How many LED/relays can Arduino control?

How many LED or relays can Arduino control individually? How many LED or relays can connect to Arduino?

Answer

Basically, the number of LED or relay can connect to Arduino is equal to the number of arduino digital pins plus analog input pins. For example, Arduino Uno has 14 digital pins (D0 to D13) and 6 analog input pins ⇒ Arduino Uno can control up to 20 LED or relays.

You can also use a I/O Expanders (e.g PCF8574T) to increase the number pins that Arduino can control LED/Relay

Please note that, try to avoid using pin D0 and D1 Because these pins are used for Serial communication with Arduino IDE

You can learn about relay and Arduino in Arduino - Relay tutorial

You can learn about LED and Arduino in Arduino - LED tutorial

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