8X Diode Murder fund

[Crazy Jay]

Incense sticks, matches, things like that help a lot, if you don't have a smoke machine.

Really? No foolin? I thought that smoke can only be made by rubbing two sticks together :crackup:

 

[bryce007]

Igor, there's no need to plot multiple diodes at the same time, it sounds like a lot of work, and you need to get some rest sometimes

 

[IgorT]

Really? No foolin? I thought that smoke can only be made by rubbing two sticks together :crackup:

Well, now you know better...

 

[IgorT]

Igor, there's no need to plot multiple diodes at the same time, it sounds like a lot of work, and you need to get some rest sometimes

I'm gonna do it.. I just can't promisse it'll be super-fast... That's all.. Altho if it threathens to cause more delays, i'll have to postpone the F03's...
With this experiment i had to be fast, because multiple people invested money and/or help in it, and i didn't want to make everyone wait...

As for time, at this moment i need it mostly for the work, i'll get some rest later...



P.S. I have to say, the new "Torture Chamber" works beautifully.. I keep checking if anything is wrong, worried that the counter would miss a powerup, but if the parts are kept well aligned and the beam covers a large part of the diffuser area, the sensor and the counter do their job...


P.P.S. Let's all hope we get to see at least another zero at the end of that number on the cycler! Otherwise we might have to kill the next diode at the same current, if not less!

But considering average use, this diode would already have lasted three months and a half at this point (375 counts and still going strong)...
So one thing's for sure, regardless of what the end results are, i'm setting at least one of my 8x's to ~300mA.... :yh:


Another thing, due to the large difference between 8x #3 and all the rest, i expect 8x #1 to withstand this torture MUCH longer!

 

[Krutz]

nice pics, setup and documentation, igor!
hmm, thats not too much degration.. but then i have no experience how much the numbers variate "normally"..

thank you again for all the effort!

manuel

 

[ZheolD]

I was not Planing on Posting here as i did not join the efforts. But i have to say Wow i love the looks of your torture chamber

Great job Igort!

Cheers
Josh

 

[HIMNL9]

I hope i'm wrong of course.. Maybe i should wish for it to die. Usually if i make a laser with the specific purpose of killing a diode, it doesn't want to die.. FrancoRob has a 320mW red that was a result of such an unobedient diode.. :crackup:

LOL ..... that may become embarassing ..... build a high-tech torture chamber, having selected the worse ones for the dead test, and then discover that the worse one is the one that don't die also if tortured ..... you risk to have your inquisitor license suspended, and to have to take "electronic torture" updating courses ..... :crackup:

Anyway, here are three separate plots. P/I, Po/Pe and Efficiency/Pe...

In all three 0h and 1h overlaps. 5h makes a distinctive new line.

Additionally, Ith climbed by 1mA - i was checking them preciselly for this reason, cos i read 405nm diodes degrade by the Ith climbing but that the slope efficiency remains the same.

This last part does not seem to be true however. Because the slope did drop in it's steepness (instead of the entire plot simply moving to the right).

In any case, the experiment continues, and i'm afraid i will have to replot the diode two or even three times a day, if i want to capture what is happening before it goes LED...


Other degradation details (from 0 to 5h):
- Ith went from 34mA to 35mA
- Slope Efficiency went from 1.339mW/mA to 1.318mW/mA
- Po @ 300mA went from 356mW to 351mW

Well, seriously, for a long time torture, it don't seem too bad, as degradation rate (also considering that you are speaking about 5 hours of effective ON work time, not 5 hours of total ON/OFF time, right ?) ..... this can also indicate a longer life, if not mistreated too much ? ..... if this is common for all the rest of the group, isn't a bad possibility, after all .....

 

[IgorT]

LOL ..... that may become embarassing ..... build a high-tech torture chamber, having selected the worse ones for the dead test, and then discover that the worse one is the one that don't die also if tortured ..... you risk to have your inquisitor license suspended, and to have to take "electronic torture" updating courses ..... :crackup:

No! Not my Inquisitor licence! :undecided:

Well, seriously, for a long time torture, it don't seem too bad, as degradation rate (also considering that you are speaking about 5 hours of effective ON work time, not 5 hours of total ON/OFF time, right ?) ..... this can also indicate a longer life, if not mistreated too much ? ..... if this is common for all the rest of the group, isn't a bad possibility, after all .....

If it was a PHR at 175mW and would degrade to a point where it's power would be 5mW lower, it would die very soon after that.

If it was a GGW, it would drop a little further, before dying. My GGW lost almost 10mW (from 193 down to 184mW @200mA after acrylic lens) through degradation, after a year of heavy use. But it did not die from that! I actually set it to a MUCH higher current (around 230mA), where it produced 236mW after acrylics, if i recall correctly. It then lasted a little longer, degraded a bit more and died soon after.


So higher power diodes can drop further (in mW) without dying. Perhaps it's like a percentage of the power, i don't know.


However, fact is, this particular 8x is overdriven WAY harder than my GGW was, approximatelly as much as a PHR at 175mW. And it already lost 5mW.. But it should be capable of going quite a bit further....


I think it's too soon to predict anything just yet, however it is degrading faster than i would wish, but i kinda expected that.


And yes, 5h9m was total ON time, it took 10h18m of cycling to get there...


Every count on the LED display is one minute of ON time @ 300mA. Right now we're at 397 minutes... :yh:



And since this is not only the lowest efficiency of them all, but a diode, that stood FAR appart from the crowd in efficiency (there was quite a gap between it and the next murder candidate), i am taking the fact that it's still alive as a good sign!

398 minutes ON-time.. 44 more minutes of cycling and we're at 7 hours... The temperature seems to be holding at 26°C...

 

[davidgdg]

Anyway, here are three separate plots. P/I, Po/Pe and Efficiency/Pe...
....
Additionally, Ith climbed by 1mA -

Could some knowledgeable soul explain to me what the horizontal axes ("El.power") on graphs 2 and 3 represents? Also, what is "Ith"? (is it related to "i" for current?)

Many thanks

David

 

[IgorT]

Could some knowledgeable soul explain to me what the horizontal axes ("El.power") on graphs 2 and 3 represents? Also, what is "Ith"? (is it related to "i" for current?)

Many thanks

David

El. Power represents electrical power in Watts going into the diode - a factor of current and voltage (P = U x I).

I left it in mW in some cases, because we mostly refer to the output power in mW. The reason i used electrical power going into the diode in some plots is, that it's electrical power that matters, when it comes to actual efficiency of a diode - how much of the ELECTRICAL power going INTO the diode comes OUT of the diode as OPTICAL power - the rest comes out as THERMAL power or heat..

Mostly we use mW per mA plots to represent the efficiency of diodes, but here i also wanted to sort them by actual efficiency, since it changed the order of the diodes, once the voltage was taken into account, instead of just the current.


As for the efficiency plot. There it only makes sense to plot efficiency against electrical input power, since the percentage represents how much of the power going in will come out as light. Plotting efficiency against current doesn't tell much, since the percentage is not directly related to current, but to the factor of current and voltage.



Ith is threshold current, which is the current where a diode starts lasing. Under that current only some spontaneous emissions occur, as the threshold is crossed, stimulated emissions start.






Everyone: The Cycler Circuit says 510... We're at 8.5h ON-Time! :yh:
The experiment has been running for 17h + interruptions (for re-plotting)... At 600 minutes i am re-plotting the diode again!

The good news is, even the weakest of all diodes does not just die without gradually degrading first! If you have an 8x, and it's not showing less and less power, it's most likelly gonna last a while longer (but this requires an LPM of course). Hopefully we can establish how much they have to degrade (approximatelly), before they die... With PHRs it was quite consistent...

 

[davidgdg]

Thanks. Understood.
Look forward to the 10 hour plots ....

 

[IgorT]

Thanks. Understood.
Look forward to the 10 hour plots ....

Well, guess what! Just this very moment i turned the Cycler OFF, because the counter reached 600! :yh:


We're at 10h ON-Time!!!

This is good, very good!

I need to wait for it to cool down to 20°C now and re-plot it...
One thing this setup would benefit from would be a constant temperature rig.. But that will take even longer to make...


Man, to be honest, i was a little jumpy over the last few hours, every time i'd hear the relay click, i'd look back to see if the diode came ON.. :undecided:
I need to put it somewhere i can't see or hear it...


But so far so good. It's a tough little diode! Let's hope it can keep this up for a while longer! :yh:
Another zero maybe? :angel: Altho at this point i'd be happy with half as much...

 

[Dusty]

Good work Igor, the results sound very promising so far...:yh:

 

[IgorT]

Here are the 10h degradation plots....


I heard degradation happens exponentially.. And if i'm not mistaken, this fact is actually noticable in the second set of plots....
The difference from 5h to 10h is larger than the difference from 1h to 5h was...



Other details:
- Ith climbed to 36mA
- Slope efficiency is now 1.300mW/mA
- Po @ 300mA is 345mW - an 11mW drop from the start of the experiment.



The experiment goes on, i just hope it's not done by this time tomorrow. Problem is, as imperfections are growing, the optical flux has more and more to "eat away" at. That's why degradation is exponential...

We'll see how tough the diode is. Like i said, the thing that still makes me hopeful is, that this one was an "outsider" while the second murder candidate is already a normal 8x... That one will provide much more interesting results, i expect it to last much longer.

 

[bryce007]

I'm sad to see those results

Hopefully it will last for a few more days.

 

[HIMNL9]

The exponential fact, can be due to the fact that the degradation is caused from faces degradation ?

I mean, the reflecting faces of the "cavity" formed inside the emitting crystal chip ..... if it start to degrade, the degraded part, instead reflect and / or pass the light, adsorb it turning it in heath, that can cause the degradation of a more large zone, that adsorb more light, and so on, in an increasing destructive loop.

And as heath, i don't mean enough heath to change significantly the temperature of a diode in a big heatsink ..... as example, if the first point that start to degrade is like 1/10 mm or less, the resulting heath can be enough to accelerate the degradation around it on the reflecting surface, but not high enough for change the temperature of the whole assembly ..... but at the same time, also if the increase of the diameter is linear, the commplexive surface involved can cause an exponential decreasing of the efficence .....

I was wondering about that, times ago, and started to make some draws for a test chamber ..... but probably is impossible to make a test chamber that incorporate a camera with a microscopy objective focused in diagonal on the face of the chip, not with hobby level tools and not with a 3mm FL lens in front of the diode, anyway ..... maybe can be done for open can diodes, but sure not for the closed cans ones