Lesson 13 Ultrasonic

Introduction

When you are reversing, you will see the distance between the car and the surrounding obstacles to avoid collision. The device for detecting the distance is an ultrasonic sensor. In this experiment, you will learn how the ultrasonic wave detects the distance.

Schematic Diagram

The schematic diagram:

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Experimental Procedures

Step 1: Build the circuit

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Step 2: Open the code file.

Step 3: Select the Board and Port.

Step 4: Upload the sketch to the board.

Note

If you receive the following error, it is because you didn’t add a library named NewPing, please refer to Add libraries.

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Now, if you use a piece of paper to approach or keep it far away from the sensor. You will see the value displayed on the LCD changes, which indicates the distance between the paper and the ultrasonic sensor.

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Code

Code Analysis

Initialize the ultrasonic sensor and LCD1602

#include <LiquidCrystal.h> // use #include to define the header file.

#include <NewPing.h> // use #include to define the header file.

LiquidCrystal lcd(4, 6, 10, 11, 12, 13); //lcd(RS,E,D4,D5,D6,D7)

#define TRIGGER_PIN 2 // trig pin on the ultrasonic sensor attach to pin2.

#define ECHO_PIN 3 // echo pin on the ultrasonic sensor attach to pin3.

#define MAX_DISTANCE 400
// Maximum distance we want to ping for (in centimeters).
// Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);
// NewPing setup of pins and maximum distance.

Create a NewPing variable sonar. The basic format of NewPing is: NewPing (uint8_t trigger_pin, uint8_t echo_pin, int max_cm_distance). Here uint means an unsigned integer and 8 means 8 bits. So a value in the uint8 format here means an unsigned-char type value.

Convert the time to distance

unsigned int uS = sonar.ping(); // Send ping, get ping time in microseconds (uS).

ping() is used to calculate the time sent from the pulse to the reception. Define a variable Us to store the received time, which should be in microseconds (us).

int distance = uS / US_ROUNDTRIP_CM;

uS / US_ROUNDTRIP_CM is a formula to convert the time between ping sending and receiving into a distance. The unit is cm.

Display the distance on the LCE1602

lcd.setCursor(0, 0);
// Place the cursor at Line 1, Column 1.From here the characters are to be displayed

lcd.print("Distance:"); // Print Distance: on the LCD

lcd.setCursor(0, 1); // Set the cursor at Line 1, Column 0

lcd.print(" "); /* Here is to leave some spaces after the characters so as
to clear the previous characters that may still remain.*/

lcd.setCursor(9, 1); // Set the cursor at Line 1, Column 9.

lcd.print(distance); /* print on the LCD the value of the distance
converted from the time between ping sending and receiving.*/

lcd.setCursor(12, 1); // Set the cursor at Line 1, Column 12.

lcd.print("cm"); // print the unit "cm"