working out heat production

Thread Starter

ktnch

Joined Jan 19, 2011
22
Hi guys, How do i work out heat produced by an led so i can find a heatsink

the leds 1700ma max @ 36v max


cheers

kev
 

someonesdad

Joined Jul 7, 2009
1,583
Voltage times current is power; thus, 1.7 A times 36 volts gives you the power in watts: 61 watts. That's a lot of power to remove from an LED -- are you sure you have your numbers right?
 

Thread Starter

ktnch

Joined Jan 19, 2011
22
Oh yes its a big bugga lol around 30mm square going to get 5 or 6 of them for a big reef tank

Trying to find some big heatsinks
 

marshallf3

Joined Jul 26, 2010
2,358
Even the old mom & pop PC stores may have a pile of small heat sinks with fans that they can't sell since they're now to small for the current processors, always worth a call. 3 fans in seres = 36V

An alternate is to use those aluminum door thresholds from a home improvement stores but watch their temperature.
 

tracecom

Joined Apr 16, 2010
3,944
Oh yes its a big bugga lol around 30mm square going to get 5 or 6 of them for a big reef tank

Trying to find some big heatsinks
It would be "cool" if you could use the water in the tank to cool the led's and the heat from the led's to heat the tank. If the led's were mounted to a piece of metal that dipped in the water...OK, I don't know anything about reef tanks; it just seemed like a green idea. :)
 

mcgyvr

Joined Oct 15, 2009
5,394
I doubt that is the correct specs for the LED in this case.
But you need the current level that you will be supplying to the LEDs x the forward voltage of the LED.
Assuming natural convection..
Example.. Cree XR-E with a forward voltage of 3V run at 700mA is .7 x 3V=2.31 Watts
Then you need to calculate the thermal resistance from LED junction to air (must include all interfaces..ex..LED junction to circuit board to thermal compound to heat sink to air.

And cooling/heating via the reef tank water has been done and is a decent idea ( I like it anyways).. However finding the proper materials that will not contaminate/leach into your tank killing the inhabitants nor corrode when exposed to salt water is a different story (well from a cost standpoint anyways). Titanium,etc.. ain't cheap
 

Thread Starter

ktnch

Joined Jan 19, 2011
22
Was thinking of water cooling but all metal and alloy is out of the question as its a marine tank could use the flex pipe

Its a marine tank 5ftx3ftx3ft see attached

Was running 2 x 150w halide bulbs but the magnetic ballasts were 1.8amp each @ 240v so was pulling 864 watts for two 150w bulbs didnt beleive it so got a wattmeter and was just about spot on, So bought an elec halide ballast and that pulls 0.7 amp each 336 watts much better



Going to order 6 of these heatsinks as i am getting 6 of the high power leds also putting 10 x 10w blue leds on the same heatsinks

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370472485909&ssPageName=STRK:MEWAX:IT


This is the led just for the none believers of the current and voltage

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270693110582&ssPageName=STRK:MEWNX:IT

50W 10000K High Power 4000LM LED Panel for Aquarium

Description:

* Color Temperature: 10000K cool white
* LED chips: Epileds EP-B3838B-A3 38*38mil
* DC Forward Voltage (VF): 32-36V DC
* DC Forward Current (IF): 1700mA Max
* Viewing Angle: 120 Degree
* Intensity Luminous (Iv): 4000LM
* Life span 30000 hours guarantee




 

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