8.5 Choosing the Right Resistor for an LED
To calculate the resistor for an LED, we need to know the forward voltage for the LED, LEDs are
different from the resistors, we need to limit the current passing through it because it does not work on
Ohm’s law.
We need to know the voltage around the LED. Usually, a 5 mm LED needs 15 - 30 mA to be in
good lighting. After knowing the forward voltage for the LED, it is easy to calculate the resistance.
To measure the forward voltage we connect a high value resistor, so we ensure that a low current
will pass through the LED.
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Mastering the Art of Measurement (DM301B Digital Multimeter) r.01 www.plusivo.com
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