Ultrasonic Sensor

HC-SR04 ultrasonic proximity sensor module
R 37.00 each Estimated Dispatch Tomorrow Total Cost R 37.00

This module is a reliable, high performance and high accuracy ultrasonic proximity sensor that seamlessly integrates with microcontrollers. It operates by transmitting a short 40kHz signal upon a pulse on the TRIG pin, after which a variable-length logic high pulse is ouput on the ECHO pin, the length of which corresponds to the distance to the object.


Voltage Supply 5VDC
Operating Current < 2mA
Sense Angle < 15o
Sense Distance 2cm - 450cm
Resolution ~0.3cm
Module Size 45mm x 20mm
Minimum TRIG pulse 10µs

Operating Principle

A measurement is initiated by applying a short (>10µs) logic HIGH pulse to the TRIG pin. Once triggered, the module will emit a 40kHz signal and detect the reflected signal. After the received signal has been detected, a logic HIGH pulse is output on the ECHO pin with a length corresponding to the signal being emitted and subsequently received. This length of time is thus the time taken for sound to travel from the module, to the object of interest, and back again.

A microcontroller can easily detect the length of this pulse, and the following formula can be used to determine the distance:

Distance = 1/(techo * c)

Where techo is the length of the HIGH pulse on the ECHO pin, and c the speed of sound in air (~340m/s). The half factor is representative of the sound travelling to the object and back again.