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flare09

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Oct 19, 2011
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Hey everyone, so I'm getting back into my old rgb build, which is great because all the diodes are so cheap now!

So after being scammed years ago, i have been left afloat to diy my own driver, cheaply.

And here's the question.

Is it possible to utilize a simple picaxe with hardware pwm outputs, to drive signal to a pnp transistor, that will be powering drivers, which power individual diodes?

Or is it better to use a ttl enabled driver, and directly provide signal to that? I believe it was the flexmod with the signal pad?

Ill ask about diodes later, but ill need case isolated diodes, in all 3 'colors' RGB
 





What kind of control do you want? Analog brightness levels or just TTL on/off control?

If you are building a scanner you really want analog control: that will be moving at 30.000 pps or something similar and any PWM control has to be extremely fast to work within that. If it's just a steady beam you want to vary in color you can use PWM on the TTL input to set brightness levels.
 
I would like intensity control. Its for a simple handheld pointer. And since I'm combining colors, contolling each lasers frequency separately is whats important. Intensity is also important, i would like to be able to drop current output. the frequencies I'm looking for shouldn't be too fast, just your basic point and shoot color changing dot
 
A driver with TTL input will work fine for that application. I'm not sure how fast you can generate a pwm signal from the picaxe, but if its over a kHz or so it will work fine.
 
After lookinh around some more i think the best thing would be to go with the sxd drives. Remove the resistor and soft start cap.

I could do some custom trim pots and set a min and max current on each driver, for each diode. That way i can manually adjust output as needed.

Thanks benm
 
Sounds like a plan, though i'm not sure what speed that driver can handle modulation/pwm. Not all switchmode supplies are too happy with being turned on and off rapidly, so i'd still connect a test load and look at the output with a scope before connecting any (expensive) laser diode.
 
I'd like to tag a question on to this thread:

I'm looking for a already built ready to play laser diode driver capable of 1 microsecond pulses with a 50% duty cycle, so; 1us on and 1us off. This would be to drive an IR diode at 780nm, 120-175 milliamps from 2.1 to 2.7VDC. Anyone know where I can find one which is a small size, perhaps no more than 20 x 20mm?
 
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