HC-SR04 Ranging Detector Mod Distance Sensor (Blue) There are 4 pins out of the module: VCC , Trig, Echo, GND . So it's a very easy interface for controller to use it ranging. The all process is : pull the Trig pin to high level for more than 10us impulse , the module start ranging ; finish ranging , If you find an object in front , Echo pin will be high level , and based on the different distance, it will take the different duration of high level. So we can calculated the distance easily :Distance = ((Duration of high level)*(Sonic :340m/s))/2 FEATURES: Using IO trigger for at least 10us high level signal • The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back • IF the signal back, through high level ,time of high output IO duration is the time from sending ultrasonic to returning. Test distance = (high level time¡Ávelocity of sound (340M/S) /2 • Power supply:5V DC, quiescent current: Arduino