HC-SR04 Ultrasonic Distance Measuring Sensor Module — 2cm to 400cm Range, 3mm Accuracy, Arduino Compatible

Measure distance without touching anything — the HC-SR04 Ultrasonic Distance Sensor uses sonar to measure the distance to an object from 2cm to 400cm (1 inch to 13 feet) with up to 3mm accuracy. It sends out a burst of 40 KHz ultrasonic sound, listens for the echo, and outputs a timed pulse that your microcontroller converts to distance with a single line of math. Works in complete darkness, isn't fooled by color or transparency, and needs just four wires — no libraries required.

Whether you're building an obstacle-avoiding robot, a parking sensor, a liquid level monitor, or a contactless ruler, the HC-SR04 is the go-to sensor for the job.

⚡ Key Features

• Non-contact distance measurement: 2cm to 400cm (1" to 13 ft) — no physical contact with the target needed.
• High accuracy: Up to 3mm resolution for precise measurements.
• ~15° beam angle: Focused enough to avoid false readings from nearby objects, wide enough for practical use.
• Works in any lighting: Ultrasonic — not affected by sunlight, darkness, or object color/transparency. Unlike IR sensors, it works on black and transparent objects.
• Simple 4-pin interface: VCC, Trig, Echo, GND. Send a 10µs trigger pulse, read the echo duration, calculate distance. No I2C, SPI, or libraries required.
• Low power: Less than 2mA quiescent, ~15mA during measurement — suitable for battery-powered projects.
• Fast: Up to 20 measurements per second (~50ms per cycle).
• Compact: 45mm × 20mm × 15mm — the two ultrasonic transducers give it a distinctive "eyes" appearance.

🔧 How It Works

1. Trigger: Send a 10-microsecond HIGH pulse to the Trig pin.
2. Transmit: The sensor emits 8 ultrasonic pulses at 40 KHz.
3. Echo: The sound bounces off the nearest object and returns to the receiver.
4. Measure: The Echo pin goes HIGH for a duration equal to the round-trip time.
5. Calculate: Distance (cm) = Echo time (µs) ÷ 58.2

That's it. One trigger, one echo, one division. No calibration, no warm-up, no configuration.

📌 Pinout

🎯 Perfect For

• Obstacle-avoiding robots — detect walls and objects, navigate autonomously
• Parking sensors — mount in a garage to show distance to the wall with LEDs or a buzzer
• Liquid level monitoring — mount above a tank, measure distance to the water surface
• Contactless ruler / tape measure — point at a wall, read distance on an LCD/OLED display
• People counter — detect people passing through a doorway
• Automatic hand sanitizer / soap dispenser — detect hand proximity and trigger a pump
• Smart trash can — auto-open lid when a hand approaches
• Musical instrument (theremin-style) — map distance to tone frequency
• Security / intrusion detection — alert when distance changes in a monitored area
• STEM education — teach speed of sound, sonar, and sensor integration

📐 Specifications

• Operating voltage: 5V DC
• Operating current: ~15mA (during measurement)
• Quiescent current: <2mA
• Ultrasonic frequency: 40 KHz
• Measuring range: 2cm – 400cm (1" – 13 ft)
• Accuracy: Up to 3mm
• Measuring angle: ~15° cone
• Trigger input: 10µs TTL pulse
• Echo output: 5V TTL pulse (duration = round-trip time)
• Measurement cycle: ~50ms minimum (20 Hz max rate)
• Dimensions: 45mm × 20mm × 15mm (1.77" × 0.79" × 0.59")
• Weight: ~11g

🔌 Compatible With

• Arduino Uno, Mega, Nano, Leonardo — direct connection, no additional components
• ESP32 / ESP8266 — requires voltage divider on Echo pin (5V → 3.3V)
• Raspberry Pi — requires voltage divider on Echo pin (5V → 3.3V)
• STM32, AVR, PIC — any microcontroller with digital I/O (voltage divider for 3.3V systems)
• NewPing library supported for simplified code and median filtering

📦 Package Contents

• 1 × HC-SR04 Ultrasonic Distance Measuring Sensor Module

Arduino, jumper wires, breadboard, and USB cable are not included.

📄 Documentation & Resources

• User Guide — Wiring, Arduino Code, NewPing Library, Accuracy Tips & Troubleshooting
• All Sensor, Detector & Input Module Guides