An upgraded ultrasonic module – improved properties and performance in various aspects
Ultrasonic ranging module HC - SR04 provides 2cm - 700cm 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:
(1) Using IO trigger for at least 10us high level signal；
(2) The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back.
(3) 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.
TRIG: Trigger Pulse Input ECHO: Echo Pulse Output GND: Ground VCC: 5V Supply
|Max Range||700cm, Ensured stable signal within 5m, gradually faded signal outside 5m till disappearing at 7m position.|
|Trigger Input Signal
+10uS TTL pulse
|Echo Output Signal||Input TTL lever signal and the range in proportion|
The Timing diagram is shown below. You only need to supply a short 10uS pulse to the trigger input to start the ranging, and then the module will send out an 8 cycle burst of ultrasound at 40 kHz and raise its echo. The Echo is a distance object that is pulse width and the range in proportion .You can calculate the range through the time interval between sending trigger signal and receiving echo signal. Formula: uS / 58 = centimeters or uS / 148 =inch; or: the range = high level time * velocity (340M/S) / 2; we suggest to use over 60ms measurement cycle, in order to prevent trigger signal to the echo signal.
Note: If you want to test in a 500cm+ distance, you need to change the NewPing library, which defines the maximum distance (i.e. 500cm). You can set it as 700 or higher. it is as shown in follwing:
#define MAX_SENSOR_DISTANCE 710