Head control electronics

The head contains several major electrical sub-assemblies:

The control box

The head control box observes the 24V trigger signal from the power supply, and the output of an energy meter between the amplifier and the frequency doubler, and generates the voltage and timing signal for the q-switch as well as a mechanical shutter in the oscillator.

The box contains a motherboard, a high voltage power supply card, and a logic card. The logic is mostly 4000 series CMOS, with a supply voltage of 14V. There are a couple of TTL timer chips, and 2N2222 transistors for level conversion.

Control card

Schematic in postscript
Schematic in gschem format

The logic card contains: (these are board coords)

A1	4020	14 bit counter
A2	555	timer, running as a 1kHz clock
B1	4013	Dual D flipflop
B2	4020	14 bit counter
B3	40174	hex D flipflop
B4	4512	8 input multiplexer
C1	4071	quad or gate
C2	4049	hex inverter
C3	4013	Dual D flipflop
C4	40106	hex schmitt trigger
C5	14538	dual monostable multivibrator
C6	74221	dual non-retriggerable monostable multivibrator
C7	74221	dual non-retriggerable monostable multivibrator

Connections to the control card are labeled con.1 to con.100, and are the pins on the edge connector.

Power supply card

The power supply card goes into a slot on the motherboard, and has a pice of high voltage wire to a BNC for HV out. The slot has 44 pins, half of which are ground. The top of the connector is 1 to 22, and the bottom is A to Z, omitting letters G, I, O, Q.
Schematic in postscript
Schematic in gschem format

The power supply card contains three separate circuits:

The power supply under the optical rail

This takes 220VAC from the umbilical, and has two D9 connectors for output. Based on the connectors, I think it just powers the heaters for the frequency doubler and trippler. It looks like a generic switching power supply.

The q-switch driver (right beside the q-switch)

This takes several thousand volts DC from the power supply, and a low level trigger signal, to generate the pulses for the Q-switch. It is physically right beside the resonator, to keep things short.
Schematic in postscript
Schematic in gschem format

The energy meter (immediately after the amp)

The energy meter has a couple of photo diodes, to observe the laser beam, for timing and a power bar graph on the remote control. The photo-diodes have IR filters on them, and just sort of look at where the beam goes by. There are no real optics.

Schematic in postscript
Schematic in gschem format

Connections to the energy meter are numbered EM.1 to EM.8 or so. They are numbered according to the header on the motherboard, and consistantly labeled everywhere. Which is why they are not in order on the EM board.

The remote control

The remote control has buttons for shutter, fire, norm, and how frequently to fire the qswitch. I'm not sure what the norm button is supposed to do... There were notes attached to my laser indicating it should be pressed.

The power for the shutter in the oscilator goes through the remote, the laser will not operate without it. The pins on the remote control are labeled D15.1 to D15.12 on the remote control, but RC.1 to RC.12 on the motherboard.

The shutter will not open if the remote control is not plugged in.

Schematic in postscript
Schematic in gschem format

Copyright 2008 Tommy Johnson