Ultrasonic Sensor's working and range calculations

Ultrasonic Sensor

Ultrasonic ranging module HC - SR04 provides the measurement of 2cm - 400cm distance, the ranging accuracy can be reached up to 3mm. The module includes ultrasonic transmitters, receiver, and a control circuit.

Electrical Parameters-

Working Voltage                     DC 5V

Working Current                     15 mA

Working Frequency                40 kHz

Max Range                                400 cm

Min Range                                 2 cm

Measurement Angle              15 Deg

Trigger Input Signal              10 uS TTL pulse

Echo Output Signal                Input TTL level Signal and range in Proportion.

Dimension                                 45*20*15 mm

Steps for an Operation-

1. Set trigger pulse HIGH for 10 microSeconds and then set it LOW (Negative Trigger).
2. The Module got triggered and sends 8 continuous pulses of 40 kHz frequency.
3. The Module waits for echo signal (Measurement cycle should be over 60 milliseconds to prevent trigger signal to the echo signal).
4. When Module detects echo it sends the microcontroller to calculate distance.

• The speed of Sound = 331.3 m/s  at  0^o C.
• The speed of Sound depends upon Temperature T ^o C.

Let the Temperature is 30^o C then, speed of Sound  -

Now, for total echo(received ultrasonic pulses) detection time t -

Example: Suppose time taken by pulses from transmit to receive is 1000 uS => 

• 't' can be calculated using a timer function in the Microcontroller.

 

Applications of  Ultrasonic Sensor-

• Distance Measurement.
• RADAR
• Obstacle Detection.
• Path Finder.
• Anti-collision Detection.
• Level Measurement.
• Robotic Sensing.
• Vehicle Detection for a car wash.
• Contouring Or Profiling Using Ultrasonic System.
• Positioning and Locating.