Created: General information on using LEDs in electric circuits

Updated: 03 September 2023

LED is short for Light Emitting Diode


LED’s are represented with the Diode symbol with 2 arrows added:

LED Symbol


When connecting an LED in a circuit it must be connected:

  1. in series with a resistor
  2. in the correct direction

Below is an example circuit:

Circuit example

Series Resistor

The resistor to be connected with a specific LED can be calculated by:

$$ R_{LED} = \frac{V_{source} - V_{LED}}{I_{LED}} $$


  • $V_{source}$ is the voltage over the LED and Resistor
  • $V_{LED}$ is the LED’s required voltage
  • $I_{LED}$ is the current required across the LED


The direction that an LED is connected in is very important, both for functioning purposes as well as to ensure the LED is not damaged.

Below is a diagram showing the direction for LED connection, from Starting Electronics

LED Connection Direction