Little help please

[Devilz Rej3ct]

Okay guys I have a PHR-803T LD on its way. I have been doing some testing lately with the LM317 circuit. I already turned two red laser diodes into LEDs.:cryyy: I am using the LM317, a 10μF capacitor, 1N5817 diode, and a 22ohm resistor. Now I am using a PC power supply to power the circuit. On the 6 volt rail(red wire)I was getting a current reading of 57mA. The laser diode was lasing and burning at these readings. Now when I hooked the LM317 circuit to 12 volt(yellow wire)the LD instantly turned to an LED. Why is this happening? I thought you can supply the LM317 circuit with 12 volts. I am getting nervous because I do not want to fry my blu-ray diode. I don't understand because I tested the circuit using a 5mm blue LED with 12 volts on the LM317 and it didnt pop the LED. Can someone help me figure out why my diodes are dying?? Oh and I do discharge the capacitor before I hook up the LD.

 

[spectral532]

Did you ever try using the driver first with a test load? The 57ma of current you are getting sounds about right for a 22Ω sense resistor. But obviously something is going wrong when you hook up the 12v rail. You might try measuring the current through a test load when you have it powered with the 12v rail. That way you can check if excessive current is flowing. Also, it might help if you uploaded a diagram/image of how you wired the circuit up.

 

[Devilz Rej3ct]

Well here it is, exactly how I have it wired.

 

[spectral532]

Do you have a multimeter? If so, measure the voltage being output between the red and black wire of the PSU. I have a feeling it might be 5v instead of the 6v you say since most ATX standard PSUs only have 3.3v, 5v, and 12 v outputs. If its 5v, then you may not be feeding the LM317 enough voltage, and thus got a lower ma reading on the output.

Also, you might try measuring the output current of your driver when you have the 12v rail hooked up.

 

[Devilz Rej3ct]

Yeah it is 5.07 on the red wire. I do not have a test load. I had a bunch of 1N4001 diodes but all I found were two. Is there another way of measuring my LM317's current? So far I have been just measuring current draw on LEDs and thus far has been around 50-55 mA. I just don't wanna blow my blu-ray diode when it comes.

 

[Devilz Rej3ct]

Ok so if I built a test load using the four 1N4001 diodes and a 1Ω resistor, would this tell me the max current output of my driver? It just didn't make sense to me because obviously the current will be higher with 12 volts than it would be with only 5.

 

[Deleted member 8382]

To measure the current just use the MM on amp mode as load. Don't forget to change the red wire into the amp mode hole

 

[Devilz Rej3ct]

Yea I get about 58 mA no matter the input voltage. So I am really wondering why my diodes blew? Should I short the capacitor, hook the LD up, then hook power up? Like I said before I don't wanna blow my blu-ray diode. But my tests prove that the current that my driver is giving off(58mA)is hardly enough to blow a LD.

 

[Deleted member 8382]

I think it's the capacitor who's killing the diodes. I simply wouldn't use it (I actually don't use it for my builds). These supposed spikes have never killed any of my diodes

 

[spectral532]

So you get 58ma regardless of whether you are using the 5v or 12v rail? If so I can't think of much else that could be going wrong. Are you sure that the red diodes you had could take 57ma? And again, make sure the capacitor is shorted before you hook up a LD. I would short the capacitor, wire the LD up, remove the capacitor short, then power up the circuit.

@Hallucynogenyc

I killed my first PHR with a voltage spike from a lab power supply. So in my experience, these spikes have been deadly. Additionally, I measured the on/off transients on a LM317 circuit I built and found that spikes could hit 12v if no capacitor is used (with 16v line in on the LM317). With a capacitor the spikes were nearly completely suppressed. What was interesting is that it generally didn't matter what size capacitor I used. I tried 100nF ceramic caps, all the way up to 1000µF electrolytics and they all did a good job of nullifying spikes. Strangely, the smaller ceramic capacitors worked slightly better than the bigger electrolytics, but both did a perfectly fine job of spike suppression.

 

[Devilz Rej3ct]

Yes 58 mA regardless of input voltage. So I guess the LM317 is doing its job. I just don't see why those diodes popped. I am using a 10 μF, 35 volt capacitor. I checked and double checked all connections and everything is okay. I hate to spend the money for a flex drive, but I don't wanna ruin my blu-ray diode the first day I get it. I'm going be very apprehensive about even hooking it up. Is there any way possible that I can be sure that it's not going to blow on me? What further tests can I carry out? I mean 58 mA is fairly low for a PHR-803. Well if anyone can think of anything further, please advise me. Thanks.

 

[Alshere]

Ok so if I built a test load using the four 1N4001 diodes and a 1Ω resistor, would this tell me the max current output of my driver? It just didn't make sense to me because obviously the current will be higher with 12 volts than it would be with only 5.

Hello sorry to restate some information but since there are still questions.

The input voltage IF enough to feed the LM 317 should be good as stated. (3 volts over the diodes requirements from what I read.) Your question above may be what you need to focus on. I am not sure. Yes if you have the 4 diodes (for red LOC diodes) and the resistor you have the proper load and you should be good. So measure across you resistor and you should get your mA. For Blue ray just set to amps as stated earlier. Discharge the capacitor or you will kill your diode as you know.

Also make sure you understand your MM. Measure amps not voltage etc. Again sorry for going back to the basics but if it saves your diodes its a good thing.

Best of luck. Here is a thread you may want to read if you haven't already. I linked into the middle (see post 58) but it is the member that made this circuit popular and a standard for everyone. Smart guy.

http://laserpointerforums.com/f42/diy-homemade-laser-diode-driver-26339-3.html

Hope this helps and the thread and the search bar is your friend.

If you get it sorted out let us know. :beer:

LOL Not sure this meets a little help but I tried.

 

[Bluefan]

@spectral532: the lab power supply probably didn't spike, but the LM317 would spike faster, the LM317 is the acting regulator after all.

I've seen people use expensive lab power supplies (delta elektronika) directly coupled to laser diode bars, I have one of those PSU's myself. All you need is proper regulation without overshoot. LM317's need caps to surpress the overshoot. The ceramic caps have better high frequency caracteristics.