My $100 mistake /w pictures

[Scotoma]

So I just learned an expensive lesson about keeping the connections between drivers and diodes solid. I was using non-insulated, crimped-on terminal connectors for the connection from my flexmod to a mitsubishi 500mw ML501P73 diode. The exposed metal from the connectors touched my aluminum base, and the diode shut-off, never to return. No LED, just an open circuit diode. Here is what it looked like in the aixiz:

It looked like the leads might be busted, so I removed (ungracefully) the diode from the aixiz, and confirmed the destruction:

Can anyone confirm that the way to avoid this is to use insulated connectors and to avoid moving a flexmod driven lab laser during operation? I hope others can learn from my mistake as well. Cheers.

 

[Things]

Always use solid, insulated connections. Drivers like the flexmod do NOT like being operated without a load, because they are unable to regulate the current without one. So when it quickly connected back to the laser diode, it got a spike of power before the flexmod was able to regulate it properly again.

I would test out the driver before you use it in another build, as you may have fried that also.

 

[Scotoma]

Thanks for the reply Things. I connected the driver up to a dummy load, and it seems to be supplying the correct amount of current at both 0V and 5V modulation, so at least it wasn't a $140 mistake. I won't be leaving connections un-insulated again.

 

[T_Warne]

Nice pictures. You really fried your poor diode!


You should always solder the connections from the driver to the diode & use heatshrink to insulate any possible shorts.

 

[swat007j]

does any one here have AIM? if so please add me @ swat007j

thanks and bro that sucks.

 

[LtKernelPanic]

Is that something that JSLE could possibly fix? I know he resolders those fine wires when he does the diode mods. Check out his thread here:

http://laserpointerforums.com/f39/d...d-re-routing-lpc-lcc-smoc-phr-805s-74040.html

 

[Scotoma]

I would definitely be willing to give it a shot, though this thing looks really fried, and I might have damaged it further taking it out of the aixiz. Maybe I'll see if JSLE wants to give it a try. Thanks for the suggestion.

 

[LtKernelPanic]

Yeah PM him and have him look at the pics you took. If you plan on building lasers you should get a set of diode in/out press tools. You can find diode presses from several sources but FlamingPyro sells the only removal tool I've seen. It works quite well on standard aixiz modules. Note that if you have one of the copper modules from the recent group buy it likely won't be able to push it out since the opening for the diode is really tight.

 

[ped]

The emission area of the diode looks tasted as well. I'll be surprised if that diode lases again.

Sorry for your loss.

 

[LaserAdct]

Drivers like the flexmod do NOT like being operated without a load, because they are unable to regulate the current without one. So when it quickly connected back to the laser diode, it got a spike of power before the flexmod was able to regulate it properly again.

Am I misunderstanding something about the FMP3? The current as far as I know stays the same regardless of the load, or at least thats what it seems to be doing. The current is set without testload etc. and the value it is set for is the same when a load is actually connected. Thats how the ones I have are doing it :beer:

The exposed metal from the connectors touched my aluminum base

Seems like a short rather than a regulation problem.

Best regards

 

[AUS]

I have killed two LOC diodes with physical damage, first one bent the internal pin as i was pressing it in and it turned sideways, second one was taken out by the spring hitting the diode...

 

[LaserAdct]

I have killed two LOC diodes with physical damage, first one bent the internal pin as i was pressing it in and it turned sideways, second one was taken out by the spring hitting the diode...

I rarely use the spring that sits between the LD and the lense. I saw somewhere on here that you can buy springs that sit on the outside of the module (aixiz). Usually I just throw the spring away and use teflon tape instead on the threading of the lense.

 

[Solonar]

I use 3 FlexMod N2's in my projector, the connections are wired to terminal blocks, and the diodes are wired to terminal blocks. I can move the lasers around just fine.

I have yet to use my P3's , but following the simple rule of never applying power to the diode with out solid connections and proper insulation, should keep things like this from happening.

 

[Scotoma]

So it sounds like there are two potential explanations for the excessive current through the diode. One is that the flexmod temporarily lost the ability to regulate current while the circuit was shorted and that upon reconnection, it sent a current spike to the diode before recovering. The other is that the short circuit itself allowed a current spike to the diode. Practically, these are both avoided the same way, by avoiding a short, but I guess I'm interested in how the flexmod regulates current.

 

[LaserAdct]

So it sounds like there are two potential explanations for the excessive current through the diode. One is that the flexmod temporarily lost the ability to regulate current while the circuit was shorted and that upon reconnection, it sent a current spike to the diode before recovering. The other is that the short circuit itself allowed a current spike to the diode. Practically, these are both avoided the same way, by avoiding a short, but I guess I'm interested in how the flexmod regulates current.

The FMP3 is a constant current driver so no matter what the load is the current will stay the same. For the same reason I think that a current spike is not possible. If you connect a DMM in amps mode and set the current, then this is the current it outputs no more no less regardless of load. If a short can make it do something else I do not know and I think you would have to ask DrLava about that. A short where + interacts with - will most likely kill your diode regardsless of which driver you use.

From the manual (http://hacylon.case.edu/laser/FlexModP3/FlexModP3_Manual.pdf):

If, at any time during operation the output circuit goes open, the driver will shut off output and illuminate the red LED until
the output circuit is closed and the interlock is reset.
If you intend to use several drivers at once, the interlock connections can be ganged with each Int input tied together.

...

I dont think it is likely that a spike killed your diode tbh.