Freak 803T Diode **A New Mystery**

[daguin]

Well IgorT, It finally happened. I got a "freak" 803T diode.

I was working on a small pointer today. I had some time and an old style Rkcstr driver (177mA) left over from making my "Matched Set" lasers sitting on my desk, so I decided to go ahead and assemble a module to use later. I didn't even hook the driver up to a dummy. I had seven of them. I checked them all when I got them. I've used the rest of them. This is the last of them. They all had the same resistors on them. I have had NO consistency issues with these old Rkcstrs. I have made several lasers with this combination of components. A Rkcstr driver set at 177mA hooked to an 803T diode gives me about 155mW after acrylic lens.

I harvested a diode from an 803T sled and pressed it into the AixiZ module. I soldered the driver on and did a quick "does it light" test. It did. I didn't get the driver soldered exactly straight so I had a bit of trouble getting the back of the module screwed on. I screwed an acrylic lens into it and powered up my LPM. I used a Sure acrylic lens. I had to strip the springs from some of them to build the "Matched sets" so I had several of them loose. I turned on the laser with 9V going to it.

I turned the laser right back off. Something was obviously wrong with the setup of my LPM. I had it set to the 200mW range, but it was reading "over-loaded"! I checked everything. It all checked out. I reset the range to 2W and fired the laser back up. It was reading at 320mW!!!!!! I turned it back off and started thinking. What could be wrong? This diode CANNOT be putting out 320mW. I thought, "maybe I got a 300mA driver mixed in with the 177ma drivers." I really doubt it, but what else could it be? However, I have never heard of one of these diodes surviving being hit with 300mA.

Remember, I said that I had trouble getting the back of the module screwed on? I'm afraid that if I try to screw it back off again, I will twist off the pins. So it is put together. It is putting out WAY too much light. I can't take it apart to check it out. So I figure, what the hey! Let's see what it can do.

I fired it back up. It was putting out 300mW. As it burned, the power started dropping. I figured I was going to watch it die. It slowly made it down to 190mW and stabilized! It was also starting to get warm so I shut it down again. I've fired it up a couple of more times this evening. It is staying about 190mW. I don't even have a heat sink here for an AixiZ module. Everything I have here is drilled for Merideth modules.

I have triple-checked my meter using known lasers. It is working fine. I put the freak away until I can get a heat sink for it. I'll have Jayrob make me one for the big "chicken leg" MXDL. That thing has enough metal in it to heat sink my truck and has the triple AAA carriage in it.! After I have it in a host, with a good heat sink, I'll start testing it again. In the mean time, I have seen 320mW of blu-ray! I just wish I could have taken it outside (or at least remembered to turn off the lights).

Peace,
dave

[highlight]**EDIT** The mystery is solved (sort of). What I couldn't possibly imagine is what happened. I got a 300mA driver mixed in with the 177mA drivers. This poor little diode is being bombarded with 300mA of current How long can it survive? . . . . .Stay tuned[/highlight]

 

[GooeyGus]

Re: Freak 803T Diode

Now come on... this is just getting ridiculous ;D

 

[IgorT]

Re: Freak 803T Diode

Umm.. Well...

190mW at 177mA is a freak diode, yeah. 320mW is not a freak diode, it's a wet dream.
Did you do a reality check?

In any case.. Since your driver is at an angle, and touching the AixiZ module, there could have been something shorted.. Or mabe not. There is not much there on the edges to short.. Hmm.


Dave, you can still measure the current without taking it appart. It's a linear driver - the current going in is the same as the current coming out. So you can measure between the battery and the driver. But since it's set up with resistors, it really can't be much else, other than 177mA +-1mA or so (from Vfb variances).. Unless there really was a short.


But if the power was higher without a short and started dropping, it might die soon. If the power was high because of shorting, it might die soon. Even if it was just a normal freak, it might die soon. My freaks always die first..

They are pretty while they last tho. Make sure you keep us posted about it. But measure the current first..

 

[IgorT]

Re: Freak 803T Diode

Otherwise, did you also see the brightness visually dropping during this?

 

[Zom-B]

Re: Freak 803T Diode

D you have a power graph for this diode? what's the treshold current?

 

[IgorT]

Re: Freak 803T Diode

If that had really been 320mW at 177mA, it would mean ~32% efficiency. It would also mean the diode suffered degradation, and will die soon.

Some kind of short is much more plausible.


The best diode i had did 193mW at 180mA. 190mW at 177mA would mean the same efficiency freak diode ~19%. 32% is hard to believe.....

 

[Zom-B]

Re: Freak 803T Diode

I've tested some HD-DVD diodes, and when overpowering them, they don't just keep getting brighter (like light bulbs), and certainly they will never get any more efficient, only lots less efficient. Overpowering by as less as 25-50% killed them.

Also see this rough diagram (not to scale):

Note that this is using my own quantitative version of the 'knee'. I have never seen anyone define a knee other than as a visual aspect. This knee may be 2-15% lower than the old definition (eg long open can red = 360mA, not 420mA). And especially for UV diodes, this new knee seems to approach the sweet spot much better than for red diodes.

 

[IgorT]

Re: Freak 803T Diode

What do you mean overpowering them by 25-50%? We are overpowering them by almost 100%! EDIT: Did you mean 25% above the "knee"?

We're driving them CW, at or above their pulsed ratings!



How long do your PHR diodes at powers above 170mW (after plastic lens) last btw?
I've had the experience of the highest efficiency diodes dying first. They can't take the optical flux at the die, and the more efficient ones reach too much flux at a lower current.

With reds, i either lost a diode at the first powerup from too much current, but if the current was not too high, they just kept on going.
But these can work for a week, then suddenly drop in power, as imperfections begin forming in the die, and after that the degradation is exponential, and it just dies at a powerup.

 

[daguin]

Re: Freak 803T Diode

Did you do a reality check?
Dave, you can still measure the current without taking it appart. It's a linear driver - the current going in is the same as the current coming out. So you can measure between the battery and the driver. But if the power was higher without a short and started dropping, it might die soon. it might die soon.

I did TWO reality checks while I was working with it. Then I checked the meter again before I went to bed. What I observed does NOT fit into my view of the world. I didn't think of checking the inline current . I'll get that done today. I thought it was going to watch it die last night. It just didn't. I do NOT believe that it can keep going for long. I just want to give it every advantage to let me enjoy it while it lives.

I am reminded of a line from Blade Runner -- "The light that burns twice as bright burns for half as long - and you have burned so very, very brightly . . . "

D you have a power graph for this diode? what's the treshold current?

Unfortunately, no. This is a combination of components that I have used many times before. I was just slapping it together to clear up the "mess" on my desk. No need to check anything. It is simply business as usual for me.

How long do your PHR diodes at powers above 170mW (after plastic lens) last btw?

I only have one that runs 170mW after acrylic. It is still here as part of the last Matched Set of lasers that I have for sale (170mW blu-ray and 250mW red)

[blatant plug] http://www.laserpointerforums.com/forums/YaBB.pl?num=1215317897 [/blatant plug]

I have three that run 160 - 165mW after acrylic. Two are owned by members of this community. The other is one of my toys. My two others that put out over 170mW have the Merideth glass lens in them.

I haven't had one survive my "hell week" of testing which has the input set at higher than 190mA ( but I'm still trying )

Peace,
dave

 

[daguin]

Re: Freak 803T Diode **Mystery Solved**

OK. The mystery is solved (sort of). The moral of the story is, "KEEP YOUR WORKSPACE CLEAN"

What I couldn't possibly imagine happened, did. I got a 300mA driver mixed in with the 177mA drivers. :-[

This poor little diode is being bombarded by 300mA of current.

It cannot possibly survive this. [smiley=evil.gif]

However, until it dies, I'm going to enjoy it

Thanks for racking your brains along with mine. :-*

Keep your workspace clean, assume nothing, double check, and don't "slap" something together when you're tired.

So sayeth the prophet


Peace,
dave

 

[daguin]

Re: Freak 803T Diode

After a week of being without a personal handheld blu ray, i made myself a 165mW yesterday (at 160mA).
I hope this one lasts this time.. BTW, i almost forgot how pretty blu rays are! Can't wait for the 6x!
Anyway, what currents did you use for the 160-165mW?

180mA

I needs me some better optics

Still hoping on the new lenses.

Peace,
dave

 

[IgorT]

Re: Freak 803T Diode **Mystery Solved**

EDIT: Oh, it wasn't a freak..


300mA!!!!!  


OMG! Well.. Wow! I didn't know it can survive that at all! Maybe it's a weirdly tough diode, and you were just lucky, that you put the wrong driver on the right one.


However, at 300mA, it should be doing more than 190mW.. The 320 sounds about right. Unfortunatelly this means degradation has begun.. The efficiency is ridiculously low at this point..



P.S. You'll get the lenses, as soon as i select the one with the lowest distortion properties. Then we can order them.. I'm getting at least one of the aspheric samples this week!
I just don't know how you'll get them into the Meredith module.. Unless you get the Meredith acrylics holder..

 

[IgorT]

Re: Freak 803T Diode **Mystery Solved**

Man, but that it could survive >300mW even for a short time!

I thought it was impossible.. I wonder what a 6x can really do.. :

 

[styropyro]

Re: Freak 803T Diode **Mystery Solved**

Even if it didn't last long, 320mW of 405nm had to be awesome! I can't believe that thing even lased running at 300mA!!! Like Igor said you probably used the right diode for your mistake.

 

[daguin]

Re: Freak 803T Diode **Mystery Solved**

Man, but that it could survive >300mW even for a short time!

It shouldn't and it can't :'(

Serendipity is a strange Goddess. You just never know when and/or where she'll show her face :

However, I'll heat sink it and shine it into the night sky at least once

Once it dies, I'll rip the pins off it unscrewing the module and hold a wake in its memory [smiley=beer.gif]

Peace,
dave

P.S. You do know that I wouldn't rush you, don't you? I'm NOT going anywhere. You just keep being Igor. I like him.

 

[IgorT]

Re: Freak 803T Diode **Mystery Solved**

Hehe, well i know you wouldn't rush me, but some people are impatient, and don't understand that making a custom lens is a big project!

Mistakes cost money, and rushing causes mistakes..