IoT Sensors and Actuators Explained with Examples

A sensor converts a physical quantity (temperature, light, distance, motion) into an electrical signal; an actuator converts an electrical command into a physical effect (light, motion, heat, flow). Almost every IoT device has at least one of each.

Common sensors and what they output

Common actuators

• Relay or solid-state relay: switches a higher-power load. Use electrical isolation and respect mains-safety rules.
• MOSFET / transistor driver: switches DC loads and PWM-controls speed or brightness.
• Servo and stepper motors: controlled positioning.
• Buzzers, LEDs, displays: local feedback to a person.

Analog or digital?

An analog sensor outputs a voltage that the microcontroller measures with an ADC; resolution is limited (10-bit on Arduino Uno, 12-bit on ESP32). A digital sensor does the conversion internally and sends numbers over a bus, which is usually more accurate and less noisy. Prefer digital sensors when a good one exists.

How to choose

1. Write down the range and accuracy you actually need.
2. Check the supply voltage and logic level against your board (3.3 V on ESP32).
3. Read the datasheet’s response time and self-heating notes.
4. Plan how you will calibrate and verify it against a reference.

Practise

Start with Arduino, where sensors and actuators are the core of the course, and use IoT Fundamentals for the system context.

References

• Arduino documentation: docs.arduino.cc
• Espressif, ESP32 Series Datasheet: espressif.com