HC-SR04 ultrasonic sensor

Measure distance like bat does, with ultrasonic waveform!

The HC-SR04 is an ultrasound module allowing the evaluation of a distance from 2cm to 400cm. The measurement is made "contactless" and has a precision of 3mm under optimal conditions. The module includes a transmitter and an ultrasonic receiver as well as an electronic control. The operation of this module is similar to that of a submarine sonar and its implementation is relatively simple. 
Unlike our other ultrasound module, HC-SR4 is not autonomous and requires the use of an Arduino (or other microcontroller) to work. 

Functional principle of the module:

1. The module emits a sonar wave consisting of a series of 8 pulse at 40 kHz.
   A sound at 40 KHz is inaudible to the human ear capable of perceiving sounds between 16Hz et 16KHz (cfr Wikipédia).
2. Using the Trig pin, you send a signal to activate the triggering of the sonar pulse.
3. The advantage of using an acute sound is that it is directional (spreads in a straight line) while the low frequencies pass through the material. It's for this reason that we hear only the bass when the neighbors make fiesta!
   
4. If the signal returns... the output goes high during the entire period the wave travels to the object and returns after being reflected by it last.

The estimated distance = time during which the output signal is high x the speed of sound (340m/s) / 2.
If the output pulse time is less than 60ms, you can also use the simplified formula distance_in_cm = pulse_time_µS / 58.

Connection

• VCC - 5V power supply
• Trig - Input to trigger the pulse
• Echo - Output, to determine the reception of the echo
• GND - The ground

Technical characteristics

• Operating voltage: 5V continuous
• Consumption (in operation): 15mA
• Operating frequency: 40Hz
• Minimum distance: 2cm
• Maximum distance: 400cm (4m) (in good conditions)
• Angle of measurement: 15 degrees
• Input signal - trig: triggering the measurement: pulse 10µS TTL
• Output signal - echo: pulse when the echo is received: TTL signal (depends on the measured distance)
• Dimensions: 45 x 20 x 15mm