How to Use a Multiplexer with Arduino to Expand Inputs & Outputs
Introduction.
Do you have more sensors or devices than your Arduino has input/output pins? Don’t worry! With a multiplexer (MUX), you can expand your Arduino’s I/O capability without changing the microcontroller. In this guide, you’ll learn what a multiplexer is, how to connect it, and how to control it using Arduino code.
Materials for the Project
- 1x Arduino Nano
- 2x 74HC595 IC
- 2x CD4021 IC
- 2x CD4051 IC
- 16x 10k Resistors
- 6x 16-Pin IC Bases
- Female And Male Headers
- JUMPER WIRES
What is a multiplexer?
A multiplexer (or MUX) is a digital switch that allows you to select one of many inputs/outputs using a few control pins. Think of it as a rotary switch controlled by the Arduino.
Common Multiplexer ICs:
| IC Name | Channels | Type |
|---|---|---|
| 74HC595 IC | Analog/Digital | |
| CD4021 IC | Analog/Digital | |
| CD4051 IC | Analog/Digital |
Download Circuit Diagram
Required Components
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Arduino Uno (or any compatible board)
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74HC595 IC andCD4051 IC Multiplexer
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Potentiometers or sensors (for inputs)
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LEDs or relays (for outputs)
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Jumper wires
-
Breadboard
-
Power supply (5V)
Why Use a Multiplexer?
✅ Save Arduino pins
✅ Read from or write to many devices
✅ Cost-effective I/O expansion
✅ Supports both analog and digital signals
Applications
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Multiple sensor reading (temperature, light, etc.)
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LED matrix control
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Keypad reading
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Robotics and automation systems
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Audio or analog signal routing
Conclusion
Using a multiplexer with Arduino is a powerful way to handle more I/O devices while using fewer pins. Whether you’re building a smart home system, a robot, or a multi-sensor data logger, MUX chips can help you scale easily.