PHR-803T batch testing.. Windowless 803Ts?

IgorT said:

Ok, i just made another laser from a diode, that did 95mW during the 109mA test (the freak did 98)..

I used a slightly lower current, in the hope, that it survives, and keeps on going.. I set it to 178mA, so i expected 160mW at most, especially since it tested lower before...

But this one is now doing 178mW! The freak did 175mW at 187mA! This diode is the real freak!  


I just hope it survives!

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Your the man!

Good luck.
Light some fireworks! Fun!

Laserrod said:

Your the man!

Good luck.
Light some fireworks! Fun!

Click to expand...

I could be wrong about this, but I doubt that Slovenians celebrate US Independence Day

Peace,
dave

;D

All the fun you're having with tons of diodes worth millions(to me :) and I'm waiting on my PHR diode for weeks now.....that's it , I'm going to the post office.Maybe it's there and I didn't get a notice for some reason. :-/

Where did you order them from? PXS-BOY? My first order from there arrived pretty quickly, but the second one took a while.


Anyway, i lowered the power of my second freak diode a little. I set the current to 168mA (10mA less), and now it's doing 171mW.. It was 10mA less than where the freak died from the start, but since it's not the current, that kills them, but the optical output, it was actually under more danger, since the power was higher at a lower current.

Now the current is 20mA less, than where the first freak died, but the power is only 3mW less. But i really don't want to go lower, than this.


This also means, a less efficient diode could easily survive a higher current. I'll set the weak one to 190mA.

And since their powers vary by so much, there might not be any simple max safe current guidelines. It's more likelly, that there would be a max safe power for these.

IgorT said:

And since their powers vary by so much, there might not be any simple max safe current guidelines. It's more likelly, that there would be a max safe power for these.

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There WILL be a simple, safe current guideline. It will just be conservative. Unfortunately, we have to kill a few more to know what that is.

Those of us willing to kill a diode, either to see what it will do or just for the power) will always enjoy higher outputs. We just take the chance that we will be replacing the diode

People who want or need their diode to last "forever", just don't get to see what their laser is capable of.

Peace,
dave

There's something else here too.. Light reflected from the lens back into the diode can help bring the optical power over what the diode can take and kill it.

With 405nm AR coated optics, the power will not only be higher, the AR coating will also make it safer, since reflections will be reduced to under 0.5%!


Unless you want to live with the same risk as now, in which case, you can push the output power by the percentage, that is currently lost in reflections.
This means, that whatever the increase from the Meredith will be, you could then increase the power by that same amount again! Imagine that!  

The low power diode, that i set to 191mA died after being left on for an hour (on purpose, to test what would happen).

It would seem, 190mA is too much for them, regardless of the optical output. It did work for a while, and it may have continued working for a long time, but not if left on for too long.


The heatsink preformed very well, and the diode wasn't hot. The entire laser body was just slightly warm, so it wasn't from heat.

I now have two diodes running at 169mA. One is putting out 168-171mW, the other 160-162mW....

After losing two diodes at 190mA, i don't want to go higher anymore.. But i will hook up another weak one to 170mA and let it run, to see what happens.

Thank you for posting those numbers. It looks like most of these diodes are good for 70-90mW @100mA.

I don't consider the variance to be extreme. I know with lower power diodes that a factor of 2 difference between power levels at a given current is common. The emitting part of the diode (P/N junction) is only a few nanometers thick, at the limits of manufacturing tolerance and control. Hence the need for APC supplies and sleds with trim pots so each diode can be adjusted.

Well, at 109mA, the differences are already quite big, almost 30mW. But they get bigger, with higher currents.

Higher power diodes are more consistent, but these were never designed to reach the powers they are reaching, so i guess you are right.

The two diodes running at 169mA are still working fine after a week now.. Sometimes i play with them for long enough, that i feel the laser getting slightly warm. And that takes a long time. I'm not even scared to turn them on anymore..  ;D


But i noticed something weird. The one that did 161-162mW at 169mA still measures the same.
But the one, that did 169mW at this same current, now does only 159mW! It's almost as if it gradually lost 10mW.. In between i measured it at 167mW and 164mW, yesterday it was 161mW, and now only 159. Some of this is probably due to ambient temperature, but that's maybe 2mW, and it'll be higher again in the evening. Oh, and the 169mW did go through more use in this time...


I noticed something similar before, when a diode did 113mW at 125mA, but when i measured all the lasers on the next day, i couldn't find it anymore. The highest power was 105m..  And the other powers didn't change, so it's not my meter.. It's as if the most efficient diodes lose some of this efficiency over time. In that case it happened over night, without any use in between.


Another strange thing is, that while the power was still 169mW, the beam of the 161mW looked a bit brighter. Now that they have the same power, the brightness difference is even more noticable! It's as if the wavelength was a little different. 

IgorT said:

Another strange thing is, that while the power was still 169mW, the beam of the 161mW looked a bit brighter. Now that they have the same power, the brightness difference is even more noticable!

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Hmm. That's odd... maybe it's because they're rated 405 +- 10nm.. maybe the 169mW one is just a lower wavelength one and is less visible to human eyes because of that... :-/

Ok, the diode, that was gradually dropping in power just died. Shortly before it died, the power actually dropped to 150mW....

I was actually scared to say, that they still work for the entire week, worried, that if i did, this would happen..  ;D



Scratch that. It was the driver. The regulator malfunctioned... That must also be the reason my 190mA diode died... And it's the reason the power was changing. When i put a new battery in, the current changed, and killed the diode. Need to replace the IC and the diode....

Looks like i didn't test the driver properly before using it...  I tested all of them with the entire input voltage range on a dummy load. All, that is, except for my own. Here i just checked if the current is correct.. :-[

IgorT said:

Ok, the diode, that was gradually dropping in power just died. Shortly before it died, the power actually dropped to 150mW....

I was actually scared to say, that they still work for the entire week, worried, that if i did, this would happen.. ;D

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I doubt that it had anything to do with "JuJu"

Someone else also observed the phenomenon of a diode gradually decreasing in output on its way to its failure. I can't remember who right now. With regard to the difference in apparent brightness, Pseudo may have something there. If the wavelength crossed a personal ability to see threshold, you would "see" the beams differently. I would think that the difference between 403nm vs. 410nm is perceivable for some.

Peace,
dave

Hehe, yeah, well, the mistery is solved, and it's good news.. It was not the diode being unable to take the current i set.. Not with the first freak, and not with the second one... It was the regulator. It crapped out, so the current was not what i set it to....

The diode dying immediatelly after a battery change was what reminded me of this possibility. I measured the Vfb, and sometimes it was correct, and other times it just jumped up. Then i raised the input voltage, and the Vfb went up by 50%! This means the current was 170mA + 50% which is what killed the diode! But it actually took this abuse for a long time!

This means i just have to replace the IC, and then i can again test higher currents!

Because this poor little diode survived a changing current for a week! Often it must have been higher, than what i thought i set it to! This also explains why the power was higher, than with the super freak.. It was the current, that was higher. And the diode just took it all!


I made a mistake, but it showed something interesting. The diodes are sturdier than i thought!
But i'm still a little sad for loosing such an amazing diode.. Should have tested the current after changing it.. I just calculated it, assuming that the regulator is good.



EDIT: Wait! After a diode dies it's not a diode anymore, and the Vf changes (drops)! That's why the current changed - the Vf of the diode was below the input voltage. Maybe there is nothing wrong with the driver, and it was just too much power..

Need to test on a dummy load. If the driver is ok, 170mA may not be safe either. Now i almost wish it was the driver..