An LED series resistor is a component used in LED circuits to limit the current flowing through the LED. It's crucial for protecting the LED from excessive current, which could damage or destroy the LED.
The Formula
The formula to calculate the required resistor value is:
\[ R = \frac{V_s - V_f}{I_f} \]
Where:
\(R\) is the resistor value in ohms (Ω)
\(V_s\) is the supply voltage in volts (V)
\(V_f\) is the LED forward voltage in volts (V)
\(I_f\) is the LED forward current in amperes (A)
Calculation Steps
Determine the supply voltage (\(V_s\)) of your power source.
Find the forward voltage (\(V_f\)) of your LED from its datasheet.
Identify the recommended forward current (\(I_f\)) for your LED from its datasheet.
Subtract the LED forward voltage from the supply voltage.
Divide the result by the forward current (in amperes).
The result is the required resistor value in ohms.
Example
Let's calculate the series resistor for an LED with these parameters: