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FrozenGate by Avery

LPC-826 diode problems

LED Maestro

LED Maestro

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Apr 18, 2012
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Hi again. I have just fitted my LPC-826 red diode into a focusing lens and housing that arrived this morning but the dot is no where near as bright as my >5mw red diode I had before. I am running it through a driver off a 9v battery. Can anyone tell me how to increase the brightness?
Many thanks
Kind regards
 





We need more info. What is the driver and at what current is it set ?
 
Hi. I am running it off the DDL driver from 'it can be done laser driver'. Not sure what current it is at. I have the pot turned all the way up but the laser is still only barely visible in pitch black.
Kind regards
 
You still need to know the resistance in order to calculate the output. The formula is 1.25/I=R.
For a LPC-826 diode you need 400-500mA for maximum output. Take 416mA example : 1.25/0.416= 3Ω
That should give you a bright dot at the near maximum.
 
Ah that explains it. I have a 100r pot in series with two 10r resistors. I will aquire a more suitable resistor as you suggested.
Many thanks for your help,
Kind regards
 
Cheers ! :beer:

You will also need resistors rated for at least 1 Watt. W=VxI=1.25x0.416=0.520 Watt
You could go away with ½ Watt rated resistors but you need to heatsink it.
 
Yeah I wondered about a heatsink. My diode does get very hot. I will get both 1/2 watt and 1 watt resistors and look into getting a heatsink.
Once again, thanks for your advice.
Best wishes
 
Hi. Just a quick update. I have put three 10r resistors in parallel (3.3 ohms by my calculations) but my diode is still no where near as bright as I expected. I am beginning to wonder if I have damaged the diode when soldering the leads on. This is not to say that this is my first time soldering but I did have the iron on the pin for quite a number of seconds. Could this be a possible cause?
Many thanks
 
The heat from the solder iron can kill diodes.
If you use 3.3Ω for the LM317 driver and it it not bright then the diode is damaged.
 
Oh dear. That's what I was affraid of. Looks like I'll be getting another diode then.
Thanks for all your help with this thread
Best wishes
 
I highly doubt it was the soldering iron that killed that diode. I've applied lots of heat during soldering and it has not affected the diode. Most of it dissipates into the case, and rarely is there enough to actually cause the little wires in the diode to fry.

More than likely the laser is LEDed (dead) because: 1) the current was not set properly to a known value using a dummy load, and 2) the lack of a heatsink so that when you turned it on, the heat generated by the power going into the laser was not dissipated properly. If #1 didn't kill it immediately, then #2 probably would have in short order. The laser diode may also have been fried from the driver not being properly shorted out before soldering.

Next time--and before spending money on another diode--you should buy a multimeter and a heatsink for your build. Then construct a dummy load and attach it to your driver, and measure the current that will be sent to the diode using the dummy load so that it is at the expected value. Then desolder the dummy load and short the leads of the driver to clear out and residual charge, and solder the driver to the laser diode you pressed into your heatsink.
 
You are correct on one of those two points. I did not have a heatsink however I do have a multimeter and I did check the current readout, although only after the suggestions made by Blord. That said, I didn't have the driver pot turned up all the way when I switched the power on and the laser was only turned on for a couple of second at a time, thanks to a push button switch.
I didn't attach the diode directly to my driver. I soldered a couple of leads onto the pins. Those then went into my breadboard. The first time I tested my laser was the first time I put any power through my drive aswel.
Anyway. Next time I will definatly have a heatsink and will short the driver to be on the safe side.
Thanks for the advice
Kind regards
 
LED Maestro said:
Yeah I wondered about a heatsink. My diode does get very
hot
Click to expand...
. I will get both 1/2 watt and 1 watt resistors and look into getting a heatsink.
Once again, thanks for your advice.
Best wishes
Click to expand...

if your diode is getting very hot and is not lasing then it is definately led:(
how do i know (from experiance of course).
i got my first build with a 826 to lase than of course i set the next one higher guessing what the current was and it lased very brightly for about 10 seconds than died.(damit)the next thing i did was order a dummy load kit and other parts from cliff at cajunlasers, but of course i could not wait for it to arrive and proceded to do the same thing to a 6x 405nm:undecided:. i decided i will wait now:o:o
 
LED Maestro said:
I didn't attach the diode directly to my driver. I soldered a couple of leads onto the pins. Those then went into my breadboard. The first time I tested my laser was the first time I put any power through my drive aswel.
Anyway. Next time I will definatly have a heatsink and will short the driver to be on the safe side.
Click to expand...

Ugh, don't use breadboards for laser diodes. Breadboards have lots of stray capacitance and the wires can often pop out causing a momentary peaks in current which destroys the diodes. They're great for controls, or even power to the driver itself, but not good for building the driver on, even for experimenting. You should always solder them up. I like to keep everything shorted with some clips while soldering just to ensure that no charge has built up as well.

Good luck on your next laser project and hopefully you see a bright red light! The reds are far more forgiving than the 405nm lasers too, so it'll be good practice for future builds.
 
Blue led. Thanks for the very funny annecdote. A lot can be taken out of that experiance. Bionic, I understand what you mean about breadboards. I did build my driver on strip board though. Your idea of keeping it shorted is something I did not think about. I will keep it in mind. Thanks for wishing me luck also. I think I will need it.
Many thanks again.
Best wishes
 
Oh. Dear.

Dear.

1. Never run any sort of diode without a heatsink. It doesn't even have to be a proper heatsink -- even the AixiZ module is sufficient for short runs.

2. Always check the current of the driver first. Never assume, even if you know you've got it right, or even if you've done it over 9000 times before.

3. Ditch the 9V battery. If you try and draw any sort of appreciable current from them, your runtime will go down the crapper.

4. Diode sockets if you want to test a diode quickly and don't want to solder to it. 5.6mm Laser diode test socket [OL-DTS] - $9.99 : Zen Cart!, The Art of E-commerce
 
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