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Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
I took apart a DVD burner from a laptop recently, and I got a nice red laser diode from it. Knowing I can make a really nice laser out of it, I decided to keep it, and use it.
My problems were finding a lens, and I found one from a cat toy laser pointer we had that had a broken switch. The lens are actually glass, so they won't burn from the intense red light!
I make a CC driver for it, using an LM317 and 7.5 ohms of resistance on it, and anywhere from 9 volts input to around 4 volts makes the laser light up different brightness, nine being painfully bright, and 4 a little brighter than an average laser pointer. Is my CC source not working properly?
I also need to make a heatsink for it, since currently it's just got a bit of aluminum stuck to the case from the sled it came from. Any ideas how to make a nice heatsink for it?
EDIT:
I got the case out of the sled, and it's one of those open air ones.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
the LM317 current source behaves not really well with laser diodes
the best is to use an op-amp with an output transistor, a current measurement resistor, a feedback on the current value, and a pot at the positive input for current set
in this document the laser diode driver 2 is the best option
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Your results sound reasonable. The LM317 has a typical dropout voltage of 1.8V or so. The voltage drop across the current setting resistor is 1.25V and the voltage drop across the laser diode is probably at least 2V, so I'm not surprised that it doesn't behave as a very good current source when fed with 4V. Your supply needs to supply at least 3V more than the voltage across the laser diode for proper operation, maybe even more.
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red Laser from DVD burner, and making a pointer with it
