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### Topic: led panel getting way hot... (Read 1 time)previous topic - next topic

#### frostin

##### Nov 08, 2009, 10:04 pm
http://www.flickr.com/photos/44464493@N02/4086575677/

#1
?

#### Nachtwind

#2
##### Nov 08, 2009, 11:26 pm
judging from your topic and the pic: Do you want to say the LEDs would get that hot that the solder melts?

#### frostin

#3
##### Nov 08, 2009, 11:43 pm
the back of the panel gets pretty hot... this normal? im running about 10-11v 1500 ma

#### PaulS

#4
##### Nov 09, 2009, 12:19 am
10 volts at 1.5 amps is 15 watts. A 15 watt light bulb will get pretty warm.
The art of getting good answers lies in asking good questions.

#### Grumpy_Mike

#5
##### Nov 09, 2009, 08:01 pm
Without seeing the schematic it is impossible to tell how hot it should get. Post one and we will see if there is anything wrong.

#### frostin

#6
##### Nov 11, 2009, 11:14 amLast Edit: Nov 11, 2009, 11:21 am by frostin Reason: 1
http://www.instructables.com/id/SWO38NYFTO53XNF/

exept im using 120 ohm resistors

the resistors get pretty warm!

i have a 12v power supply but when i put volt meter on it its like 13ish... im going to have to regulate the voltage its an ac to dc 12v 1500 ma... how come its showing lil over 13?

anyways if I get around 10-11v they get warm but not hot...
am thinking of using a lm317t to drop it down 2.5v...

i run power to each resistor since im running 3 leds in seriers
then after the resistor i put 3 leds and tie them to ground..

confused...

#### Grumpy_Mike

#7
##### Nov 12, 2009, 11:14 am
Assuming the forward volt drop across the LED is 3.4V (check this) then the resistor is taking 13 - 3*(3.4) = 2.8V
So that means each resistor is dissipating 65mW with a total of 28 resistors that gives 1.8W of pure heat. This is not including any heat you get from the LED. So yes it will get hot.

Quote
how come its showing lil over 13?

because it is a liner power supply and the regulation on those is not very good. You will find that when you draw the rated current from it it will drop down to 12V.
Yes if you can drop the voltage it will be better but the thing dropping the voltage will then generate that heat so the total heat dissipation will remain the same. It's just the board will not get as hot.

#### frostin

#8
##### Nov 12, 2009, 07:56 pm
many thankS will post pics when done with it

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