How to Determine an LED's Polarity

by Contributor

LED stands for Light Emitting Diode. LEDs are made of a semiconductor that perfects light output. LEDs only burn out if the light goes over the current limit. LEDs have anodes and cathodes like many other diodes. There are a few ways to determine an LED's polarity.

Look for the flat spot on the edge of the LED. The flat spot is located on the cathode of the light. When a current passes through the LED, you see a specific color in this flat spot. The color indicates the amount of volts the LED uses.

Locate the anode on the LED. The anode is a positive terminal for an electrical device. The cathode is a negative terminal for an electrical device. If you see the anode, it is generally larger than the cathode. It also emits a faint color.

Find the metal strip inside the LED. This strip may be hard to see. It is usually closest to the anode of the LED light. When the current passes through the LED, this metal strip emits a faint color.

Know what each color represents. A red color indicates the LED is 1.2 volts. A yellow glow represents 1.4 volts. A green hue indicates the LED runs on 1.7 volts. A blue light means the LED voltage is 2.8.


  • check Polarity testers for LED lights are under development, however none are currently on the market.