Old 12-13-2008, 02:39 AM #17
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Default Re: Power Requirements for a Laser Module

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Originally Posted by QuackMasterDan
Having changed my voltage regulator to 2.92 volts my spirograph is fully functional. I've been using it over the past two hours and the laser has not burnt out, and the rig seems to be relatively stable. However there is an oddity that is going on with brightness. After being left on for around 5 minutes, the brightness of the laser drops sharply. If I power it off and quickly on again, it will return to full brightness for about 1-2 seconds.
If I had to guess, my LM317 is near its heat-limit and is dropping the voltage to compensate, however I have a very large heatsink applied with thermal grease attached to it. To the touch the heatsink doesn't burn my finger, but is still very warm. The laser module itself is noticeably warm.
What could be causing the shift in brightness after 5+ minutes of use?

After it drops in power, shine the laser through a magnifying glass onto a flat surface. Take a picture of the spot or describe it to us.

Peace,
dave


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Old 12-13-2008, 10:57 AM #18
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Default Re: Power Requirements for a Laser Module

Why would you wanna build custom drivers in the first place? Just use the driver it came with. You're not gonna get much more power.
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Old 12-14-2008, 12:45 AM #19
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Default Re: Power Requirements for a Laser Module

I misunderstood what was needed to supply the correct power to my laser module. The original lasers were toasted at 3.08v for a 5mW Green module, so I figured it was something other than voltage (Turns out voltage was the only issue, just 3.08 was too high). I then was told I needed to create a current regulator for my laser module as is done for a diode by itself, not realizing that the board attached to the module is one already, making me effectively regulate current twice and hit the module with 12v @250mA, toasting another. I now know all I needed was to have my voltage at 2.92v and everything works fine now, except for this weird lowering in brightness after 4-5 minutes of being continuously on, I'll take a picture of the laser with a magnifying glass later tonight.
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Old 12-14-2008, 09:37 AM #20
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Default Re: Power Requirements for a Laser Module

Never trust a "wall wart" power supply!
These are unregulated and all the ones I've ever meter tested were producing more voltage than their stated specs.
Youre "12 volt" wall transformer was probably really puting out between 14 to 16 volts.

If you want an inexpensive (usually free) regulated supply, remove the power supply from some old desktop computer.
One of these old power supplies will give you pure 12v, 7.5v and 5v DC connections and all the power (wattage) you'd ever need.

~SK
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