Arduino HC-SR04 with LCD I2C.

In this tutorial we will learn how to use Ultrasonic Sensor HC-SR04 and LCD I2C.

Parts or tools you will need

Arduino Uno

Ultrasonic Sensor HC-SR04

LCD (Liquid Crystal Display) I2C 16x2

Breadboard

Some male and female wires.

Libraries

LiquidCrystal I2C: https://github.com/fmalpartida/New-LiquidCrystal
HC-SR04: https://github.com/halina20011/HC-SR04-Library

What is LCD I2C (Liquid Crystal Display with I2C Bus)

LCD I2C is quite a popular LCD module. The main reasons are:

  • I2C interface uses only two wires "SCL (serial clock)" and "SDA (serial data)". This speeds up circuit connection time and also reduces circuit complexity.
  • Connect up to 8 LCDs. Limit is given by number of address (0x20 to 0x27) on I2C adapter.

    • How to use Ultrasonic Sensor HC-SR04

    Connect HC-SR04 module:

    HC-SR04 module Arduino Uno
    Vcc 5V
    Trig Digital pin 3
    Echo Digital pin 2
    GND GND

    To initialize HC-SR04 module send 10µs signal to Trig pin and in same time start counting time.

    HC-SR04 module will make 8 pulse sound waves with frequency around 40MHz and send it with transmitter.

    As waves bounce back from object to the receiver it will turn on Echo pin. In the same time stop mesuring time.

    Now you can calculate distance with formula "d=(v * t/2)".

  • d = distance
  • v = speed of sound (343 m/s = 0.343 mm/s)
  • t = measured time (it is devided by two because sound needed to go to tge object and then bounce back).

    • HC-SR04 Code

    int echoPin = 2;

    int trigPin = 3;

    float d;

    float t;

    void setup(){

    Serial.begin(115200);

    pinMode(trigPin, OUTPUT);

    pinMode(echoPin, INPUT);

    }

    void loop(){

    digitalWrite(trigPin, LOW);

    delayMicroseconds(2);

    digitalWrite(trigPin, HIGH);

    delayMicroseconds(10);

    digitalWrite(trigPin, LOW);

    t = pulseIn(echoPin, HIGH);

    d = t * 0.343 / 2;

    Serial.print("Distance: ");

    Serial.print(d);

    Serial.println(" mm.");

    delay(1000);

    }

    Pulseview

    For better visualization, this is a screenshot of a digital pins with logic analyzer.

    pulseview
  • Pulse is connected to HC-SR04 transmitter.

    • Circuit diagram

    Now we can connect the circuit according to the following circuit:

    Code

    Code explanation

    #include <HC-SR04.h>

    #include <Wire.h>

    #include <LiquidCrystal_I2C.h>

    So that you wouldn't write everything by yourself, you first need to import these libraries.

    #define echoPin 2

    #define trigPin 3

    LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

    HCSR04 hc(echoPin, trigPin);

    In this section for convenients we define echoPin, trigPin. Even if these values are only used once it is good practice to define them (Note that this we could use too: int echoPin = 2; int trigPin = 3;). After that we make instances of LiquidCrystal_I2C and HC-SR04 libraries.

    void setup(){

    Serial.begin(115200);

    lcd.begin(16,2);

    lcd.backlight();

    lcd.clear();

    }

    In the setup function the first think that we do is begin Serial communications at 115200 bits per second. Then we begin lcd with number of rows and columns, turn on the backlight and clear the display.

    void loop(){

    lcd.setCursor(0, 0);

    lcd.print(hc.distance());

    Serial.println(hc.distance());

    lcd.setCursor(14, 0);

    lcd.print("mm");

    lcd.setCursor(0, 1);

    lcd.print(hc.distanceInch());

    lcd.setCursor(12, 1);

    lcd.print("inch");

    delay(200);

    }

    In loop function you can find code that is responsible for showing the correct values on the display. To achieve this we need to use lcd.setCursor() to move cursor on the correct place on the screen and lcd.print() to print text on display. To get distance in millimeters from HC-SR04 module use hc.distance(). If you want to get distance in inches use hc.distanceInch() function or multiply hc.distance() by 0.039.

    Table of contents