Lesson 12 Making a Voltmeter

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Introduction

In this lesson, we will use a potentiometer and an I2C LCD1602 to make a voltmeter.

Components

– 1* SunFounder Uno board

– 1 * USB data cable

– 1 * Potentiometer (50KΩ)

– 1 * I2C LCD1602

– Several jumper wires

– 1 * Breadboard

Experimental Principle

In this experiment, a potentiometer is used to divide voltage. Since the SunFounder Uno board can only read digital signals, but what the sliding end of the potentiometer outputs are analog signals, we need to convert these analog signals into digital ones with an Analog-to-Digital Convertor (ADC). Fortunately, the SunFounder Uno board itself comes with a 10-bit ADC which we can use to implement this conversion. Then display this digital output voltage on the I2C LCD1602.

Experimental Procedures

Step 1: Build the circuit

Step 2: Program (Please refer to the example code in LEARN -> Get Tutorials on our website)

Note: Here you need to add a library. Refer to the description in Lesson 4 previously in the manual.

Step 3: Compile the code

Step 4: Upload the sketch to the SunFounder Uno board

Now, adjust the potentiometer and you will see the voltage displayed on the I2C LCD1602 varies accordingly.

Code 

/****************************************
name: Voltmeter
function:adjust the potentiometer and you will see the voltage displayed on the I2C LCD1602 varies accordingly.
******************************************/
//Email:support@sunfounder.com
//Website:www.sunfounder.com/*************************************/
// include the library code
#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
/****************************************************/
LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to 0x27 for a 16 chars and 2 line display
float val = 0;
/****************************************************/
void setup()
{
  Serial.begin(9600);//initialize the serial
  lcd.init(); //initialize the lcd
  lcd.backlight(); //open the backlight 
  lcd.print(“Voltage Value:”);//print “Voltage Value:”
}
/****************************************************/
void loop()
{
  val = analogRead(A0);//Read the value of the potentiometer to val
  val = val/1024*5.0;// Convert the data to the corresponding voltage value in a math way
  Serial.print(val);//Print the number of val on the serial monitor
  Serial.print(“V”); // print the unit as V, short for voltage on the serial monitor
  lcd.setCursor(6,1);//Place the cursor at Line 1, Column 6. From here the characters are to be displayed
  Serial.println( );
  lcd.setCursor(6,1);//Place the cursor at Line 1, Column 6. From here the characters are to be displayed
  lcd.print(val);//Print the number of val on the LCD
  lcd.print(“V”);//Then print the unit as V, short for voltage on the LCD
  delay(200); //Wait for 200ms
}