Official Arduino Sensor Guide
1. DHT11 (Temperature & Humidity)
Working: It contains a thermistor for temperature and a capacitive humidity sensor. The internal IC converts resistance changes into a digital signal.
🔗 Official DHT11 Library2. HC-SR04 (Ultrasonic Distance)
Working: Sends a 40kHz ultrasound wave. The time it takes to bounce back determines distance: Distance = (Speed × Time) / 2.
🔗 HC-SR04 Guide (Project Hub)3. LDR (Light Dependent Resistor)
Working: A variable resistor. In the dark, resistance is high; in light, resistance drops. Used with a voltage divider circuit.
🔗 LDR Tutorial (Project Hub)4. PIR (Passive Infrared)
Working: Detects infrared radiation (heat) emitted by living beings. A Fresnel lens focuses this IR onto a pyroelectric sensor.
🔗 PIR Sensor Guide (Project Hub)5. MQ-2 (Gas/Smoke Sensor)
Working: Uses a heated sensing element (SnO2). When gas exists, conductivity increases. Can detect LPG, Smoke, and Methane.
🔗 MQ-2 Intro (Project Hub)6. Soil Moisture Sensor
Working: Measures conductivity between two probes. Wet soil conducts better (low resistance); dry soil conducts poorly (high resistance).
🔗 Soil Sensor Guide (Project Hub)7. IR Proximity Sensor
Working: An IR LED emits light. If an object is close, light reflects into the Photodiode. The Op-Amp sets the output pin HIGH.
🔗 IR Sensor Guide (Project Hub)8. BMP180 (Barometric Pressure)
Working: Uses piezoresistive technology to detect atmospheric pressure. Essential for calculating altitude in drones.
🔗 BMP180 Guide (Project Hub)9. Rain Sensor Module
Working: Similar to soil moisture. Raindrops bridge the nickel traces on the board, lowering resistance and triggering the signal.
🔗 Rain Detector (Project Hub)10. Servo Motor (SG90)
Working: Controlled by PWM (Pulse Width Modulation). The width of the pulse (e.g., 1.5ms) determines the exact angle of the shaft.
🔗 Official Servo Docs