Killed 2 LOC diodes last night, don't know why...

Kind of ironic I had an LOC running straight off 2 AAA batteries for over 20 minutes total time. And the person I traded it to says its still going.

Touching any plumbing pipe will discharge ESD from your body. Kitchen sink faucets work well.

TJ, that's what puzzles me here. Hardwood floor, bare foot.
Those diodes need another pass at a known good driver.
Mine has been off and on an LM317 @ 467ma from 2 li-ions and it lives now.
I'm still in for trying a standard LED for current adjusting on a diff 1117 or 317 and see how it does. Make sure you discharge that cap just before soldering.

You can also just touch your computer case, which should be grounded. Really, all you're trying to do is drop off charge onto a large conductor that can sink it.

I have my doubts about the ESD theory as well. Surely ESD can kill electronic components, but in reality this does not happen all that often. You generally do not need special equipment for laser diodes, just a bit of common sense.

You will generally notice bad ESD conditions, because you will get little shocks when touching grounded metal objects like radiators, or a tap. I think everyone is familiar with this - its similar to the zap you get from touching the car door on a dry winter day.

If you notice none of these effects, i think you can almost exclude ESD as a cause to all of these diodes dying. I suspect the problem is in the driver, and it would be better to build a new one, and test that with a dummy load extensively before proceeding.

Tech_Junkie said:

Touching any plumbing pipe will discharge ESD from your body. Kitchen sink faucets work well.

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Should I do this near my work area, preferably right before touching the diode? I have hot water baseboard heating in my apt, I could probably attach an anti-static wristwrap to the pipe that runs inside of it.

Tech_Junkie said:

Kind of ironic I had an LOC running straight off 2 AAA batteries for over 20 minutes total time. And the person I traded it to says its still going.

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Hmm, just more and more evidence that my driver was at fault.

Vaporizer said:

Those diodes need another pass at a known good driver.

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I will try them soon. GF hates lasers, I have to pick and chose "good" days for playing with toys... I think today might happen because she'll be distracted with work she's bringing home

Vaporizer said:

I'm still in for trying a standard LED for current adjusting on a diff 1117 or 317 and see how it does.

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I do have LEDs, but they have a much lower voltage drop. Was Daedal suggesting that I put enough of them in series to make ~3V, aka. "test-load with LEDs instead of regular diodes"?

Daedal said:

pots tend to have the horrible ability to short out when you get near the end of their turn and that would instantly kill your diode... :'(

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Something else he said in post #14. My pot was near it's "0" value, not actually 0 Ohm, but close. Maybe like Eudamonium was saying from the start, the pot shorted and spiked the current too high.

Benm said:

You will generally notice bad ESD conditions, because you will get little shocks when touching grounded metal objects like radiators, or a tap. I think everyone is familiar with this - its similar to the zap you get from touching the car door on a dry winter day.

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I never get shocked in my apt, and I've never noticed any static electricity effects. I think it's the wooden floors that help the most, I can easily get shocks at my parents' house which has carpet.

Bionic-Badger said:

You can also just touch your computer case, which should be grounded. Really, all you're trying to do is drop off charge onto a large conductor that can sink it.

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I don't have any computers, at some point I got tired of constantly upgrading every card in there to keep up and gave up. That was 4 years ago, I've just been using work laptops, and recently got an EEE as a present. How about I take a PC PSU, plug it in, and without turning anything on touch its case?

Have you disassembled your setup ?

If not, just measure entire resistance between middle and left pin of the LM1117.

If lower than let's say, 3 ohms, it's shorted.

Also, just short out your DMM probes before measuring to see what the resistance probes themselves is.

And I can't help not to say, but middle pin of the LM chip is electrically connected to the metal back of the chip... make sure that the metal back is not touching anything, that's the same as if middle pin is touching it.

comradmax said:

Should I do this near my work area, preferably right before touching the diode? I have hot water baseboard heating in my apt, I could probably attach an anti-static wristwrap to the pipe that runs inside of it.

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Yes, that will work. I had mine hooked right up to the ground wire inside of the an outlet. Just be careful you dont electrocute yourself. :tinfoil: I guess you could also hack a 3 prong plug off, and hook it up to the green ground wire.

I have never had a problem with ESD, or even bother taking those precautions. Very rarely would a diode ever be DOA, and they would almost never lase for jsut a few seconds and die, unless there was something wrong with the driver. I can recall one laser that lased for about 1 second and died, i later found out the driver was putting out over 900mA to a LOC.
If all else fails just get one of rkcstr's drivers. It's based off the DDL driver and works great. it's only $13 preassembled, or $8 if you want to solder all the components onto the circuit board yourself.

it's at rkcstr.com, Micro-Drive and laser diode electronics

as far as pots go, i've never been a huge fan. My favorite driver use to be rkcstr's fixed driver. It was the same as his current but it used SMD resistors instead of a pot. You just
for the purpose of that driver i always used 1250 / R = current (1250/33.3Ohms=37.5mA)
You could jsut combine different resistors to get your desired output with no DMM needed

Even with hardwood floors, ESD is unlikely. Normally only in dry winter air anyway.
From what Daedal says, the regular LED will only take the voltage it needs, just like a LD.
If you go with an LM317 a 10ohm resistor will output 125ma. You had a capacitor and it should have caught a spike, but it may be a toss up there. Not discharging that cap is an instant dump of everything it has stored and will kill the LD. LED's are much more forgiving and cheaper. Daedal indicated only one LED. Rat Shacks 25ohm pot has worked well for me. Its wire wound and normally less prone to being "scratchy" as the wiper touches the next wind before leaving the wrap its on. Resistor film trimmer pots, well they are diff. They can "scratch" anywhere.

Edit: Even though rkcstr's and other drivers use the small trimmer pots, they also have more small caps in the circuit to trap any spiked from a scratchy pot.

Eudaimonium, I checked the resistance and it's 2.5 Ohm, measured 2.8 and the probes alone gave me 0.3.

Mohrenberg said:

I have never had a problem with ESD, or even bother taking those precautions.

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I watched your videos for harvesting the LOC and PHR, and I noted you touching the diode heatsink with your fingers. Based on that I figured static isn't a huge issue.

Vaporizer, I should get some wirewound pots on my next mouser order.

I made an LM317 driver, just the chip and 3 Ohm resistance. Tried the 3 dead LOC's, they are all still dead Noticed that the current would be the same with any load, 4x diodes, 5x diodes, or 1 diode. This was not the case with the LD1117 chip! So there is the culprit of my blown LOCs... With the LD1117 I would get different, but consistent, current readings from different loads - 5x diodes or 4x diodes with the same resistance setting would draw different mA.

Good news
I ordered from hightechdealz on tuesday and got my package yesterday: 3x LPC and 3x PHR sleds. Extracted, pressed and soldered leads to a LOC. Put it in a short heatsink, just the head. Tested with the fresh LM317 driver, and eventually turned it all the way up. Tested the batteries too, i get the same current from them as i do with my bench-top PSU. No problems yet, been running consistently 375-380mA with this setup on the 2xLiIon power source

Next up is mounting the 2 part driver inside a host, I feel like I can fit it in there with a TO-220 heatsink too. GF is home already so no more tinkering, but I would like to take a fresh LD1117 chip and see if I can get it to work as a CC driver.

P.S. taking beamshots is hard. Also red is so hard to see without smoke or other particles, I almost never see the beam. I'm also somewhat colorblind and red is hard to see in the first place.

^^:gj: Buddy glad you stuck it through and dint give up.

comradmax said:

Eudaimonium, I checked the resistance and it's 2.5 Ohm, measured 2.8 and the probes alone gave me 0.3.

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1.25 / 2.5 = 0.5 amperes.

500mA would be too much in certain circumstances.

What kind of diodes were those that died, 5 of them?

Long dye diodes should be able to hold out to 500mA, Dave has one in his Kryton at half amp, but the utput should be fairly smoothed out, too sudden start could explain a lot of symthoms you described.

I killed 2 LOC diodes from LPC-815 sleds using my LD1117 driver. I was saying 5 total now because I also killed 2x PHR and another LOC a few weeks ago, but for different reasons: I was using a breadboard and accidentally would put the wires into the wrong pin...

GF is working for half a day today, yay laser time! I am going to take a fresh LD1117 chip and my 3 Ohm resistance and see what happens. I think now I understand that a CC driver would keep the same current based on the resistance value no matter how many diodes I use in the test load: 1 diode will have the same current as 4 diodes, but the voltage drop will be lower for the 1 diode and so the chip will have to dissipate more voltage through heat. This was not the case with the driver I made that killed the 2 LOC's - it would give different currents for different number of diodes in the test-load... So either that specific chip is bad or I did not actually make a CC driver with it (most likely). I'll post my results a little bit later today.

comradmax said:

I killed 2 LOC diodes from LPC-815 sleds using my LD1117 driver. I was saying 5 total now because I also killed 2x PHR and another LOC a few weeks ago, but for different reasons: I was using a breadboard and accidentally would put the wires into the wrong pin...

GF is working for half a day today, yay laser time! I am going to take a fresh LD1117 chip and my 3 Ohm resistance and see what happens. I think now I understand that a CC driver would keep the same current based on the resistance value no matter how many diodes I use in the test load: 1 diode will have the same current as 4 diodes, but the voltage drop will be lower for the 1 diode and so the chip will have to dissipate more voltage through heat. This was not the case with the driver I made that killed the 2 LOC's - it would give different currents for different number of diodes in the test-load... So either that specific chip is bad or I did not actually make a CC driver with it (most likely). I'll post my results a little bit later today.

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Interesting results there. Different current with different load? Definetly not properly connected.

You are right about current output. People just grab a DMM , set to current mode, and measure current directly off the output when they can't be bothered to make a test load. Works too, though not as precise. And capacitor in that case should be avoided otherwise damage to DMM is possible.

comradmax said:

I think now I understand that a CC driver would keep the same current based on the resistance value no matter how many diodes I use in the test load: 1 diode will have the same current as 4 diodes, but the voltage drop will be lower for the 1 diode and so the chip will have to dissipate more voltage through heat. This was not the case with the driver I made that killed the 2 LOC's - it would give different currents for different number of diodes in the test-load... So either that specific chip is bad or I did not actually make a CC driver with it (most likely). I'll post my results a little bit later today.

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As long as your battery/input voltage is high enough, the current should indeed remain the same regardless of the number of diodes in your test load. And if you use fewer diodes the lm317 should run hotter.

I think you must have mis-wired something with the other driver, but throw the 317 you used out for good measure. These voltage regulators are generally very hard to kill when properly installed, but it is possible when you connect it completely wrong (adjust as input or something). The are short-circuit and overheat proof, but not completely foolproof.

Glad to see you hanging in there and have one going. The figures posted above (2.5ohm) would indeed give you 500ma. Thats a quick death sentence for a 815 LD. It will run, not long though and heat build up is fast. Even pressed in an AixiZ head, that not much for them at that current. I have one at 453ma. 30 seconds is time to shut off in just an AixiZ head....to hot. You have to consider that if the Aixiz head feels warm or getting hot, its much hotter in the center of the diode. Expect COD.
To be measuring 380ma the resistance should read 3.3ohms on an LM317.