PAGE 055 OF 150 · WIRING LEDS
Common-Anode vs Common-Cathode
A shared pin simplifies multi-LED packages.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
The difference
In a common anode LED all colours share a positive connection, and each colour is switched by pulling its own cathode low. In a common cathode LED the cathodes are shared and each colour is driven high.
Practical effects
- Common cathode is easier with a microcontroller: output high gives light.
- Common anode needs outputs to sink current, and PWM works inverted, with low as bright.
- Identify the type with the diode test on a multimeter.
Always check the datasheet, as pin order varies between makers.
REMEMBER
In series the same current flows through every LED.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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