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Arduino UNO R3/MEGA 2560 R3 Project 15: Analog Value Reading

Posted by Fiona Su on

Introduction

In this experiment, we will begin the learning of analog I/O interfaces. On an Arduino, there are 6 analog interfaces numbered from 0 to 5. These 6 interfaces can also be used as digital ones numbered as 14-19.
After a brief introduction, let's begin our project. Potentiometer used here is a typical output component of analog value that is familiar to us.

Hardware Required

  • Potentiometer *1
  • REV4 board *1
  • Breadboard*1
  • USB cable *1
  • Breadboard jumper wire * 3

Video Tutorial

Connection

In this experiment, we will convert the resistance value of the potentiometer to analog ones and display it on the screen. This is an application you need to master well for our future experiments.
Connection circuit as below:
Connection for REV4:

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Connection for 2560 R3:

thumb

The analog interface we use here is interface A0.

Sample Code:

The program compiling is simple. An analogRead () Statement can read the value of the interface. The A/D acquisition of Arduino 328 is in 10 bits, so the value it reads is among 0 to 1023.
One difficulty in this project is to display the value on the screen, which is actually easy to learn. First, we need to set the baud rate in voidsetup (). Displaying the value is a communication between Arduino and PC, so the baud rate of the Arduino should match the the one in the PC's software set up.
Otherwise, the display will be messy codes or no display at all. In the lower right corner of the Arduino software monitor window, there is a button for baud rate set up. The set up here needs to match the one in the program. The statement in the program is Serial.begin(); enclosed is the baud rate value, followed by statement for displaying. You can either use Serial.print() or Serial.println() statement.

int potpin=0;// initialize analog pin 0
int ledpin=13;// initialize digital pin 13
int val=0;// define val, assign initial value 0
void setup()
{
pinMode(ledpin,OUTPUT);// set digital pin as “output”
Serial.begin(9600);// set baud rate at 9600

}
void loop()
{
digitalWrite(ledpin,HIGH);// turn on the LED on pin 13
delay(50);// wait for 0.05 second
digitalWrite(ledpin,LOW);// turn off the LED on pin 13
delay(50);// wait for 0.05 second
val=analogRead(potpin);// read the analog value of analog pin 0, and assign it to val 
Serial.println(val);// display val’s value
}

Result:
The sample program uses the built-in LED connected to pin 13. Each time the device reads a value, the LED blinks.
Below is the analog value it reads.

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When you rotate the potentiometer knob, you can see the displayed value change. The reading of analog value is a very common function for most sensors output analog value. After calculation, you can get the corresponding value you need.
The experiment is now completed. Thank you.

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