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April 23, 2018

Learn: Difference Between a Common Anode and Common Cathode Tri-Colour LED

OVERVIEW

A tri-colour LED can be either common anode (the longer pin is positive) or common anode (the longer pin is negative). The best way to identify which tri-colour LED you have is to set up a circuit to test it.

Pin-out of a common cathode tri-colour LED

 

Pin-out of a common anode tri-colour LED

 


PART 1: IDENTIFYING THE TRI-COLOUR LED

Checking common cathode:

Connect the tri-colour LED as shown below. If the tri-colour LED lights up, then it is common cathode.

NOTE: The longer leg is connected to ground.

 

Checking common anode:

To confirm the tri-colour LED is common anode, connect it as shown below. The tri-colour LED should light up.

NOTE: The longer leg is connected to 5V.

 

 


PART 2: USING THE TRI-COLOUR LED

Common cathode tri-colour LED

Connect a common cathode tri-colour LED as shown.

NOTE: The longer leg is connected to ground.

 

Here are examples of how you control the tri-colour LED using Arduino IDE and Scratch.

NOTE: When the output is HIGH, the LED lights up.

Left: Arduino IDE; Right: Scratch

 

Common anode tri-color LED

Connect a common anode tri-colour LED as shown.

NOTE: The longer leg is connected to 5V.

 

Here are examples of how you control the tri-colour LED using Arduino IDE and Scratch.

NOTE: When the output is LOW, the LED lights up.

Left: Arduino IDE; Right: Scratch

 

 

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