HC-SR04 Ultrasonic Sensor

Background

An ultrasonic sensor works similar to echo-location in bats. The sensor emits high-frequency sound waves and calculates the time until the waves are reflected back to the sensor. It is used to detect distance to obstacles. To take a reading, a 10 microsecond pulse is sent on the trigger pin. This tells the senor to emit eight 40 kHz sound waves outward. The echo pin goes high and stays high until the sound waves are received back to the sensor. You can calculate the distance using the time-of-flight or ToF by computing how long the echo pin is high.

 

 

Hardware Description

Pinout

• VCC – 5V
• Trig – connected as a digital output to Arduino
• Echo – connected as a digital input to Arduino
• GND – GND

 

 

Software Description

Use the pulseIn() to determine the time it takes for the sound waves to travel out and back.

• pulseIn(pin, value) – detects the duration of a pulse.
  • pin – the Arduino pin number you want to monitor.
  • value – the type of pulse to read: either HIGH or LOW.
  • Returns the length of the pulse (in microseconds) or 0 if no pulse.
  • For HC-SR04, we want to measure how long the echo pulse is HIGH.
  • https://www.arduino.cc/reference/en/language/functions/advanced-io/pulsein/
• get_distance() - function I have provided that returns the distance in inches to the obstacle.
  • Takes no arguments.
  • Returns distance to object as an integer value in inches.
  • Requires #define macros for ultrasonic sensor pins. In this case, I used TRIG_PIN, ECHO_PIN
  • https://create.arduino.cc/editor/mjdargen_ravens/e51f655b-d97e-42c5-8537-7fe64a640dbe/preview