Electronics

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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.

Simple Parallel LED Circuit

Simple Series LED Circuit