Hi, i'm new to THP and I have a question. I built an LED grow light, and I was wondering if my heatsink was too small. It is 12x3.5 inches with 24 "3" watt leds on it (it only uses ~45 watts). I have a 4.75 inch 12 volt fan on top of it (don't know the rpm). It never gets hot even during long use (I do have thermal paste under the leds) so i'm thinking it's ok. Any answers would be nice, thanks!
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Heatsink Question
- Thread starter Jalabenjo
- Start date
Way more info needed in heat sink design but the short answer is if the aluminum (it is aluminum right?) is not too hot to touch your fine as long as the LED's are securely mounted with a good connection. When we design them you have to choose the correct alloy, do a ton of calc's along with color of anodizing, type of anodizing etc, etc... Gets boring quickly.
"24 "3" watt leds on it (it only uses ~45 watts)" I get 72 watts, how are you driving them?
"24 "3" watt leds on it (it only uses ~45 watts)" I get 72 watts, how are you driving them?
to T.H.P. ! 
Ok, to answer the questions, you can barely feel the heat on the heatsink when you touch it, it is made out of aluminum U channel, and the "3" watts is the measurement given by the manufacturer, the true watts (V*A) add up to ~45. I'm just using a driver that I got on amazon to run them.
juanitos said:
Say watt? Sorry, I don't mean to be smart arse but what exactly do you mean by that? It does take a lower voltage to achieve the correct forward biasing on red die than blue (won't get into the various doping specs here). But wattage is wattage. It does take fewer volts to forward bias a red or orange etc LED than blue, green, UV etc so if using say a 3w driver to bias blue or red the same current flow across the junction will occur, just use less voltage to achieve it.
