Ultrasonic Distance Sensor HC-SR04

Tech Support: services@elecfreaks.com Ultrasonic Ranging Module HC -SR04 Product features:
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:
(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, Wire connecting direct as following: 5V Supply
Trigger Pulse Input
Echo Pulse Output
0V Ground Electric Parameter
Working Voltage DC 5 V Working Current 15mA Working Frequency 40Hz Max Range 4m Min Range 2cm MeasuringAngle 15 degree Trigger Input Signal 10uS TTL pulse Echo Output Signal Input TTL lever signal and the range in
proportion Dimension 45*20*15mm Vcc Trig Echo GND Timing diagram
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 …

HC-SR04 User Guide
Part 1 Ultrasonic Introduction 1. 1 Ultrasonic Definition The human ear can hear sound frequency around 20HZ ~ 20KHZ, and
ultrasonic is the sound wave beyond the human ability of 20KHZ . 1.2 Ultrasonic distance measurement principle
Ultrasonic transmitter emitted an ultrasonic wave in one direction, and started
timing when it launched. Ultrasonic spread in the air, and would return
immediately when it encountered obstacles on the way. At last, the ultrasonic
receiver would stop timing when it received the reflected wave. As Ultrasonic
spread velocity is 340m / s in the air, based on the timer record t, we can
calculate the distance (s) between the obstacle and transmitter, namely: s =
340t / 2, which is so-called time difference distance measurement principle
The principle of ultrasonic distance measurement used the already-known air
spreading velocity, measuring the time from launch to reflection when it
encountered obstacle, and then calculate the distance between the transmitter
and the obstacle according to the time and the velocity. Thus, the principle of
ultrasonic distance measurement is the same with radar.
Distance Measurement formula is expressed as: L = C X T
In the formula, L is the measured distance, and C is the ultrasonic spreading
velocity in air, also, T represents time (T is half the time value from transmitting
to receiving ).
1 1.3 Ultrasonic Application
Ultrasonic Application Technology is the thing which developed in recent
decades. With the ultrasonic advance, and the electronic technology
development, especially as high-power semiconductor device technology …