Once the Blink sketch works, the next question is always the same: which part do I actually need for this project? This guide sorts 39 of the sensors and modules you'll run into most often into five groups — environmental, motion, general-purpose, displays, and communication — with a one-line answer for each: what it measures or does, and the situation it's built for.
A sample of the boards covered below
How To Use This
Most of these connect over just three interfaces: plain analog/digital pins, I2C (2 wires, multiple devices on one bus), or SPI (faster, one device per chip-select line). If you already know which interface a module uses, wiring the rest is mostly the same pattern every time.
Environmental Sensors
13 components
DHT11 / DHT22
Cheap digital temperature + humidity combo; DHT22 trades a bit of cost for better accuracy and range.
DS18B20
One-wire digital temperature probe; the waterproof version is the go-to for liquids and outdoor use.
LM35 / LM335 / LM34
Analog temperature ICs — output voltage scales directly with °C, K or °F depending on the part.
MAX6675 + K-Type Thermocouple
SPI amplifier for a thermocouple probe — reads up to roughly 1260°C for ovens and 3D-printer hotends.
BMP180
I2C barometric pressure sensor with built-in temperature compensation.
BME280
Pressure, temperature and humidity in one I2C package — the standard pick for a mini weather station.
BME680
Everything the BME280 does, plus a gas/VOC sensor for basic air-quality readings.
BMP388
Higher-precision barometric sensor tuned for altitude estimation — common in drones and altimeters.
MQ-2 Gas / Smoke
Analog sensor tuned to LPG, butane, propane, methane, alcohol and hydrogen — a basic smoke/leak alarm part.
BH1750
16-bit I2C ambient light sensor that reports directly in lux — no manual calibration needed.
TDS Sensor
Estimates total dissolved solids in water — a quick proxy for water quality.
FC-37 / YL-83 Rain Sensor
Detects direct water contact on its exposed traces — catches rain that a humidity sensor would miss.
YL-69 / HL-69 Soil Moisture
Reads soil conductivity to gauge moisture — the core sensor in automated plant-watering builds.
Motion & Position Sensors
7 components
PIR Motion Sensor
Passive infrared — trips on the change in a body's heat signature moving across its field of view.
HC-SR04 Ultrasonic
Time-of-flight distance sensor, roughly 2cm–400cm — the default choice for obstacle-avoidance robots.
RCWL-0516
Microwave doppler radar motion sensor — works behind thin plastic or glass where PIR can't see through.
Reed Switch (Door Sensor)
Magnetic contact switch for door, window or drawer open/close detection.
Tilt Sensor
A rolling ball breaks or makes contact past a set angle — a cheap binary tilt switch.
MPU6050
6-axis IMU — 3-axis accelerometer plus 3-axis gyroscope with onboard temperature, over I2C.
NEO-6M GPS
UART GPS receiver for outdoor location and speed tracking.
General-Purpose Sensors & Modules
7 components
DS1307 / DS3231 RTC
Battery-backed real-time clock for timestamping and scheduling that survives a power cycle.
Sound Sensor (KY-038)
Microphone module with a digital output that goes HIGH once ambient sound crosses a set threshold.
Relay Module
Electromechanical switch that lets 5V logic safely control mains-voltage appliances.
microSD Card Module
SPI file storage — read and write files for on-board data logging.
Load Cell + HX711
Strain gauge paired with a 24-bit amplifier — the standard combo for weighing projects.
Fingerprint Sensor (FPM10A)
Optical biometric scanner for fingerprint-based access-control projects.
TCS3200 / TCS3230
Reads reflected light through RGB filters to identify color — used for sorting and color-matching.
Displays
6 components
OLED Display
Self-lit monochrome display — pixels only draw power when they're actually lit.
8×8 Dot Matrix (MAX7219)
LED matrix driver chip for scrolling text and simple pixel animations.
16×2 LCD (I2C)
The classic character display for status text — the I2C backpack cuts wiring down to 4 pins.
1.8″ TFT Display
128×160 color display, often bundled with a microSD slot for images and UI graphics.
RGB LED
Red, green and blue dies in one package — mix any color with three PWM channels.
WS2812B Addressable Strip
Individually addressable RGB LEDs, each with its own driver chip — full control over one data pin.
Communication Modules
6 components
MFRC522 RFID Reader
Reads and writes 13.56MHz RFID tags over SPI — access control and inventory tagging.
nRF24L01
Cheap, low-power 2.4GHz transceiver for board-to-board wireless communication.
433MHz Transmitter/Receiver
Simple one-way RF pair for basic remote control and sensor links over open-air distance.
IR Receiver (TSOP)
Demodulates infrared remote signals — the basis of any universal-remote project.
SIM900 GSM Shield
Adds cellular SMS, voice and data connectivity for projects out of WiFi range.
Membrane Keypad
Flat 3×4 or 4×4 button matrix for numeric or text input.
Where To Start
If you're picking your first three sensors: an HC-SR04 for distance, a DHT22 for temperature/humidity, and an I2C LCD to display readings without a laptop attached. That combination alone covers most beginner project ideas.