Laser diodes, and pulses

[Adrian Crenshaw]

Hi All,
    Some of you may have seen my bar code flasher. I'm tring to make it a barcode sniper :) I got a low powered laser to work off of it, and it can send barcodes, but the range is not very good. I hooked up a more powerful one, but I can never get it to read. I've read a little about "constant wave vs. pulse" lasers, it is possible the more powerful one is already pulsing/flashing, screwing up my own modulation?

As a side note, I'm driving the lasers directly from a Teensy's output, but I know that can only source so much current. I'm trying to get a pn2222a to work for controlling power, but if anyone has a good schematic I can use to apply TTL logic to control a high current device that switches in microsecs, please let me know.

Thanks,
Adrian

[Bill Piepmeyer]

Try a tip120 (you can most likely drop this directly in place of you
2n2222, but that is totally a guess on you circuit). uln2003 and
uln2008's work well for multiple outputs and can sink more than
2n2222's while drawing less current on the input (base). You may also
want to consider using a mosfet. How much current are you looking for
and at what voltage?
--Bill

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[iron...@gmail.com]

I think it's a 20mW laser, at 3.7 volts or so.

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