Instructions for Stabilized HeNe Laser
Controller Kit 2
Version 1.00 (30-Aug-09)
Sam's Laser FAQ, Copyright © 1994-2009
Samuel M. Goldwasser
--- All Rights Reserved --For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page.
Introduction
This document contains notes on the construction of Stabilized HeNe Laser
Controller Kit 2, SGHS2. This provides for frequency or intensity stabilization of
a home-built HeNe laser using a 5 to 10 inch random polarized HeNe laser tube,
photodiode beam sampler, and heater, or a Spectra-Physics 117 or 117A laser
head.
The following components are included in HENESTAB1.5:
Blank SGHS2 PCB.
Electronic components to populate the PCB.
Parts list and assembly instructions (in this file).
Testing procedure.
The completed SGHS2 will look similar to the photo below:
What you will have to provide:
12 VDC regulated power supply. The maximum current is under 1 A.
These may be easily constructed using an old modem power adapter
(typically 13.8 VAC), a 3 terminal IC regulator with heat-sink, and a
handful of other parts. Or, even easier, a regulated 12 VDC, 1 A wall
adapter from an electronics distributor like Jameco.
Home-built HeNe laser head with photodiode beam sampler and heater to
be controlled by SGHS2 or a working Spectra-Physics 117 or 117A laser
head.
Compatible HeNe laser power supply for the laser head.
Low power soldering iron, thin rosin-core solder, and soldering skills to
construct the SGHS2 controller and cables. If you have never done fine
soldering, do not attempt to learn this skill here! Practice on something
else first or have someone else build this kit for you. Sweating copper
plumbing does NOT qualify as soldering experience! :)
Familiarity with the standard resistor color code! There is a chart below
and Any number of Web sites can help further.
SGHS2 Stabilized Laser Controller Specifications
Pin and functionally compatible with the Spectra-Physics 117 and 117A
stabilized HeNe laser heads.
Photodiode input: Adjustable from about 10 uW to 1 mW peak for each
mode. (May be reduced by changing one resistor value.)
Tuning range: From near peak to near minimum of gain curve on either
side.
Recommended heater resistance: 18-30 ohms.
Switch: Heater Mode (On/Off/Lock, SPST center off toggle switch.
Adjustments: Input gain and Lock Offset.
Indicators: Power (Green LED), Modes (Red LEDs), Heater Voltage
(Yellow LED).
SGHS2 Assembly Instructions
1. Check the contents of the box against the parts list below. In addition to
confirming that everything is present and accounted for, this will give you
some experience in identifying the components, should that be rusty. :)
2. Install components in groups of 5 or 10 starting with the resistors and
other low/small parts.
o Most parts are labelled on the PCB silkscreen so it should be
difficult to screw up.
o It's good practice to orient the parts facing all the same way even if
not required (especially with the resistors). Face them so that the
first color band is at the left or top (as with the parts numbering on
the PCB).
o Take care to have the parts flush with the PCB - carefully press
them in place and bend their leads out at an angle to hold them
there for soldering.
o Double check that the correct parts are in each location BEFORE
soldering. Removing a part is not fun and will likely damage the
PCB if you do not have a proper desoldering tool (and possibly even
if you do). In particular, it's easy to accidentally swap the transistors
or get the LEDs in backwards.
Use just enough solder to fill each hole where a lead is inserted.
There doesn't need to (and should not) be significant solder above
the component side of the PCB. Less is better!
o Clip the component leads about 1 mm from the PCB surface.
o Check for solder or component lead shorts.
3. Install the larger components like the pots, switch(es), and connectors last.
o
SGHS2 Testing
The following assumes that a known working SP-117, SP-117A, or home-built
equivalent laser head is available.
1. Before installing the LM358, apply power. The green Power LED should
be on as should the Mode LEDs (at about half brightness). Confirm that
there is +12 VDC at pin 8 and 0 V at pin 4 of U1. Remove power.
2. Set R3 (Offset) to its mid-point. Set R4 (Gain) fully clockwise. Set S1 to its
middle position (heater off). Install the LM358.
3.
SGHS2 Parts List
Part#
Description
---------------------------------------------------------------------------C1
0.1 uF (104)
C2
100 pF (101)
C3
1 uF (105)
C4
0.1 uF (104)
D1
D2
1N4148
1N4148
J1
J2
J3
HDR, 3 pin
DB9F RA PCB mount
HDR, 2 pin
P1
P2
P3
Mating housing for J1
DB9M for J2
Mating housing for J3
Power
Laser head
Modulation input
Pins 6 pins for P1 and P3
LED1
LED2
LED3
LED4
Green T1 LED
Red T1 LED
Red T1 LED
Yellow T1 LED
Q1
Q2
Q3
MJE3055T
2N3904
2N3906
Power
S Mode
P Mode
Heater
NPN power transistor
NPN transistor
PNP transistor
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
1K, 1/4 W
470, 1/4 W
100K pot
1M pot
2M, 1/4 W
1M, 1/4 W
220K, 1/4 W
6.8M, 1/4 W
470, 1/4 W
2.2K, 1/4 W
1K, 1/4 W
1K, 1/4 W
470, 1/4 W
S1
Switch, SPDTCO Sub-miniature Toggle
U1
LM358
Dual op-amp
ZD1
1N4732A
Zener, 4.7 V, 1 W
SGHS2-PCB
Schematic:
Offset
Gain
Blank PCB
Mode Select: Preheat/Off/Lock
Resistor Color Code Chart:
