is much weirdness. It can only fire the laser when using the testing configuration. when using the test supply for the 3.3, and on-board for +-15, it will charge but not fire. And there is something about the safe-light switch which prevents the CPU from starting (or at least getting to the CLI).
Something is consuming a lot of 3.3V. The MSP430 should be sub 10 ma... It seems to be the LEDs (but there are only two... 20ma each. That is regulating down from more like 12VAC though so that may make sense.).
Attempting to debug the power supply weirdness: In debugging mode, C22 is tied to C16 and AC is applied to connector K1. So the +3.3V is regulated down from the unregulated +-15V supply, and bypasses its bridge rectifier. In that state, the fire pulse looks perfect (The amplitude, at 1.7V, is a bit low, but that is across a terminating resistor.) When the capacitors are disconnected, and both bridge rectifiers are in use, all the DC voltages look right, but there is much unhappiness, noise, and the fire pulse is taller but not square. It goes from 0 to 1.7V (approx) and then keeps rising at a slower rate to nearly 3V. Why?
Are the bridge rectifying diodes on the 3.3V supply fried?
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The 3.3V diodes are fine (brand new). There were some poor vias causing really nasty transients on the 3.3V lines around the CPU (fixed).
The problem is not the 3.3V supply, the crystal clock is not starting, and the cpuInit() function will not return until it starts. Tapping on the crystal will generally start the clock... (So its the usual MSP430 problem.)
Increasing the voltage into the 3.3V regulator doesn't help. Its something to do with the +-15V supply having to come up at the same time. If the 3.3V is up, and the CPU is hanging, applying the 15V supply will make it come up.
Negative voltages on analog inputs again? I measured that, and its on the order of -0.3 millivolts.
So the trick to make the clock work is to assert all the outputs first. Then things don't float and the negative voltages don't happen. Then get the capacitor config correct and wait not just for the fault flag to clear but to stay clear for 250 loops. The clock is now starting very reliably.
Then, the trick to get the trigger circuit to work is to connect to the collector on the PNP transistor, not the emitter. Then the line hangs out at 0 volts, until the PNP goes poink and drags it up to 15V. The 1K and 470 ohm resistors are terminating resistors for the transmission line. The trigger is also happy.
The interlock detection is wrong... The optocoupler is too sensitive, the 48VAC noise generates a false positive and it looks like the interlock is closed when its open. Measure relative to frame GND? That didn't seem to work very well with the multi-meter. The interlock is /not/ happy... :-P
I also swapped the 390 ohm for 82 ohm resistor, so the shunt SCR driver is now properly driving. It didn't explode... but didn't seem to do much either. The opamp still overshoots, so the ready LED never goes out. I haven't adjusted the gain resistor on it though.
Current theory is to bail on the interlock for now, and populate the amp energy control. The rework is simple enough.
Populated the amp energy control block, the rest of the LED drivers, the qswitch trigger, the panel buttons, and the fire input.
The amp charged, but there is a high voltage leak somewhere. There is lots of ominous popping when it is charged. It did fire though, so there is light. The amp Ready LED works too.
Initially, with RV at 5K 0xFFFF = -7.32V, 0x1E00 = -0.856 and 1E00 will exceed the set point on the OV card. So we will adjust, so that 0xFFFF will get -1.0V, and that will get us more than full range. Except that when RV2 is at min setting, its -5V.
So OV is at about 0x2c00 we have between 13 and 14 bits of precision.
Set the osc and amp to the same thing. (DAC 0xFFFF = -5V)
Attempting to find/understand the HV leak in the amp: ADC values recorded at approx 30 second intervals without head connected:
osc amp 1 380 372 3 374 360 4 369 355 5 364 349
The amp drops slightly faster than the osc.
Amp connected:
1 384 379 2 380 372 3 377 363 4 371 360 5 366 351 6 363 344Amp connected, started at a higher voltage:
1 449 432 2 443 426 3 438 416 4 433 411 5 431 404
Need to detect dump button being pressed, to reset the state machine.
Every once in a while, the amp DAC gets out of sync, and setting the set point fails. It can be reset by power-cycling everything (including the 3.3V). Which is weird.
The Ready flags "stick" (and possibly overshoot) because of the 0.022uf cap on the voltage sense line. Remove it? I kinda like the low-pass filter. Need to adjust the feedback on comparator, to see if that makes it happier.
If after firing, the measured voltages don't drop, report a miss-fire.
The amp DAC has quit working. After working fine for a while. There is much nastiness on SDA (SCL is clean). I replaced the pull-up resistor, no joy. I removed the DAC, and the noise went away. Guess I fried it while soldering. Two spares remaining...
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(all numbers in decimal) AMP: DAC volts adc 1024 710 714 1280 760 763 1536 810 814 1792 860 864 2048 900 914 2304 950 967
Max voltage for an 8 inch lamp is 3500 Volts. ADC is 12 bits, or 4096, and right now is resulting in almost exactly 1 volt/bit. So we're going to leave it there...
(all numbers in decimal) OSC: DAC volts adc(dec) 512 620 621 768 670 678 1024 720 730 1280 780 790 1536 820 827
The Osc is similarly almost exactly 1 volt/bit.
The function from DAC to cap volts is not linear. It looks exponential. The osc and the amp are very similar. (though the above data only overlaps at three points.)
The Osc has stopped firing. My circuitry is OK, the signal leaving my board and arriving at the trigger card looks fine. After poking at things, and comparing the signal at the gate to the big SCR on the Osc and the Amp, I think the little SCR got fried. I guess this project has achieved the wack-a-mole phase.
1K smt replacement SCRs rectifying diodes
Should have added a way for the MSP to directly detect dump being pressed as well as trigger a dump itself. There are extra contacts on the dump button... Optical alignment and qswitch first I think.
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Fun with curve fitting... I found an example using numpy and curve-fitted the DAC to voltage curves. If you neglect the Y intercept (which is approx 500 volts) and assume its 0, the ratio from DAC to volts looks really weird. But, once you get the Y intercept correct its all happy and linear.
And, below 500V, 8 inches of arc is not going to be very happy anyway. So, the minimum voltage is the Y intercept, which is about 520V, so I'm calling it 600.
The horrible hack of momentarily increasing the set-point to reset the comparator also works.
firecomplete() gets called during the pulse, it tends to see around 350V. It'll be down to 50V seconds later. Do I want to delay longer and see the <100V, or stay were I'm at and just see the drop from at least 600 down to 350?
Switching the trigger cards just made neither osc nor amp fire. But the osc will fire if you try enough times. Found out what the issue was... The trigger card charges a cap with the 15V signal. When the cap voltage exceeds 6.8V (from a zener diode) then the gate is below the anode, and the SCR goes boink. So, leave the 15V on long enough and it'll fire. If the 15V drops too fast, the cap never charges and no pulse.
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Fun with optical alignment. I need to build another alignment stand, to shine a laser pointer into the OC. There is just too much loss trying to get through the HR.
Then, what is the threshold voltage? According to the laser-FAQ, the resonant reflector of the hughs ruby range finder is 5 percent to 42 percent depending on the angle. ( http://www.repairfaq.org/sam/laserscl.htm ) So I need to read Solid State Laser Engineering, and ponder gains/losses in the resonator. There are A Lot of unknowns...
From the laser-FAQ, the hughs ruby puts out 50mJ output at 1095 VDC, 150uf cap, arc length 3 inches rod length 3 inches by 1/4 inch diameter. Or, threshold at 75 Joules (electric) input. rod volume==0.1472621545 in^3 Divide by volume... 509 Joules per in^3
Osc is 250 uf 8 inch arc length (two 4 inch lamps in series) 4 inch rod 3/8" diameter volume=.4417864635 in^3 Amp is 250 uf 8 inch arc length two lamps in parallel each with their own cap and PFN. (so really *2 joules)
Given the osc volume is 0.4417864635 in^3, and we need 509 Joules per in^3 threshold at 224.86 Joules. I've been testing at 900V, is barely enough to fire the lamp (good for testing the controller though), which is 101 Joules... way too low. At 1400V, we get 245 Joules. Max voltage for 8 inches of arc is 3500 Volts (EG&G catalog). The OV card trips at about 2500 Volts.
2000V = 500 Joules 2500V = 781 Joules
Got coherent photons, threshold poorly aligned at V=2100. Weirdness at 2200V, the DAC didn't set right, rc=0x40.
I aligned the alignment laser by putting paper disks with holes on the OC and etalon. The outer edge of the disk lined up with the big cylinder, and then the laser went through a small hole in the center of the disk. I then reflected the laser off the front of the OC back to the laser, then did the same with the HR. I removed the axial mode aperture, polarizer, Qswitch, and etalon.
It then made /lots/ of photons and was extremely multi-mode. I then put the mode control aperture back in, and it made more like 11 millijoules, at 2100V (about 214 joules of electricity). I also cleaned everything (except the rod, which is nigh-impossible to get to), all the optics were filthy. Even the axial mode aperture was all blackened on the back. So I polished it with 2000 grit sand paper and a dremel, to get rid of the black marks.
This laser puts a whole lot more heat into the coolant than my YAG Quantel. Ambient temp was 66 degrees F, and the coolant was 74 F when I stopped playing with it. (4 gallons of coolant, delta of 8 degrees F = 4.44 degrees C, 4.1 J per degree C per ml, so about 275914 Joules. When that is divided by 551 Joules (for a 250uf cap at 2100V), its 500.7 which is remarkably round but I can't believe I fired the laser 500 times. This model fails to take into account heating from the pump, which is putting about 200 watts into the system.
TODO: check voltage regularly and clear READY flag if it drops too low. software flow control. max-charge-time sanity check. Perhaps a specific FAULT state, which blinks ready or something?
thin tubing for secondary cooling loop
1/4" ID stuff to get to garden hose fitting.
solenoid valve
coolant temp probe
or little circulating pump, to put ice on the cooler.
bigger torch
Beware of polarization of the alignment laser. And the laser printer transparency stuff does /something/ to the alignment laser beam which makes it impossible to observe the reflections off the etalon. Use a piece of B&W film instead. triacetate is cast, not extruded, and does not affect polarization.
Fabricated a glass water to water heat exchanger for the cooler. Its about 6 feet of 1/4 inch OD tubing more or less coiled up (I am a lousy glass blower). The theory is to siphon ice water through it as opposed to doing something more long term, since the only time that a high repetition rate is relevant is when aligning.
All the optics are now in, and OSC is achieving 13 mJ at 2100V, single axial mode, unknown longitudinal mode, no qswitch. Need a "1 mm 65%R" etalon. The adjustment of the etalon is very touchy, and makes an amazing difference, right is 13mJ, wrong is 2mJ.
5 pin male din, numbered 1 to 5 from left to right looking into the connector, with the tab on the bottom.. (That is not correct DIN pin numbering...) 1 green temp sensor 2 black frame gnd 3 red heater 4 yellow temp sensor 5 blue heaterThe heater is 18 ohms total, consisting of 6 series resistors at 60 degree intervals around the etalon. temp sensor is between two of the resistors.
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Fun with an aixiz LED driver for a brighter alignment laser:
With 5.6K current resistors: Vcc---------Voltage Out () Max Output (1mv = 1ma) 3VDC----------2.9VDC-----------27ma 3.5VDC--------3.1VDC-----------76ma 4.0VDC--------3.3VDC----------144ma 4.5VDC--------3.5VDC----------226ma 5.0VDC--------3.6VDC----------310ma 5.5VDC--------3.6VDC----------400ma 6.0VDC--------3.75VDC---------430ma With 100ohm current resistors: (which mine has) Vcc---------Voltage Out () Max Output (1mv = 1ma) 3.0VDC---------2.88VDC--------22ma 3.5VDC---------3.12VDC--------54ma 4.0VDC---------3.17VDC--------79ma 4.5VDC---------3.24VDC-------150ma 5.0VDC---------3.39VDC-------222ma 5.5VDC---------3.39VDC-------243ma 6.0VDC---------3.40VDC-------243ma
From http://laserpointerforums.com/f67/making-your-aixiz-driver-work-solution-56733.html
My 200mw laser diode thresholds at 80ma, and wants 210ma at 2.5V for 160mW of output. So feed it 4.5V, and see what happens...
The laser diode is getting about 2.2V after the regulator (getting 4.5V from 3 AA's). I turned the current limit up till it stopped getting brighter then backed off a bit.
Firmware fix: if the observed cap voltage drops too far, go back to idle or something...
Re-assess maxdac (0x2000), amp only goes up to 2000V, need 2100 to 2500.
I put an aluminum foil pin hole on the 200mw laser diode, and put it behind the HR. It can just barely get a useful number of photons through the HR. The optical lever arm is probably too short to align the HR itself with, but the alignment from the front is still valid. I then aligned the laser diode with the paper disks on the etalon and OC. The laser diode spot is relatively easy to see until the spatial filter.
I aligned the amp by putting the paper disks on the spatial filter mounts and aligning with them. I then did the fog-the-end-of-the-rod trick and observed the spot on the ends of the amp rod. So the amp is finally aligned.
I then put the spatial filter lens in, and aligned its output with the paper disk on the pinhole mount. I then put the pinhole in, and aligned it with the laser diode. Then I put the joule-meter after the pinhole, and fired the real laser, tweaking the pinhole positions to maximize the joule-meter reading.
At osc=2100V amp=2000V, got 122 millijoules after the amp. Don't entirely trust spatial filter alignment, and voltage is low. the amp will not go above 2000V, due to the current value of maxdac. Inch it up a bit, but avoid the over-voltage interlock.
Need coolant temp monitoring, and possibly thermostatic control of primary coolant loop. The secondary coolant loop will cool the primary coolant pretty well, but goes through ice rather quickly.
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The current theory is that the lumonics circuitry has SCR stacks which generate large negative going pulses. There is then an inductor which does something, and its capacitively coupled to the pockel cell. Since its capacitively coupled, the pockel cell sees a square pulse.
Two of these pulses are generated, such that they cover the entire lamp flash, and have a gap between them.
So, we need two trigger pulses, for two avalanche transistor stacks, possibly microseconds apart, but with a relative position precision in nanoseconds.
So, we use two of the MSP430 timer outputs... and put a DS1123 delay chip on one of them. It will delay from 0 to 255 steps, at 1 ns/step. So for delays of less than 125 ns, we set the two msp430 outputs to the same time, and then add delay. For >125ns, set one to clock n, one to clock n+1, and then add the remainder with the delay chip.
The D9 on the qswitch control card is backwards, pin 1 is where pin 5 should be. The photo diodes are also backwards, should not have been flipped, but the pins are sufficiently flexible.
And of course the clock doesn't want to start.
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The photo-diode inputs moved between versions 1 and 2, so I added a pile of macros to move the software around, but I forgot to use the macros in the init function. So, I chased what I thought was a hardware problem for at least an hour before realizing it was software. :-P
The clock starts now, the problem was insufficient solder on the pads, so it looked soldered but was actually open. The two photo-diode inputs also now work. The RS-232 is happy, and talking to the computer through the controller. The delay chip is not installed yet, and none of the software for the accopian DAC is present.
Getting the optical fiber into the amplifier is easy, the hole in the cover is large enough for it to easily get close enough to the end of the rod without blocking the beam. The oscillator is more difficult. The axial mode aperture blocks one end, and the polarizer blocks the other. Fish it though the bottom with the power lines? Then it needs a rather sharp bend. Drill a hole in the end piece? Probably, but I will need to work up the enthusiasm to extract that part, and hopefully not un-align the OC.
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osc and amp offset to 0x200 clocks. Assembled qswitch driver, taped optical fiber to ends of the flash lamps, and defeated interlocks so the cover doesn't get in the way.
The RS-232 driver on the controller needed to be re-flowed. Its amazing how things work for a while, then spontaneously quit.
Got first light into the qswitch trigger.
firecomplete decision at 0xd324 val= 0x8287 min= 0xd044 max= 0xd466 delta= 0x422 134 usec lamp 0 0x0 0xd031 len 6777 usec lamp 1 0xd243 0xe586 len 627 usec lamp 2 0xd466 0xdd5d len 291 usec lamp 3 0x0 0x0 len 0 usec Qswitch missfire Voltage: 14996 Vdc Current: 14.996 ma temp: 300 K &buff= 0x970
The thing labeled lamp 0 is really the trigger out from the controller.
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Moved the interlock measurement to the key switch, and put a 10K resistor across it. The problem is that the 48VAC lines waggle around enough that the optocoupler can get a signal from the capacitive load. The 10K resistor shorts that out, without letting enough current flow to close the relay. The only problem is that when the +-15VDC is on, the interlock gets a false open indication. If the power is on, then the indication is false. Unfortunately the micro-controller can't read the state of the +-15VDC power directly. But, the DACs on the energy control modules are powered by the +-15VDC, so if we don't get an i2c error, then the power is on.
MEH... Fixes in version 2: micro controller can read the power state directly, AND add a relay so software can break the interlock.
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The voltage monitoring for the AMP quit working. It would charge, but not get any indication that there was a charge, so would never say STOP, and would hit the over-voltage interlock. Which definitely validates the design of having the separate over-voltage interlock board. So I poked at it, and then it started working again. Blea.
Lots of looking for the flaky solder joint... Might have found it.
decision at 0x2fe3 val= 0x8583 min= 0x2d03 max= 0x3314 delta= 0x611 197 usec lamp 0 0x2fc3 0x4130 len 567 usec lamp 1 0x3314 0x3c68 len 303 usec lamp 2 0x2d03 0x5c0a len 1530 usec lamp 3 0x0 0x0 len 0 usec Qswitch missfirelamp 2 is qswitch signal from main CPU. Why is it so long? lamp 1 is OSC
decision at 0x5bfc val= 0x8583 min= 0x591c max= 0x6afd delta= 0x11e1 581 usec lamp 0 0x5b9b 0x6d57 len 577 usec lamp 1 0x6afd 0x6b85 len 17 usec lamp 2 0x58fc 0x8801 len 1530 usec lamp 3 0x0 0x0 len 0 usec Qswitch missfire
The qswitch pulse is very long because the lamp trigger signals charge a capacitor, which dumps a small SCR, which dumps a bigger SCR, which ionizes the lamp. A short pulse will not set it off, and the qswitch pulse code got the same treatment. So I moved it, the qswitch pulse should be very short now. I also suspect that the lamp 1 input is not happy.
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The trigger sometimes gets wonky if you play with testfire too much. I lengthened ENDOFFSET to 17000 clocks to address it. It may not have. I had previously shortened the qswitch pulse to 4 usec, to have a nice crisp pulse. But then the qswitch msp430 didn't have enough time to grab the rising edge, and thus missed the falling edge. So I put it back to ENDOFFSET like the rest. That results in a 1700 usec pulse.
There was also lots of RF interference in the qswitch board due to the HV trigger for the lamps. It can't sit on the capacitor cabinet, it must be several inches away, then everything is fine. So I have it sitting on a cardboard box beside the optical rail for now.
There is some weirdness where the lamps seem to be on longer when the optical fiber is closer to the lamp. So take the durations with a grain of salt for now.
Three shots with the OSC only: timing is 12 usec delay for qswitch, 13 usec for osc and amp.
decision at 0x137 val= 0x93 min= 0xfe57 max= 0x7a delta= 0x223 69 usec lamp 0 0x7a 0x185f len 777 usec lamp 1 0x0 0x0 len 0 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0xfe57 0x351d len 1782 usec Qswitch missfire decision at 0x8b2b val= 0x95 min= 0x884b max= 0x8a69 delta= 0x21e 68 usec lamp 0 0x8a69 0xa236 len 774 usec lamp 1 0x0 0x0 len 0 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x884b 0xbf0d len 1782 usec Qswitch missfire decision at 0x8481 val= 0x97 min= 0x81a1 max= 0x83c1 delta= 0x220 69 usec lamp 0 0x83c1 0x9b87 len 773 usec lamp 1 0x0 0x0 len 0 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x81a1 0xb864 len 1782 usec Qswitch missfireThree shots with OSC and AMP:
decision at 0x98ef val= 0x9b min= 0x960f max= 0x9819 delta= 0x20a 66 usec lamp 0 0x9819 0xb060 len 790 usec lamp 1 0x979d 0xc458 len 1456 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x960f 0xccd2 len 1782 usec Qswitch missfire decision at 0x9f32 val= 0x9d min= 0x9c52 max= 0x9e53 delta= 0x201 65 usec lamp 0 0x9e53 0xb698 len 790 usec lamp 1 0x9de6 0xcabf len 1459 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x9c52 0xd314 len 1782 usec Qswitch missfire decision at 0xaf16 val= 0x9f min= 0xac36 max= 0xae40 delta= 0x20a 66 usec lamp 0 0xae40 0xc689 len 790 usec lamp 1 0xadce 0xdae8 len 1468 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0xac36 0xe2fb len 1782 usec Qswitch missfire
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Mounting holes for the qswitch driver board: board is 4x6 inches, mounting holes are 1/8 inches in on the sides, 1/8 inches in on the top (away from the avalanche transistors), and 1 inch in on the bottom. That puts a HV line kinda close to one, but not actually touching.
The transistor sockets are epsilon too close. A trivial quantity of filing (per socket...) enables them to fit.
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Trigger pulse, into the base of the bottom transistor is 5V tall, and 8.1 usec long.
250 volts across the bottom transistor (a 2N5551, its good for it).
At 118 V across the transistor, still no switching. 1937V across the stack.
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The diode on the bottom of the avalanche transistor stack is a 1N4734 zener diode, 5.6V 45ma 1W. A standard diode will not work.
So what happens is the trigger puts approx 5V from base to GND. There is a voltage fall from the base to the emitter, and then a reverse biased zener, which doesn't do anything until the zener voltage is crossed, then it avalanche conducts and a very sharp pulse is put from base to emitter. The bottom transistor then conducts, and adds its approx 180V to the 180V across the next transistor up. Then /it/ avalanche conducts, and now 180+180+180 volts are across the next transistor up (repeat up the stack, gaining voltage as you go).
It worked... Once. The pulse was short though. The OSC pump light is about 1500 usec long (assuming the trigger board is right, the photo-diode might have a long recovery time), need to be able to cover that length of time with the qswitch pulse.
Now its prematurely avalanching, and way too low of a voltage. The zener diode I currently have installed is under-sized, 300mw instead of 1W. Perhaps it fried. It did work, with everything assembled, exactly once...
I replaced the power in cable with a 4 conductor one, so now neutral is available for the 120V pumps. The only 4 conductor cable Lowes has is 10 gauge. Its pretty monstrous, but matches my extension cord so things are consistent. Its slightly weird to be plugging 15A devices into a 30A cable (which is on a 20A breaker...), but the controller does have a whole heap of 13.5A breakers, so I believe it is to code, or at least safe.
The power break-out is now a set of four terminal strips mounted on a plexiglas panel (with a cover). Its much easier to poke at than the original little junction box full of split nuts.
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I checked all the transistors on the qswitch driver with my meter's hfe mode. Pretty much every transistor is fried. I suspect the inductor rang, and FOOM. Or the zener diode on the bottom fried...
I ordered the proper 5kv accopian power supply. Next steps are probably to finish populating and implementing its control circuitry.
Replaced all the fried transistors. Disconnected the 100 ohm resistor (ie: everything after the avalanche string). Its now triggering more or less happily. Voltage in is 2960V, voltage at top of stack is 1830V, pulse gets down to 17V. The low voltage varies, I'm interpreting it as not all the transistors avalanching. It will be interesting when the 5kv supply arrives. Then sometimes just one transistor starts self-avalanching (but not setting off the whole string) and one gets a saw-tooth overlaid on the expected waveform.
2M resistor is hot 117 deg F... the transistors are also warm, 87 deg F.
Added some code to the qswitch trigger to repeatedly fire at about 1 Hz. Burning the transistors in seems to make it more consistent. Vmin for triggering at all is about 1430 volts across the stack (1971V in).
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Measured the Hfe of all the transistors. Q1 is a 2n5551, the rest are 2n3904. An unmolested 2n3904 is 172. An unmolested 2n5551 is 202. (sample size of 1, but plausible from the datasheet)
1 189 (2n5551, trigger) 2 166 3 176 4 180 5 165 6 170 7 164 8 187 9 160 10 170 11 170 12 154 <-- replaced new one is 165 13 170 14 159 <-- replaced new one is 180
To test HV diodes, put a 9V in series with the meter, and measure volts. One must exceed the voltage drop to get the diode to conduct... on a NTE517 diode, its about 3V. So when the diode conducts, the meter will read 6V. When the diode does not conduct, the apparatus will do a weird relaxation oscillator thing, going from 0 to about 2V and then dropping back to 0.
Mouser PN 897-lz100U600 Manufacturer LZ1-00U600 LEDEngine
Reconnected 100 ohm resistor to the rest of the circuitry. Inductor is still disconnected. The output of the first cap hangs out at 0. When the transistors fire it drops to -1800 volts, and then returns to 0 in about 42 usec. Scope reports the pulse to be 14 usec, I suspect its using the RMS definition.
Connected the inductor... Its now doing -130V, and a 3.2 usec pulse which looks all nasty, like the transistors are self-avalanching again.
Started replacing 2n3904's with 2n5551's, from Q14.
Q14 was 180, is 180 Q13 was 170 is 1040 (fried) Q12 was 154 is 7 (fried) Q11 was 170 is 142 Q10 2680 (fried) Q9 29 (fried) Q8 off scale high (very fried) Q7 138 Q6 101
Much happier with some 2n5551's on the high end.
With more 2n5551's will not trigger. I suspect insufficient voltage across the individual transistors to avalanche.
I got the accopian power supply, and integrated all the software for controlling it. The inhibit input works, but takes hundreds of milliseconds to stabilize, so its not sufficient as a rising edge for the qswitch pulse. The avalanche stack is happy at 3700 volts (2830 after the 2M resistor) with the first four transistors above the triggered one being 2n3904's and the rest 2n5551's.
The avalanche pulse is 2830 volts to 250 volts in 6 ns.
So the current question is how to get the 0 to 3000 volt step, then hold it for on the order of 3 milliseconds of ruby fluorescence.
Stiffer i2c pull-up resistors seem to be indicated. Went for 4.7K, based on some random web pages.
The end of one of the big caps is arcing to the HV line going past it. I applied electrical tape to the trace.
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Got a new idea... leave the avalanche stack shorted, to hold the power supply down. Then at the first lamp edge, let go so it pops up to +V. Then at the time of the trigger, short it again.
But, it doesn't work. The avalanche stack drags the power supply down, but then the voltage across the transistors is too low and they go out of avalanche mode. The trigger transistor at the bottom stays on (so you see a 200V delta) but the rest go back to non-conducting. The final output is +V-200V, up to +V, and then a proper avalanche switch down to a couple hundred volts, with the usual exponential climb back up to +V-200V.
So plan letter-plus-one is 4000V mosfets (IXTV03N400S) to apply the high voltage, and then the avalanche transistor stack (crowbar) to turn it off. Go for 2 in series, to handle the 5000V power supply max. Plan A is to have the MOSFETS on the low-side and crowbar the power supply. The fact that there are two complicates that, only one can be at GND potential with the MSP430. Can the MOSFET gates be driven by an optocoupler in photo-voltaic mode?
A PVI5080NSPBF is designed to drive a MOSFET gate... but is only rated for 4000Vrms isolation. $5 A VHS1-S12-S12-SIP is an isolated 12V supply. 6000V isolation. $10 An OPI1264A optocoupler is good for 10000Vrms. $2
The MOSFET crowbar scheme works. With a but...
I put the MOSFETs on the low side, to crowbar the power supply. I generated the gate current with photo-voltaic optocouplers (apv1122a). Then drove the optocouplers with a PNP transistor on the high side, to be compatible with the drivers on the rest of the outputs. (They are unfortunately broken as designed, and will be replaced in the next revision.)
So now the problem is that the 2M current regulator resistor is overheating. Its dumping 12.5W of energy when crowbarred, and rated for 1. And I forgot the 100 ohm current limiting resistor on the avalanche stack. (5000V across 100 ohms is 50A)
What is the RC time of 2M and 12 pf? Rise time after the avalanche pulse seems slow (70 usec?).
And then there are the ovens which the OC and etalon are in. They have an 18 ohm resistor for heating, and something which I believe is a type K thermocouple for the sensor. A MAX31855 is the amp and ADC all stuck into a single chip.
MAX6682 is similar, only for thermistors. It puts out 10 bits of data, and a sign bit.
It is not a thermocouple. If it were a thermocouple, it would have a voltage across it. Except it would be in microvolts, and my meter doesn't go down that far. So I'm going to point at its resistance, its 108.6 ohms at a room temperature of about 67 degrees F. I believe a thermocouple would be much lower resistance.
So after pondering the ovens for the etalon and OC, I was thinking the ruby needs a similar thing, or at least a temp sensor. Possibly the amp too.
And perhaps the interlock loop should go through the head, such that a temperature excursion could break it.
How much power into the oven heater? Lets just call it 2W for now. We have a 24V bus, for the accopian power supply. at 24W, 2W is 84 mA, so the current limiting resistor is 285 ohms. Subtract the 18 ohms which is already there?
I rearranged the HV stuff so that the MOSFETS just switch the HV instead of crowbaring the power supply. Its switch-on time is about 12 milliseconds. So the controller needs to provide a fire signal at least 12 milliseconds early. Thats awfully long, the 8 MHz clock rolls over at about 8 milliseconds. The switch-off time is sub 0.1 millisecond...
So the plan is to go back to the crowbar arrangement. Ten 20M resistors in parallel will be able to handle 25W of power (12W expected). (5000v * 0.002A == 10W) They cost $3.89 each (quantity 10). MEH...
I modified the foo2lava filter which drives my printer so that black pixels are converted to all four toner pixels. That increased the amount of toner and made the toner transfer slightly happier. There are still lots of dropouts.
Aligning the two layers with a light table, and then taping them together to form a thing like an envelope works OK. Then insert the PCB into the envelope, put the whole assembly in a folded piece of paper, and then run it through the laminator. The folded piece of paper seems to reduce the rollers pulling on the blue stuff, so it doesn't get moved, and seems better aligned.
Six passes seems to smudge it, such that lines between traces get filled. Yet six passes will still not fill in all the dropouts. Does the paper insulate it too much? Does it reduce the pressure? Or increase it, due to additional thickness? The thinner PCB stock seems to work better, but I typically ran two pieces through, to increase the thickness/pressure.
The thin stuff is 2/64'th thick, the thick stuff is 3/64's. Two pieces of thin stuff would thus be thicker than the thick stuff, so my pressure is low. The single sided PCB used for the HV boards is 6/64's thick.
So double the thick stuff, and only 4 passes? double the thick stuff didn't fit... 4 passes. Some wide spaces had no problems, some narrow spaces had the blue stuff bend down and fill it.
Took the laminator apart again, removed the top "cooling plate", so it would not block the boards, and cranked a variable resistor to the end stop. The temp, before I adjusted it, was maybe 260, after was 310 or so. Apparently best practices is 350. I was measuring the temp with one of those infrared thermometers, so the measurement may be low because of the field of view of the sensor (it effectively averages over its whole field of view).
Second board: holder, black only, thick 2 sided, 4 passes.
Got the color thing working. So all four colors of toner are applied. This causes the artwork to look soft. And lots of stuff between the traces.
Third board: no holder, all colors, thick 2 sided PCB, 2 passes.
stuff between the traces can not be removed with packing tape. While it does pull off "loose" stuff, the blue stuff between traces is lower than the stuff on top of the toner, so it doesn't get suck to. Abrasives are similarly ineffective. (eraser, scrunge, brush)
Fourth board: on thin stuff, not doubled, black only, 3 passes.
The blue stuff starts warping after multiple passes. Fourth board was very spotty, but didn't have as much junk between the traces. There seems to be two cases of stuff between traces: there are stripes parallel to the paper motion in the printer from the toner going onto the blue stuff unevenly. Then there is if a space is exactly the right width a narrow strip down the middle.
There is a general blotchiness which matches a texture in the blue stuff from how it was coated. You can see droplets in its density.
I've been playing with a plotter, and random pens. The trick is to find a pen with permanent ink and a sufficiently fine point.
Staedtler permanent special F number 319? staedtler lomocolor 313 red? <-- two votes for this one they make actual plotter pens too: 31HP03K-2 black medium 317 ? micropigma pens with staedlter ink? technical pens with thinned fingernail polish?
Bug zapper and aquarium lamps can be used to expose photo resist. Two bulbs 6 inches away, about 12 minutes?
Current theory is that a faber-castell extra super fine is narrow enough for QFP pins (claims 0.01mm, I'd believe 0.1). Its waterproof when it dries, but may be smudged. I haven't tried it in etchant yet. The biggest problem is the pen gets bumped in the pen holder, and shifts 20 mils or so, spoiling the details. I need to build a new pen adaptor with a larger diameter ring around its body. (20120409: Turns out that the etchant knocked the faber-castell ink's socks off in seconds... Only sharpie ink could deal with it.)
Pins 9 and 10 are reversed on the accopian connector. Resistor between msp430 and inhibit transistor needs to be 1K (or smaller?), it has to overcome the 10K to 3.3V pull-up.
at 68 degrees, the sensor is 108.5 ohms.
Increased to 108.7 after several minutes of 24V in series with a 100 ohm 10W resistor, which was at 165 degrees. Bypassed the current limiting resistor (all of them). Got to 109.2 ohms in seconds. Which made no difference to the ADC. (reads 1252 units.)
I suspect the 108 to 109 ohms with Rext=10K is below the resolution of the ADC.
resistor change... 10K to 1500 ohm.
66 1162 78 1158 90 1156 115.7 ohms
Values are always even, I suspect SPI code is shifting one too far. Poll code also isn't working right, the timestamp is not inited correctly.
Values are also way too far apart, the thermistor resistance range is too small for a 1500 ohm Rext, but any lower and it exceeds the current load that the ADC voltage ref can handle (1 ma).
Measurement of 24V rail is pegged. change voltage divider to make output less than 1.5V. measurement of 3.3V rail is also pegged... :-P
Measurement of the output voltage: set for 5000, reading 4156v, actual is 4140v with the HV probe. I suspect the 10K on the output of the DAC is forming a voltage divider with the circuitry in the accopian supply, and reducing the 5V control voltage. Disconnected, Vout is 5V, with the accopian connected its 3.8V. Replace 10K resistors with 1500 ohm resistors. The load resistance is 1500+31666 ohms (according to that 3.8V drop), so within the 2K test load from the DAC data sheet.
The always even value was a bug.
code 581 65 degrees (beginning, so temp at sensor is 65 deg F) code 579 75 degrees (measured with IR thermometer on outside surface) code 580 83 degrees
Internal temp is much higher... Al collar is more like 93 degrees (at 83 deg point.) The power supply seems to push the temp reading slightly.
OK, screw the original sensors... Replace them with 10K NTP thermistors.
Of course that means disassembling aligned optics. :-P Strangely, the alignment of the OC survived the operation. The etalon also got back in, but the power seems reduced.
There is an open somewhere in flash-lamp input 0, and a lose connection in the thermistor input such that it only operates when the card is upside down.
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Found the opens...
Assembled a bunch of boxen, to mount the qswitch trigger and driver in.
There is a failure mode where if the PWM value for the heater is updated at exactly the wrong time, it never resets, and fails on. Time to read the datasheet again.
The two photo-diodes are working. The thermal control hardware is working, but the software is weak. The accopian supply control is working. The AC power control is working.
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room DAC 20 209 21 215 22 222 23 230 24 238 25 246 26 253 27 262 28 269 29 277 30 284 31 292 32 300 33 307 34 314 35 321 36 327 37 335 38 342 39 349 40 356 42 369 (and now going down...) 42 370 38 342 36 329 35 321 33 308 29 278 27 264 26 256
And then I broke my good thermometer, when it rolled off the table as I was disassembling the calibration apparatus. :-( You can't buy proper mercury thermometers anymore.
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Finished assembly of the new qswitch driver board. It more or less works, but the current limiting resistors overheat. They get to about 200 deg F. 5000v at 2.5ma is 12.5 watts. There are 10 resistors in parallel each rated at 2.5W. It shouldn't even be breaking a sweat. Pondering the datasheet, the resistors are Ohmite part number SM108032005FE, which is coated with silicone, and rated to 110 degrees C, or 230 degrees F, or 180 degrees C (356 degrees F). The datasheet is ambiguous, one section says the series is rated to 230F, and another says silicone coated is rated to 356F. So they are either right on the edge of spec, or within spec, but I think the real issue is getting 12.5W out of the enclosure.
The TNC connector on the qswitch is not a normal size TNC connector. The center pin is normal, but the threads are smaller diameter. So I kludged it. A Mini-UHF connector is closer, but the connector's knurled part hits the bottom before the middle of the connector is completely seated.
The amp photo-diode doesn't seem to be reading right. Its way too short, 903 usec instead of the osc's 2355 usec.
Switching the fibers on the inputs, the osc was 2355 now its 773, and the amp which was 903 is now 3518. An old observation is that the photo-diodes are sensitive to amplitude of the light, and perceive a brighter pulse as longer.
Dan suggested putting both diodes into the same light source, and comparing their measurements. Do they both see the rise at the same time but one is truncated? Thats what the timestamps would indicate... Or are they both centered, but one sees the rise later and the fall earlier?
decision at 0x9beb val= 0x8b81min= 0x950b max= 0x96c7 delta= 0x1bc 56 usec lamp 0 0x96a6 0xdee1 len 2351 usec lamp 1 0x96c7 0xb26a len 899 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x950b 0xdb65 len 2290 usec Qswitch target 0xdb66 actual 0xdb66 2237 usec
lamp 0 is osc, lamp 1 is amp, lamp 3 is timing signal from the main controller. The delta is pretty much always 56 usec, so the expected jitter from the 3.3V to 12V driver having to charge a cap may be too small to measure.
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I implemented Dan's idea, and put optical fiber in each photo-diode then taped the other ends together and illuminated them both with a camera flash. The observation, with both timestamps and oscilloscope, is that the leading edge of the pulse is always right on, but the trailing edge comes earlier if the light is attenuated. (tested by putting my finger over one of the optical fibers, I am not especially opaque...)
See both_photodiodes_same_light.hpgl
So then I got my det10a photo-diode (Thor labs), as a ground truth. The rising edges are pretty much exactly right. The problem is the light pulse is /much/ shorter than observed electrical pulse. The falling edges are pretty much 2000 usec late. The electrical pulse is 10 to 20 times longer than the light.
See both_photodiodes_same_light_anddet10a.hpgl
decision at 0x1b0e val= 0x8380min= 0x142e max= 0x1473 delta= 0x45 8 usec lamp 0 0x142e 0x6b40 len 2834 usec lamp 1 0x1473 0x615e len 2503 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0x0 0x0 len 0 usec Qswitch missfire
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The bottom of the diode is pulled down with a 4.7K resistor to GND. The top of the diode has a 220K resistor to +12V, and a 0.1uf cap to GND. So when the diode conducts, it dumps the cap into the 4.7K resistor. When it ceases to conduct, the bottom of the diode should be pulled back down to GND by the 4.7K resistor. But it isn't.
The bottom of the photo-diode is monitored by an opamp. So it should be a very high impedance (with a 4.7K resistor across it).
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See osclamps.hpgl. The lamp pulse, as observed with the det10 sensor is about 700 usec long. The photo-diode output looks about the same, about 700 usec long. The opamp output is stretched, to 1260 usec. Why?
The amp pulse is the same approx 700 usec long.
The opamps report 1241 usec long, 359 usec long. One is stretched and one is compressed. I trust the rising edges right now though...
And the fire pulses are still not reliable. I suspect the transistor drivers suck... It has the voltage gain, but not current gain, and how much can the MSP430 sink?
Current draw of the head electronics box is about 0.67A (120V). Thats with both heaters and HV supply running. Coolant pump is 1.6A. So if the head electronics are plugged in with the cooler is 2.27A, over wire which is probably too thin (18 or 20 gauge, came from a hamfest...), but was not noticeably warming.
Corrected the power supply voltage monitoring ratios. The 3.3V rail is more like 3.5V... Which may be why the msp430 is running warm (312K), though its also directly above a 24V switching supply.
The thermal control works, but every once in a while a max6682 chip seems to crash. It starts reporting just 0. A power cycle gets it sane again. The cover is currently off, hopefully better RF shielding from the flash lamps will improve things.
Started tweaking the optical alignment. Before doing much, OSC is 10 mJ/pulse free-running. After tweaking the OC and HR a bit... OSC is 16 mJ/pulse free running at V=2100.
Pondering everything_20120424.hpgl... The top trace is the voltage on the qswitch. Middle is output from the photo-diode. Bottom is light from the DET10, observing a post-it of the laser output.
Observe how the qswitch isn't stopping the laser from lasing. (qswitch is on driver 1, driver 0 is the MOSFET... need to clean up that code.) I think the qswitch will need to be realigned from scratch. Blea... I managed to get a diffuser polarizer and screen into the resonator, its definitely off. The alignment laser happens to be polarized, which simplified things a bit.
And why isn't the rising edge of the qswitch waveform on the qswitch trigger in from the main CPU? The signal is arriving a good 70 usec before everything... It needs about 100 usec to get to 5kv. (timing defaults on the controller recomputed...) Why are there multiple peaks on the DET10? They don't "feel" like the laser doing the relaxation oscillation thing, too randomly spaced.
I need a better heat-sink, things get weird when the coolant hits 77 degrees F. The osc is about 1000J, the amp is 2000J. So 3000J/shot of thermal load, into 3 gallons of water. 1J increases the entire thermal mass's temp by .0000213949 degree K (or C...). So one shot should be 0.064 degrees C, or 0.10 degrees F. I'm seeing a rise from 72 to 77 degrees in far less than 50 shots... The circulating pump is a not insignificant load, the temp will go up with just the pump running. If we call the pump a 100% efficient heater, then its putting 200W into the coolant.
My laser apparently came out of a holocopier.
Lase off the etalon, by blocking the HR and qswitch. That puts the etalon normal to the beam. Then shift 0.3mm... and ponder the contrast in the fringes of an analyzing etalon.
analyzing etalon fringe contrast co2 reflector as analyzing etalon optical flat 1/8 inch or so thick. Investigate things with a C315m to find something which does the etalon trick.
coolant temp is supposed to be 20 deg C
The qswitch is definitely aligned... The Maltese cross is centered on the beam. The resonator is more or less back in alignment as well. The Maltese cross goes inside-out when voltage is applied, just like the drawing in the service manual. So /why/ isn't it q-switching? Is the voltage wrong? I've tried 3k, 4k, and 5k, with no apparent difference.
The qswitch trigger timing is also just not working right. (This turned out to be operator error, the avalanche transistors will not avalanche below 4kv.)
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The laser was lasing off the etalon, bypassing the qswitch, which is why the qswitch appears to not work. (But I've been wrong before...)
Micrometer positions for etalon: (normal to beam, not final pos) top: 6.140 side: 6.305 (these values are now out of date.)
The qswitch works... yay technology. See qswitchcontrol_worked_20120408.hpgl And the timing report for that shot is:
decision at 0xc9aa val= 0x1 min= 0xbeaa max= 0xc249 delta= 0x39f 117 usec lamp 0 0xc249 0xc2c2 len 15 usec lamp 1 0x0 0x0 len 0 usec lamp 2 0x0 0x0 len 0 usec lamp 3 0xbeaa 0x1359 len 2756 usec Qswitch target 0xcd49 actual 0xcd49 358 usec
The configuration was decision 0xb00 offset 1 0x1800. Don't remember the voltage, but (looking at the oscilloscope plot) its too high. Note the triangles, one of the transistors is prematurely avalanching. The lamda/4 voltage is 3.2kv in the configuration information for a different laser. My qswitch driver won't work below 4kv, but some of the 2n5551 transistors could be swapped for 2n3904s to reduce that voltage.
I don't believe that timing report though. I rewrote the edge detection code on the lamp inputs so it records just the first rising and first falling edge. I believe lamp0 saw a glitch caused by the flash lamps going off.
There are two time-bases for the qswitch. When the trigger (from the main CPU) arrives, the decision is scheduled and the MOSFET driver drops to 0, so the qswitch voltage starts climbing. It takes on the order of 200 usec to get to Vmax. The second time-base is the rising edge of lamp 0 (the oscillator). If both lamps are on and the jitter is close enough at decision time then the qswitch will be dropped back to 0 volts at lamp 0 + offset ticks.
The pockel cell eats about 1/2 of the power output. The etalon eats on the order of 90% of the rest. The osc power output is probably single digit millijoules. Though I have not increased the lamp voltage (from 2100V) yet.
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The correct analyzing etalon is 1mm long, 65 percent reflective. Thats actually a more or less standard part. Which costs $570. http://lightmachinery.com/catalog.html#solidetalons
Assembled the cases around the qswitch driver board and trigger board. The spurious pulses are no longer showing up in the timing report. The cases need a little more cutting, I forgot to leave clearance for the cover between the 24V supply and the side of the case.
Q-switching eats a lot of energy. The output isn't even detectable until the osc voltage is increased to 2300V. I went up to 2400, and was getting on the order of 25 mJ/pulse out of the oscillator.
Resoldered the D9 connector for the Accopian supply. All the pins were cold soldered and falling out. I also enlarged the mounting holes for the 24V supply and moved it away from the side of the box, so the cover will now go on properly.
Assembled a second 200mw alignment laser ($50, from Axiz), and put it behind the second steering mirror so it shines through the mirror and the amp. Most of the energy is lost trying to get through the mirror, 650nm is too close to 694nm, but its a usable amount of light for aligning down-stream optics.
I currently have the spatial filter removed.
I then aligned the osc beam with the amp alignment beam, and then fired q-switched though the amp. It was more or less happy, and pretty close to aligned after crossing the room (15 or 20 feet, to a piece of zappit paper taped to the wall.) I tweaked the ruby beam slightly to more accurately hit the laser-diode spot.
Unfortunately its not tem00. The spot is donut shaped, both q-switched and free-running. I tried moving the etalon slightly to see of that was doing it, but nothing changed.
I wonder if its not aligned with the correct side of the HR. I'm not sure how that would make a donut though.
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Played with the spatial filter a little. Easy to align to the alignment laser...
Started drawing an enclosure for the head. The current plan is an aluminum frame to hold everything, and then the sides made of oak plywood. Its cheaper than aluminum and should look cooler anyway.
The diameter of the mode selection aperture is 0.073 inches, or a bit less than 2 mm. According to the laser design spreadsheet thats not good enough. And its definitely multi-mode. The aperture is definitely as-manufactured. How did it ever work? 1.3mm at the OC will work. And if the beam is smaller, it will actually fit through the amp...
Removing the polarizer and the pockel cell at the same time is important... The deviation they each add to the beam cancel out. Adding and removing them as a pair leaves the resonator more or less aligned.
Etalon normal to the beam: top 6.135 side 6.315. Side was then reduced by 0.3 mm. Thats actually pretty close to the previous time I had it in alignment.
I seem to have fried the alignment laser which shone into the OC. I suspect it reacted poorly to having the ruby fire into it... At least it wasn't one of the $50 lasers...
Osc only 12.7mJ, at 2300V. After spatial filter 10 mJ. The blob makes me think the beam isn't /quite/ centered in the amp.
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Spent a bunch of time building an enclosure for the head. It has a frame made of aluminum angle, the lid is 1/4 inch thick oak plywood. Oak costs $30 for a 4x8 foot sheet. A 4x8 foot sheet 1/16 inch aluminum from McMaster-Carr is $160. So oak it is. I think it looks cooler than the aluminum would too.
I put a 1.3mm aperture on the axial mode selection aperture. Its actually 52 mils in diameter, which is a little over sized but its also not right on the OC. The beam out of the osc looked pretty good, but after the amp is the same slightly flattened ring as before. Why? Is the amp not sufficiently pumped? Out of sync?
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Charles gave me a hand getting the head into its box. The electronics boxes will need some brackets, and the cables will need some cable ties.
Then we put a diverging lens into the beam after the osc, in an attempt to find where the donuts are coming from. Its not in the osc. The beam looks great, very Gaussian, straight out of the osc. We were even bouncing the beam off the two steering mirrors to the amp before going to the diverging lens. The donuts must be coming from the amp somehow. Internal reflection off the interior of the rod? That would explain the oval-ness of the spot. Though it sure looks round immediately after the amp.
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I cropped the image of the osc spot, and plotted it with gnuplot. Which had issues with the size of the dataset... But the beam profile out of the osc is extremely happy, and IMHO Gaussian.
So whats going on in the amp?
Free-running, with the new 1.3mm aperture, the osc output is 15.8mv, or 7.5 uJoules, Vosc=2300.
There is weirdness with the avalanche transistors going off immediately after they are turned on. I don't know where its coming from, it might be a glitch in the analog circuitry, I have been unable to find it in the software.
Ideally, the qswitch would open right at the end of the lamp pulse. So I have all the stuff to time the flashes. Unfortunately it doesn't work. While it can observe the rising edge OK, the falling edge is not accurate. So I'll find a good delay more empirically.
First I looked at the timing with an oscilloscope and the fast photo diode. What are the minimum and maximum delays where the laser lases.
decision at 0xb00 offset 0 at 0xb00 offset 0x0b00 540 usec from the first voltage onto the qswitch very wimpy 0x0f00 670 usec from first voltage, less wimpy 0x1000 700 usec, still increasing 0x1400 840 usec pretty robust 0x1500 860 usec, very robust 0x1600 900 usec, nothing 0x1800 960 usec, nothing
So its going to be from 0xc00 to 0x1600. But the photo diode doesn't give energy, which is what I really want. So switch to the joule-meter...
0x0c00 7.1 7.2 0x0d00 6.6 6.7 0x0e00 10.0 10.5 0x0f00 11.65 12.25 0x1000 8.7 9.9 0x1100 10.6 11.45 0x1200 8.8 7.9 0x1300 8.4 10.3 0x1400 7.0 5.3 0x1500 3.6 3.1
The numbers are millivolts, divide by 2.2 to get millijoules. I went for 0xf00. Though 0x1100 might make more sense.
Then I went back to playing with the amp. After the amp, free running, Vosc=2300 Vamp=2100 output is 410 mv or 186 mJ. Q-switched, the output is 330mv or 150 mJ. So its running at about 15% of advertised output. I haven't increased the osc or amp voltages above threshold, hopefully that will get the rest of the power...
Screen is 120 inches from the front of the optical rail. The piece of tape in the middle of the frame is 1" wide.
Images: (in 2012050502)
I am unconvinced that the alignment laser is centered in the amp.
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According to a graph in the back of "Solid State Laser Engineering", 10^-7 J/cm^2 is safe at 700nm. Actually a bit under 10^-6 is, so 10^-7 has a safety margin.
So given a 1J laser, if the light is spread out over 10^7 cm^2 its safe. Thats a disk with a radius of 1.78 meters. MEH, might need a more accurate definition of where the safe value is. I had something more like two 1 foot disks in mind...
OBDisclaimer: I am not a laser safety officer. It is assumed that the reader is competent to arrange for their own safety.
A 1 foot disk has an area of 113 in^2, or 730 cm^2.
Ambient 77 F, coolant temp 75 F. etalon and OC are 298 K.
VO=2300 VA=2100 SF lens installed power out = 102mv (46mJ) repeated the observation twice: 100mv, off-scale high got a charge fault, est VA=2900 power out = 425mv (193 mJ)
The amp charge circuit is acting up again. Same symptoms as before, the ready signal is never generated. Kludged the software to continue. I suspect the board is to flexible, and popped components off.
With attenuator, VA=2900 145mv, assume output was 193mJ divide by 0.75 for mJ
Removed SF lens, power is not significantly reduced. So I'm putting it back...
With attenuator, VO=2600 VA=2900 joule meter says 330 mv, output is 440 mJ coolant temp 70 F.
The alignment laser is pretty accurate, but with the diverging lens installed, the reference beam is too dim to see projected. The ref beam is also way off center, and the over head mirrors are not adjustable enough to get it back in line.
Attempted to make the first hologram (number 96.1). It went black in the developer (SM-6) but there was no diffraction.
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Kludged an etalon into the optics, in search of interference. It was way off center, so the spatial frequency was high, but there was definitely an interference pattern.
The qswitch is also verified to be single pulse.
And then the ready indication on the amp quit working... output was 430 mv (195 mJ) at Vamp=2300 free-running. It can still report the voltage, so the problem is in the voltage comparator again. Its like there must be a constant number of things which aren't working, and I got the count too low. :-P I have kludged the firmware to continue working on optical issues.
Rearranged the optics to get the big overhead reference beam mirrors square. Beam splitter is now a horizontal prism.
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I have finally gotten a viable hologram, number 99.1, the fifth attempt with this apparatus.
The problem is that PFG-01 sensitivity rolls off at 680nm, and we're at 694nm. The datasheet specificly says not for use with ruby. (I should have read more carefully... MEH) So I tried some of an ancient roll of 10E75 holotest film. According to the datasheet, its looking for on the order of 2 uJ/cm^2.
The hologram went black nearly instantly, and had contrast to an unexposed corner. I pulled it out of the developer at 45 seconds (as opposed to the specified 2 minutes). It bleached in 4 minutes, but had lots of fog. The fog is not present on the unexposed corner, so its not from the age of the film.
There is a pattern of lines over everything. My first thought is that the etalon in the osc is not aligned and its multi-mode. But the last bounce mirror for illumination is second-surface, I bet its coming from there.
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Chapter 23 of the "Electro-Optics Handbook (2nd Edition)" "Laser Safety in the Research and Development Environment" states that the intrabeam laser ocular exposure limit at 700nm 1ns to 18us is 0.5 uJ/cm^2.
http://www.magergy.com/documents/Ebooks/Electro-Optics Handbook (2nd Edition)/87161_23.pdf
To get 1J (rated output, not observed) to 0.5uJ/cm^2 it would have to be spread over 2 million cm^2, or a disk 900 cm in diameter (35 inches). Not entirely possible for my configuration.
But, for extended source ocular exposure (IE: diffuse reflection) there is a correction factor, provided that the reflection covers large enough of the viewer's field of view (a). amin must be larger than 1.5 (0.08 degrees) mrad viewing angle. Greater than 100 mrad (5.7 degrees) is no longer considered beneficial (amax).
CE = a/amin for amin < a < 100 mrad. CE = a2/(amin * amax) for a > 100 mrad
Assuming its 100mrad (my configuration should be larger...) the correction factor is 8.5*10^3. That number is from the book, and I'm not sure how they are getting it given the equation for CE above. I keep getting 1333.
But, given the correction of 8.5*10^3, now we get 4.2 mJ/cm^2, which will have an area of 238 cm^2, or an disk 10cm in diameter (about 4 inches).
Given the correction of 1333, the illumination can be 666 uJ/cm^2. So 1J would be 1501 cm^2, or a disk 24.6 cm in diameter (9.7 inches).
Or, with a correction of 8500, its 4250 uJ/cm^2, or a disk 7 cm in diameter (3.8 inches). The number cited in Practical holography is a disk 6 inches in diameter.
OBDisclaimer: I am not a laser safety officer. It is assumed that the reader is competent to arrange for their own safety.
wave plate 1" diameter 10J/cm^2 670nm $304 polarizing beam splitter 1" 2J/cm^2 620-1000nm $203 polarizing beam splitter 1" 10J/cm^2 532nm $500 analyzing etalon $570I would also like a pony.
ref beam length 129 inches. 4+38+58+29 obj beam length 3+14 to get off optics board 1/2" diameter (approx) 23 bounce to bounce 3.375" diameter 23 bounce to bounce 6.25" diameter 30 bounce to diffuser 10" diameter 21 diffuser to subject 12 subject to film
Found the popping sound. The illumination beam expanding lens was in backwards, and the reflection focused to a point, ionizing the air. (see images)
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Started working on V2 of the main control board. The board is too thin, and keeps flexing and popping components off, I don't feel like trying to fix it any more.
I also want to replace all the random connections to the board with an edge connector. I underestimated how annoying it would be to work on the board, or how often I'd end up doing so... :-P
So, given a 44 pin edge connector (used on other projects...) its amazing how quickly they went. I didn't realize there were that many lines.
More or less finished the board layout, though the majority is unchanged. I bailed on having separate GNDs for every signal to the osc and amp power supplies, and that saved enough pins to get everything through a 44 pin edge connector.
The panel is now a 2x6 matrix, one column is the mode switch, and the other has charge, fire, and dump. The dump switch has multiple contacts, so it will break the interlock in hardware as well as inform the msp430.
The msp430 now has a pair of relay drivers, one so software can break the interlock, and possibly the other so software can turn on the main power as well.
The interlock observation is now fully implemented, as opposed to having an extra resistor tacked to some wires. It indicates open when actually closed, but there is now a separate line to observe that the +12V rail is powered. The 12V rail is also now connected to an analog input via a voltage divider. It would be nice to observe the -12V rail too, but I don't feel like messing with yet another opamp, and it would have to be powered by the rails its supposed to be observing.
I have reduced the I2C pullup resistors to 4.7K.
Given that a laser is required to have a key switch for the main power... Is a password controlled software implementation acceptable? (The FDA says it is.)
So we got the CNC mill running, which means: Fun with the heat exchanger...
Body is plexiglass, and about 6 hours on a CNC mill. Sides are 47 mil thick 304 stainless steel, gasket is locktite 587. Barb fittings are nylon 1/4 NPT to 1/2" ID tubing, sealed with teflon tape.
The max temp a TEC can survive is 80 degrees C, or 176 degrees F.
The TECs I have are weird ones off ebay. They are approximately a Nord TM-127-1.4-8.5. Imax is 8.5A, Vmax is 14.6V, delta Tmax is 71 (C), and will move up to 74W.
I have no idea what the cooling capacity of my heat sinks are. They are generic extruded aluminum with a fan, surplus CPU heat sink assemblies.
The power supply I have is 300W at 12V, or about 24A. At 6A (2 ohm current limiting resistor) we will be dumping 72W into the TEC, and with 0 degree delta can move 74W of heat. We won't be at a 0 degree delta... at a 30 degree C delta we can move 45W (there is a graph on the datasheet).
So the heat sink needs to move 72+45W=117W. Which is extremely optimistic.
At 12V, no current limiting resistor (it would have to be rated for 70W, that is not the right answer) the heat sink hits 150F. That is not sustainable. So, put two TECs in series. At 6V, the heat sink stabilizes at around 100F. Which is sustainable. So temp delta of 40F, (22C) which is well within range. Current into the switching supply is 0.7A at 120VAC, 84W.
With 2 strings of two TECs, current into the supply is 1.25A, or 150W.
With 3 strings of two TECs, current into the supply is 1.78A, or 213W.
19.0 66.5 18.9 66.5 18.5 66.0 18.5 66.0 18.1 65.6 18.0 65.0 18.0 64.5 17.9 64.5 17.6 64.0 17.5 64.0 17.4 64.0 17.1 63.5 17.0 63.5 17.0 63.0 16.9 62.5Heatsink was 100F, current was 1.52A at 120Vac (observed at the end)
Drop of 2.1 degrees C in 15 minutes, which is 35169.12000J in 15 minutes. Or 2344J per minute, or 39 watts. For which we used 182W. I'm uncertain that is sufficient.
Or 2344J per minute, or 39 watts. For which we used 182W. I'm uncertain that is sufficient.
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Lots and lots of assembly. The V2 board is completely populated.
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I put some heat sink grease on the cold side of the TEC modules, and increased the voltage of the power supply to about 13.5 volts. Any higher and the power supply got weird. During alignment tests, the coolant did not get above 68 F. Ambient is approx 69 F.
More fun with geometry, rearranging so we can do a transmission diffuser instead of a reflection.
ref beam length 129 inches. 4+38+58+29 obj beam length 3+14 to get off optics board 1/2" diameter (approx) 39 bounce to bounce 29 bounce to bounce 27 bounce to subject 12 subject to film
The max osc voltage is 2500V (assuming current calibration). Its actually a tad higher, but the OV card trips at 2600 just after the ready indication.
The max amp voltage is more than 2900. I didn't go above 2900 due to the ominous crackling that tends to happen at that voltage.
The qswitch may or may not be very well timed, due to the falling edge bug. However it put a very firm hole in the zappit paper compared to free-running.
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ref beam length 129 inches. 4+38+58+29 obj beam length 3+14 to get off optics board 1/2" diameter (approx) 42 bounce to bounce 33 bounce to bounce 18+13 bounce to subject 12 subject to film total 135
I suspect I'm actually wrong, and mistook where the spot from the diffuser is shining for beam length problems.
After much debugging, It is finally time to shoot a hologram on some fresh film.
Hologram number 104.2 on a harman holo fx plate in SM6 developer for 2 minutes and Ferric EDTA bleach for 2 minutes was extremely successful and I'm calling the project a complete Success.
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Poking at the peltier cooler a bit, with gruntier heatsinks.
The datasheet describes the TEC's performance with a hot side temp of 50 degrees C, or about 123 degrees F.
I got a pair of copper heatsinks, to see if they work any better than the aluminum ones. With the copper heatsink, the hot side seems to be about 108 degrees F.
The aluminum heatsink hit 122 deg F, and 5.5K on a thermistor (which is allegedly 105 F). It had not quite stabilized when I pulled the power.
ref beam length 129 inches. 4+38+58+29
obj beam length
total 131
The lens expanding the green laser is a -8mm lens.
Saving some old notes from paper:
The pin out of the etalon heater assembly:
DIN connector, not the "correct" pin out
looking into male
3
2 4
1 5
1 green temp sensor
2 black frame GND
3 red heater
4 yellow temp sensor GND
5 blue heater GND
heater is 18 ohms total, and consists of 6 resistors
So, I successfully used the laser and my pulsed apparatus for several years here. Unfortunately, Ilford then decided to discontinue the holographic plates I was using (again). This is why people like second sources. There is some interesting history there though. The Illford "holoeffect" plates were really Agfa's Holotest film from the 90's, the companies in question bought each other a couple of times.
So now the only available deep red (694 nm) sensitive plates are made by Yeves Genet at Ultimate Holography. Unfortunately, my laser is not bright enough to expose them. The obvious solution is... a bigger laser.
The beam diameter straight out of the osc is 0.052 inches, which matches the axial mode aperture. Looking at it just before the spatial filter, it is not measurably (with calipers) diverged.
At the entrance to the amp (flat against the outside of the HV enclosure) the beam is also 0.052 inches.
At the exit of the amp, zappit paper is ineffective... absorbed by the amp, or too bright and get the entire 3/8 inch disk of the amp.
The model, assuming a 150mm focal length lens (found that number in the manual somewhere) says that the beam enters the amp with a diameter of 0.103 inches and exits with a diameter of 0.228 inches.
frame 15, the 3/8 circle is 150x145 pixels, the beam is 99x98 pixels, making the beam 0.244 inches in diameter.
frame 18 3/8 circle is 1464 pixels tall, beam is 887x1002 (which is odd). Using only the height numbers because the 3/8 circle width was cropped by a shadow. Beam diameter is 0.257 inches.
So why the approx 0.03 inch difference?
And is moving the spatial filter worth the effort?
Model, before: entrance 0.103 exit 0.228 length 8 inches 11.75 from pinhole 0.2687852392 - .0326347978 v= 0.2361504414 (of 0.88357)
Model, after: entrance 0.130 exit 0.255 length 8 inches 14.75 from pinhole 0.3872847387 - 0.0652600416 v= .3220246971
So model says about 1.36 times the energy. increasing from 27 percent of the amp volume to 36 percent of the amp volume
real numbers: Before: 0.052 to 0.244 in 8 inches (we'll be optimists) 11.75 from pinhole 0.3415088551 - 0.0083178896 v= .3331909655 (38 percent of amp volume)
Removed the pinhole, unqswitched output is 0.980V or 0.445J. (maybe)
Removed the spatial filter lens too, unqswitched output is 0.548V or 0.249J.
So 56 percent of the power. volume without spatial filter is 0.170 inches^3 volume ratio is 0.056 So we're off by an order of magnitude. what is r=0.142 inches? (as measured with zappit paper and calipers) v= .1266941472 ratio is 38 percent.
So pure volumetric model is poor.
frame 41 is amp and lens without pinhole. Is it bigger? Comparing to frame 36, I'm going to say Yes. frame 41 3/8's is 1339x1306 beam is (approx) 1068x1117 (0.299 x 0.321) frame 36 3/8's is 1163x1179 beam is (approx) 682x706 (0.220 x 0.224)
I am uncertain about the measurement. The camera didn't move, so the 3/8's circle should not have changed. But its bigger in pixels too. I bet the camera refocused, and the lens breathed (size of the image varies with the focus, a very common problem.).
Removed the pinhole, alignment failed... unqswitched output is 0.992V or 0.451J Whee.
Got the pinhole back into the system... used the resonator laser to get the pinhole close enough to find it. Then got the other laser back into alignment.
Pondering frame 61. 3/8 circle is 1482 pixels high, beam is 1076 x 1107 So beam is about 0.272 by 0.280. We have acquired a about 0.036 inches of diameter.
Increasing the amp voltage to 3300 was more productive, about 25 percent more light. See table in paper notebook.
Frame 62, the alignment laser's disk is 1479 x 1762 (not round because camera is off-axis)
subtracting frames 61 and 62... calling the alignment laser's disk the 3/8 circle, the beam is 1032 x 1092 pixels, or 0.262 x 0.232 inches (average is 0.247). The [incorrect] model predicts an output size of 0.255 inches.
The model has the wrong focal length for the lens... its -180mm not -150mm.
The alignment laser disk is 3/8 of an inch in diameter. As measured without the lens. So there is the real dimension. The beam really is 0.262 x 0.232 inches as observed in frames 61 and 62. So we can make it larger, assuming that a larger volume will increase our gain.
Correcting the model for 180mm lens. Before entrance 0.078 exit 0.181 length 8 inches 11.75 from the pin hole v= 0.1506767396022389 After entrance 0.100 exit 0.203 length 8 inches 14.75 from the pin hole v= 0.20682275990842008 Without the lens, diameter= 0.052 length of 8 inches v= 0.0169897330706136 import math rin=0.078/2.0 rout=0.181/2.0 l=8.0 p=11.75 (1/3.0*math.pi*math.pow(rout,2.0)*(p+l)) - (1/3.0*math.pi*math.pow(rin,2.0)*p) volume of a cone is 1/3*pi*r^2*h
The distance between the spatial filter lens and pinhole on Ed's laser is 156 mm. Which matches the 150mm focal length documented elsewhere.
The resonator is 23 inches long, with a 4 inch long rod. Two 4 inch lamps in series 2500V in a 250uf cap.
Oscillator volume as a function of aperture (approx) mm inches inches^3 1.3 0.052 0.00849 <---- current config (best, according to spreadsheet) 1.6 0.062 0.01208 (OK, according to spreadsheet) 1.8 0.070 0.01539 <---- stock (stock) transverse mode loss: aperture mm inch tem00 tem01 osc volume 1.3 0.052 14.1% 41.8% 0.00849 1.6 0.063 5.12% 26.7% 0.01208 (1.4x) 0.066 3.92% 23.73% 0.01369 (1.61x) 1.8 0.070 1.3% 14.5% 0.01539 (1.8x)
The minimum loss for tem01 for usable single-mode is 25%, 35% is better.
osc only output Frame 12 joulemeter reports 26.6mV 12 mJ. (wheeeee) aperture is 0.052 inches.
0.066 inches diameter frame 13, 14 joulemeter reports 62mV 28.18 mJ aperture is 0.066 inches (stock, measured with calipers)
So that is 2.3 times as much energy. volumetric model predicted 1.61 times. While thats better, I'd prefer an accurate model.
Ron Michael's spreadsheet says 25% or better... we're getting 24%, and lots of energy. That the stock part landed so close to Ron Michael's spec is encouraging. Its worth continuing with that configuration, and seeing what it does to coherence length. (We were better than 6 feet with the 0.052 inch aperture, as observed with holograms.)
frame 15 is the osc and amp not qswitched. (mode D) frame 16 is the alignment laser through the amp.
3/8 disk is 1799 x 2080, beam is 1324 x 1531 so beam is 0.276 x 0.276 inches.
So we have increased the osc volume, increased the amp volume, increased the amp voltage.
34.? (15.4 mJ) free running qswitched: 17.65 17.9 (8.0mJ) joulemeter in the illumination beam right behind the diffuser.
Moving joulemeter to ref beam, to match older observations... 4.51 mV or 2 mJ per 20.25 cm^2 so ref beam is 98 uJ/cm^2. That is up from 1.714 mV (38uJ/cm^2) on 20170909. so maybe 2.6 times brighter.
Reobserving just the ref beam (blocking obj beam) got 2.36mV or 1.07mJ or 53 uJ per cm^2. More like 39 percent brighter. I don't remember if I properly blocked the obj beam for the observation on 20170909.
Moved the sensor to be exactly where the middle of the plate goes. The power was too low to reliably measure. Both with and without an object. Not a good sign...
The beam height is 90mm, according to a drawing in the manual. I do not believe that number. Measuring the actual laser, the beam height is 60mm. This may be another difference between a system 2000 laser and the later ones.
the PFN inductor on the oscillator is 127 uH. the wire is about 0.185 x 0.080 inches (rectangular) the coil is 3.25 inches in diameter (OD) and 2 inches long. the series trigger transformer is 12.633 mH. the isolation inductor on the amp is 4.77 mH.
The pfn program is extremely wrong...
More fun with the key switch... I want a JD7510A mouser has a LK5ANB126N3 A "one position" key switch has 2 positions...
6.5 inches from the end of the amp to the end of the rail. 9.5 inches from the end of the amp to the inside of the lid. The lamps are 11.5 inches long.
People on ebay sell high power crossover inductors, 12mH is not even a large value... So acquire one, and add a primary for the series trigger transformer?
So the PD2000 observes the capacitor voltage, it is 20M and 33K, so it has a ratio of .00164728198472520341 which puts 3000V at about 5V. Which is a pretty convenient value for 5V DACs and stuff. (Except that mine is 2.5V.)
The msp430's DAC is 0 to 2.5V. So set the gain of the inverting opamp (since the main cap is actually negative polarity) to about -1/2, so that 3000V is full scale?
Except that right now the amplifier voltage is set to 3300 volts. I don't entirely trust that number, need to re-observe with more trustworthy instrumentation.
Re-measured the amplifier voltage of the current JK laser circuitry. The meter reported 2905 volts, the controller reported 3583. The set point was 3300. So everyone is wrong. I bet the OV card is set to 3000V.
The ADC pegs at 5.98V, which would be 3630 V, which is over our max voltage for the original JK circuitry. I haven't actually determined the operating voltage of the additional amp yet.
LED part numbers for the control panel. red TLHR5401 yellow TLHY5401 green TLHG5401
Dinking with the over-voltage card. I failed to re-re-re-re-flood the ground plane, so Vcc is shorted to GND. yay technology.
The PD2000 for the OV card is 20M into a 1M resistor, so its ratio is 0.0476190476. But the input resistors on the OV card are in parallel with the 1M resistor on the PD2000. Which will get things down to the OV card's adjustment range.
We want the set point, 4000V to be 6V. Which is a ratio of 0.0015. If the bottom resistor is 30K, that will work.
The variable resistor on the OV card has a range from 5 to 6.5 volts. Lets get the voltage to 6V.
pin 2 is system GND. pin 1 goes negative, and will trip the card at about 3.7V, with r1=10K and r2=not installed.
I permuted the pins of both SCRs. There is also an error where D7 should not be connected to D8. The voltage from the 6.8V zener is fine... but the 600V is more like 440V. I had figured at the time that it was caused by the capacitor not being connected, and the lumpy DC confusing my meter.
There is much unhappiness with overheating diodes. D11 overheats when there is no output connected (but D11 should not be seeing any current, C4 should block the DC). D9 overheats when there is. I'm not sure why either of them are conducting at all. Its like the rectifiers aren't.
The inductance of the primary of the trigger transformer isn't -32 uH. MEH.
The secondary has 23x20 or 460 turns. We need about 20KV to trigger the lamp, the input is 600V we need about 33x, so the primary would be 14 turns. Which is surprisingly few. Perhaps too few. :-P
The pump chamber seems to be coming out. The clamps for the rod need to be a little larger. (drawings adjusted) The base plate for the pump chamber is annoyingly large, it might fit in my mill, by the skin of its teeth.
Then there is the trigger board... The problem is that the little SCR /isn't/ an SCR, its a programmable unijunction transistor. It has 4 layers like an SCR, but the gate is the other inner layer. So the symbol was not a conveniently drawn SCR. So it was incorrectly on, and the big SCR was conducting, which pissed off everything.
The part is still available, but should probably be re-engineered at some point.
Finished all the wiring. Need to get another roll of bigish stranded hookup wire. Reversed hot1 and hot2 on amp0, but that was the only error on the 240V stuff.
The panel button and mode switch issues were caused by poor soldering of the pull-down resistors (couple of opens, and position 0 was shorted to GND) and polling the bits too quickly after asserting one of the column pins. The 10K pull-down didn't discharge the line fast enough. So I added a delay.
It still turns on but immediately turns off, and the interlock optocoupler is returning GOOD when it should be BAD.
The trigger transformer primary is 15 feet of purple wire, and has 14 turns.
The procedures in the manual tend to set the OC, and then only move the HR. The OC is definitely flat, its a resonant optic on my laser. Since a flat to flat resonator is a pain in the neck to align, the HR is most likely curved, with a long focal length, like 3 feet.
I removed the aperture and drilled out its hole a little, because I am concerned about reflections off the edge of the rather ragged hole screwing things up. The original measured diameter was 0.065 inches. I drilled it out to 0.073. I then drilled a 0.063 inch hole in a piece of brass shim stock, and epoxied that to the aperture. So the final diameter is 0.063, and has nice square edges.
I then spent a whole lot of quality time with the HR, finding the brightest spot, and then reducing the lamp voltage and doing it again.
I then replaced the aperture, and did the same operation.
I then put in the analyzing etalon, and dinked with many things. One significant observation is that if the osc lamp voltage exceeds 2400V, the ring contrast drops. This is my current favorite explanation for the contouring in the holograms made with Rain.
I finally managed to measure the flash lamp pulse length. I did it with the big divide by 100 probe, and then a divide by 10 probe. The capacitor is taking on the order of 4 milliseconds to discharge. The pulse can not be seen by the DET10A and the qswitch controller because it slope is too flat.
The problem is that the trigger transformer is 12 mH air core. The JK trigger transformer has an iron core, it saturates when the pulse goes off and that reduces the induction. But mine are air core and do not saturate, so the induction stays high and the PFN is very very slow.
New inductor... Got dropped during shipping... Its coil is 15 x 20 turns, so 300 total. To get 20Kv from 650V we need 30x, so 10 turns of primary. The question is if it will saturate "correctly".
The original is 460 turns... so not many fewer... I have a bad feeling.
7 turns on the new inductor doesn't work. Nor does about 14, but it was not well wound. Should be 10, for a ratio of 30, so 650 * 30 = 19500 14 turns also doesn't work.
New inductor... 2.5 mH 13 x 17 turns so 221 turns. so 7 turns of primary.
I thought I had ordered an iron-core inductor. But I got two air-cores.
Tends to work once or twice, and then quit working.
12-14 turns on a 460 turn secondary (23 x 20) 38.333 to 32.857 times 7 turns on a 221 turn secondary 31.5 times 6 turns on a 221 turn secondary 36.8 times 12-14 turns on 221 turn secondary 18.4 to 15.7 times 11960 to 10205 volts
The 460 turn one is reliable... but the 221 turn one generally sucks. One time it worked, and got a fall-time of 3 milliseconds. Which is 1/3 to 1/2 of the required speed. The same voltage would be 6 or 7 turns of primary on the 221 turn secondary. but that also sucks.
primary of 13 turn on 460 turn secondary is 26 uH primary of 13 turn on 221 turn secondary is 23 uH doesn't work with 1 cap reversed polarity, still sucks primary of 5 turn on 221 turn secondary is 4.7 uH There were a couple of large arcs somewhere in the charging supply. Works fine with the 14 to 460 inductor, except for the uselessly slow part.
I bypassed the 132uH inductor on the trigger card, which sped up the edge of the 650V pulse, and now the 5 turn to 221 turn trigger transformer is reliably firing the lamp. The pulse is now about 2.5 milliseconds long, still too slow though possibly usable. It is visible to the DET10 and sometimes visible to the qswitch controller. It is extremely delayed compared to the other lamps though. Is that a polarity issue?
The discharge time through the 12mH trigger transformer is about 5.4 milliseconds perhaps a bit shorter, I'm interpolating off a screen shot. The 2.5 mH got it down to 2.5 msec. So I'm thinking 0.5 to 1 mH?
The 285 uH inductor with 2 turn primary didn't work. Not surprising.
iron core 2.5mH about 148 turns primary 3 49x 32064V air core 0.8 mH about 128 turns primary 3 42x 27300V air core 1.0 mH about 162 turns primary 4 40x 26000V air core 2.5 mH about 221 turns primary 4.5 49.1x 31850V 2.5 milliseconds The lamp is probably more like a max trigger of 16kv, all those ratios are too big iron core 2.5mH about 148 turns primary 6 24.6x 16032V air core 0.8 mH about 128 turns primary 5 25.6x 16640V air core 1.0 mH about 162 turns primary 6 27.0x 17550V air core 2.5 mH about 221 turns primary 8 27.6x 17956V Trying air core 0.8mH 5 turn primary: It only triggers maybe 60% of the time. DET10a says flash length is 1.55 msec, qswitch reports 657 usec. rise time 380 usec firecomplete decision at 0x6d13 val= 0x8780 min= 0x6345 max= 0x6391 delta= 0x4c 9 usec lamp 0 0x6213 0x0 len 5140 usec lamp 1 0x6391 0x7cec len 825 usec lamp 2 0x6345 0x8624 len 1135 usec lamp 3 0x6ca8 0x84b9 len 783 usec lamp 4 0x0 0x0 len 0 usec Qswitch target 0x7391 actual 0x7391 569 usec
Not especially reliable triggering. maybe 50%
The sound is a much sharper pop than with 2.5 mH. The qswitch controller is getting pretty much every pulse, with the optical fiber wedged between the lamp clamp and the rod clamp. I think that pretty much proves the pulse slope theory.
I put a 5 turn primary on the iron core 2.5 mH, and it failed to trigger. Not especially surprising.
So I removed a turn from the 0.8 mH air core trigger, so 4 turn primary. That then triggered three of three times.
With a total inductance of 0.9 mH and a pulse length of 1.5 milliseconds, I think its a little long but viable.
12mH + 0.1mH 5.4 msec 2.5mh + 0.1mH 2.5 msec 0.8 + 0.1mH 1.5 msec
So I fried something... The trigger board SCR, the PUT (which drives the SCR) the transistor which drives the transmission line to the PUT, and just because I was there, the inverter transistor for the driver transistor since its a PNP.
I then finally managed to see what happens when you don't bother with a 100uH inductor in series with a 800 uH inductor. It was slightly shorter, maybe 1.54 milliseconds instead of 1.55 milliseconds. Within spec, and fitting the big 100uH inductor on the board was being annoying. When it doubt cut it out.
I then fabricated another trigger transformer (IE: wrapped a primary around a 0.8 mH inductor) and assembled all the stuff for the second flash lamp. The two trigger transformers are in parallel, from previous experiments series did not work.
I then tried the second flash lamp alone. It worked the first time... (suspicious...)
I then connected the 12mH inductor between the two caps as an isolating inductor, and tried firing both flash lamps at once. The waveform looked pretty much the same. The qswitch controller said it was 1248 microseconds long, which was slightly longer than the 1145 or so that the single lamp would do.
I unfortunately have no good way to determine that both lamps are firing. Though if one did it would discharge its own cap and then the other cap through the 12mH inductor which should be a significantly longer pulse.
I could put them on separate diodes from the charger, such that they can not both discharge through a single lamp. However which cap should be monitored for the voltage? Up-stream from the diodes? How asymmetric could they be?
More enlightenment... the second amp is extremely late, 7 milliseconds late. So the qswitch controller clock wrapped, and indicated it was in sync when it extremely was not. I have added some more code to the qswitch controller so it has a 32 bit clock, so the error is more easily observed.
So, why is it 7 ms late? And thats about the period of the 16 bit clock. Looking at the trigger pulse vs the flash lamp output, it seems to be triggering on the falling edge of the trigger pulse. Why?
The exact behavior of the flash lamp controller is that it does the rising edge when specified, leaving the output high, and then lets the clock loop on the last one (AMP2), then sets all the outputs low. So the trigger pulses are all about 7ms long. The reason for that behavior is that in previous efforts, with shorter trigger pulses, the trigger boards would not reliably trigger.
So the first theory is that its triggering on the falling edge, but that may also be a coincidence and the flash lamp just takes that long to trigger. And that delay is from the extremely large PFN inductance of the trigger injection transformer (800 uH).
So I shortened the trigger pulse in software. Amp1 is definitely triggering on the falling edge of the pulse. No idea why... So I reset all the delays so it gets fired first and the osc and amp0 get fired later. So the timing is closeish... And I think its actually amplifying. I haven't determined how much of an improvement it is. The timing is definitely poor though.
Amp1 does seem to work. Except when the timing glitches. The problem is that its gain is less than its loss. Straight out of amp0, the joulemeter reports 306mV attenuated, and with amp1 in place it does about 96 mV.
And the trigger board fried itself again. But the PUT and line driver are still intact.
Sometimes it does the weird double-hump thing. I suspect that only a single lamp fired.
Amp0's trigger transformer is a single primary and two secondaries. I have OK results with two primaries in parallel, but there is nothing that keeps them balanced. I'd like to do it in series, but then it doesn't like to trigger.
Replaced 4.7K resistors with 3.3 ohm resistors. The trigger board still works. (This was an old error, I miss-read JK's schematic).
At amp1=2000V, it should achieve the same number of joules per cubic inch in Amp1 as in Amp0. Except that for 130 mV (reading from the joulemeter) out of amp0, it achieves 32mV out of amp1. I believe the pump chamber is insufficiently reflective. Stainless steel is not known for its reflectivity, aluminum is much more reflective (and completely incompatible with deionized water). The illuminated volume is also quite a bit bigger on amp1 than amp0.
Pondering reflectiveness of stainless compared to aluminum, teflon, PVC, polystyrene. The stainless is better than all of my other samples, despite what wikipedia says about how reflective things should be. I believe the surface finish is conflating the results.
6 inch piece of pipe, position flashlight and power meter to do a glancing reflection off the inside of the pipe. The stainless pipe is about 10 microwatts/cm^2, while the PVC pipe is more like 3.5 microwatts/cm^2. The PVC also noticeably leaks.
Then put the flat samples in the glancing reflection configuration. Same result: stainless is better than aluminum, teflon, and polystyrene.
The surface finish is too significant for my apparatus to make a meaningful comparison between materials.
I acquired a 1.5 inch OD piece of stainless steel tubing, cut it to 6 inches, and then mushed it with a vise to make a more or less elliptical pump chamber. It is sized so that its largest OD is the same is the ID of the 2 inch OD tube which is the pump chamber. So this second piece of tube sort of floats in the middle, completely submerged in coolant, and hopefully reflecting more light from the lamps into the rod.
I also painted a piece of PVC tubing with the gloss white paint I got to patch Square One. It is significantly more opaque than the straight PVC. It looks slightly brighter, but the flashlight and power meter reflectance apparatus is inconclusive, the angle dominates the measurement.
Other ideas include getting some alumina off ebay, and sticking it in the pump chamber as diffuse reflectors above and below the rod and lamps.
Lamp OD on the oscillator is 9mm.
The trigger board ate itself again. This is with all the 3.3 ohm resistors on the anti-ring diodes. The inductor is very low right now, but that was needed to get it to fire reliably. Even bigger SCR?
The new pump chamber improved things, 130 to 150 mv is now to about 70 mV, instead of 36. If the amp does not fire, its 21 mV.
The alignment laser is currently hitting the side of the rod mounting tube on amp1, but the alignment laser is a little off, and larger than the real beam. So I don't think its hitting the side of the rod.
TN5050H-12WY 50A 1200V SCR in a TO-247-3 package TN3050G-12WY 30A 1200V SCR (the one we're using right now) both are 200 A/u-sec and 1000V/u-sec CS60-16io1 60A 1600V 150 A/usec and 1000V/usec
What is the rise time? LC circuit?
The trigger transformer has a ratio of 25.6 times (approx). So the main pulse at 2000V will put a 78V current through the trigger board.
A 325K resistor at 650V will conduct about 1.5 ma of current, which is about a watt.
I got the CS60-16io1 SCR. I also realized that the PUT was incorrectly wired, which is why it was triggering on the falling edge. The trigger board got burnt by the last "excursion", so I populated a new one (yay spares!). I also increased the current limiting resistor to 10K (30W), and the 1K current limiting resistor to 5K (was 10K, but it wasn't working, but that may have been the PUT error, but I haven't gone back and tried it. Either way, the new board actually runs at 600V, instead of 650V, making me suspect that the zener diodes were being overwhelmed.
I got some 10uH extremely grunty inductors for the inductor on top of the SCR, however it will not fire with the inductor in place. 5uH? 2uH? 0 uH seems to work...
I wonder if the PUT error caused the SCR failure.
So I am stopping for now, with it actually sort of working (except for the gain being 0.5 instead of greater than 1.0.).
Removed 6 turns from the 10uH inductor, resulting in a 3.5 uH inductor. Didn't work. Replaced with 0 uH inductor. (Buying an expensive LCR meter was a wise investment.)
Just the pump light is 16 mV of energy (postit attenuated joulemeter).
2400, 1800, 2000 V (osc, amp0, amp1) 70 mV of energy output. joulemeter 6 inches from amp1 same voltages, 19 inches from amp1, 60 mV of energy.
Pondering the voltages and currents of amp1 according to pfncalc1.xls.
V Ipk Joules (both lamps) 1800 542 810 2000 603 1000 <-- crosses blackbody 2200 663 1210 2400 723 1440 <-- crosses UV damage 2500 753 1562 2600 783 1690 2700 814 1822 <-- exceeds lamp rating (800A)
The Do Not Exceed number is currently 2000V. The arc goes opaque, and thats pointless.
amp0 is 2400V max, 1440 joules. I have other notes quoting 2900V (2102 J) There was a calibration error in the previous control hardware revision, so not sure what the correct value is.
amp0 lamp diameter is 9mm. Maybe. (measured at the electrode.) So arc diameter is probably 7mm.
amp1 needs at least 1609 J (electrical) to achieve the same energy density (J/cm^3 in the rod)) as amp0. Which is well beyond UV damage threshold.
Want 350J/cm^3 of electrical input? (solid state laser engineering) So 3879 joules for amp1, to get 4.1 J/cm^3 stored energy. We are Nowhere Near. At 2000V, we are achieving 90 J/cm^3, which is off the bottom of the scale.
Goal is 4000 J of electrical input. So 2000J/lamp, which is 4000V in a 250uF cap.
10 mm bore 150mm arc length has a mav voltage of 2500 to 3000V (depending on the catalog you look at). We need 4000V.
2000V in 500 uf is 1000 J 90 J/cm^3 (gain is <1) 2500V in 500 uf is 1562 J 140.9 J/cm^3 3000V in 500 uf is 2250 J 202 J/cm^3 3500V in 500 uf is 3062 J 276 J/cm^3 4000V in 500 uf is 4000 J 360 J/cm^3
rod is 11.08421 cm^3
amp0 is 2900V in 500uf = 2102 J = 145 J/cm^2 gain is surprisingly high amp0's arc length is 200 mm, bore is probably 7 mm.
Bunch of observations:
Amp1 has the alumina reflector. coolant temp 24 C joulemeter is 17 inches from amp1, just pump is joulemeter 3 mV 2400 1800 2000 output 30mV joulemeter 2400 1900 2000 joulemeter 41 mV 2400 1800 --- joulemeter 96, 98, 92 mV (removed amp1) 2400 1900 --- joulemeter 132 mV (removed amp1) 2400 2000 --- joulemeter 175, 171, 173 2400 2100 --- joulemeter 218, 203, 208 2400 2400 -- joulemeter 310, 315, 308 2400 2500 -- joulemeter 332, 320, 343 2400 2600 -- joulemeter 347, 347, 351 moved the joulemeter, to determine how sensitive it is to position. 2400 2500 -- joulemeter 328, 332, 347 Observed gain with alumina diffuser is 41/175 put amp1 back... 2400 2500 1500 joulemeter 88, 89, 93 2400 1800 1500 joulemeter 25, 23, 25 2400 1800 1800 joulemeter 24, 25, 24 2400 1800 2100 joulemeter 27, 25, evaluate timing... amp1 needs to be about 500 usec earlier. delays were 100 500 300 100 100 (qswitch, osc, amp...) try 100 4000 4500 100 100 firecomplete decision at 0xec8f20a5 val= 0x8f81 min= 0x15a5 max= 0x2025 delta= 0xa80 341 usec lamp 0 0xec8f1c68 0xec8f1e60 len 64 usec lamp 1 0xec8f1dfd 0xec8f370b len 815 usec lamp 2 0xec8f2025 0xec8f409c len 1056 usec lamp 3 0xec8f15a5 0xec8f2e2d len 798 usec lamp 4 0x0 0x0 len 0 usec Qswitch target 0x2dfd actual 0xec8f2dfd 572 usec rflags 0x8f fflags 0x8f Looks much better on oscilloscope (which I trust more) 2400 1800 1900 joulemeter 32, 33, 32 2400 1900 2000 joulemeter 44, 42, 41 gain 0.32 2400 2400 2000 joulemeter 127 124 127 gain 0.41
Swapped amp1 back to the stainless steel reflector, since it works better. The alumina was yellowed by the flash lamps. Its darker yellow closer to the lamp. So the stainless steel definitely works better.
So I consulted the google, and alumina can be yellowed by UV, its caused by iron and manganese, both of which are present in stainless steel.
coolant temp 24 C replaced stainless steel elliptical pump chamber joulemeter is 17 inches from amp1, just pump is joulemeter 3 mV amp1 offset 2000, due to misfires 2400 2400 2000 joulemeter mv 100, 111, 107 which is worse than alumina reflector 2400 1900 2000 joulemeter mv 48, 49, 42 2400 1900 2100 joulemeter mv 53, 57, 59 amp1 offset to 1000 2400 1900 2100 joulemeter mv 55, 56, 54 amp1 offset to 3000 2400 1900 2100 joulemeter mv 43, 45, 44 amp1 offset to 500 2400 1900 2100 joulemeter mv 64, 67, 63 amp1 offset to 200 2400 1900 2100 joulemeter mv 63, miss, miss so amp1 offset back to 500 amp0 offset 4000 from 4300 2400 1900 2100 joulemeter mv 54, 54, 55 amp0 offset 4500 from 4000 2400 1900 2100 joulemeter mv 55, 47, 47 amp0 offset 4300 from 4500 2400 1900 2100 joulemeter mv 42, 47, 50I want a 10mm bore, 150mm arc length xenon 450 torr. (and a superluminal pony)
Pondering CatalogueVQF... DU series lamps, 7x152mm ... VQX R 9P6 JA ?? 1 M
So... new lamps. Arc diameter is 10mm, arc length is 150mm, unfortunately its not cerium quartz. They came from TJS, who seem capable of doing business with individuals (so they will get my business :-). The lamps do not match the drawings, there is a part number on the lamp (TJS-1198), which does not match the box (TJS-1686).
So, who knows what they are... I assume its xenon.
The new do not exceed number is 5100 Volts, which exceeds the smaller capacitor's rating. A 1500 Joule pulse will be 3500 volts. 2000 Joules (per lamp) is 4000V.
I get to fabricate new end caps for the pump chamber, and probably new clamp tubes for the rod. The new lamps are shorter, so the rod will not be hanging quite as far out.
Fabricated a new pump chamber for the 10mm lamps. The machining went quite a bit better than previous attempts. Circles are still smaller than they should be though. Lots of assembly... right now, it is just the 2 inch tube, no inner reflector at all.
Freerunning, voltages 2400 1900 2100 coolant 22 C ambient 74 F osc and amp0 only: Joulemeter 134, 127, 129 mV with a single lamp and cap missfire, joulemeter 32 both lamps, joulemeter 48 mV (probably)
That 48 mV number is extremely close to the performance of the previous chamber at the same voltage. Which is encouraging, for the same amount of energy in, its putting out the same energy.
2500V missfire 2400 1900 2400 55mV gain=0.42 2400 1900 2600 61, 58 mV gain=0.46 2400 1900 2700 62, 64 mV gain=0.48 2400 1900 2800 71 mV gain=0.54 2400 1900 3000 74 71 32 mV gain=0.56 2400 1900 3200 73 78 mV gain=0.58 2400 1900 3300 75 75 80 mV gain=0.59 missfire 2400 2400 fail 94 mv 2400 2400 3300 > 177 148 loud pops from amp1 power supply... and power dropoff... 2400 2400 3300 missfire 48 mV 2400 2400 3300 52 255 261 mV At 3300V, that is over twice the energy of 2100V. 2100V is 1102 J, output of 48mV 3300V is 2722 J, output of 75mV. input ratio is 1 to 2.47, output is 1 to 1.625
And the gain is STILL less than 1. With nearly 3 times the input energy. 2722 J is 245 J/cm^3 in the rod. The 350J/cm^3 number is 4000V
Try the alumina reflector? That got a gain of 0.41 at 2000V
The trigger transformer (or something in the trigger circuitry) is uselessly unreliable.
Curve fitting the data from above... data is:
2400 0.42 2600 0.46 2700 0.48 2800 0.54 3000 0.56 3200 0.58 3300 0.59line is: x*0.00019395 -0.03556054
So gain=1.0 is at v=4972. Which is too high, and pointless. We need more than 1.0.
Constructed a terminal block for the GND point, the screw terminal things were stacked too high and had problems with arcing or something. Also bolted down the trigger transformers (with nylon and plexiglass hardware), Lorenz forces were yanking them out of terminal blocks. (Thats an interesting problem to have.) Redid the wiring for the trigger transformer primaries, but I don't expect that to improve anything.
Also rebuilt the peltier heatsinks, so it can get down to 20 deg C now. There are definite issues when the coolant gets warm (greater than 20 C). The chiller is still not especially capable, but its now more capable than the pump's energy input, and will need a thermostat.
Cooler performance:
ambient is 72 F (quite a bit lower than summer temps)
replaced second heatsink assembly with new copper heat spreader thing. Temperatures from startup:
11:07 21 11:08 21 11:09 20 11:10 20 11:12 20 11:15 20 11:18 20 11:24 19 11:30 19 11:38 19, thinking about 18 11:42 18 12:24 17 thinking about 16 12:36 16 12:41 16 12:52 16 13:01 16 thinking about 15 13:21 15 14:37 15 thinking about 14 14:54 14 15:28 14 15:48 14 16:51 14 17:32 1411:34 temps of the heat spreaders are 40C and 47C (left, right) The newer heatsink goo definitely works better. Though left's airflow is better.
Put the alumina reflector, into new pump chamber with 10mm lamps.
ambient 71F coolant temp 19 C joulemeter 17" from amp1 2400 1900 2400 109 gain=0.83 2400 1900 2600 104 102 100 gain=0.78 2400 1900 2800 114 112 gain=0.87 2400 1900 3000 119 117 gain=0.91 2400 1900 3200 124 gain=0.95
The alumina reflector approximately doubled the gain, as observed with the other lamps.
The trigger stills sucks a black vacuum.
ideas for reducing the trigger transformer's suck:
Separate triggers for the two lamps. Test by driving only one lamp. complicated by possibly needing two voltage regulators. there is a fourth channel on the controller vary turns on the primary. do we need more voltage or more current move the secondary, to reduce the capacitor filtering the pulse out (not sure if thats happening). doesn't happen... when the lamp is not ionized the trigger is completely isolated.
coolant temp 19 degrees C. Amp1 coolant temp unknown.
2400 1900 3000 147 123 130 gain=1.02 joules=2250 2400 1900 3200 145 150 144 gain=1.12 joules=2560 2x missfire timing failure 2400 1900 3400 154 156 159 gain=1.20 joules=2890
amp1 3600v took too long to charge
Having a solid GND on the pump chamber seems to have fixed the unreliable triggering. This is a bit of nod and smile...
Coolant leak... (which sounds so much more dramatic than the actual event) The seal on the end of the rod leaked, and drooled coolant everywhere. It had the wrong clamp tubes. I replaced them with the right ones (713 mils long, not 708) and labeled them better.
Large pulses spuriously trip the dump circuitry. Induction into the over-voltage boards?
This gain curve is steeper than the curve from 20181111. Why? My first theory is that the coolant is cooler, so the osc and amp0 are happier. But its the same temp. The joulemeter was moved, but recalibrating the amp0 only number requires moving amp1, which is expensive.
There is spurious mode switch switching as well, while charging. Rearranged the cables a bit, to get the control lines away from the power lines. moved the joulemeter...
V=2400 1900 3400 134 140 V=2400 2400 3400 405 409 409 gain=1.3 historic values: 2400 2400 -- joulemeter 310, 315, 308
407 mV at 2.2V per joule is 0.185 Joules, with the postit. So maybe 0.37 Joules, the postit is historically a 50 percent attenuator, but don't have a calibration point.
on 2017.10.21, with the old controller osc and amp got 322 mV with postit. amp0 might be good to 2900V, but at that point may be in opaque arc mode.
Put a lens in front of the amp, and tried it without the postit. Lots of miss-fires or something. The image looked good, but the oscilloscope didn't trigger. Worked OK with a flash. It did work a couple of times, on the wrong scale, and got >970 mV. So maybe > 440 mJ/pulse.
I trust the oscilloscope more than the laser right now, but it would have been nice if the picture of the laser spot didn't look so consistent between miss-fires and normals.
Without the postit, with diverging lens to avoid damaging sensor, freerunning, timing may be poor. Amp1 is not well aligned, the light is hitting the top of the tube or rod.
2400 2400 3400 1752 1674 1726 or 0.780 J/pulse.
Nothing to write home about, but I suspect thats the largest amount of energy this laser has ever produced.
The coolant leak is back. Through the rod clamps on the positive end. It got a droplet of water on the end of the rod, so the tube will probably have to come off.
See line 3067 for historic power output numbers.
Fabricated new stainless steel pump chamber end caps. Assembled with alumina reflectors. Still getting UV damage with new lamps (so not cerium doped).
Joule meter without postit, with diverging lens. Laser free running, timing not evaluated, alignment through the amp probably sub-optimal (its drooping).
2400 2400 3400 joulemeter 1.576 miss 1.522 1.446 1.432 1.450 1.380 1.388 1.300 1.336 1.438 coolant temp 18.2 C at end of tests
Energies for above are 0.716 0.692 0.657 0.651 0.659 0.627 0.631 0.591 0.607 0.654 average is 1.427 volts or 0.649 joules
That is computed with the max voltage indication on the oscilloscope, it is not integrated under the curve. The gentec documentation for the correct definition is ambiguous.
Lid extension segment dimensions.
top 12 x 16 5/8 sides 12 x 9 bottom 12 3/4 x 17 strips 1 1/2 by 9, 1 1/2 by 16 1/8 1/4 round inset from the end 3/4 inch need more 1/4 round.
Added optical rail segment, and more carefully aligned amp1. Still haven't done the timing. Free running, not q-switched.
V=2400 2400 3400 1.732 1.794 1.682 1.706 1.782
avg energy is 1.7475 V, or 0.794 joules
coolant temp 19.0 down to 18.2
The alignment laser is well centered, but the real beam is not, and is hitting the top edge of the amp.
So if the unreliable triggering was addressed by grounding the pump chamber, does that mean we can put the inductor on the top of the big SCR on the trigger board back in? That slows down the pulse, and is easier on the big SCR.
There is a bubble in the second amp ruby. I don't remember seeing it before, and it isn't visible in any of the old pictures. Its not on the end of the rod, its about 1/2 an inch from the output end.
I've reversed the rod, so its 1/2 inch from the input side, so the energy hitting it will be less. Nothing to lose...
The osc beam profile is very multiple axial mode. Not sure why. The aperture is 0.063 inches, it was historically 0.052, and I've made a new one but not installed it yet.
Walking the osc delay, to find the peak. expect 0xf00, from historic performance. osc v=2400 offset oxc00 missfire 0xd00 11.18 12.12 12.82 avg 12.04 mV 0xe00 12.4 12.16 11.62 avg 12.06 mV 0xf00 10.58 11.52 12.38 avg 11.49 mV 0x1000 9.6 9.3 9.3 avg 9.4 mV 0xe00 12.92 12.54 13.6 avg 13.02 mV 0xf00 12.0 12.2 11.92 avg 12.04 mV lets use 0xe00. These numbers are extremely similar to the historic performance on 20120505. At least I didn't screw it up more... after amp0... walking amp0 offset Diffuse reflector in the beam (postit), joulemeter balanced on the pump chamber enclosure, above it. Its not an absolute measurement, but we're looking for relative. 4000 182 183 180 avg 181.6 mV 4800 201 191 202 avg 198.0 mV 5000 207.0 201 202 avg 203.3 mV 5100 188 212 188 avg 196.0 mV 5200 193.0 208.0 197 avg 199.3 mV 5400 195 193 200 avg 196.0 mV Using 5000. The peak is not dramatic. On to amp1. Joulemeter is in line, with postit on the front. 1000 270 missfire 1100 253 245 269 avg 255.6 mV 1200 269 269 270 avg 269.3 mV 1300 252 259 258 avg 253.3 mV 1600 237 264 257 avg 252.6 mV using 1200
Then some absolute power measurements. The joulemeter was in line, angled to the beam so the spot was as spread out as possible (still damaged the sensor). There are a whole bunch of pictures in 2019020901.
qswitched unattenuated 513 598 600 avg 570.3 mV or 259 mJ freerunning unattenuated 944 974 985 avg 967.6 mV or 439 mJ I was rather expecting more energy...
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Pondering things to try... increase oscillator transverse mode aperture, to increase energy output. that energy may go into the higher modes though. diam frac of 0.063 area gain of second mode 0.052 0.68 35.4% Works frame 3648 0.055 0.76 31.3% Works, I think See frame 3649 0.059 0.87 26.3% min viable number is 25% 0.063 1.00 21.8% inches is too big, goes multi-mode Multimode osc voltage is already at the max value. Increase amp0 voltage, to increase gain. May already be at point of diminishing returns due to blackbody problem. diminishing returns is at about 2800V, 2700V is about 30 percent brighter. amp1 voltage can not be increased, 3400V already exceeds the recommended max. Increase amp1 charge speed by reducing current limiting resistor. May exceed breaker limit. May increase energy output because less time for the caps to self-discharge on osc and amp0. Added instrumentation to observe the self-discharge the self-discharge is not amazingly significant. Shorten amp1 pulse. Will require new pulse injection transformers. Already shorter than the fluorescence lifetime... not sure if it will improve things. Improve synchronization of the two lamps in amp1 They really should be simultaneous... :-P measure caps and inductors, get them more symmetrical, and possibly swap so the LC time of the two lamps is closer. caps are 230.1 and 254.9 uf (gray, green respectively) inductors are 733 and 730 uH (gray, green respectively) LC circuit is 1/2*pi*sqrt(L*C) LC time constant is .0025799343 and .0027156152 seconds (gray, green respectively) So allegedly green is delayed by 0.1 milliseconds, except that the delta is much larger than that. to reduce the offset, gray should be on 733. And it is. MEH. That is shorter than the delta I'm observing Add 67 uH inductor to gray circuit? Added 75 uH inductor to the gray circuit. Nothing happened. waveform was completely unchanged. Is it actually very under-damped, and ringing? Measuring voltage on cap will answer that question.
Fun with potting the trigger transformers:
Volume of the first layer is 42 ml. Going for about 1/4 inch of material.
Volume of the coil is 70ml (approx).
blue tape mold leaks patheticly.
amp0 lamps are 9mm OD
The new transformers seem quieter (acousticly). The waveform is identical to before.
frame 3819 2.9 mV voltages are 2400 2700 3400 freerunning 45 uJ cm^2 frame 3820 1.86 mV voltages 2400 2700 3400 qswitched 29 uJ cm^2
after amp0 56.5 mv qswitch missfire rise jitter to 0x2000 433 411 >580 402 off 0 f00 454 451 456 mv off 0 1000 478 374 408 445 430 significant pause between 478 and 374. too cold? significant delay... and increase temp set point to 19.0 C 343 425 356 401 439 pause... temp at 19.0 C 339 327 332 421 423 321 rose to 19.4 set to 20 C wait for a bit at 19.7 409 393 319 348 temp set point increased to 20 pause... at 21.1 283 400 299 311 305 avg 319 off 0 e00 407 318 437 avg 387 off 0 d00 408 428 416 avg 417 off 0 c00 381 374 392 avg 392.3 off 0 d00 438 419 394 avg avg 417Walk the offset of the amp0 flash lamp trigger relative to the osc flash lamp trigger:
amp0 o 4600 (was 4200) 384 408 385 avg 392.3 amp0 o 4000 395 410 428 avg 411 amp0 o 4400 426 403 422 avg 417Walk the offset of the amp1 flash lamp trigger relative to the osc flash lamp trigger:
moved sensor to after amp1 amp0 o 4200 520 429 517 agv 488 gain of 17% not impressed amp1 o 500 501 501 493 avg 498.3 amp1 o 10 522 526 538 avg 528.6 osc o 5000 amp0 o 5000 amp1 o 800 dec 16f4 (should be unchanged ) 549 537 519 avg 535 missfire 116 amp1 o 400 526 503 550 avg 526 missfire 110 amp1 o 600 561 540 539 agv 546 wait a while. temp=20.1C 520 540 509 avg 523Moved sensor to plate holder.
ref beam 1.43 mV 3832 1.34mV frame 3833 is 21 uJ/cm^2 (1.34/2.2 / 20.25 ) * 0.70 obj is 330 uV is 7 uJ/cm^2 (330/2.2 / 20.25 ) frame 3834, 3835 ratio 3 to 1 want ref brighter... it is 330 280 300 uV dropping temp to 18C at 18.4 object only 450 470 430 unblocked ref frame 3836 1170 990 uV ref and obj, about 26 uJ/cm^2 at 18.1 C 980 1230 800 990 replaced -179mm lens with -200mm lens on ref beam. 3630 3610 3580 3830 uV frame 3843 3844 call it 56 uJ/cm^2so ref to obj 8:1 high but within U25 spec
joulemeter just after amp1 with tube diffuser. voltages 2400 2700 3400 qswitched 447 490 434 avg 457 Rather the opposite of better. Though might be measurement noise. 9.81 + 10 45.7 (top) 11.37 (diameter) so beam height is 9.81 + 10 + (45.7 - (11.37/2)) is 59.825 or 60mm with presumed measurement error realign ALL THE THINGS... ref beam is 3560 uV 55 uJ/cm^2 (3560 /2.2 / 20.25 ) * 0.70 frame 3899 doesn't look like its covering 8x10 ref beam is 3270 uV 51 uJ/cm^2 loud bang... carbon on terminals to one of the lamps on amp1. arced? Lorenz forces keep yanking connections out... (some problems are more interesting than others...) bolt down all the things! with nylon hardware... all light 2800 uV 44.0 uJ/cm^2 all light 2540 uV 39.9 uJ/cm^2
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before: joulemeter after amp0, voltage 2400 2700 3400 freerunning 827 806 810 mV avg 814.3 remove pinhole... 880 877 888 mV avg 881.6 Move the lens to old pos... 818 785 814 mV avg 805.6 so loss of about 8 percent amp1 enable joulemeter moved to after amp1 pinhole still out 686 679 679 avg 681.3 So amp1's gain is less than 1. Though the sensor is not well calibrated (using the tube) move sensor to plate holder, vertical 2490 2630 uV Test hologram made, number 167.1. first viable hologram on U25.pondering inductors...
looking at amp1_3200V_single_underdamped_800mH.hpgl The voltage goes past 0, all the way to 1200V, reversing the polarity on the lamp. Sub-optimal... Thats single lamp with 800 uH inductor.
Fabricated two 330 mH trigger transformers.
They fire reliably only when a single one is connected. When both are connected, it might be 1 in 5. Tested with a single cap, but both lamps. See amp1_3200V_single_underdamped_330uH_3.hpgl for a waveform. Bounce voltage is about 860 reverse polarity.
Reversed polarity of primaries of triggers. (If it works on Star Trek...) fired successfully 3 times in a row. Then failed.
Put the polarity back.
Added a cap to the trigger board, for a total of 3.
For the Ukrainian rod, 5/16 inches diameter use 109 O rings, and 707 mil long clamp tubes. The 3/8 rod uses 012 O rings and 714 mil clamp tubes.
The silicone O rings are too small. Which is odd, since they are size 32. So there was a gap, and coolant sprayed everywhere, and getting to take the pump chamber completely apart and put it back together again. Used the EDPM O rings instead, since they are the correct size. (They also have not significantly eroded as of 20190709, so EDPM seems to deal with the pump light.)
The trigger is still not reliable with 330 uH trigger transformers. Added third cap. What else can be done?
Currently Ukrainian rod is installed. Haven't actually let beam light hit it yet.
Installed the Ukrainian rod, put a 210 mil diameter aperture just up stream to avoid reflections off interior of tubes, frame 3951. There are striations in the alignment beam (frame 3952 - 3954). If they are present in the real beam, it is unusable. Only one amp1 lamp is hooked up. V=2400 2700 3200 freerunning amp1 didn't fire. frame 3955 increased to V=2400 2700 3300
unplugged unused trigger transformer... fired
frame 3957 striations are in real beam, and vertical not horizontal. They match the polarization of the respective lasers. spurious beam is also present.
3958 and 3959 replaced the spatial filter and aligned to alignment laser.
3971, 3972 main beam through expanding lens, paper taped to input of amp0.
3973 is alignment laser,
3989 osc beam profile, magnified with lens, projected on paper by steering mirror. No sign of spurious beam.
3994 beam on first steering mirror. extremely non-centered, and extra blob from something on left side of mirror. Feels like something closer to camera out of focus. Doesn't line up with anything, reflection off steering mirror?
Through frame 3989 OSC beam profile, are we hitting something in the steering mirrors? Spurious beam is not present after OSC, but IS after the steering mirrors.
3998 to 4003 alignment on input of amp0, magnified with lens main beam aligned with alignment, on input of amp0. yet spatial filter not aligned.
4004 output after amp1, badly missing...
4006 input of amp1, with bit of stuff reflecting off aperture.
4010 output of amp1, no visible secondary beam.
4011 output of am1, now with visible secondary beam.
frame 4016 after amp1, V=2400 1800 3000 freerunning one lamp in amp1, spatial filter in and aligned. The striations are from the Ukrainian ruby. Yay technology. Secondary beam is present but very subtle.
V=2400 2700 3200 single lamp in amp1
frame 4017 secondary beam appears.
V=2400 2500 3200 single lamp in amp1
frame 4018 reduced amp0 voltage no significant change in secondary beam
frame 4019 pulled amp1 away from osc slightly. secondary beam is not
significantly changed, though main beam is.
V=2400 2000 3200frame 4020 secondary beam still present. But moved from 4019, a little
V=2400 1800 3200frame 4021 secondary beam sufficiently reduced, but so is main beam.
V=2400 2500 3200
frame 4022 put voltages back
frame 4032 removed pinhole
spatial filter lens X is 275 units moved to X=270 units
frame 4023 to frame 4024 no significant change to secondary beam when spatial filter lens is moved.
The secondary beam is not significantly changed with the different amp1 rods?
V=2400 2700 3200
The spurious reflection is definitely coming from amp1. From the beam inspection lens? (Eventual theory is that its a reflection caused by the rod C axis being 90 degrees off.)
The striations are definitely from the Ukrainian rod. It is unusable.
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Which way is the C axis oriented?
Placed a diffuse reflector behind amp0, and then stared at it a lot. (do not look into laser with remaining eye.) There is a double image side to side. frame 4038. Camera is looking into side of laser, with bounce mirror (first surface). When the 3/8 inch rod is in that orientation, the blob is wider than tall. In historic frame 3925, beam profile just after amp 1, the blob is taller than wide.
IE: the rod was installed 90 degrees off.
Frame 4044 is LED through Ukrainian rod. It does not show the bifringence of the 3/8" rod, or amp0.
Putting the 3/8" rod back in... correctly oriented. (maybe...) frame 4045 bifringence through 3/8 rod.
frame 4049 V=2400 2500 3200 free running one lamp in amp1 no significant stray beam.
frame 4052 V=2400 2600 3200 free running one lamp in amp1 output is 539 mV 245 mJ
Couple of test shots here with single lamp and 800 mH trigger transformers Output was 226 mV. Which is half of what the 330 mH trigger transformer did. So, getting the 330 mH trigger transformers to reliably trigger may be Worth The Trouble (tm).
frame 4057 V=2400 2600 3200 free running both lamps output pegged frame 4058 1252 mV 1330 1206 mV avg 1262 mV 573 mJ
V=2400 2700 3200 qswitched both lamps 800 mH 1000 mVMoved joulemeter to plate holder. 3.2mV ref beam is 50 uJ/cm^2. U25 needs 30 uJ/cm^2.
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Build a secondary trigger thing, to try and get both lamps to fire with 330mH trigger transformers.
V=2400 2600 3200 freerunning single lamp mode 4 368 390 396 mVframe 4070 is 396 mV sample swapped lamps, to secondary trigger board.
V=2400 2600 3200 freerunning single lamp mode 4 492 522 516 mVframe 4071 is 522 mV sample
The energy difference is from the caps... brighter lamp is the 250 uF cap. dimmer lamp s 230 uF cap.
And now: in stereo. Both lamps connected.
V=2400 2600 3200 freerunning both lamps mode 4 2230 2230 2245 avg=2235.0 1.015 Joules
frame 4072 pegged joulemeter, >1700 mV
So it has finally achieved the 1J it was allegedly capable of doing before the whole second amplifier adventure. (Found a sales brochure, it was actually rated for 0.6 J.)
amp0 output is 1450 1450 1310 mV avg=1403.3
So amp1 gain is about 1.59 times. MEH. But I'll take it.
moved joulemeter to plate holder.
frame 4089, 7.5 mV or 117 uJ/cm^2 (7500 /2.2 / 20.25 ) * 0.70 free running... maybe 3/4 of that?
mode 5...
V=2400 2700 3200frame 4090 5.5 mV or 86.5 uJ/cm^2 qswitched
swapped -200mm lens for -179mm lens
frame 4105 2340 uV 36 uJ cm^2
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V=2400 2700 3200 freerunning both lamp mode 4 3620 3780 3720 uVframe 4125 4126
mode 5 qswitched V=2400 2700 3200 qswitched both lamp mode 5 2720 42 uJ/cm^2frame 4129
osc only, free running is 24.5 mV 11 mJ
put spatial filter pinhole back in replaced ruby with new one.
frame 4223 alignment laser
V=2400 2700 3200 freerunning mode 4
frame 4224 ref beam set to minimum
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The 12V battery charger creates an amazing amount of RF noise, interfering with joulemeter.
mode 5, V=2400 2700 3200 qswitched both lamps ref only 2580 uV 38.9 uJ cm^2 frame 4231
object about 10" from plate joulemeter reads 2340 uV, significant amplitude modulation
frame 4236 shadow check. front of beaker is 10" from plate. sound of high voltage leak while charging.
frame 4241 is hologram 168.1
frame 4242 is hologram 168.2
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new capacitors, 830 uF rated, observed 807 and 824 uF.
firing single lamp... outer lamp, closest to edge of board 2400 2700 1700 V 91 82 mV with attenuator freerunning
Firing other single lamp... V=1700
(inner lamp, furthest from edge of board)
2400 2700 1700 V 77 77 76 mV with attenuator freerunning
charge time is about 1500 millisec.
both lamps...
2400 2700 1700 V 425 414
v=1900 (1480 J)
2400 2700 1900 V 821 833
energy in ref beam only, freerunning 2400 2700 1900 5.12 5.37 5.23 mV energy in ref beam only, qswitched 2400 2700 1900 3.66 4.00 4.21 mV avg 3.956 mV 62 uJ/cm^2
Measuring voltage in cap, to precisely measure pulse time, to see how close we are to explosion energy...
amp1 circuit breaker tripped.
The 100:1 probe to the oscilloscope caused it. dump resistor was not warm after breaker pop, the caps were apparently not charged at all.
Probe was incorrectly connected, and HV end of cap was GNDed through the oscilloscope. Yay circuit breakers.
V=2400 2700 1900 reported pulse length from qswitch trigger 1328 1331 1331 avg=1327.3 usec
observed with oscilloscope time to V=0: 1050 1040 1160 avg= 1083.3 useconds (See hpgl in 20190629)
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So we're going to call the pulse 1000 useconds long, which should put the error on the safe side.
Volts Joules percent of J per cm^3 lifetime (825 uf) Ee (spreadsheet) (both lamps) (pulses) 1700 1192 21.8 216.7 426007 1900 1489 27.2 270.7 64293 2000 1652 30.2 300.4 26588 2100 1819 33.2 330.7 11727 2200 1996 36.4 362.9 5326
So, 2200V is just beyond the pointless point, assuming the 350 J/cm^3 rule of thumb in Solid State Laser Engineering is valid (I believe my coupling losses from lamp to rod are higher though). 33 percent of Ee is about 10^4 pulses. Kinda hard on the lamps.
26 percent of Ee is 10^5 pulses. If the pulse is actually 1200 useconds long, V=2200 drops to 33 percent of Ee. (not really significant)
V=2400 2700 2000 ref only qswitched 6220 uV or 97uJ/cm^2. Adjusting beam splitter down to get 30 uJ of ref. (never gotten to do this before...) about 1/2 way... 3660 uV 57 uJ cm^2 about 1/4 1570 uV 24 uJ/cm^2 up a tad... 2100 uV= 33 uJ/cm^2Made hologram 173.1, yet another flower, on U25 in ultimate developer. Not as bright as 172.2, however looks very usable.