Description This is the HC-SR04 ultrasonic ranging sensor. This economical sensor provides 2cm to 400cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm. Each HC-SR04 module includes an ultrasonic transmitter, a receiver and a control circuit. There are only four pins that you need to worry about on the HC-SR04: VCC (Power), Trig (Trigger), Echo (Receive), and GND (Ground). Module Working Principle Give trigger input signal of at least 10us of high level at trig (T) pin. The module automatically sends 40khz square wave and automatically returns pulse signal at echo (R) pin. Distance can be calulated from the time difference between Input pulse and response pulse by following formula: Test distance = Time difference * sound velocity (340M/S) Note : The module is ESD Sensetive, let the GND terminal of this module be connected at first. Technical Specifications Operating Voltage: 5V DC Operating Current: 15mA Static current: Less than 2mA. Output signal: Electric frequency signal, high level 5V, low level 0V. Measure Angle: ~15° Detection distance: 2cm-400cm. High precision: Up to 0.3cm Input trigger signal: 10us TTL impulse Echo signal : output TTL PWL signal Pinouts VCC trig(T) echo(R) GND Documents and Downloads Arduino example code Instructable – Simple Arduino and HC-SR04 Example by jsvester in arduino HC-SR04 Datasheet Package Includes 1x HC-SR04 – Ultrasonic Module Distance Measuring Sensor