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Topic: resistor heat (Read 762 times) previous topic - next topic


Conventional resistors of 1/4, 1/2, 1, 2 watts run HOT at their maximum rating.. As I recall you can not keep you finger on them for more than a couple of seconds.

1/4 watt in a 1 watt rated resistor will feel more than just warm..

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You could perhaps find 10w power resistors which are meant to dissapate heat faster



A 12 V source , 270 ohms getting hot, and a LED....All the resistors are hot ? 270 ohm is a bit low for a 12 V circuit. I will choose a 910 ohms or 1000 ohms. That will be a 10 mA across the resistors and the LED, assuming the LED is 2 V drop type.  What purpose the LED's have ? Just to show a LED on , 10  mA is enough.  I have a DIY AM Radio and the power indicator is a LED. it have a 680 ohms , the V is about 13.5 V. The resistor is a 1/4 W. I just touch it... just a "little" warm. That it. So if your resistors are THAT hot, well something is "wrong" here....

My 2 cents

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