DIY Homemade laser diode driver

[yangjack]

I'm a noob and first build laser (cd-r 52x)
Today I use this driver pumb LD ..
I did not know has had any matter.
My LD is burned down ... :'( :'(

Maybe I first connect to 4 x AA batterys then connect to LD is wrong. :'(

 

[danielbriggs]

Aren't CD-r's Infrared diodes? It's dangerous, as you wouldn't see it.

DON'T connect any diodes straight to some batteries!!! At the very least use a capacitor and a resistor. But DDL's circuit would be the best!


Dan

 

[aaronX987]

Daedal, Please use my picture. I'm glad to help out anyone who needs it (even though I am no expert). I also deleted the initial post of the wrong picture. I probably should have just modified it but I was not thinking straight (it's late).

By the way I finished my laser flashlight mod and its got a good beam barely visible at night. However, it cannot burn anything. But I guess It should not at 5 ohms of resistance. On a seperate note, do I need to re adjust the POT when I switch from standard cr123's 3.0v to rechargeable ones 3.7v? Because I really do not want to open the unit again. I had a bit of trouble closing it and don't really feel like going through it again.

Maybe I will try blue-ray for my next build. :

 

[IgorT]

I'm a noob and first build laser (cd-r 52x)
Today I use this driver pumb LD ..
I did not know has had any matter.
My LD is burned down ... :'( :'(

I'm amazed, again and again, when people say "This $hit doesn't work! I took apart my CD-RW drive, like the instructions say, and don't see any light coming out, even if i look directly into it.."

CD-RW use infrared lasers, and very strong ones at that.. It can be turned into a laser, but i don't see the point, since it would be invisible (unless you use a CCD camera) and MUCH more dangerous than a red beam of the same power, since you wouldn't even blink, if it would shine in your eye..

Where in the instructions does it say take the laser diode out of a CD-RW drive?

It says DVD! And it has to be a fast one (16x or more), because if the DVD is spinning faster, the laser has to be MUCH stronger, to achieve the same change on the DVD surface in less time..


It's a wonder you're not blind yet.. Stop trying to use IR LDs. Since there are IR LDs in DVD burners as well (for burning CDs) you can find out, which one you got by using a web cam, or a cell phone cam.. And even this can get damaged if hit by too much light.. Use the camera only to observe the reflection (from the desk, or even better, something dark)..

 

[Gazoo]

Well since he connected it to 4 batteries, it probably burned out before he had a chance to look into it. But you make a very valid point. There will always be those that do not take the time to read and comprehend. Fortunately, they are few in comparison to the people that do read.

 

[IgorT]

Well since he connected it to 4 batteries, it probably burned out before he had a chance to look into it. But you make a very valid point. There will always be those that do not take the time to read and comprehend. Fortunately, they are few in comparison to the people that do read.

From what i understood, he connected the circuit to the batteries first, and then the LD to it.. The capacitor was then able to do the exact oposite of what it's intended to do and probably really killed the IR ld.

But in this case, it protected something else.. His eyes..

 

[IgorT]

The topic of the 78XX regulators has been discussed in another thread... and the results (to me) seem very shoddy... The LM317 is a MUCH better regulator.

--DDL

Daedal...

I believe, he meant to use the LM7806 BEFORE the LM317 circuit, to supply the 317 with exactly 6V, when using batteries..

I was thinking the same way, before.. Luckily, after much explanation from you and Gazoo, i now know better.. Thanks again, BTW..



numberonekiwi:
You don't need the LM7806 in front of the LM317.. This driver circuit will supply the LD with the desired current over the most of the battery capacity.. As the battery discharges from 9V, all the way down to 6V, the LD will always get the same current AND voltage.

Unfortunatelly as Gazoo told you, a 9V battery is not a very good power source for this, since they have a very low capacity.. If you use a rechargable 9V, for example, you will only get 200mAh capacity.. This would only last about an hour, depending on the current you set..

On the other hand, in my miniature burning laser project, i also used a similiar capacity battery - a 260mAh LiPo, so it could work, but you would have to recharge often...

 

[Daedal]

Thank you Igor

--DDL

 

[IgorT]

Thank you Igor

No. Thank you!

See, this is why i believe it should say "6V or more" in the circuit description..

 

[IgorT]

By the way I finished my laser flashlight mod and its got a good beam barely visible at night. However, it cannot burn anything. But I guess It should not at 5 ohms of resistance. On a seperate note, do I need to re adjust the POT when I switch from standard cr123's 3.0v to rechargeable ones 3.7v? Because I really do not want to open the unit again. I had a bit of trouble closing it and don't really feel like going through it again.

As far as i understand the current and the voltage should stay the same, even if the imput voltage is higher than 6V. I will be testing the circuit tonight, to simulate the input voltages, the LiPos go through when discharging, and measuring the output voltage and current..

Two rechargable LiPos should actually work better than with two 3V batteries, since the voltage on these would drop below 6V very soon and wouldn't be able to supply the LD with enough current anymore. Maybe this is why your laser isn't burning stuff?
When the LiPos are full, they'll give you 8.4V and 6V when totally empty. This way you'll have constant power on your LD through the entire battery capacity. But it's better to charge them before they drop below 3.6V. You'll get a longer life from them.


On the other hand, you should always be able to reach the guts again, in case they need an adjustment. What current did you set yours to?

 

[Daedal]

I wanted to bring to everyone's attention the fact that you can use an EXTREMELY simple voltage regulation method reliant on a Zener Diode (in case you didn't know).

Do a little bit of research on how a Zener Diode works as a voltage regulator and you would realize just how simple this can be... it could be a smaller solution than using a 7806 in the circuit if needed

--DDL

 

[IgorT]

I wanted to bring to everyone's attention the fact that you can use an EXTREMELY simple voltage regulation method reliant on a Zener Diode (in case you didn't know).
--DDL

Here's a nice link about this, with good explanations: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/zenereg.html

But i'm still hoping it's not needed in the first place.. I should know for sure by tomorrow..

 

[Gazoo]

Voltage regulation is not needed...........all you need is the 317. I know you will have to see it with your own eyes before you believe me...lol. But that's ok, so did I..just ask Daedal...ha..ha.

And yes, I agree 6 volts or more. There have been many people that have found the regulator doesn't function properly with 2 cr123's or 4 alkaline's for example. Two li-ions or a lipo pack are ideal for this circuit. So are 6 AA or AAA nimh or alkalines.

 

[IgorT]

Voltage regulation is not needed...........all you need is the 317. I know you will have to see it with your own eyes before you believe me...lol. But that's ok, so did I..just ask Daedal...ha..ha.

I know this by now.. But all this talk about voltage regulation made me want to see it with my own eyes, just like you said..

This means this circuit is perfect for battery applications, as it is, no further complications needed.

Also, for those, who go from two 3V batteries, to two 3.6V ones, this means, they don't have to change anything.. Their laser will actually work better afterwards - completely stable output power over the entire capacity..


Thanks again, BTW!

 

[a_pyro_is]

If this causes too much confusion I’ll delete it.

My limited understanding is that a LASER Diode will draw a certain current at a given voltage. When using the 317 as a current regulator, it is still regulating voltage. The 317 always tried to maintain a 1.25 Volt difference between the Vout and Adj pins, but because we have a fixed value of resistance between the Vout and Adj pins the 317 raises the voltage until the resistor is dropping 1.25 Volts.

*Note* all LD forward drop voltages are numbers I pulled out of my…well, you can guess.

If one were to use a 5 Ohm resistor (or combination of resistors equaling 5 Ohms) between the Vout and Adj pins, the supply would be set for 250 mA. The resistor would have a voltage drop of 1.25 V and there would be 250 mA passing through it. Let’s assume that the LD at 250 mA has a forward voltage drop of 2.79 V, 1.25 V + 2.79 V = 4.04 V. The 317 will have to supply 4.04 V to maintain a 1.25 V drop across the 5 Ohm resistor.

Now let’s try with a 10 Ohm resistor, which would set the supply for 125 mA. Again, the resistor will have a voltage drop of 1.25 V, but at 125 mA the LD might have a forward voltage drop of only 2.62 V, 1.25 V + 2.62 V = 3.87 V. The 317 will have to supply only 3.87 V to drive the LD with only 125 mA.

So as I hope is now made clearer, the 317 is really regulating the current supplied to the LD by very precisely regulating the voltage.

 

[IgorT]

So as I hope is now made clearer, the 317 is really regulating the current supplied to the LD by very precisely regulating the voltage.

That is exactly how i think about it as well, since it's basically a voltage regulator.. Besides, is there any other way? Very good explanation BTW..


It's very similiar to the way a lab PSU works, if you set the voltage to 30V but limit the current to 200mA and then connect a LD. It will immediatelly drop the voltage to around 3V (or whatever the specific LD needs to draw 200mA).

The initial shock in this case could be bad for the diode and possibly kill it tho.. Maybe this is why my first two LDs died...


EDIT: And no, i didn't really set the voltage to 30V, just to 4V, but it's possible, there was still a voltage spike.. I should have used a capacitor..