IR Detector Circuit

In many ways testing of 0.5 W and higher laser diodes is easier than low power types groene 1000mw laserpointer . The main reason is that while overcurrent spikes can still destroy or damage the laser diode instantly, the difference between the threshold current and max current is much greater for high power laser diodes. However, they are definitely susceptible to instant death from reverse voltage above a few volts and all other handling, ESD, and driving precautions still apply. A bit of static may not result in instant destruction but can easily cause a microscopic defect which will only grow with time. Keep the laser diodes in antistatic (black foam) material when not in use with their connections shorted together. Make it a habit to touch an earth ground before touching the laser diode.

If there are only two terminals or wires, then all that needs to be determined is which one is the anode and which one is the cathode of the laser diode. In most cases, the anode ( ) will be connected to the metal case. This can be tested with a DMM on the low ohms range (not an analog VOM which may produce too much voltage/current and damage the laser diode).

What I have used is a high current switchmode power supply intended for large TTL digital systems. It regulates well at any load and is capable of 50 A at 5 VDC. I also have one that will do 150 A if needed. :) Make sure whatever you use has no significant spikes/ripple and is well behaved on power cycling with no overshoot when switched on at both light and heavy load laser pen 50mw rood . A linear power supply might be preferred due to lower noise and ripple, but high current linear power supplies are large, heavy, and are relatively uncommon these days. And, such a supply may not necessarily be any safer for the laser diode.

Component values are not critical. Purchase photodiode sensitive to near IR (750-900 um) or salvage from opto-coupler or photosensor. Dead computer mice, not the furry kind, usually contain IR sensitive photodiodes. For convenience, use a 9V battery for power. Even a weak one will work fine. Construct so that LED does not illuminate the photodiode!

This combination is designed to fit entirely inside NVG's machined brass Laser Diode Module Housing which provides the much needed heat sink (the laser diode current would begin to creep up almost immediately due to the small thermal mass of the 5.6 mm laser diode package) and an adjustable collimating/focusing lens groene 3000mw laser pen . Once assembled, the commercial units are potted in Epoxy and the laser safety sticker is wrapped around the outside. :)