Ultrasonic ranging module HC-SR04 provides 2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules includes ultrasonic transmitters, receiver and control circuit.
The basic principle of work:
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×velocity of sound (340M/S) /2
Wire connecting direct as following: 1. 5V Supply
2. Trigger Pulse Input
3. Echo Pulse Output
If you are sourcing a ultrasonic ranging module , the HC-SR04 is good choose . Its stable performance and high ranging accuracy make it a popular module in electronic market .
Compared to the Shape IR ranging module , HC-SR04 is more inexpensive than it . But it has the same ranging accuracy and longer ranging distance.
power supply :5V DC
quiescent current : <2mA
effectual angle: <15°
ranging distance : 2cm – 500 cm
resolution : 0.3 cm
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