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8X Diode Murder fund

Meatball

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if it lasts 100 hours I vote for pushing it until it pops to see how far can they be pushed for short periods. Even if it's a freak diode it's degraded now, so we could get reasonable data...

OR, we could also make a lottery and donate it to the donators... :D

That wouldn't tell us anything useful. It would only show what would happen if we kicked up the current after 100 hours. Who does that on a regular basis? Who needs to know what happens?

I say that keeping the current the same throughout this kind of experiment is the best thing to do. You don't go changing variables during the experiment upon a whim. We can set the current higher on the next torture diode. This one ought to stay put.

If you want to see one pop, try it with a diode of your own. Not with one that has already been tortured for 100 hours or so.
 



jayrob

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One idea to try if the first one makes it 100 hrs., is to not change the current, but maybe change the 'on time'...

Could your unit be set to cycle for 5 min. on / 5 min. off? Just curious, but not necessary.

As for the second one, I would think that 330mA's would be a nice place to test. As you had suggested Igor...
 

bryce007

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I think we should wait to torture the second diode until the first one is dead or we rule the experiment over, we are only half way to our goal of 100 hours.
 

IgorT

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I was about to write a long post explaining what should and should not be done and why, but i have a whole lot of work to do and two weeks worth of emails to answer, so i'll be short.

I never intended to stop the first experiment for anything other than re-plotting, nor change it's conditions... In this hobby, the "useful life" of a diode ends when a diode pops... And we usually don't change currents after a laser is built.

The experiments are meant to give builders an approximate idea of what to expect. And that's why the experiments should relate to what we usually build.


Also, the 100h mark was just one of my suggestions for a standard of "reliability". In the meanwhile i realized even half as much is plenty for a hobby pointer.

But i don't want to stop the test because i want to know:
- How long the diode will survive this current
- How fast it will degrade with time
- How much it will degrade before dying

All these bits of info will be of EXTREME importance during the following tests, including that of the 12x!

And we can't get to them, unless i leave the first diode as it is, and test it often enough not to miss any big changes in it's behavior.

Since degradation is slowing down, i won't even re-plot it until the 60h mark, unless of course i notice a kink developing, which is why i still check it's beam profile twice a day.



I was mostly wondering what current to test the second diode at. And when i thought about starting the second experiment sooner, it did not imply stopping the first (the torture chamber can handle multiple diodes at once, if i add sensors and counters).


When it comes to the second diode, there are several things that interest me.

Obviously i want to know how long it can live at higher currents/powers.
But believe it or not, i am just as interested in how long it would survive at the same current (i'll explain why)!

Problem is, i can't test both. And testing higher currents/powers is of interest to many of us. That's why i was thinking of a middle ground. A current, which would give answers about higher powers, but not make the second experiment completelly unrelateable to the first one...


And the reason i can't test both - as Dave already explained - is, that if the diode is tortured at one current first, and then the current is raised, the data from the second or third current does not tell us how long the diode would have lived there! It only tells us how long it lived there AFTER having been tortured at lower currents first.

Unfortunatelly every diode will degrade at a different rate and to a different level before dying, making it impossible to extrapolate data from a single step. In fact, we've seen that degradation slows down with.... ....degradation, making things even more complicated!



Unfortunatelly, my experience with torturing and killing diodes is mostly limited to PHRs, a small number of 4x's and some GGWs...

PHRs would usually degrade by around 3% before dying, when overdriven hard.. The 4x i cycled seemed to degrade a lot, but it fell into a kink, making the numbers meaningless.. My first GGW degraded almost 5%, but then i set the current higher, after which it died rapidly, and now i don't know how far it would have degraded if i left everything the same...


With GGWs, i can rely on the efficiency being a good sign of health, there higher efficiency diodes will outlive lower efficiency ones, when set to same currents. With PHRs (and 4x's) kinks made things a little more complicated.

But since those were all reject sleds, and evidence exists some of them were even prototype sleds, i can't say for sure the same will hold true with 8x's from drives...


It's unlikelly, but in theory at least, a higher efficiency diode could kill itself faster, due to the higher optical flux it produces at the same current.
While i'm pretty sure efficiency is a sign of diode health, it's not the only factor involved...


I have killed many diodes and quite a few in stupid ways, but none of them cost almost $200 a pop...


We have a very limited number of diodes available for sacrifice to the lazor gawdz, and that's why we need to squeeze them for as much info as possible.

But for the same reason, we also have to squeeze very carefully.


P.S. And yes, this was the short version. :angel:
 

Krutz

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hmm, do we even know if diodes degrade at their rated output?

manuel
 

Krutz

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..if we knew how much diodes degrade at their rated output (datasheets), we maybe can find out what an unknown diode is rated for? i am sure manufacturers rate their diodes depending on their degrading, so the degradion-to-rating-formula should be somewhat common for all diodes?

manuel
 

HIMNL9

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Uhm, sorry, but i doubt about that ..... it may be too easy ;)

Seriously, no, i don't think, the diode chips are produced from different manufacturers, and the degradation have too much variable and possible causes, for this ..... maybe if you can test 20 or 30 diodes for each serie, then at the end you can have a medium-shape curve valid for all the serie, but just from one or two diode, i doubt it works .....
 

daguin

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..if we knew how much diodes degrade at their rated output (datasheets), we maybe can find out what an unknown diode is rated for? i am sure manufacturers rate their diodes depending on their degrading, so the degradion-to-rating-formula should be somewhat common for all diodes?

manuel
That would, first, require us to be able to really identify the diode , and second, require us to be able to get the datasheets from the manufacturer.

We have been very ineffective at accomplishing either of those tasks :(

:thinking:I wonder if PBD's university association could convince the drive manufacturer (Pioneer and/or LG) to give us that info . . . . . .:thinking:

Peace,
dave
 

Krutz

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but but but!
but it should be possible to find out how diodes degrade at their rated output? from the manufacturer, datasheets, pressreleases? i expected its simply stated in datasheets?
we dont have to identify unknown diodes. we simply try & error until we know at what output they degrade like 1% every 100 hours? (if thats what the other datasheets say about rated output)

sure, if we cant find out what the "rated degradion" is like, we are out of luck again.

perhaps the datasheet wouldnt help too much anyway? we want to know at what output the diodes survive many hours, not at what rated output they survive several thousand hours..

manuel
 

daguin

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but but but!
but it should be possible to find out how diodes degrade at their rated output? from the manufacturer, datasheets, pressreleases? i expected its simply stated in datasheets?
we dont have to identify unknown diodes. we simply try & error until we know at what output they degrade like 1% every 100 hours? (if thats what the other datasheets say about rated output)
sure, if we cant find out what the "rated degradion" is like, we are out of luck again.
perhaps the datasheet wouldnt help too much anyway? we want to know at what output the diodes survive many hours, not at what rated output they survive several thousand hours..
manuel
All of that begins with the correct identification of the diode and getting the datasheet. "8X" is not a "rating." Without those two things all we have is what we do. We buy what we can afford and we experiment with them. This "fund" and the 12X fund are the first time I know of that the forum members have thrown together this way. Usually it is one or two of us taking the chance and blowing the first couple of diodes.

Peace,
dave
 

IgorT

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The diode just reached the 60h mark!

Just stopped it for a quick test, to record degradation patterns, but the diode still seems to have some life left in it!

Couldn't be happier with the results so far! :yh:
 

LarryDFW

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Igor;

60 Hours is very good news.

This diode is surprising in durability.

It should make 100 hours at the current rate of power loss (~7.5% @ 60hr.).

I am starting to think that other problems,
like electrostatic discharge are responsible for some premature "in the field" failures.

LarryDFW
 
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bryce007

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Igor;

60 Hours is very good news.

This diode is surprising in durability.

It should make 100 hours at the current rate of power loss (~8% @ 60hr.).

I am starting to think that other problems,
like electrostatic discharge are responsible for some premature "in the field" failures.

LarryDFW
I was thinking about the same thing, ESD damage. I'm actually considering connecting a Lasorb, or maybe IgorT has another idea on the matter.
 




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