// LAB 02 · INTERACTIVE
LED resistor calculator
Pick a supply, an LED and a current — get the right resistor (and see what happens without one).
⚡ POWERING UP THE LAB…
// HOW IT WORKS
The idea in 30 seconds
- R = (supply voltage − LED forward voltage) ÷ current.
- Typical forward voltages: red ≈ 2.0 V, yellow ≈ 2.1 V, green ≈ 2.2 V, blue and white ≈ 3.2 V (check your datasheet).
- Most 5 mm LEDs are happy at 10–20 mA. Always pick the next standard (E12) value up.
- Check the resistor's heat: P = I² × R. Under 0.125 W, a common ¼ W resistor is fine.
Watch the lessons
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