12x Murder Experiment - Take 2 (With 12x Comparison Plots)

^ Dave, then there is a possibility, after all ..... that "beam shaping" can be an element that, shaping better the beam, also take away part of the power, and taking away it (and maybe using a little different lenses inside the focusing carriage), they reached the 12X speed still using the 8X diodes, or very similar ones .....

Still just a personal opinion, but can be kept in consideration that, maybe, some manufacturers still use this system, and others instead changed the diodes types .....

HIMNL9 said:

^ Dave, then there is a possibility, after all ..... that "beam shaping" can be an element that, shaping better the beam, also take away part of the power, and taking away it (and maybe using a little different lenses inside the focusing carriage), they reached the 12X speed still using the 8X diodes, or very similar ones .....

Still just a personal opinion, but can be kept in consideration that, maybe, some manufacturers still use this system, and others instead changed the diodes types .....

Click to expand...

It is still possible. I am inclined to view it from your position as well.

We are seeing a lot of "overlap" in the graphs of the 8X and the 12X. Also, in the 12X graphs, we seem to be seeing two different "groups" of IP/OP slopes. However, this may simply be us "seeing" what we want to see or just having not graphed the ones between yet.

Some 8X's are being pushed to very high currents. Some 12X's degrade rapidly at "low" currents. It is possible that these are all the same diodes, but we are treating them differently so they are acting differently. I did some "range" comparisons earlier (I would have to search it up again) in which I showed that the range of performance was at a very similar percentage to earlier violet diodes. The actual numbers are larger because the absolute power is larger. However, the percentage was very similar.

Peace,
dave

Dave;

I am inclined to think the 12X diodes are different.

Because of all the 320 mw laser PR releases from Nichia and Sharp,
I think that the 12X writers are using these new diodes.

This also seems to indicated from the high power levels,
we are seeing with some overdriving users.

Anyone care to operate their 8X at 7-800mw for several hours ?
The highest on FrancoRob's 8X chart is 571mw.

LarryDFW

We have to take all possibilities in option not just border ones: First two were lemon;
or All of them are weak

For example , if you grabbed 10 PHR diodes, one will die at 130mA.
However, you should know that the rest won't live identical life.
Two will die in first week,
5 in two weeks,
the rest in three weeks or longer maybe...
(^I am just thinking out loud, these ARE NOT FACTS)

So, let's say that these two Zombies in Igor's possesion were of those two that die in first week.
The 7 of rest will live much longer, and one will even die at such current.

However, I am NOT implying that such current is dangerious for 12 X as I have no rock solid fundations for that statement.


About Exerd 880 mW 12x,
if you grab 50 PHRs, there is a good chance you will find one that will outlive previous examples , at 150-160 mA!

So, Exerd is maybe very lucky to recieve a very strong diode (how did you get an idea of pushing it that high? ).
Or maybe it will die in 2 months... you knever know.

Also, since such drives are VERY expensive, you must always take into account that there was NEVER enough diodes tested,
unless you tested 200 diodes or so.

We had 2 die on us so far,
let's say that next ... five for example, behave like so at 420mA:
two die at 50 hours
two die at 100 hours
One outlives Igor's torture chamber.

BUT! What if those 7 tested are among those 7 lowest performing PHRs out of 50?
So basically we would not know the average even then.


What is my point? I don't know either ! :crackup:
Just Kidding folks.

I want to applaude for all the money invested here to determine parameters for expensive diode operation, so that others do not have to learn frm their own mistakes...

IgorT - Don't get down because of two dead diodes.
2 out of 50 PHRs will die at 120 or so, as stated by Dave.

It is, first of all, NOT your fault,
and it is obviously supposed to happen...
It is after all, highly unlikely that they are same diodes, because as you said yourself, threshold current is 10 mA or so lower than average of GREAT quantity of 8x.

So, chin up!
Even if they turn out same as 8x - you still tested them to determine that and that is what the test was all about!

jayrob said:

Seems like a huge difference in power for low efficiency vs high efficiency...

When I donated for this second 12X diode, I thought we were going to keep it at a lower current for a longer test. But I don't want to be the only one to say 'set it lower'. So go ahead and set it at what ever you think is good for your testing.

Just hate to see it die too soon...

Click to expand...

Well, me too, but it's too late now. And believe it or not, i actually feared i was testing too low for other's wishes...

But the thing is, there was something very wrong with this diode from the start.
Not only did it have an absurdly low slope efficiency, all it's characteristics were so unusual, it almost made me think it's an 8x!

But i checked all three sleds and they were 12x sleds. The likellyhood of an 8x diode getting into a 12x sled is negligable, so it must have been a 12x diode.


However i am not even sure if this particular diode would have worked in a 12x disk writer... If nothing else, because of it's horrible efficiency.

The diode was so far away from all the other 12x's - the difference from the highest efficiency ones to this one was MUCH greater than the difference between the high efficiency and the low efficiency 8x's!

Every sled is separatelly adjusted, to compensate for diode efficiency - the lower the efficiency, the higher they set the current. For this one, they would have to set it so much higher, i can't imagine how it would have even passed the factory testing!


I was worried about this diode from the moment i plotted it. As soon as i saw the numbers, i was very dissapointed, because i started doubting, if it could provide any results that would relate to other 12x's.


My only hope was, that efficiency really doesn't matter for diode toughness. If so, the diode may have given some answers, but instead it popped instantly at a power even low efficiency 8x's would survive for a while...


This diode would be useless for a laser, and just as useless for our testing purposes. I really hope no other 12x's are like this.


I was just unlucky, that i got such a poor diode with my order. But i can't say i wish i would have tested it lower, because if i did, it would only "proove" that it's weaker than the two tested 8x's. I really don't think it could provide any answers related to other, healthy 12x's.

The first 12x was also of a lower efficiency, but it was still completelly normal, and infinitelly superior to this one.


One thing is for sure, with 12x's efficiency apparently can be an indication of diode health. At least in this case it was.

I still don't know why the previous diode went zombie, because it should have been a normal one, but with this one i am 99.9% sure there was something wrong with it and that it was weaker than either of the two tested 8x's.



At least now we get to see the torture and degradation of a very good high efficiency 12x diode instead. One of the best at that!






In any case, i started the torture of the third 12x last week. I had to pause it over the weekend, because i had a bunch of important paperwork to prepare and the way i am testing this diode now consumes a lot more of my time (i can't just let it cycle away).


I restarted the testing today, and the first step is almost finished. Altho i need to do at least one more replot, before i can be sure.



It's a multi-step approach, where i am testing different powers and comparing the degradation to that of the 8x's, to determine whether or not the 12x's are actually better.


The first step is testing the same power as with the second 8x Murder Candidate and comparing the degradation speed.

For this i set 12x #3 to 315mA where it produced 452mW, and let it cycle for a fixed amount of time with checks every 20 minutes and a replot every hour (unless the checks on the optical "LPM" in the sensor should indicate a replot is needed sooner).


Once i am happy the diode ran long enough (once it produces a long enough Po over Time degradation curve to be comparable to 8x's), i can decide if it showed it's tougher or not, and continue the testing at a higher power.


The second step will be testing the same current as with the second 8x.

For this the diode will be set to 345mA, where it should produce just over 500mW.


After i see the results of both tests, i will decide where the third step will be. Hopefully 550mW.


Also, until i reach the final test power (whatever i end up being comfortable with based on test results), the test duration at any current/power will all be very short - just enough to allow a degradation speed comparison to 8x's, but not as much as to influence the results of the following steps too much.


In this case, i am taking advantage of the fact, that the difference from one 12x to another is usually greater than the difference between this 12x before and after each step will be, from the degradation it suffers in between...

Because of this, if the steps are kept short enough, we can imagine we are testing another random diode at a higher current/power, with each step.

Sure, the diode will become slightly degraded with each test, but if this one turns out to be tougher than 8x's (and it hopefully will!), the short intervals at lower powers will not cause enough change to make a difference.


This way, the end results will be as if we tested multiple 12x's at different powers, altho without the total lifetime at the lower powers.

The lower powers are only being tested to compare degradation speed, and to find out at which power the 12x will degrade as fast as the second 8x did.

This would tell us just how much tougher 12x's are from 8x's.


After i find a power level where degradation speed is equal or similar to that of the second 8x, i can then let the 12x cycle away until it pops, to determine the total lifetime at that power.


It should be a very thorough and informative experiment in the end. And this time it's going well so far!

I just hope the level where the 12x diode degrades as fast as the second 8x turns out to be at around 580mW (or better yet higher), as it should by calculation...

That 3rd 12X sounds likes it is just like the one that I have. You said it was giving 452mW's @ 315mA's...

Mine is giving 465mW's @ 320mA's. (405-G-1)

IgorT said:

After i find a power level where degradation speed is equal or similar to that of the second 8x, i can then let the 12x cycle away until it pops, to determine the total lifetime at that power.

It should be a very thorough and informative experiment in the end. And this time it's going well so far!

Click to expand...

Glad to hear the third one's behaving, Igor! FWIW, if you (or Dave) decide to run another murder fund, I'm in! Just make sure you post a link in this (or Franco's) thread as not everyone's scouring the BR subforum on a regular basis.

I finally have some good news about 12x's!


I finished the first step of the experiment last night, and the results were encouraging!


Here is the Zero Hour plot of the diode i am testing:




It's a VERY high efficiency 12x diode, from the very top of the efficiency group.


I started by testing it at the same power as the second 8x was tested - 452mW. For this i set it to 315mA.

The testing was very slow, partially because i was very paranoid and re-plotted every hour of cycling and because i have to pause it at night, so i couldn't get nearly as many hours of cycling done as usually, but if it continues to go well, i will only replot it every hour of ON-Time during the following gradually increasing steps.


Anyway, the idea is to carefully measure degradation speed and compare it to 8x's, to get a feeling of how far the 12x's can actually go.


Here are the results of the first step:



This is 8 hourly re-plots of the diode, or 4 hours of ON-time.

Because of the higher number of re-plots, the line is a little "bendy" in comparison to the 8x's, but an average trend can be seen from it.


It shows, that at 452mW initial power, the 12x diode is degrading much slower than the second 8x did! In fact the 12x is almost degrading as slow as the first 8x at 356mW...

IF 12x's can degrade as far as 8x's before dying, it is possible the 12x would survive this power twice as long or more (around 400 hours perhaps? The first 8x is at 500h+)

It's impossible to tell for sure, but that wasn't the point of the first step - the total lifetime will only be measured at the last step...
One thing that can be said for sure is, that the 12x would survive the same power quite a bit longer than the second 8x did (195h)...


This is a very promissing result, so i started the second step today, testing the same current that was tested with the second 8x diode - 348mA.

I should be done with the second step sometime tomorrow. Once the degradation line is long enough for comparison again, i can keep increasing, until i find a power at which the 12x will degrade as fast as the second 8x.

Once i find that power, i can then let it cycle on normally, to see if same degradation speed means the same lifetime.


I have a feeling we will come to around 550mW or even a bit more before the degradation becomes too fast. Unlike the second 12x diode which was very weak, this one should be able to reach that power with a reasonable enough lifetime. But only time will tell.



Unfortunatelly, this kind of testing takes a lot more time, than the cycling i did with 8x's. Once i find the power where degradation speed equals that of the second 8x, i will finally be able to let it cycle away.

Until then, i have to do extremelly careful accurate re-plots, to make the relativelly short steps comparable. It can be hard, because i am comparing minute power differences, so the temperature has to be identical with every re-plot.

For that i thermal-epoxied a tiny high accuracy SMD thermistor on the diode back and record it's resistance together with each step of the PIV plotting. Even so (or rather because of it), i have to go back and forth several times, before i can be sure i made accurate enough measurements.


But it's working as intended. A few hours of ON-time seem to be enough to compare degradation speed from the angle of the line.



Anyway, this is it for now, i'll post the results of the second step tomorrow.

Igor;

I'm glad the 3rd 12X is lasing well.

It looks like the 3rd 12X diode is considerably tougher than the 8X diodes tested.

498mw/356mw is about 40% more power for very little degradation.

Do you think at this point,
we can say that the 12X is a different & more powerful diode than the 8X ??

LarryDFW

More good news!

The second step of testing at 348mA / 498mW is complete, and the results look promissing again. It looks like this 12x is a tough diode...


First, here is the second "Zero-Hour" plot:




I left it together with the first one, because the difference is so small it would not otherwise be noticable.

The new "Zero-Hour" plot is just the last re-plot from the previous step. As you can see, the difference between the diode before and after the first step is smaller than the difference from one 12x to another, so the following steps should hopefully not be influenced too much.

The first step may have used up approx 1% of the lifetime the diode would have had at that power, perhaps even less. If anything, it's as if another diode with a fractionally lower slope efficiency was tested during every following step.


The changes happening during the steps are so small that i sometimes find them hard to detect during re-plotting. The testing would definitely benefit from a constant temperature TEC setup, the re-plotting would go faster, but so far i am managing to keep the temperature consistent through the tests.



I was hoping i could do with only 3 hours of ON-time for the second step, but the diode started acting in a strange way.

But not in a bad way... Degradation slowed down so much, the resulting degradation plot didn't make much sense. I let it cycle for a total of 8 hours again, but it didn't clear things up.


Here are the results of Step 2 - 4 hours of ON-time at 348mA / 498mW:




As you can see, the new curve not only crosses the old one, but the power at 348mA actually returns to 100%. Degradation first slowed down and then it actually reversed!

It looks even more odd because the curve bends so much, compared to the relativelly straight lines of the 8x's. But the 8x's were plotted with much longer intervals, so their plots averaged out over the tested time. They could have been behaving in a similar fashion during the early hours, they definitelly changed the speed and even reversed once or twice later..


This makes a speed comparison impossible at this point, because no trend can be observed yet... But with the diode at 100% of it's initial power again, it can't be bad.


It seems to me, i can make another 50mW step up with this diode. If i left it to cycle for 8h straight before replotting, i would think no degradation took place at all during the last 4h ON-time...



I would very much like to spread out the re-plotting intervals a bit and speed up the testing, but since i'm increasing the power with every step, i feel like i have to keep a very close eye on the diode.

I guess i'll see what happens after the first two re-plots of the next step at 550mW (approx 385mA). If we are lucky, it might not even be the final step...

I was getting ready to start the third step of the experiment, but instead of using the last re-plot from the last step for the new "Zero-Hour" plot, i decided to test again.

Strangelly i got slightly different results this time. All that happened in between was, that i let the diode rest overnight. Everything else was the same.


I think i must have gone back and forth some 15 times before i was happy with the accuracy of the plot.


I corrected the data of the last Step 2 replot, and inserted it into the degradation speed graph.


Here is the corrected Step 2 degradation curve:




The 4h result was identical to the 3h result.


At least now the 348mA / 498mW curve makes more sense, and shows a general direction, but degradation still appears slower than it did at 315mA / 452mW.

It actually looks slower than the degradation of the first 8x at 356mW, if that's even possible.




In any case, i started Step 3 of the testing @ 385mA, where the diode produces 550mW.
If 12x's degrade even slightly similar to 8x's, the diode should keep up.

After a few more hours of cycling, we shall see how much degradation increased, but it's possible it might not even become as fast as it was with the second 8x just yet.

Good stuff Igor...

Thanks for all your hard work!

Igor;

So, actually @ 8 hours of run time ....

the diode degraded ...
1.2% the 1st 4 hrs @ 452mw
+ 0.6% the 2nd 4hrs @ 498mw ....

= 1.8% total degradation @ 8 hrs.

Looks like good power maintenance so far.

LarryDFW

I completed the second two hours of Step 3 today, at 385mA / 551mW. The diode is holding up well, but i realized some new things about how they work.


First, here is the Step 3 "Zero-Hour" plot:




Again, only a very small difference from before...



Degradation Speed Comparison @ 385mA / 551mW:




I made the plot linear from 0 to 4h of Step 3, because the differences in between were smaller than i could measure, no matter how accuratelly i tried to match the temperature and zero-in the meter...


The degradation at this point is at it's slowest so far, even tho the power is now 100mW higher than during the first step.
Instead of speeding up, the degradation is slowing down with every next step of the test.



Now we already know that degradation is fastest at the start and then slows down, but i was expecting it would start fast again with each higher power level.

But it seems that's not how diodes work. Apparently there is such a thing as a "burn-in effect", and after the degradation slows down, it will remain slower even if the power is increased...

I was expecting to see the slope get steeper with every step, but i'm getting the opposite results. During the last step i could barelly measure any difference at all.



It looks like even tho the difference between this diode before and after each step in terms of efficiency and lifetime is smaller than the difference from one 12x to another, the simple fact that it already ran for a few hours beforehand affects the degradation of the following steps.



Now this is a problem, because as of this moment, i have practically no indication of how fast the diode is actually degrading, nothing that could be compared to the 8x's, to figure out how much further it is safe to go.

This means, that a gradually increasing step by step approach can't really help figure out at which point degradation becomes too fast, since the steps can not even be compared to each other.



In trying to make some sense of it, i added the three degradation plots into one, as if only a single power had been tested.


This is the combined degradation plot:




In this plot, the numbers on the left don't really have a meaning, but there is one thing i am sure of:
- IF the power was left the same since the first step and until now (452mW), the second and third part of the curve would be almost the same, except sligtly slower dropping.

From this point of view, degradation at that power seems to be even slower than that of an 8x at 356mW! It slows down sooner and doesn't seem to want to drop down that far.




In any case, i'll repeat the last re-plot a couple times more to see if i got it accurate enough, and i need to think about this a little, but then i'll have to decide what to do next.

Do i go even higher, or do i test the total lifetime here?

Right now it feels like i'm flying blind again, so i would much rather err on the side of caution, than go too far, especially nearing the currents where some 12x's start dying...

I am loving all of this op:

IgorT you're like the Doc on back to the future. I always looked up to that guy

Igor;

It looks as if the degradation is less than the 1st 8X during the first 12 hours.

I added some 4-hour degradation boxes to Igor's graph:


Less degradation implies a better diode with less internal imperfections.

I would vote to leave it at 551mw.

LarryDFW