6.1 - Measuring Distance

The ultrasonic sensor module works on the principle of sonar and radar systems for determining the distance to an object.

Schematic

sch_ultrasonic

Wiring

wiring_ultrasonic

Code

Note

  • You can open the file 6.1_ultrasonic.ino under the path of kepler-kit-main/arduino/6.1_ultrasonic.

  • Or copy this code into Arduino IDE.

  • For detailed tutorials, please refer to Open & Run Code Directly.

  • Or run this code directly in the Arduino Web Editor.

Don’t forget to select the Raspberry Pi Pico W board and the correct port before clicking the Upload button.

Once the program is running, the Serial Monitor will print out the distance of the ultrasonic sensor from the obstacle ahead.

How it works?

About the application of ultrasonic sensor, we can directly check the subfunction.

float readSensorData(){// ...}

PING is triggered by a HIGH pulse of 2 or more microseconds. (Give a short LOW pulse beforehand to ensure a clean HIGH pulse.)

digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

The echo pin is used to read signal from PING, a HIGH pulse whose duration is the time (in microseconds) from the sending of the ping to the reception of echo of the object.

microsecond=pulseIn(echoPin, HIGH);

The speed of sound is 340 m/s or 29 microseconds per centimeter.

This gives the distance travelled by the ping, outbound and return, so we divide by 2 to get the distance of the obstacle.

float distance = microsecond / 29.00 / 2;

Note that the ultrasonic sensor will pause the program when it is working, which may cause some lagging when writing complex projects.