Pulled out the IR camera to check temperature. This is running at approx 500ma total, or 125ma per LED. I let it warm up for 5+ minutes.
I placed scotch tape pieces on the aluminum so I could read an accurate temp. Otherwise, it just reads whatever is reflected off the aluminum.
Looking online, I see some derating charts for LEDs like this one from here (
http://www.mouser.com/applications/lighting-derating/):
Quote:
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Graph 1 shows an ideal LED current verses temperature relationship. Up to the manufacturer’s specified maximum operating temperature, the LED current remains constant. As the LED temperature exceeds the limit, the current and therefore the power is reduced and the LED dimmed to protect it from overheating. This curve is called a “Derating Curve” and keeps the LED working within its safe power dissipation limits. The 55°C “threshold” temperature in the above graph is the base plate or heat sink temperature – the LED itself will be typically 15°C warmer (i.e. 70°C) and the internal junction temperature close to 35°C warmer (i.e. 90°C). Thus 55°C is thus a safe full power limit, although it could be increased to a maximum of 65°C for high performance LED lamps.
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That implies that I can run up to about 55c at the LED base-plate without impacting performance.