Help, what mA for 5mW Green Laser driver - LM317

Hey, I just opened up a "broken" green laser I had. I tried to take care of the case in order to maybe make a PHR pointer, but I messed it up... ohh well. Anyway, I took out the module, and tested it. Obviously it didn't work (it wasn't working before I opened it, why should it now?), but I found out that if I bent the whole driver, it would work. I then tested it further by removing the driver and then soldering wires from the pins of the diode to the driver, and discovered it was still the driver that needed to be bent (there was nothing wrong with the diode's pins).

Well, after spending some time on it and still not discovering what's wrong with the driver, I decided I'll build a LM317 driver for it... esp. since I don't care about size because I'll probably use this as a Lab module, or a module for a liquid sky or something. So, my question is this: at what mA should I run a LM317 driver at? I haven't the slightest clue. Also, I think I read somewhere that the IR diodes use up 2V, so... I should be fine hooking up 5V or higher to the driver right? (I'd probably use a power supply.. maybe around 5, 6 or even 9V.... but I guess 9V would heat up the driver a lot wouldn't it?).

Edit: Forgot to say, thanks in advance for any help, I really appreciate it.

Re: Help, what mA for 5mW Green Laser driver - LM3

Between the driver and the diode, they'll figure out their voltage on their own, based on what voltage the diode likes to take at a given current. No need to worry that your driver isn't the right voltage.

I'd set it to around 100mA to start, though I should expect the pump diode will take at least 200mA with no problems. You might want to change your test load though, use 2x 1NXXX diodes in series instead of the 3 or 6 people normally use for red or BR, respectively.

Re: Help, what mA for 5mW Green Laser driver - LM3

Thx, I appreciate the input ^^.

Also, bump - anyone have any other opinions on this? Often times opinions vary, such as how high to run a PHR. I personally run PHRs at 125mA, soo.. seeing that thats around the range I'd go... how much would you recommend I drive the IR (Green) diode?

Re: Help, what mA for 5mW Green Laser driver - LM3

Most pump diodes for 5mW greens are run at 250mA..

Re: Help, what mA for 5mW Green Laser driver - LM3

Alexizupinhea said:

...anyone have any other opinions on this? ... how much would you recommend I drive the IR (Green) diode?

Click to expand...

What every one else here has said is correct.  I have one of these <5 mw greens that is taking 270 mA.  

The thing is, even if you knew the specs on the diode, the crystals, and the heat sinking, there would still be a range of currents that would be "correct."  

As pseudolobster said, start with low current and work your way up.  If you had previously compared its brightness to another of your lasers, or have a power reading of what it was doing before, then increase the current until you get back to that point and set it there.

Running the current too low isn't going to hurt anything, of course.  It just won't be as bright.

Running the current too high may do one or more of the following:
- cause the laser to exceed the safty class it is in, making it more dangerous (most on this forum consider that to be a plus ;D)
- overheat the diode, causing it to fail sooner.
- exceed the maximum optical output for the diode, causing it to degrade instantly.

Unfortunately, no-one besides the manufacturer knows where the heat and optical limits are, hence the advice to get it back to the brightness it was before.

OTOH, many folks have reported boosting the output of one of these <5mw greens to around 50 mw and having it last for a while.

If you have no way of knowing how bright it was before, you can use an inexpensive LPM (like the Simple LPM) to set it to 5 mW or how ever high you decide to go.

Re: Help, what mA for 5mW Green Laser driver - LM3

Have you got any microscope or magnifier?
If your driver needs to be bent, that's probably a "cracked" solder. Bend it slightly in the other direction and check if you can see any fissure in any solder. If you see any, just heat that solder with the iron until it melts and you are done. That's most lilely your problem. Even if you don't find any cracked solder, re-melt every solder you see (be careful)


Seriously, this happens a LOT with other electronic devices. My TV's remote had a cracked solder in the IR led, 3 mp3's i repaired had cracked solders in their earphones plug...
It's a "common" problem with new Pb-Free solders.

Thell me if this worked!

Re: Help, what mA for 5mW Green Laser driver - LM3

Wow... thanks for all the input. And yeah, I'm a moron. I can't believe I'm this stupid lol. I'm asking a question I already could've easily found the answer to. I saw that it said laserss.com on it, and I went to their site and saw the specs on it ROFL before I asked this question. I didn't look in order to find out the operating current, but I looked in order to see if they had prices on just the modules wholesale. So yeah, it ends up saying <300mA on their webtsite, so I guess I'll use two 10 ohm resistors in parallel, which would be 5ohms for the DDL, which should end up giving 250mA (I don't have a 4.166666667 resistor, nor can I think of a SIMPLE way to re-arrange to make one). Also, erdabyz, THANKS for the input (no sarcasm here).... I've never really repaired much electronics before, and I've never heard of cracked solder. I will try doing that first, and if that works, I'll post it back here (and will def. give u +1 rep).

BTW, did/does anyone ever try to do a GB on laserss.com.tw? I'm pretty sure they are a HEAD laser company which makes most of the lasers on DX or other sites (looks like A LOT, just not the TRUE ones). For example, the hybrid laser (5mW red, 5mW green): http://laserss.com.tw/doc/GL-1-RL1-081007135609.pdf would be GREAT if we could get it cheap, and then use rog's mod so we make it yellow: http://www.laserpointerforums.com/forums/YaBB.pl?num=1212787199/0

Re: Help, what mA for 5mW Green Laser driver - LM3

Nope, am an idiot again. After seeing that the operating voltage was 3V, I just realized that they're talking about the WHOLE module (driver included), so that means that the diode definitely uses LESS than 300mA. Ehh, I think I'll still run 250mA and see if all is well. If it breaks/burns out, its only just a cheap broken 5mW. Also, this is all only IF i cannot fix the regular driver.

Re: Help, what mA for 5mW Green Laser driver - LM3

Can you post a high resolution macro picture of your driver?
Both sides of the PCB.

It's just to see what kin of componets are there, to see what tools would be required to fix it, if it finally turns out to be a bad solder.

Also tell me if the driver works if you bend it in both directions, or only in one.
If it only works in one direction, then check first the side of the PCB towards the curvature center of the bending.

Solders can crack for a lot of reasons. Lead free solders tend to be less plastic so they crack easier. Also, the gold plating of the PCB contacts is "dissolved" into the molten solder, creating zones with different composition, usually creating "planes". If the solder has thermal stress (continuous temperature changes, like for example in a laser, where the components get hot and you tend to turn it on and off lots of times) the different thermal expansion coefficient of the different composition zones can make the solder crack. For example, 3 red lights of death (Xbox360) and yellow light of death (PS3) are both usually consequence of cracked solders in the GPU or CPU of the consoles.


If you have a heating gun (those used to remove paints or to fix rubber adhesives in roofs) just turn it on at a not very high temperature, and heat the driver's PCB with it until you see that the solders are melting. Wait until it's cool, and do the same with the other side. That way you'll reflow all the solders at a time.

Re: Help, what mA for 5mW Green Laser driver - LM3

erdabyz definitely has the right idea re-melting those solder joints.  You might even be able to do it in a toaster oven if you are careful, but that would be a last resort!  

Alexizupinhea said:

I'll use two 10 ohm resistors in parallel, which would be 5ohms for the DDL, which should end up giving 250mA (I don't have a 4.166666667 resistor, nor can I think of a SIMPLE way to re-arrange to make one).

Click to expand...

Starting with 5 ohms, you can get to 4.166666667 ohms by putting another resistor in parallel with it.

The value of the extra parallel resistor is:
1 / (1/4.166666667 - 1/5)
= 25 ohms

Even if you use a more standard value of 27 ohms, it gets you down to
1 / (1/5 + 1/27)
= 4.21875 ohms, which is pretty close to 4.166666667 ohms

Alexizupinhea said:

I just realized that they're talking about the WHOLE module (driver included), so that means that the diode definitely uses LESS than 300mA.

Click to expand...

Some of those drivers are switching regulators, which means they can actually take LESS current than they are providing to the diode.  For example, a 100% efficient (most are around 80%) switcher taking 300 mA at 3 v would actually deliver 450 mA to a 2 v diode.

Re: Help, what mA for 5mW Green Laser driver - LM3

Warske said:

Some of those drivers are switching regulators, which means they can actually take LESS current than they are providing to the diode.  For example, a 100% efficient (most are around 80%) switcher taking 300 mA at 3 v would actually deliver 450 mA to a 2 v diode.

Click to expand...

Yeah, I'm surprised I didn't think of that. Also, I just happened to fix my driver!! (I think anyways). What happened was, I resoldered every joint (I thought), and it still didn't work. Then, I left the batteries in, and tried re-soldering while the driver was on (prob not the best idea. Especially with me using a huge chisel tip on smd parts.) Anyway, I ended up seeing the laser turn on when I resoldered this one piece on. So, I immediately disconnected my batteries (was using a 2x AA battery holder), and then put a good amount of solder on that one part. Then, it didn't work. I ended up realizing that when I connected the end of that part (I have NO idea what type of part it was. It it is the same size and shape as an smd resistor, but I don't think it says anything on it. It just has a brown top.).... so, I realized that when I connected the end of that part to the end of this smd resistor which was right next to it, the laser turned on (my soldering iron must've bridged them before). So, it's working fine now, and when I think about it, I think it really was the exact spot where everything was messed up. It was at the corner of the circuit board, and I think the edge got undone and so me soldering them together traced it back fine.

BTW, thanks to everyone for all your help. You guys helped me fix what would've been a "broken" laser. . Also, I messed up the case, but ended up sandpapering it down, and it came out quite nicely (took a LONG time, just did it by hand and I must say... it WASN'T easy).

I'll post a few pics in like 5min.

Re: Help, what mA for 5mW Green Laser driver - LM3

Well, here's the pics:


The top right is where I bridged the brown thing and the resistor.


It looks nice alone, but as a whole w/ the bottom part (Black), I don't really like it. I may spray paint it black or something (maybe w/ a splash of red)


Last it just everything, plus me connecting the case positive and the laser lasing (I didn't put the top on it to focus it).


Well, thanks again every1