DIY Homemade laser diode driver

What do i need to add to the driver for a blu-ray. what value should the resistor after the pot be.

10-15 ohms, the pot is 100 ohms .

hi i was wondering how i could test this circuit for use with blue ray i have 10 1n4004 diodes can i use some of these to test it, if so can someone tell me how many i would need to do it.

hi i was wondering how i could test this circuit for use with blue ray i have 10 1n4004 diodes can i use some of these to test it, if so can someone tell me how many i would need to do it

Click to expand...

Do the same tests as per this thread
http://www.laserpointerforums.com/forums/YaBB.pl?num=1197651171
But replace the 4 diodes with a 100ohm resistor and you should be good

Regards rog8811

would this capacitor work?
WX52G on http://www.maplin.co.uk/Search.aspx?criteria=WX52G&DOY=24m3
that is a 47uf capacitor as far as i can tell, and look similar to the one in your first post

So basically... the value of the 4ohm resistor doesn't matter (a 10ohm would work), and secondly, it wouldn't matter what voltage you hooked up? (3x AA batteries or say a 9v battery would work?). Lastly, does it matter if I try this with a 20x Sony DVD Burner?

robjdixon said:

would this capacitor work?
WX52G on <link>
that is a 47uf capacitor as far as i can tell, and look similar to the one in your first post

Click to expand...

That's a 47 pF (pico farad) capacitor. You're off by a factor million. Try the 47 micro farad radial electrolytic (code VH32K on the same website)

(3x AA batteries or say a 9v battery would work?).

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Niether of the above.....
3 X AA = 4.5v, you need to be looking at 7.2v which is 2 X RCR123A or 2 X TR10440

9V in PP3 form will not have the required ma/hr output to to drive the LD.

Regards rog8811

hydro said:

Quick question, how hot doest the LM317 heatsink get?  I just notice my get real hot to where it hurt if I leave my finger on it for more then 5 seconds.  Is this normal or is it shorting some where?  Every thing is working normally, with the red laser at 416 mA.  

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hydro said:

I'm running the DDL driver with 2 CR123S and a 3 Ohm resistor.  The reason for the question is people are cutting off the heatsink to fit it in the falshlight and if this is a normal operating temp. then wouldn't cause problems?

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Pd = ((Vin - Vout) * Iload)

That's the equation to calculated the amount of power disspated by the chip (Pd) at a given output current.

Assuming the highest input voltage of 8.4V (2x 3.6V CR123A rechargeables), Vout is about 2.9V, then the output differential is 5.5V.  

5.5V * 0.416A = 2.23W

Now assuming the batteries reach their nominal voltage of 3.6V, the power dissapation drops to:

(7.2 - 2.9) * 0.416 = 1.8W

Without a heatsink, that's a lot of heat to be dissipated by the chip.  The maximum temperature the die on the chip should reach is 125C, which if you can't keep your finger on the chip for more than 5-10 seconds, it's most likely too hot.

To keep using the output you have, I'd suggest either decreasing the amount of time you run the laser at a time (and allow it to cool down before running again), or add a small heatsink to the regulator.  Try something like this:

http://www.radioshack.com/product/i...&cp=2032058.2032230.2032272&parentPage=family

I'd suggest using one of these between the regulator and heatsink too (along with some thermal grease), so you don't have to work about accidently shorting anything by touching the heatsink:

http://www.radioshack.com/product/i...&cp=2032058.2032230.2032272&parentPage=family

rkcstr, thanks for the responce. It looks like I have to find a way to keep the heatsink on my mxdl mod and reduce my cycle time also.

Thanks again

hydro said:

rkcstr, thanks for the responce.  It looks like I have to find a way to keep the heatsink on my mxdl mod and reduce my cycle time also.

Thanks again

Click to expand...

If you're using it in a flashlight with limited space, you could instead just try a small piece of aluminum. A hardware or hobby shop may carry a flat bar of aluminum that you can cut a piece to fit the back of the regulator.

Zom-B said:

[quote author=robjdixon link=1185701612/885#885 date=1206393805]would this capacitor work?
WX52G on <link>
that is a 47uf capacitor as far as i can tell, and look similar to the one in your first post

Click to expand...

That's a 47 pF (pico farad) capacitor. You're off by a factor million. Try the 47 micro farad radial electrolytic (code VH32K on the same website)[/quote]

thanks.
would that contribute to the death of my diode, as one has just died on me. The whole circuit gets incredibly hot, so hot in fact that it burns my skin.

Hi,

My driver is finally working ;D Turned out i was using the ir diode instead of the red diode. I thought my driver wasn't functioning right but it was my diode that caused the problem. So always check that, it saves you allot of work :-/

It's still needs a litte bit of tweeking, Because when i put in non-rechargeble cr123 3.0v battery's in i'm only getting 2.75v @ the diode. And with this voltage its not burning. Diode: 18x speed closed can harvested from an LG Bruner so it should be able to burn matches . Right now i'm recharging my cr123 rechargeble battery's Because they are about 3.6 volt when fully charged, i hope this is enough.

If not ,Witch resistor should i take then. Now i'm using 2 10ohm risistors in parralel.

But i'm glad that my driver is giving at last some result

Greetz, Yoeri

Are you sure the diode you're using isn't the IR diode? Because a diode from an LG 18x DVD burner should be an open can diode.

Yes I'm sure. My ir diode was a open can though.

But its clearley the closed can that is the red diode, I think i'm jst not getting enought voltage.

The IR diode is never an open can, just a windowless diode, and you never think of voltage when using this driver, think current. Current is what matters, the diode will take whatever voltage it needs so you don't need to worry about it.