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DVD Diode question.. (use driver or not?)

Bionuker

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Hi there :).

I want to make a DVD Burner handheld laser...
I just got my 16x LG DVD burner, and I have a housing for my module. The module (dealextreme.com sku.5914 - Can't post any links -_-) I ordered seems pretty OK. Can I use this one with a 3,6v power source, without frying my 250mw diode?
Or do I have to build a driver? I don't get it.. It's all very confusing. Some people say "use the driver from the module", and some people don't.

Regards, Bionuker.
 



Phazonx

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trust me! you need a driver.


I though that would not need one at all, but I came here and everyone says that you need one.



ask Daedal. He can sell you one. I bought one from him and I got it 2 days after I bought it.
 

Kenom

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You most defenitly need a driver of some sort. without it your spelling certain doom for your diode.
 

Bionuker

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Thanks for the quick response!

If I make sure the current never gets higher then 3 volts.. Can the Diode still be fried?
 

Gazoo

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It doesn't matter, you need some way to limit the current and prevent voltage spikes. At the bare minimum you can get by with a resistor and capacitor, but the safest bet is to use Daedal's circuit.
 

rog8811

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Its the current that kills it more than the volts, straight on 3 volts worth of batteries it could draw 500ma, that equals instant death to the LD.

Current control is everything for success.

Regards rog8811
 

Zarniwoop

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Just a pet peeve here - Yes it's the current that kills a diode, but current regulation works by varying the voltage so that the current comes out to what you want. (V=I*R) So you can't really have the situation where the voltage is too high but the current is ok for the diode, unless you mean the voltage with no load (i.e. without the diode connected). If you measure the voltage across the diode, if your current is in-spec, then your voltage will be too.

Anyway...
Some LDs (like open-can types) may have a max operating voltage of 3V, while others (like the Senkat GB diodes and many 16x DVDs) are spec'ed for 2.5V. I ran an open-can diode from an 18x DVD directly off 2 AA batts for a couple of months (not continuously), getting away with it because of the internal resistance of the batteries. The same thing fried a different diode immediately. If I had used batts with lower resistance, it probably would have even fried my open-can LD. (I've since pulled it out of the mag-light and added a regulator.)
The BARE minimum would be a resistor. But the regulator approach varies less with temperature and allows using a higher source voltage to avoid immediately getting into battery-sag.
Using a DC-DC converter like in a Dorcy Mini may allow even longer battery life because less current is dissipated in heat, although the only current tweak you can do is by adding a resistor, and they you're back to heat dissipation again.
 

Bionuker

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Thnx :)

So I can't use the on-board controller from the 5mW module? That would make things a hell of a lot easier.
 

LarryQ

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Unfortunately, No..that driver won't drive anything much more than the <5mw diode.

It sure would be nice though..it's so small!!!

If this is your first laser mod..I highly reccomend you give the Mini Dorcy Mod a whirl!

http://www.laserpointerforums.com/forums/YaBB.pl?num=1181635652


The Mini Dorcy already has a nice circuit in it..and makes for a very easy / quick project for you.

The only thing you might want to add to the circuit might be a 47Uv 16 volt capacitor across the Laser diode leads just to absorb any volatage spikes when the laser is turned on.

A lot of people will say that even this is not needed...but I think an ounce of prevention could save you a Laser diode!

Good luck!!!
Lot's of great info around this forum!
LarryQ
 




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