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Red DIY DVD laser burner.

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chimo

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No.

It will get you in the ball park but that's it. LDs are very sensitive devices, some people have had some luck slapping them in a minimag but othres have fried them in the process of hooking them up.

Each LD can have a different voltage current curve. The curve is very steep (or shallow depending how you plot it). What that means is that for a VERY SMALL change in voltage you will get a VERY LARGE change in current. In addition, as the LD heats up, the curve shifts so an applied voltage that resulted in a current that was safe when the LD was cold can result in a burned out LD when it gets hot.

Unless you don't mind the risk, I recommend driving them with a current source. There are several examples posted on this forum.

photongeek said:
Is this online calculator sufficient for determining the proper current limiting resistor for these LD's?

http://ledcalc.com/
Click to expand...
 





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photongeek

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Thanks Chimo:
I was looking for a cheap and easy way. I guess bread boarding and experimenting is necessary :mad:
Does 5 ohms look like a good place to start?
 
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Zarniwoop

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I'm using a 1 Ohm 1W resistor in series with the LD, powered by a Dorcy mini, and that gets me a current right at 250ma. I put the cap and reverse polarity protection diode inside the module.
It's not as nice as getting the converter to regulate to 250ma instead of 350, because that resistor is wasting battery life by dissipating a little heat, but it is simple to do. In practice the resistor just gets barely warm.
BTW, the Fry's electronics around here has a lot more components (like low Ohm high wattage resistors) than Radio Shack, which is downright pathetic these days.

I've ordered a batch of 350ma DC-DC converters from Deal Extreme it's $14.50 for 20 of them. I'll probably keep 4 or 5 then sell the rest here for a buck each. Dunno how long it'll take for them to arrive though.
 
Gazoo

Gazoo

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photongeek said:
Thanks Chimo:
I was looking for a cheap and easy way. I guess bread boarding and experimenting is necessary :mad:
Does 5 ohms look like a good place to start?
Click to expand...

A 5 ohm resistor will deliver 250ma's to the diode using it with the LM317. To figure out the resistor you need, simply divide
1.25 by the amount of current you want to apply to the diode. R = 1.25/Current
 
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CHP

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The Dealextreme circuit is a boost switcher. It has a boost inductor, diode, switching transistor, control IC, and a couple resistors.
 
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Zarniwoop

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So is the circuit in a mini Dorcy. I'd expect it to work, especially if you use a capacitor across your LD.

I ordered the 350ma circuit because I want to use it with an open can diode, which can take more current.
 
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photongeek

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Gazoo said:
[quote author=photongeek link=1181635652/225#225 date=1191330784]Thanks Chimo:
I was looking for a cheap and easy way. I guess bread boarding and experimenting is necessary :mad:
Does 5 ohms look like a good place to start?
Click to expand...

A 5 ohm resistor will deliver 250ma's to the diode using it with the LM317. To figure out the resistor you need, simply divide
1.25 by the amount of current you want to apply to the diode. R = 1.25/Current[/quote]
I really don't want to sound stupid but I guess I will anyway. How did you derive the constant 1.25? Thanks.
 
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Zarniwoop

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I recently mounted my GB diode in a mini Dorcy, but I took a slightly different approach.
I didn't use any of the LED assembly.  I use a protection capacitor and diode inside the Aixiz module, and use the entire module.
I found a bronze flange bearing at the hardware store that was just the right diameter to accept the Aixiz module, and tapped an allen set-screw on the side of it.  This piece is fairly massive and provides a good heat-sink.
Used thermal epoxy to mount it in the outer screw-on tube.
Attaching the wires to the Dorcy was interesting.  For the positive lead I just put a screw in the center hole with a nut and washer on it.  For the negative lead, I couldn't get solder to stick to the outer ring, so I drilled a small hole in the ring, added a small screw there, and soldered to that.
I've also got a 1 Ohm resistor in series, to bring the current down to 250ma.
 

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Zarniwoop

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Shooting across the yard at night, hitting the fence.
You can see the beam, no smoke required.
 

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Kenom

Kenom

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not bad at all. I'm glad that someone was able to use the flashlight as a good host. having it's own circuit inside was kinda handy and adding the extra circuitry is just going to make it last all teh longer.

Nice Job!
 
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Zarniwoop

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Yeah, I think it makes a perfect host for a GB diode. I use Daedal's regulator circuit on my workbench, but for running off batteries I really like using a DC-DC converter like in the Dorcy. You can run off one CR123, and you don't waste nearly as much energy as disspiated heat from the regulator. I think my battery's down to about 2.5V now and it's still able to burn.
The only catch is having to buy a $20 flashlight. But it looks like DX has some cheap converter circuits that could be built into all sorts of enclosures.
 
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