LEDs
# Resistors
Which resistor should I use? When in doubt use 220 ohm. Otherwise, these are common resistor values:
| LED Color | 3.3V | 3.7V | 5V | 6V | 9V | 12V |
|---|---|---|---|---|---|---|
| AMBER 2.1V, 20mA | 68 Ohm | 82 Ohm | 150 Ohm | 220 Ohm | 390 Ohm | 560 Ohm |
| BLUE 3.2V, 20mA | 5.6 Ohm | 27 Ohm | 100 Ohm | 150 Ohm | 330 Ohm | 470 Ohm |
| GREEN 2.1V, 20mA | 68 Ohm | 82 Ohm | 150 Ohm | 220 Ohm | 390 Ohm | 560 Ohm |
| ORANGE 2V, 20mA | 68 Ohm | 100 Ohm | 180 Ohm | 220 Ohm | 390 Ohm | 560 Ohm |
| PINK 3.2V, 20mA | 5.6 Ohm | 27 Ohm | 100 Ohm | 150 Ohm | 330 Ohm | 470 Ohm |
| PURPLE 3.2V, 20mA | 5.6 Ohm | 27 Ohm | 100 Ohm | 150 Ohm | 330 Ohm | 470 Ohm |
| RED 1.8V, 20mA | 82 Ohm | 100 Ohm | 180 Ohm | 220 Ohm | 390 Ohm | 560 Ohm |
| WHITE 3.2V, 20mA | 5.6 Ohm | 27 Ohm | 100 Ohm | 150 Ohm | 330 Ohm | 470 Ohm |
| YELLOW 2V, 20mA | 68 Ohm | 100 Ohm | 180 Ohm | 220 Ohm | 390 Ohm | 560 Ohm |
Ohms Law: v = ir
1 red LED on 5v circuit
r = (5.0 - 1.8) / 0.02
160.0
3 blue LEDs in parallel on 5v circuit
r = (5.0 - 3.2) / (3 * 0.02)
30.000000000000004