Elecfreaks HC-SR04 User manual

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Ultrasonic Ranging Module HC - SR04
Product features:
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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:
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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
measurement cycle, in order to prevent trigger signal to the echo signal.

Attention:
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The module is not suggested to connect directly to electric, if connected
electric, the GND terminal should be connected the module first, otherwise,
it will affect the normal work of the module.
When tested objects, the range of area is not less than 0.5 square meters
and the plane requests as smooth as possible, otherwise ,it will affect the
results of measuring.
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