Electronics
Concepts: Voltage, current, resistance.
Ohm’s Law
$ V = I \cdot R $
where:
- V is the voltage (in volts),
- I is the current (in amperes),
- R is the resistance (in ohms).
$$ R = \frac{V_{\text{source}} - V_f}{I_f} = \frac{5 \, \text{V} - 2.0 \, \text{V}}{0.020 \, \text{A}} = \frac{3.0 \, \text{V}}{0.020 \, \text{A}} = 150 \, \Omega $$
For a 5 Volt Supply, just choose a resistor greater than 150 Ohms. the larger the R, the dimmer the LED will be.
LED Voltage:
- WGB LED: 3.0V to 3.2V (average: 3.1V)
- RY LED: 2.0V to 2.2V (average: 2.1V)
| Supply Voltage (V) | WGB LED Resistor (ohms) | RY LED Resistor (ohms) |
|---|---|---|
| 5 | 95 | 145 |
| 10 | 226 | 390 |
| 15 | 357 | 635 |
| 20 | 488 | 880 |