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I need help identifying SMT components of a laser pointer driver. Answered

I recently dismantled my 5mW green laser pointer because I was sick of feeding it AAA batteries. I'm using 4 18650 Li Ion batteries now. I found a little trim pot that increases the power output and when I turn it up, two of the driver components get really hot. I would like to build my own laser driver based on the original, but I need help reverse engineering it. I've attached a few photos, including the circuit I determined so far. The node voltages when the laser is operating normally are included in blue.

The two main (I'm guessing) components are marked Y2 and MY and I have no idea what they are. MY becomes very hot at high load. Please help me ID them!!

Oh right, and I had to put the big resistor on there. It's a 1Mohm. Somehow it's necessary for the circuit to turn on without the pointer body. It's connected from battery positive to the bottom of Y2.

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steveastroukBest Answer (author)2012-01-03

Its a constnat current source. Start from scratch with an LM317 regulator and a circuit like this one.

Measure the diode current, and use that to set the resistor you need.

steve

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laserjocky (author)steveastrouk2012-01-03

Yeah, I've seen the LM317 driver before, I was hoping to use the original design but I may have to resort to this. I eventually want to be able to hook a DVD burner diode to a similar driver and my guess is I'll need something a little more robust. I've seen nice driving circuits that use a large transistor to control current but they require a low voltage op amp and I'd rather use radio shack parts for this. Maybe I'm just being snobby. Thanks for the post!

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steveastrouk (author)laserjocky2012-01-03

An lm317 IS a large transistor with an opamp...

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laserjocky (author)steveastrouk2012-01-03

well, yeah. But it's cheating :) ok, ok I'll try it out.

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