Arduino - Ultrasonic Sensor

Sensors are widely used for detecting devices by approximating their distance from the source. One such example of a sensor is the HC-SR04 ultrasonic sensor which uses the SONAR technique for the sensing purpose. The main feature of this sensor is to mimic the nature of bats and therefore predict the distance of objects without actually establishing contact with the device.

In this article, we will study how to design this ultrasonic sensor using the Arduino board and programming software. We will study the specifications needed for this sensor, and the methods and circuit diagrams used for designing this sensor. In addition to this, we will see the Arduino code written on IDE that will result in a sensor.

What is an Ultrasonic Sensor?

Similar to any other sensor, the Arduino Ultrasonic Sensor is used to sense the presence of any object and predict the distance of the object in appropriate units which is inches in this case. Therefore, we can define the Arduino Ultrasonic Sensor as a device that uses the ultrasonic sensing technique to estimate the distance of an object.

Arduino is used for creating this sensor since it needs to be programmed to detect the reflected rays from objects and display the distance in the desired format.

Technical Specifications

Before getting started with the sensor, we need to mention some specifications of the sensor that can ensure proper working conditions for the sensor.

• The Arduino board needs a minimum power supply of 5V which is required to turn the Arduino on. This must be Direct Voltage.
• The Arduino board needs a Quiescent Current which is at most 2mA and a working current of 15mA. Higher current values can burn the Arduino components.
• It is preferred that the object must be placed at the center line of the sensor but it can also be present at a certain angle from the center. This is known as effectual angle which should be less than 15°.
• The distance at which an object must be placed so that it can be detected by a sensor is around 2cm – 400 cm. The accuracy of detection decreases with an increase in distance.

Apparatus

Apparatus refers to the components that are needed for the project. The components required for designing a sensor using Arduino include.

• One Breadboard
• Arduino Uno R3 (Generally this model is only preferred_
• One Ultrasonic Sensor (HC-SR04)
• Some wires for making connections.

These devices are easily available at nearby electronics shops.

Working of the Ultrasonic Sensor

The Ultrasonic Sensor works on the principle of reflection, let us see how

• The sensor is used to emit waves known as ultrasound with a frequency of 40 KHz.
• The transmitted wave moves in a straight line path and gets obstructed by an object if present.
• After being obstructed, the wave reflects and is detected by the sensor. The time of transmission and reflection of the wave is noticed and the distance of the object is calculated using the speed-time formula.

Given Below is the Ultrasonic Sensor

Principle: If you carefully look at the diagram above, you will see that there is a transmitter. This component is responsible for emitting waves of an appropriate frequency that can travel far i.e. it should be able to transmit the ultrasound. Once the ultrasound waves are emitted, they continue a straight line path until they find an object. As shown in the figure, when the ultrasound waves are blocked by any object, the waves reflect. The receiver is present to receive the incoming waves after reflection. Once the reflected wave is received, we note the time taken by the waves to detect the object and predict the distance using this formula.

s= 2d/t

where s is the speed of the wave,

d is the distance traveled until reaching the object,

and t is the total time taken

Note that the factor '2' appears because the time noted is for the period when the wave strikes the object and then comes back.

Circuit Diagram

Here is the circuit diagram for making connections.

Circuit Diagram

Given Below is the circuit diagram of

Carefully observe the diagram given above for making connections on the breadboard. Note that the ultrasonic sensor has four terminals namely +5V, Trigger, Echo, and GND, follow the steps given for making connections:

• Connect a wire to supply V_cc with 5V to the appropriate pin on Arduino.
• Make a ground-to-ground connection from GND to GND on Arduino.
• Connect the trigger i.e. Trig to any pin on Arduino like pin 8.
• Connect the Echo to any pin on Arduino like pin 9.

Arduino Code

Here is the pseudocode and code for making an ultrasonic Sensor using Arduino.

Pseudocode

Firstly, we need to initialize the constants that denote the pins to be used. 

We will set PINs 8 and 9 as trigger pins and echo pins respectively.

We need to set up the Arduino in the setup() function by determining the starting terminal.

Then we set which pin will be used for output and use digitalWrite() to ensure that the pin is low first.
We will introduce a delay of 2 milliseconds using the delay() function.

We will set which pin will be used for input using the digitalWrite() function with another delay of 10 milliseconds.

We create two functions microsecondsToInches() and microsecondsToCentimeters() to give the distance at which the object is present. The parameter of this function will be the time at which the object was sensed.

Code

const int pingPin = 8; // Trigger Pin of Ultrasonic Sensor
const int echoPin = 9; // Echo Pin of Ultrasonic Sensor
void setup() {
   Serial.begin(9600); // Starting Serial Terminal
}
void loop() {
   long duration, inches, cm;
   pinMode(pingPin, OUTPUT);                              //Set which pin will be used for output
   digitalWrite(pingPin, LOW);                                //Ensure that the pin in low first
   delayMicroseconds(2);                                        //Introducing delay of 2 milliseconds
   digitalWrite(pingPin, HIGH);                               //Set which pin will be used for input
   delayMicroseconds(10);
   digitalWrite(pingPin, LOW);
   pinMode(echoPin, INPUT);
   duration = pulseIn(echoPin, HIGH);                  //Function for collecting the waves
   inches = microsecondsToInches(duration);
   cm = microsecondsToCentimeters(duration);
   Serial.print(inches);
   Serial.print("in, ");
   Serial.print(cm);
   Serial.print("cm");
   Serial.println();
   delay(100);
}
long microsecondsToInches(long microseconds) {
   return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds) {
   return microseconds / 29 / 2;
}

Conclusion

Once you have uploaded this code on Arduino, the sensor will begin working. The Arduino will successfully display the distance measured by a sensor in inches and cm. It will appear on the computer screen depending on the function that you use. The sensor will work accurately in different conditions like sunlight but it might not detect certain light items. You can make further modifications to improve the project according to your needs by incorporating some advanced boards.