Ultrasonic Sensor

Ultrasonic sensors are a lot like other distance sensors: they measure the distance between them and another object with waves. In this case, they use ultrasonic waves, which means they use sound waves that have a higher frequency than any human is capable of hearing. Ultrasonic sensors measure distance by timing how long it takes for a wave to be sent and then come back.

You will need four female to female jumper cables and an ultrasonic sensor.

Connect the VCC (red) wire to the V pin of the Smart Inventor Board. Now make sure the trig (orange) wire is connected to pin 27 and the echo (yellow) wire is connected to pin 28. You will find both of these pins in the S row. Attach the GND (green) wire to G on the board.

Warning: this can be confusing, so make sure you look at the diagram! Pay attention to the trig and echo wires; if they are mixed up, the ultrasonic sensor will not output the correct distance.

You are now done wiring it up. Since the holes on the sensor are not big enough to fit the bolts provided in your kit, it is recommended to use some mounting foam. The double-sided sticky foam both insulates the exposed metal contacts on the sensor and can be stuck on just about anywhere.

First, begin the code by including the Smart Inventor library. Enter the following before void setup():

#include <SmartInventor.h>

Next, name the pins you will be using for the ultrasonic sensors. These will be global variables so they should have descriptive names.

int trigPin = 27;
int echoPin = 28;

Inside void setup(), enter the following line:

Serial.begin(9600);

This command will allow the Smart Inventor Board to send data back to the computer at a rate of 9600 bits per second.

Finally, use pinMode() to assign both the trigger and echo pins.

pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);

Inside void loop(), create the number variables for the duration and distance that will be measured.

long duration, distance;

Next, include the following lines that will turn off the ultrasonic speaker.

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

Type the command below afterwards. This will turn on the trigger speaker and emit a burst of high-frequency sound for 10 microseconds and then turn off the trigger speaker.

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

The way this program is able to measure distance is in this following line. The pulseIn(pinNumber,State function saves the amount of time it takes for the sound burst to travel back and forth from an object to reach the echo speaker. Once the state changes value on the chosen pin between HIGH to LOW or LOW to HIGH, the timer ends. The output is the amount of time in milliseconds.

duration = pulseIn(echoPin, HIGH);

Next, code the math that converts the time traveled by the ultrasonic sound into centimeters.

distance = (duration/2) / 29.1;

Finally, include this command to allow for the distance to be displayed on the serial monitor on your computer.

Serial.println(distance);

Your final program should look like this:

#include <SmartInventor.h>

int trigPin = 27;
int echoPin = 28;

void setup(){

    Serial.begin(9600);

    pinMode(trigPin, OUTPUT);
    pinMode(echoPin, INPUT);
}

void loop(){

    long duration, distance;

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

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

    duration = pulseIn(echoPin, HIGH);

    distance = (duration/2) / 29.1;

    Serial.println(distance);
}

Once you have uploaded your program, keep the upload cable connected and turn off all dip switches. Next, click on the serial monitor eyeglass icon on the top right. Make sure you have the baud rate selected at 9600. and you should be able to see the distance output from the ultrasonic sensor.

Need a better visual? Watch the ultrasonic sensor programming video!