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Old 01-17-2011, 12:14 AM #1
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Default Direct driving 445nm diode with single cell?

Are there huge flaws in my reasoning here - ?

I have a tiny single AA host that I want to turn into a 445nm laser. Suppose I used a 14500 (AA form factor) lithium cell. At peak charge, it should provide around 4.2V, which is enough for a 445nm diode.

Could I not simply direct drive the diode, counting on the fact that a single 14500 cell won't supply more than the ~1A current that these diodes can handle anyway? IE, would it be imperative to have a current limiting driver, if a single 14500 lithium cell won't (I don't think) deliver more current than the diode can handle anyway?

If I added a small capacitor to handle voltage spikes, wouldn't this plan work?


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Old 01-17-2011, 12:23 AM #2
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Default Re: Direct driving 445nm diode with single cell?

Im guilty of doing this once, I figured that the voltage is right, and that the battery wont be able to supply a current large enough to kill a diode.

I used 3X AAs in series for the voltage (4.5V IIRC), after messuring that thier internal resistance will hinder them from supplying the current even needed to achive 1W. I havent tried this with lithiums yet.

The A-140 survived, and was working like this for about an hour, before I actually went and bothered to make a driver for it.

I dont know how reliable it will be, nor do I say its a good idea, but if the battery cannot even supply the current on a short, the diode will probably be fine, but your really risking it.

spike wise, a capacitor will work.
my case I just solder a bi-polar TVS diode (with clamping voltage that of 5V) onto the diode's pins directly, it handles spikes and static quite nicely.
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Old 01-17-2011, 12:24 AM #3
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Default Re: Direct driving 445nm diode with single cell?

It's been done:
Direct-Drive 445 Host
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