What kind of resistor should I use with an LED?

The important considerations when you’re selecting a current-limiting resistor are the value in Ohms and the power rating in Watts. The LED resistor calculator can help you determine both values for your application. The resistance determines the current that will flow to your LED, while the power dissipation is largely a function of the difference between your LED’s forward voltage and your available supply voltage. Resistors don’t have polarity like LEDs, so orientation doesn’t matter, and the current-limiting resistor can be installed anywhere in the series circuit.

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