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ArcticMyst Security by Avery

opposite DDL question

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Aug 1, 2008
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I've recently started on a 1W 808nm project. I have my 9mm diodes and the person I bought them from says they can be driven up to 1000mA, I tried using a DDL circuit I had laying around but it will only go up to 480mA with the .5ohm resistor and 100ohm pot turned to the highest mA. Ive tried wiring it up a couple different ways, it worked once and it went up to about 2amps, but then it didn't work once i got it soldered together onto a board.

I was wondering, rather than using 1 driver to power 2 diodes like other threads that have come up in my search, but using 2 drivers to power 1 diode? Ive tried wiring it up a couple different ways, it worked once and it went up to about 2amps, but then it didn't work once I got it soldered together onto a board. I'm sure they can be put in parallel but I'm not sure how to hook it up (drawings appreciated)
 





ReNNo

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Mar 27, 2009
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Here you can see how circuit should look:
LM317%20components01.jpg


With .5ohm resistor current can go up to 2.5A and that is not safe even if you have pot.
One more thing is power of resistors and pots.

You can calculate power like this..
P=1.25 x current
For Example:
If you have .5ohm resistor power that dissipates on resistor is 1.25x2.5 = 3.125W
Low power resistors will heat up very quickly and that is not safe.

If you need current above 1.5A you should use LM350 instead of LM317 and you need
heatsink to cool chip down.
LM350 can go up to 3A.

Recommended current for 1W 9mm diodes is about 1.2A
For this current you need 1.041Ohm resistor and power of resistor should be greater than 1.3W.
But you can use 1ohm resistor if you have enough good heatsink.
 
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ok sweet. ill keep it around 900-1000mA for now. thanks for the help, ill try it out
 





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