Learn me something electronical...(Flexmod)

[Bradfo69]

Humm.... Strange. I wonder if I went LED. Hooked up the Scientec meter and ran it up to about 2.5 watts and unplugged it. A little while later plugged it back in and was only getting a dim glow with a fairly wide and tall stripe. I hooked up the second identical module and it was reading more like 3.5 watts so I quick unplugged it, turned the gain pot down, plugged it back in and set it at 2.95 watts. Hooked the first module back up and am still getting a dim output/wide/tall stripe. Hooked the second back up and it still seems to be around 2.95 watts. There was no flash or anything else to suggest I did anything wrong with the first module. 'tis a puzzlement.

Not certain I enjoy this.

[swamidog]

sounds like you toasted it. how well heatsinked was the diode?

2.5W is pretty hot. i wouldn't go that high.

Humm.... Strange. I wonder if I went LED. Hooked up the Scientec meter and ran it up to about 2.5 watts and unplugged it. A little while later plugged it back in and was only getting a dim glow with a fairly wide and tall stripe. I hooked up the second identical module and it was reading more like 3.5 watts so I quick unplugged it, turned the gain pot down, plugged it back in and set it at 2.95 watts. Hooked the first module back up and am still getting a dim output/wide/tall stripe. Hooked the second back up and it still seems to be around 2.95 watts. There was no flash or anything else to suggest I did anything wrong with the first module. 'tis a puzzlement.

Not certain I enjoy this.

[Bradfo69]

I'm working with these that I bought from buffo. (See link below.) He ran them at 3.3 watts. (12v and 1.8 amps) They have a TEC as well although I didn't wire it up. The diodes were running for probably around 45 seconds to a minute max, as I adjusted the gain pot. Once I was seeing around 2.5 watts on the power meter, I unplugged the power supplies. As I said, later when I went to plug it back in again, all I am now getting is a fair sized blue square with a bit of a hotspot top center of the square.


http://www.photonlexicon.com/forums/...ll-the-goodies

[m0f]

One possibility is tecs do act as an insulator when not powered up, and so is much harder to move the heat away through an unpowered tec than say a direct contact to aluminum would be. At 2.5 Watts they do generate quite a bit of heat.

Another possibility if it happened when disconnecting / reconnecting. Did you short the leads together on the driver prior to re-connecting the diode ? The reason being as capacitors will hold enough power to damage a diode.

[Bradfo69]

No, that I didn't do. Basically for all of this testing, I've had leads running off the power supply and leads running off the modules. I have "attached" them using test leads with alligator clips on each end. I simply unclipped the module and then clipped on the other one. I didn't touch the leads together in between to short them out.

I don't think the TEC's would have acted as an insulator in the short time they were powered on, The actual brass mounts the diodes are in weren't even warm to the touch.

[WolfMax]

I think m0f's 2nd question needs some expanding. Did you disconnect the Flexmod from the first laser diode and swap over to the second laser diode or are you using two Flexmods that you are swapping on the power supply?

If you disconnected the laser from the flexmod, you run the risk of ESD damage to the laser. Are you using Lasorbs?
Also, how many lasers are you setting up? You would do better to have a Flexmod unit for each, wire the lasers permanently and set the Flexmod for that one laser.

[m0f]

^ From the description, alligator clips were used to temporarily connect two different diodes at separate times to a single driver.

In my experience anything with the potential for an intermittent connection such as clip on leads or even a bad solder joint can do it. If a diode is disconnected even for a fraction of a second during operation, most drivers will reach full power supply voltage potential, 12V in this case. It's always safest to use a permanent solder connection from driver to diode, though some quick disconnects do seem to work ok, but it's just inherently a bit risky.

As far as capacitance within the driver, that's another easy way to kill a diode. Shorting the diode out leads on the driver prior to connecting the diode is really a worthwhile habit to develop as with many driver designs it's a very necessary thing. A lasorb will not necesssarily help in this case either as it's not esd.

And as mentioned esd is also another possibility, though with today's diodes it's much less of an issue then it used to be. My guess would be either of the above possibilities, but since it didn't happen during operation I'd tend to lean towards not shorting the leads being the source of trouble.

[Bradfo69]

Well.... I suppose I'll chalk it up to "job security" for DTR. From what little experience I have with diodes, I think I've just about come to the conclusion I'd rather just buy a finished product. I'm ok with having to replace something I fucked up when I realize what I did but, unexplainable disasters... not so much.

@Colin - It's two M140's in series for each module.

[m0f]

It can be discouraging to pop a diode, many here have learned the hard way, I know I did But don't give up! Thankfully it was just an M140, they're not so expensive a mistake to make as some. Sometimes it takes a mistake or two to learn what not to do

For me I had similar luck in the beginning and made a couple of seemingly required mistakes back in the days when they had to be pulled out of dvd and bluray drives or sleds so they were a total pain to replace, but all it took was a couple of mistakes and I'm at the point now where I'd be comfortable working with a 1W 520nm.

I hadn't blown a diode in years, and a few months back I soldered one and ended up with one tiny strand of wire hanging off it, I didn't think much of it at the time but ended up shorting while powered on and led'd an H1600 blue, so things happen from time to time. I know I'll be heatshrinking my connections right away from now on! So just keep at it and you'll be a self proclaimed expert in no time

[buffo]

Hey Brad;

Sorry I'm a little late getting to this thread. Wish you had called me before you hooked this up - I might have been able to save you a little headache.

Regarding the module with little to no output, yeah, it sounds like they're toasted. I have a feeling it was probably an intermittent connection as m0f suggested. With regard to static, that could also kill them, but in my experience these 445 nm blue diodes are remarkably robust. They're no where near as fragile as the long open-can red diodes we all used to use back in the day. But an intermittent connection will blow a diode for sure.

Fortunately, those M140 diodes are quite affordable these days. If you don't mind waiting, bring all the parts to SELEM and I'll solder the new diodes in and mount them for you.

Regarding the TEC, all you really need to do is feed it +5 volts and just let it run. It will draw about 1.5 amps, and it will keep the diodes nice and cool. Just be sure the module base is attached to a large metal plate so the heat has someplace to go! But for short duration testing (less than a minute) you can run those modules at full current without any power on the TEC and they won't overheat.

One thing: You mentioned that at 2 amps you only had 2.98 watts of output. It's possible that the knife-edge mirror shifted during shipping. Because you should have been getting well over 3 watts at that current level. But if the mirror shifted, you might be losing power from the straight through diode because some of the beam is being blocked by the back side of the mirror. Put on a set of googles and look closely at the edge of the mirror. If you see a lot of splash from the edge, you need to re-adjust the mirror position.

Adam