Essential Arduino Sensors and How to Use ThemArduino boards are a popular platform for learning electronics and building interactive projects. Sensors are the bridge between the physical world and your Arduino: they let your project perceive temperature, light, motion, distance, sound, and much more. This article covers essential sensors often used with Arduino, explains how they work, shows wiring and basic code examples, and gives project ideas so you can start building reliably.
Table of contents
- Temperature sensors
- Light sensors
- Motion and proximity sensors
- Distance sensors
- Sound sensors
- Humidity sensors
- Gas and air-quality sensors
- Touch and force sensors
- IMU (accelerometer + gyroscope) sensors
- Tips for sensor selection, wiring, and data reading
1. Temperature sensors
DHT11 / DHT22
- What they measure: temperature and humidity.
- Differences: DHT22 is more accurate and has a wider range than DHT11.
- Typical use: environmental monitoring, weather stations.
Wiring:
- VCC to 5V (DHT11) or 3.3–5V (DHT22)
- GND to GND
- Data pin to a digital input with a pull-up resistor (often built into modules)
Basic Arduino code (using the DHT library):
#include "DHT.h" #define DHTPIN 2 #define DHTTYPE DHT22 // or DHT11 DHT dht(DHTPIN, DHTTYPE); void setup() { Serial.begin(9600); dht.begin(); } void loop() { float h = dht.readHumidity(); float t = dht.readTemperature(); // Celsius if (isnan(h) || isnan(t)) { Serial.println("Failed to read from DHT sensor!"); delay(2000); return; } Serial.print("Humidity: "); Serial.print(h); Serial.print("% Temperature: "); Serial.print(t); Serial.println("°C"); delay(2000); } DS18B20 (digital waterproof sensor)
- What it measures: temperature (single-wire digital).
- Use when you need precise readings or waterproof probes.
- Wiring: uses one-wire bus. VCC to 5V, GND to GND, data to a digital pin with a 4.7k pull-up resistor to VCC.
2. Light sensors
LDR (Photoresistor)
- What it measures: ambient light level (analog).
- Cheap and simple; used in light-sensitive switches.
- Wiring: voltage divider with a resistor; read analog value.
Basic read:
int sensorPin = A0; void setup() { Serial.begin(9600); } void loop() { int val = analogRead(sensorPin); Serial.println(val); delay(500); } BH1750 / TSL2561 (digital light sensors)
- What they measure: lux (more accurate, I2C interface).
- Use for projects needing calibrated light intensity (photography, plant grow lights).
Wiring: SDA to A4, SCL to A5 on Uno (or corresponding SDA/SCL pins), VCC to 3.3–5V, GND to GND. Use Wire and sensor-specific libraries.
3. Motion and proximity sensors
PIR (Passive Infrared) sensor
- What it detects: movement of warm objects (people, animals).
- Simple on/off output when motion detected.
- Wiring: VCC to 5V, GND to GND, OUT to digital input.
Debounce and timing considerations: PIRs have a retrigger interval and sensitivity potentiometers on modules.
HC-SR501 vs higher-quality PIRs
- HC-SR501 is common and inexpensive; adjust sensitivity and time delay with onboard pots.
4. Distance sensors
Ultrasonic HC-SR04
- Measures distance using ultrasonic pulses (approx. 2 cm–400 cm).
- Pins: VCC, GND, Trig, Echo. Trig: send 10µs pulse; Echo: measure pulse width.
Basic code:
const int trig = 9; const int echoPin = 10; void setup() { Serial.begin(9600); pinMode(trig, OUTPUT); pinMode(echoPin, INPUT); } void loop() { digitalWrite(trig, LOW); delayMicroseconds(2); digitalWrite(trig, HIGH); delayMicroseconds(10); digitalWrite(trig, LOW); long duration = pulseIn(echoPin, HIGH); float distanceCm = duration * 0.0343 / 2; Serial.println(distanceCm); delay(200); } Time-of-Flight (ToF) VL53L0X / VL53L1X
- Laser-based, more accurate and works on small reflective targets, better for short ranges and edges.
- Use I2C, library available.
5. Sound sensors
Microphone modules (analog) and electret mics
- Provide sound level as analog voltage — useful for detecting loud events.
- For real audio capture, use external ADC and processing; for level detection, analogRead is fine.
MAX9814 / INMP441
- MAX9814: amplified electret mic with AGC.
- INMP441: I2S digital microphone for audio processing on capable boards.
6. Humidity sensors
Covered with DHT11/DHT22 earlier. For separate high-accuracy humidity sensing, use SHT3x series (I2C, higher accuracy and stability).
7. Gas and air-quality sensors
MQ-series (MQ-2, MQ-7, MQ-135, etc.)
- Detect combustible gases, smoke, CO, air quality index proxies.
- Cheap but require calibration and are affected by temperature/humidity.
- Wiring: analog output to Arduino. Allow warm-up time (often 24–48 hours for best stability).
CCS811 / BME680 / SGP30
- Digital air-quality sensors measuring VOCs, equivalent CO2, and sometimes temperature/humidity/pressure.
- Use I2C and libraries; better for indoor air-monitoring projects.
8. Touch and force sensors
Capacitive touch sensors (TTP223) and touch pads
- Detect human touch; easy to use with digital output.
- Wiring: VCC, GND, OUT.
Force Sensitive Resistor (FSR)
- Measures pressure/force with variable resistance; good for simple pressure sensing.
- Wiring as a voltage divider to an analog input.
9. IMU (accelerometer + gyroscope) sensors
MPU6050 / MPU9250 / BNO055
- Measure acceleration, rotation rates; BNO055 adds onboard sensor fusion to give absolute orientation.
- Use I2C. MPU6050 is common and inexpensive but requires software fusion for orientation. BNO055 gives quaternion/euler directly.
Basic use: read raw acceleration/gyro, apply filtering (complementary filter or Kalman) or use library that provides fused data.
10. Tips for sensor selection, wiring, and data reading
- Voltage compatibility: confirm sensor voltage (3.3V vs 5V) before wiring.
- Pull-ups/pull-downs: some digital sensors need external pull-up resistors.
- Debounce and filtering: use software smoothing (moving average) or hardware (RC filter) for noisy analog sensors.
- Calibration: many sensors (gas, force, light) need calibration for meaningful units.
- Libraries: use well-maintained libraries to simplify initialization and reading.
- Power and grounding: share a common ground; avoid long unshielded wires for analog signals.
- Sampling rate: choose sampling rate suitable for the phenomenon (e.g., high for audio, low for temperature).
- Sensor fusion: combine sensors (e.g., IMU + magnetometer + GPS) to improve accuracy.
Practical project ideas
- Weather station: DHT22 + BMP280 (pressure) + light sensor + SD card logging.
- Intruder alert: PIR + camera module + Wi-Fi notification.
- Robot obstacle avoidance: HC-SR04 or VL53L0X + motors + IMU.
- Smart plant monitor: soil moisture + light + temperature/humidity + MQTT alerts.
- Air-quality monitor: BME680 + CCS811 for VOC/eCO2 estimates with web dashboard.
If you want, I can:
- provide complete wiring diagrams for any sensor above,
- generate ready-to-upload Arduino sketches for a specific board (Uno, Nano, ESP32),
- or recommend specific sensor modules to buy based on budget and accuracy.