Sensor

M4-R5.1 · Chapter 3: Sensors, Actuators and Microcontrollers · 3 min read

Sensors

A sensor is an electrical device that converts a physical quantity (temperature, pressure, humidity, etc.) of the environment into an electrical signal that can be easily understood by humans or machines.

Examples: Light sensor, Pressure sensor, Temperature sensor

Classification of Sensors

A) Based on Power Supply

  1. Passive Sensors
    • Operate without an external power supply
    • Examples: PIR motion sensors, Passive RFID tags
    • Advantages: Low power consumption, simplicity
  2. Active Sensors
    • Require an external power supply to operate
    • Examples: Active RFID tags, most electronic sensors
    • Advantages: Greater functionality, continuous operation
  3. Self-Powered Sensors
    • Generate power from the surrounding environment (Energy Harvesting)
    • Examples: Solar-powered sensors, Piezoelectric sensors
    • Advantages: Energy-efficient, sustainable

B) Based on Output

  1. Analog Sensors
    • Provide a continuous output proportional to the quantity being measured
    • Examples: Analog temperature sensors, Analog pressure sensors
  2. Digital Sensors
    • Output discrete digital signals, often in the form of binary code
    • Examples: Digital temperature sensors, Digital accelerometers

Common IoT Sensors

1. Proximity Sensor

IoT proximity sensors provide non-contact detection of objects that are enclosed proximity to the sensor.

They usually do this by emitting electromagnetic fields or beams of radiation such as infrared. in other words, A device that detects the presence or absence of a nearby object, or properties of that object, and converts it into signal which can be easily read by user or a simple electronic instrument without getting in contact with them.

Proximity sensors may also be found in parking lots of malls, stadiums, or airports to indicate available parking spots.

Applications: Parking lots in malls, stadiums, airports

2. Ultrasonic Sensor (HC-SR04)

An ultrasonic sensor is an electronic device that measures the distance to an object using ultrasonic sound waves.

It works by emitting an ultrasonic pulse (usually at 40 kHz), then measuring the time it takes for the echo to return after bouncing off a nearby surface. Using this time and the speed of sound, the sensor calculates the distance.