driving a 1000 mW laser diode

I want to power a laser diode (the kind used for engraving) in a portable device for short periods with a 9V battery. The laser diode comes in a tube with a focusing lens and trailing wires, and the spec says 5V 1A. This diagram seems to be the standard circuit for driving these. The LM317 spec says Vout is 1.25V above Va and it needs 3V of headroom.

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+9V----o-----| LM317 |---o-----o-----o-----o | ---------- | | | | | | > |+ ? ? === | R1< === ^ V D1 | C1 | | |C2 |D2 | | o-------o | | | | | | | | | > | | | | R2< | | | | | | | | GND----o------------------o-----o-----o-----o

C1 = 0.1 uF C2 = 1 uF R2 = 3 * R1 (calculated to get 3.75V to Va and 5V to Vout) D2 = 1N4148 or similar D1 = laser diode

Would it also work with the simpler circuit using LM7805 regulator? WouldI need the backwards signal diode at the end of this one too? The LM7805 is supposed to put out up to 1A -- is it a problem that that limit is right at the diode's current?

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+9V---o---| LM7805 |---o---- Vout = 5V (to laser diode) | ---------- | === | === C2 | C1 | | | | | GND---o-------o--------o----

C1 = 0.33 uF C2 = 0.1 uF

thanks

Reply to
Ingmar Webb
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I found another diode driverthat uses the LM317 for controlled output current to a LED, but the example was for a much lower (not laser diode) current:

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+9V-----| LM317 |----o --------- | | > | < R | | o--------o-----o-----o | | | | |+ | - === V D1 D2 ^ |C1 - | | | GND------------------o-----o-----o

D1 = LED D2 = 1N4001 C1 = 10 uF R = combination of resistors and pot so I = 1.25V/R

Would this work for a 5V 1A laser diode too?

Reply to
Ingmar Webb

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