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A-140 diode died at 300mA

T

TomTheDragon

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Hello everyone,

i just seen some A-140 diodes for a really good price on ebay so i decide it to build my first 445nm laser. My idea was to use it as a low power blue (100-200mw) with two old HDDs to build a simple laser projector ;)
I already had some spare parts like, hosts and drivers from older laser-kits, so i chosen one i also used for a couple of DVD-burner diodes.

So i started some testing on this baby and set the driver (LM317 based) to 300mA (which should be ~100mW) and tried to burn something, to test the power output which was working fine and i was so happy about this nice color from this little diode but.. then it happens: I turn it on and after maybe 0,5sec it was dead.. or at least very dim as you can see on the pictures. I am really not sure what happened because i was turning it on and off a couple times wile i was testing :yabbem:


I am thinking to maybe get an another diode but i first need to know what i can do better or if that guy on ebay solid me a shitty diode.. so i am asking you guys.
 





You shouldn't put the build on blanket. Static electricity can easily kill you diode.
 
Did you short your capacitor out before you reconnected your diode after your DMM measurement? There would be energy left in there that will kill a diode if you had to re-make a connection to the diode.
 
One thing I would suggest is to always have solid soldered connections between the driver and the diode. Intermittent connections could cause a spike. It is possible that in power cycling it there could have been a spike as well. Also all the A140 projectors that can be purchased right now are either used or manufacturer refurbished so the diodes will have an unknown amount of time on them so there could be questionable quality with them as well.
 
If that's the heatsink, it's really not enough. Output power of 100-200mW is definitely too much power to trust to a plain ol' Aixiz module and that tiny heatsink; I've burned out reds at 60mW with "heatsinking" like that.
 
Meatball said:
Did you short your capacitor out before you reconnected your diode after your DMM measurement? There would be energy left in there that will kill a diode if you had to re-make a connection to the diode.
Click to expand...
I killed two other red diodes by doing this.. so i installed a little extra resistor to the out of the driver (under the black tape), which unloads it. But i never disconnected the diode, i always had it in this setup wile testing with the multimeter turned on.

Bionic-Badger said:
If that's the heatsink, it's really not enough. Output power of 100-200mW is definitely too much power to trust to a plain ol' Aixiz module and that tiny heatsink; I've burned out reds at 60mW with "heatsinking" like that.
Click to expand...
It was just for the testing, i never run it longer then a half minute or so and it never was getting much warmer then my hand.. i wanted to add a much bigger cooler later and also add a 90mm fan for cooling the diode and the driver.
I was running a 300mw DVD-burner diode with this little cooler and 90mm fan before i used it for this tests and it was running at 220mA just fine for hours ;)


I personally think that maybe the power supply could be the problem, so i just need an better driver or make this one safer..
I also have two other drivers which are by far better but they can be just used for red diodes (because of the working voltage) and can only set to max 150mA i think.. but they have a nice soft on feature. So you can see how the diode fades in an ~0.5sec. I wonder if i could get something like this cheap for a 445mn diode.
 
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Could be just a crappy diode from the seller !
On your next diode do all ESD precautions add a little heatsink and test you driver and it shouldn't happen again !
 
Wrong,

I'll say it's not the heatsinking, I've ran diodes way past 1W in plain old Aixiz. You'd be surprised how much heat energy can those diodes actually endure. It's not a problem.

It's the non-solid connection. The alligator clamps between driver and diode killed your diode. Basically all you need is a few microseconds of dropped connection. In that time, the capacitor charges up, and at next re-connection, it discharges into the diode - Bad sh*t.

Next time, either get rid of capacitor, or make solid soldered connections.

A diode ran at 300mA would need what, 4.0 Volts, which is 1.5 W, which is around 1.3-1.4 Watts of heat - it's not critical and plain Aixiz will do for short 10-seconds-max runs.
 
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