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First build-need some power supply advice

Cvmangia47

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So I built my own driver and although I do not have the laser module installed into the heat sink yet I have put my meter on the output terminals for testing and used a simple led diode for testing also. I read about 340mA output and 6.5V when my meter is on the output terminals . I intend to hookup to a Mitsubishi LPC-836 . Data sheet requires 340mA max and operating voltage of 3V. I am using a 9v battery as my supply and built the following driver circuit :

http://laserpointerforums.com/attachments/f42/11702-diy-homemade-laser-diode-driver-ld_driver_schematic.jpg

Except in my circuit I used (3) 10ohm resistors in parallel, not 2 . I've read that the lm317t will dissipate any unwanted voltage once the LD is connected to the output of the driver but I'm nervous about jus hooking it up since I only have 1 . My question is should I reduce my power supply to (2) AA batteries in series to achieve 3V or can I leave the 9V battery supply?
 
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Cvmangia47

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EDIT: when the device is powered on and the test LED diode is hooked up I can achieve 3V by turning my pot with the 9V power supply still hooked up . Does this answer my own question ?!?! Lol
 

APEX1

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what are you trying to do? your last comment doesn't make sense?? unless I'm reading this all wrong
 

marcuspeh

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I dont get your second post but to answer the first post, you cannot use 3v power supply to power the driver. The lm317 drops out around 3v so you will need a power supply with at least 5v. So just continue using the 9v battery.
 

KrowBar

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The driver supplies a constant current at whatever voltage drop the load requires to draw that current. If you are concerned because the voltage drop on your LED is higher than that of the laser diode you plan to use, then your LED might not have been an appropriate test load. You could try using plain old rectifier diodes as a test load, using as many in series as you need to get close to the voltage drop you want to test at.
 




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