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4. Introduce Ultrasonic Module

image

  • TRIG: Trigger Pulse Input
  • ECHO: Echo Pulse Output
  • GND: Ground
  • VCC: 5V Supply

This is the HC-SR04 ultrasonic distance sensor, providing non-contact measurement from 2 cm to 400 cm with a range accuracy of up to 3 mm. Included on the module is an ultrasonic transmitter, a receiver and a control circuit.

You only need to connect 4 pins: VCC (power), Trig (trigger), Echo (receive) and GND (ground) to make it easy to use for your measurement projects.

Features

  • Working Voltage: DC5V
  • Working Current: 16mA
  • Working Frequency: 40Hz
  • Max Range: 500cm
  • Min Range: 2cm
  • Trigger Input Signal: 10uS TTL pulse
  • Echo Output Signal: Input TTL lever signal and the range in proportion
  • Connector: XH2.54-4P
  • Dimension: 46x20.5x15 mm

Principle

The basic principles are as follows:

  • Using IO trigger for at least 10us high level signal.
  • The module sends an 8 cycle burst of ultrasound at 40 kHz and detects whether a pulse signal is received.
  • Echo will output a high level if a signal is returned; the duration of the high level is the time from emission to return.

  • Distance = (high level time x velocity of sound (340M/S)) / 2

    image

Formula:

  • us / 58 = centimeters distance
  • us / 148 = inch distance
  • distance = high level time x velocity (340M/S) / 2

Note

  • This module should not be connected under power up, if necessary, let the module's GND be connected first. Otherwise, it will affect the work of the module.
  • The area of the object to be measured should be at least 0.5 square meters and as flat as possible. Otherwise, it will affect results.