How to test LED using Multimeter? How to identify LED terminals?

How to test LED using Multimeter & How to identify LED terminals?

LED_SymbolIf you are new to electronics projects, start with LED based simple projects. They are comparatively simple and while seeing the LEDs connected in your circuit glows,  you will get impressed to do more projects on your own.

In this short post let us see how to test the LED using multimeter, before that we will discuss what is LED and  How LED is glowing?

What is LED?

LED = Light Emitting Diode.
As the name indicates, it will emit the light energy when sufficient amount of current will flow across its terminals.
Generally LED are available in the market with 3mm size or 5mm size.
When the forward current is around 20mA, these LEDs will provide reasonable level of light output.

How LEDs are glowing?

P-N junction using gallium arsenide or gallium phosphide releases light energy when electrical energy is applied across it. Such kind of P-N junction diode is called as Light Emitting Diode (LED).

The color of the light depends on the type of material used.

  • Gallium Phosphide (GAP) - Red or Green
  • Gallium Arsonide (GaAs) - Infrared

How to test LED with the help of Multimeter?

To check whether the LED is working or not, do the following steps

  1. Keep the Diode mode in the multimeter.
  2. Connect the LED anode terminal to positive probe of the multimeter and cathode terminal to negative probe.
  3. The LED will glow.
  4. Connect the LED cathode terminal to positive probe of multimeter and anode terminal to negative probe.
  5. The multimeter will display 0.7V.

How to identify LED terminals?

  1. LED has two terminals namely anode(A)  and cathode(K).
  2. The terminal near to the flat surface(refer the figure) is cathode terminal and the other one is an anode terminal.
  3. In Commercially available 3mm / 5mm thru hole LEDs, the cathode lead will be longer than anode lead. (In the above figure, the upper terminal is cathode and the lower terminal is anode)

You may also like to read:

How to Identify NPN and PNP Transistor using Multimeter?
How to test transistor using Multimeter?

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