Old 07-26-2010, 08:07 AM #1
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Default A little battery help

Hey,

So I'm working on my first build and i'm building the driver circuit (rather than - buying one). I'm going off of this circuit diagram that I found in another thread - http://laserpointerforums.com/attach..._schematic.jpg

The laser diode that I'm using however, has a threshold current of about 40mA and an operating current of 100mA.

Right now, however, I'm not entirely sure what battery we should be using. I'd like to use a AA battery, but I don't know if that will give me enough voltage. For button cells, will that give me enough amp?

Help would be much appreciated! My friend and I are quite new to this.


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Old 07-26-2010, 08:49 AM #2
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Default Re: A little battery help

That laser circuit uses a LM317 linear regulator, which requires a voltage about 2.5 volts above what you're trying to drive. Reds need about 3V, 445nm's need about 4.2V, and blu-rays need about 5V. So you'll need 2.5V above each of those ratings in order to use the LM317.

A single AA battery will not work as it's only 1.5V, you'll need more voltage, and I'd also suggest looking at LiPol or other battery types that can source more current. Alkaline batteries often aren't up to the task. See if you can get multiple LiPol CR123A or 18650 batteries, as they have 3.6V at a minimum.

That circuit is a good one to start with, just make sure you have enough voltage. Others like the Flexdrive can actually boost the voltage to whatever is needed, so single batteries can be used (not sure if single AAs will still be too low though).
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Old 07-29-2010, 03:33 AM #3
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Default Re: A little battery help

Hmm... Okay. Thanks a lot!

Any chance that this driver might work?
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