jtr1962
Flashaholic
Re: .·´¯`·-> !! 4000+ Lumen Test & BridgeLux LED Review!! <-·´¯`·.
Very nice testing although I have a few questions/comments about your peltier setup:
1) First off, that heat sink is way too small for a 40mm peltier, even if it's one of the 3 amp ones. If you're going to use a microprocessor heatsink, then the ones for the P4 or the recent multicore processors work best.
2) Did you raise the heat sink so that the fan can still suck in air to cool the heat sink?
3) What is the maximum current rating of your peltier?
4) What was the current you were actually running it at? This is important because the way to get the most cooling from a given peltier/heatsink arrangement is to increase the current in small intervals, wait until the cold side temperature stabilizes (can take 10 minutes or more), increase current again, measure temperature, etc. You stop when the temperature starts increasing, and drop the current back to the previous increment. For an 8.5A peltier running with one of my P4 heatsinks I found that 5.8 amps is the maximum. At that current the temperature of the cold plate, when well insulated, stabilizes at around 48° to 51° C under room temperature. This is usually -30°C, give or take a few degrees, depending upon the temperature in my workshop.
5) You really should have had an aluminum plate on the cold side of the peltier so that all of the thermocouples would be cooling the LED. And it should have been bolted to the heatsink with stainless steel screws and fiber insulating washers, sandwiching the peltier in between the plate and the heatsink. See here (scroll to bottom). Unless mounted properly, you'll get poor performance from peltiers.
Don't mean to be overly critical but I made these comments because it seems like the temperature of the LED shouldn't have gone as high as it did. In fact, just mounting the LED on a decent air-cooled P4 heatsink without a peltier it should have gone no higher than about 40° to 45°C. Temps with a peltier might be better or worse depending upon the peltier's rating. In general if you're cooling a load of ~77 watts like that LED then you'll need a peltier with Qmax of at least twice that. Just for reference Qmax of a typical 8.5 amp peltier is around 70 to 75 watts.
Very nice testing although I have a few questions/comments about your peltier setup:
1) First off, that heat sink is way too small for a 40mm peltier, even if it's one of the 3 amp ones. If you're going to use a microprocessor heatsink, then the ones for the P4 or the recent multicore processors work best.
2) Did you raise the heat sink so that the fan can still suck in air to cool the heat sink?
3) What is the maximum current rating of your peltier?
4) What was the current you were actually running it at? This is important because the way to get the most cooling from a given peltier/heatsink arrangement is to increase the current in small intervals, wait until the cold side temperature stabilizes (can take 10 minutes or more), increase current again, measure temperature, etc. You stop when the temperature starts increasing, and drop the current back to the previous increment. For an 8.5A peltier running with one of my P4 heatsinks I found that 5.8 amps is the maximum. At that current the temperature of the cold plate, when well insulated, stabilizes at around 48° to 51° C under room temperature. This is usually -30°C, give or take a few degrees, depending upon the temperature in my workshop.
5) You really should have had an aluminum plate on the cold side of the peltier so that all of the thermocouples would be cooling the LED. And it should have been bolted to the heatsink with stainless steel screws and fiber insulating washers, sandwiching the peltier in between the plate and the heatsink. See here (scroll to bottom). Unless mounted properly, you'll get poor performance from peltiers.
Don't mean to be overly critical but I made these comments because it seems like the temperature of the LED shouldn't have gone as high as it did. In fact, just mounting the LED on a decent air-cooled P4 heatsink without a peltier it should have gone no higher than about 40° to 45°C. Temps with a peltier might be better or worse depending upon the peltier's rating. In general if you're cooling a load of ~77 watts like that LED then you'll need a peltier with Qmax of at least twice that. Just for reference Qmax of a typical 8.5 amp peltier is around 70 to 75 watts.
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