Very Cute Miniature-Neon Laser and Power Supply, 0.5 to 1 mW
Before there were diode lasers, there were barcode scanners which used HeNe
lasers. Hand-held units also used HeNe lasers and smaller is of course
better. This system is the laser from a very popular unit, the Metrologic
MH290. More information on it can be found at
Metrologic Model MH290 Hand-Held Barcode
Scanner. It consists of one of the smallest HeNe laser tubes mass produced
along with a power supply that runs on 12 VDC (will probably be fine on 10
to 14 VDC). The tube is a Melles Griot 05-LHR-002 (or equivalent) which is
just over 5 inches in length by 3/4 inch in diameter. The power supply is
a high frequency inverter which is conformal coated with some rubbery material
but this can be removed with a bit of work if desired.
The actual HeNe laser tube may be from Melles Griot, Siemens, or Uniphase
but they have the same specifications.
I have had no problems running these for a few minutes but a heatsink may be
desirable for continuous operation as this wasn't needed in their original
application. However, a virtually identical setup was used in the Metrologic
ML811 HeNe laser based laser pointer which was designed for continuous
To power these units, you will need a source of 12 VDC at around 0.5 A.
This can be a wall adapter as long as the no-load voltage isn't higher than
14 or 15 V (my estimate - these seem fairly robust):
- Positive (+) input: terminal marked "A".
- Negative (-) input: terminal marked "B".
- Enable: The positive voltage is also required on pin 15 of the PWM IC
to enable the laser. This may be attached at pin 3 of the tiny connector
nearest the end of the PCB.
CAUTION: Double check your polarity - bad things happen if it is backwards!
The voltage on A and B can be left attached with the Enable switching the laser
on and off. This is the way the barcode scanner operated.