2x NICHIAs NDG7475 520nm 1W COOLING TEST

[jors]

Hi!!
Ok, so here is a cooling test for 2x NICHIA 1W green. Both greens are side to 2x 9mm 445 (NDB7875). This is for building 8W PJ.

-greens are running in series at 1,7A, delivering 2,15W
-blues are running in series at 2A delivering 5W
-All 4 diodes in DAVE's 9mm copper mounts.

Baseplate is 200x250x40mm (fins) cooled with fans. I would avoid going to a larger baseplate if possible, so taking this into account:

-Initially, I tec'ed all 4 diodes at 20ºC for better life expectance, but this induces LOTS of heat to baseplate and it reach easily 35-42ºC (very hot at touch!). Im afraid this temp baseplate could affect negatively to scanners, drivers, PSU and so on....

So, after that, I decided to passively cooling greens and blues and only tec reds at 14ºC (two P73 overdrived 1W each), in order to maintain a lower temp on baseplate:

On this 2nd setup, baseplate (so also greens and blues) is stable at 29ºC after 10minutes (so not 40ºC when tec'ed!!) . Greens power is also stable delivering 2,15W. Ambient temp is 25ºC aprox.
As the greens are stable in power at 2,15W, I suppose they are running confortable at 29ºC ?¿ On NICHIA NDG7475 datasheet max diode working temp is 50ºC, so 29-30ºC should be ok.
Baseplate is cooled by two arctic F12 (57 cfm /each)

So, what do you think guys?

-is ok passively cooling greens at 29-30ºC...or perhaps... I'm pushing them so hard?
-other option could be tec all (like initially I did), but if so, I need a larger baseplate than 200x250x40 (fins) in order to achieve less than 35-40ºC on baseplate.
I would avoid this last option, cause I want the projector small and portable.
-Maybe another option is tec all but increasing the cfm on fans to +200 cfm, but if so, the PJ is going to be VERY noisy and maybe not a significant gain on temp baseplate.

Please, what are your thoughts?

Thanks for watching!!
Jordi

[norty303]

Thanks for doing this. Its really helped confirm the decision to go with passive cooling for our 6x 520 and 6x 462 modules was the right choice.
If you haven't already done it, add heatsink underneath your baseplate to be cooled by the fans. As much surface area and good thermal interfaces are going to be your friends here.

Also remember that your 10 min test (CW presumably?) is totally NOT characteristic of a laser show where the modules will be off for as much time as they're on with modulation applied. You have effectively tested a worse case scenario.

Perhaps try the test again but connected to a DAC running through some typical beam shows, graphic shows, etc and see what the temps look like then. This is how you'll be using the modules, not FULL ON all the time

[jors]

Many Thanks Norty )
Yes, CW by 5v on analog with PSU, and yes, this is a worse case scenario, but on the other hand, I'm at 25ºC ambient temp, and PJ should also work up to 35ºC ambient.
I have 2 fans below fins heatsink (2 arctic F12). This is heatsink alone, so I suppose overall temp will be lower when all is screwed on aluminum case PJ ie case also dissipates some heat.

I've done another test now: I am tecing all diodes at 23ºC instead 20ºC, but baseplate rises 35ºC
So the question is:
keep diodes working comfortable at 23ºC and baseplate at 35ºC-38ºC (affecting drivers, scanners...) VS. passive cooling (diodes and baseplate at 30º, except teced reds at 14ºC) ??
what do you think?
thanks!

[planters]

Good tests and the results make sense. The difference of a few degrees in the operating temperature of these GaN diodes is not important. TECs are so inefficient that only when they are cooling very small thermal loads like a couple of red diodes (which are the most responsive to cooling improvements) is the substantial increase in the heat load to the projector, justified.

You are not over driving those diodes and using much larger and louder fans is not a good idea. You will be better off to spend your effort on the optical challenges of combining and manipulating the beams to produce the finest output.

[jors]

Thanks Eric,
Well, this is my last test... greens & blues passively and 2 P73 tec'ed at 14ºC and pushed at 1W each.
On this setup, due hard cooling on mitsus, baseplate goes again up to 36ºC too much?
(greens are delivering 2W at 36ºC instead 2,15W at 30ºC baseplate when mitsus were off)

[jors]

I have no DAC here to test, but, maybe with DAC diodes are powered equal than 50% (2,5V) with CW?
any ideas in order to test now?
Many thanks!

Thanks for doing this. Its really helped confirm the decision to go with passive cooling for our 6x 520 and 6x 462 modules was the right choice.
If you haven't already done it, add heatsink underneath your baseplate to be cooled by the fans. As much surface area and good thermal interfaces are going to be your friends here.

Also remember that your 10 min test (CW presumably?) is totally NOT characteristic of a laser show where the modules will be off for as much time as they're on with modulation applied. You have effectively tested a worse case scenario.

Perhaps try the test again but connected to a DAC running through some typical beam shows, graphic shows, etc and see what the temps look like then. This is how you'll be using the modules, not FULL ON all the time

[planters]

Two P73's operating at 14C should not produce enough thermal load to heat a base plate from ambient to 36 degrees unless your fans are operating very poorly. Maybe the heat sink area on the base plate is too small. If I were doing this and I was not going to go my usual deep cooling of the red diodes then I would load the underside of the base plate with well mounted heat sinks with fine fins, use high volume/ low velocity fans to cover the heat sinks. Direct the fans to draw outside (cooler) air at the fins and dump the laser/power supply and even the fan motor heat outside. Then I would use no TECS at all.

[jors]

Thanks Eric,
Well baseplate is a heat-sink with fins (250x200x40), so is small. Also I'm cooling with 2 Arctic F12 fans, which are very silent (for computer case), but 'only' 57 cfm /each. Also heatsink is not attached to case yet. For all these reasons I think baseplate goes 36ºC with teced mitsus at 14ºC and blues & greens passively. Also, I am CW modulation at 5V all diodes with a lab PSU.
However, as Norty pointed, I finally removed a DAC from another projector and tested some shows.....what a great improvement!!! baseplate with DAC is at 30ºC instead 36ºC , so I was really pushing diodes very hard with CW at 5V.
About not using TEC as you point, what about mitsus? I can't push them at 1W/each at ambient, so need to cool them at 14ºC...is that correct?

[planters]

You could probably run them at 1W at 30C seeing that this 1W is a CW reading. However, you can expect approx. 1% more power/ degree C of cooling and so this depends on what "ambient" means. Or, you might consider actually isolating them from the base thermally and cooling them directly with a small fan. I think your initial color ratios are a little blue heavy anyway and you might want to think about a four diode red set up with each diode run at say 800mW with a conservative 3W out. This allows you to ignore these thermal issues, have additional red power and move on to the optics issues.

[jors]

Thanks again Eric for your help.
Well, the idea to tec P73s is after reading post #25 from Adam (Buffo):
http://www.photonlexicon.com/forums/...-and-Mitsu-P73
My P73s are mounted on Dave mounts, and they will be run at 30-33C if passively cooled so I'm afraid I could fry them at 800mw at this temp, as Buffo point. 30-33C baseplate is at 25C ambient temp, sure will be higher if ambient temp is say..30C..perhaps baseplate at 38
But you say, I can run them passively... so a bit confused here,...do you agree with Buffo comments?
thanks!

You could probably run them at 1W at 30C seeing that this 1W is a CW reading. However, you can expect approx. 1% more power/ degree C of cooling and so this depends on what "ambient" means. Or, you might consider actually isolating them from the base thermally and cooling them directly with a small fan. I think your initial color ratios are a little blue heavy anyway and you might want to think about a four diode red set up with each diode run at say 800mW with a conservative 3W out. This allows you to ignore these thermal issues, have additional red power and move on to the optics issues.