LED Indicator for DIY power supply

bertus

Joined Apr 5, 2008
20,108
Hello,

That looks like a blue led, those will have a forward voltage of about 3 Volts.
When used on a 12 Volts supply, a resistor is needed.
I assume the Vled is 3 Volts and a current of 20 mA is needed.
You can calculate the resistors like this:
R = (Vsupply - Vled) / I led = (12 - 3) / 0.02 = 450 Ohm.
The closest in the E12 series will be 470 Ohms.

Bertus
 
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