IgorT
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I did some thinking and tried to see if i could interpret the available data in any useful way that would help, but i'm afraid the only way to really tell for sure how safe a certain power is, is to actually cycle the diode to death at that power.
Because of the way degradation speed is changing, it doesn't seem possible using it as a gauge, at least not reliably enough.
After i saw the first 4 hours of degradation, i expected the following steps to look something like this:
In this graph, i used actual data, but i multiplied the degradation of every step with that of the steps before it.
I thought it might provide a sort of "worst case scenario", but after seeing it, i don't think it looks right. I believe the steps would have to be further spread appart for this to be correct.
It could be close, but the ratios between the Po increase and the degradation difference don't seem correct,
But if the previous steps were not influencing the following ones, and the plots would look like this, i'd probably take it to mean it is possible to go even further - approximatelly until the slope was as steep as with the second 8x Murder Candidate.
The only thing possible to extrapolate somewhat accuratelly is, what the degradation would look like if the diode was left at the initial power of 452mW.
I posted this before (Combined Degradation), but only a short plot up to 12h, here is the full one showing almost the full life of both 8x's:
The encouraging thing here is, the combined 12x plot seems to indicate, that if left at 315mA/452mW the 12x would outlive even the first tested 8x (300mA/356mW), which is still alive at 500h+!
At a slightly higher current and a much higher power, the 12x would most likelly live longer (as long as they degrade even slightly similarly).
I was thinking about the possibilities after seeing the effect of 12x efficiency on the power they can deliver - what if the 12x diodes were increased in their power rating mostly by increasing the efficiency? Perhaps the manufacturer somehow created a diode that can't necessarily survive much higher currents, but can still deliver a higher power reliably, because of it's higher efficiency...
Normally, a higher power diode would need more current to reach higher powers, but would be able to survive them, here we have diodes that are significantly higher in efficiency than 8x's on average, and deliver higher powers at the same currents.
If so, we might be nearing the limits of the diode at almost 400mA...
A while ago i was calculating, that on average 12x's should be able to survive ~580mW for as long as 8x's survive 450mW, which was 195h in the second 8x test (if same ratio of overdriving means the "same" lifetime)..
If the available 12x degradation data isn't too far off, that might actually be close. It's even possible that this particular diode would live longer, since the tested 8x was a low efficiency one.
Until recently, i thought that the power the diode produces matters much more than the current required to produce it (since it's their own light output diodes have to withstand), but i only thought so because the 8x's impressed me that much.
It now seems quite possible higher efficiency 8x's would survive same powers even longer, due to the lower currents required.
I assumed this ever since PHR times, and i used it for diode selection with GGWs as well with good results. It definitelly seems to be the case with 12x's, since obviously the lowest efficiency ones can't deliver 550mW even for seconds, while the diode tested now is doing fine so far (hopefully diodes like 12x #5 are a rare exception!).
In this case it would be possible to go even further with this diode with a good enough lifetime. Only problem is, it looks like there is no way to use the available data to figure out how far it is safe to go.
Also, we don't have a comparison with an 8x from the high end of the efficiency spectrum, they might very likelly be even better than the two tested ones, and very good 8x's could perhaps even outlive some weaker 12x's, when set to the same power, so a comparison between them is becoming very complicated... With 8x's we tested the worst-case scenario, here it's most likelly the opposite now that i'm testing a high efficiency 12x...
The only thing i can say for sure is, that so far degradation of the 12x was very small in comparison to 8x's, as can be seen in the second plot above. We barelly lost 2% total in the starting hours (all steps combined) and degradation is slowing down rapidly, while the first 8x to die lost almost 14% before finally giving up....
Both 8x's dropped almost linearly down to 93% before slowing down, while even the combined degradation plot of the 12x is slowing down much sooner (again, the combined plot is only "accurate" for what would have happened if left at ~450mW, it would drop a bit further before slowing down if tested at higher powers from the start)..
I'm just trying to figure out what to do next:
- Do i test this power (550mW @ 385mA) for total lifetime and risk getting "too many" hours?
- Or do i try to go higher up blind and risk losing another diode?
Normally i wouldn't say there is such a thing as too many hours, but ~200 is way more than required to declare a hobby pointer very reliable.
If i keep testing 550mW, there is a "risk" of getting even more than that. That's if we're lucky. And it would indicate it is safelly possible to go even further. It just wouldn't tell exactly how much further.
To be honest, i would rather risk getting too many hours, than too little. As i mentioned above, we are already at a power not all 12x's can deliver. It's quite possible, if not likelly, that we are testing the best-case scenario with this high efficiency diode.
Would everyone be OK, if i start cycling away at this power, or is there a big desire to go further?
I have some work to finish, then i'll check back for input on this.
I also need to read up on how far the other 12x's are being pushed recently and the results...
Because of the way degradation speed is changing, it doesn't seem possible using it as a gauge, at least not reliably enough.
After i saw the first 4 hours of degradation, i expected the following steps to look something like this:
In this graph, i used actual data, but i multiplied the degradation of every step with that of the steps before it.
I thought it might provide a sort of "worst case scenario", but after seeing it, i don't think it looks right. I believe the steps would have to be further spread appart for this to be correct.
It could be close, but the ratios between the Po increase and the degradation difference don't seem correct,
But if the previous steps were not influencing the following ones, and the plots would look like this, i'd probably take it to mean it is possible to go even further - approximatelly until the slope was as steep as with the second 8x Murder Candidate.
The only thing possible to extrapolate somewhat accuratelly is, what the degradation would look like if the diode was left at the initial power of 452mW.
I posted this before (Combined Degradation), but only a short plot up to 12h, here is the full one showing almost the full life of both 8x's:
The encouraging thing here is, the combined 12x plot seems to indicate, that if left at 315mA/452mW the 12x would outlive even the first tested 8x (300mA/356mW), which is still alive at 500h+!
At a slightly higher current and a much higher power, the 12x would most likelly live longer (as long as they degrade even slightly similarly).
I was thinking about the possibilities after seeing the effect of 12x efficiency on the power they can deliver - what if the 12x diodes were increased in their power rating mostly by increasing the efficiency? Perhaps the manufacturer somehow created a diode that can't necessarily survive much higher currents, but can still deliver a higher power reliably, because of it's higher efficiency...
Normally, a higher power diode would need more current to reach higher powers, but would be able to survive them, here we have diodes that are significantly higher in efficiency than 8x's on average, and deliver higher powers at the same currents.
If so, we might be nearing the limits of the diode at almost 400mA...
A while ago i was calculating, that on average 12x's should be able to survive ~580mW for as long as 8x's survive 450mW, which was 195h in the second 8x test (if same ratio of overdriving means the "same" lifetime)..
If the available 12x degradation data isn't too far off, that might actually be close. It's even possible that this particular diode would live longer, since the tested 8x was a low efficiency one.
Until recently, i thought that the power the diode produces matters much more than the current required to produce it (since it's their own light output diodes have to withstand), but i only thought so because the 8x's impressed me that much.
It now seems quite possible higher efficiency 8x's would survive same powers even longer, due to the lower currents required.
I assumed this ever since PHR times, and i used it for diode selection with GGWs as well with good results. It definitelly seems to be the case with 12x's, since obviously the lowest efficiency ones can't deliver 550mW even for seconds, while the diode tested now is doing fine so far (hopefully diodes like 12x #5 are a rare exception!).
In this case it would be possible to go even further with this diode with a good enough lifetime. Only problem is, it looks like there is no way to use the available data to figure out how far it is safe to go.
Also, we don't have a comparison with an 8x from the high end of the efficiency spectrum, they might very likelly be even better than the two tested ones, and very good 8x's could perhaps even outlive some weaker 12x's, when set to the same power, so a comparison between them is becoming very complicated... With 8x's we tested the worst-case scenario, here it's most likelly the opposite now that i'm testing a high efficiency 12x...
The only thing i can say for sure is, that so far degradation of the 12x was very small in comparison to 8x's, as can be seen in the second plot above. We barelly lost 2% total in the starting hours (all steps combined) and degradation is slowing down rapidly, while the first 8x to die lost almost 14% before finally giving up....
Both 8x's dropped almost linearly down to 93% before slowing down, while even the combined degradation plot of the 12x is slowing down much sooner (again, the combined plot is only "accurate" for what would have happened if left at ~450mW, it would drop a bit further before slowing down if tested at higher powers from the start)..
I'm just trying to figure out what to do next:
- Do i test this power (550mW @ 385mA) for total lifetime and risk getting "too many" hours?
- Or do i try to go higher up blind and risk losing another diode?
Normally i wouldn't say there is such a thing as too many hours, but ~200 is way more than required to declare a hobby pointer very reliable.
If i keep testing 550mW, there is a "risk" of getting even more than that. That's if we're lucky. And it would indicate it is safelly possible to go even further. It just wouldn't tell exactly how much further.
To be honest, i would rather risk getting too many hours, than too little. As i mentioned above, we are already at a power not all 12x's can deliver. It's quite possible, if not likelly, that we are testing the best-case scenario with this high efficiency diode.
Would everyone be OK, if i start cycling away at this power, or is there a big desire to go further?
I have some work to finish, then i'll check back for input on this.
I also need to read up on how far the other 12x's are being pushed recently and the results...
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