Sensors
A beginner's guide to sensors
8 min read
Ultrasonic distance (HC-SR04)
Sends an ultrasonic ping and times the echo, measuring distance from about 2 cm to 4 m. The classic choice for obstacle-avoiding robots and tank-level sensing.
PIR motion (HC-SR501)
Detects the moving body heat of people and animals. Ideal for security alarms and automatic lighting. It senses motion, not presence — someone sitting still becomes invisible to it.
Temperature & humidity (DHT11/DHT22)
Digital climate sensors that need only one data pin. The DHT22 costs more but is noticeably more accurate and covers a wider range — worth it for greenhouses and incubators.
Light (LDR)
A light-dependent resistor is the simplest analogue sensor: resistance falls as light rises. Perfect for teaching voltage dividers and analogRead().
Line/IR reflectance
Infrared pairs that detect dark lines on light floors — the heart of every line-following robot competition.
Soil moisture
Measures how wet soil is, enabling automatic irrigation projects. Prefer capacitive versions over cheap resistive probes, which corrode within weeks.
Ready to put it into practice?