How to Read Analog Input & Use PWM pin as Analog Output

 

Analog Input:

An analog signal can take on any number of values. To measure the value of analog signals, Arduino has a built-in analog-to-digital converter (ADC). The ADC turns the analog voltage into a digital value.

There is an inbuilt function to read Analog value; analogRead(pin_number). This function converts the value of the voltage on the analog input pin and returns a digital value ranges from 0 to 1023, relative to the reference value. The default reference voltage is 5 V (for 5 V Arduino boards) or 3.3 V (for 3.3 V Arduino boards). This function has only one parameter, which is the pin number.

  

Analog Output:

The Arduino does not have any built-in digital-to-analog converter (DAC), but it can do pulse-width modulation (PWM); a digital signal to achieve some of the functions of an analog output.

The function analogWrite(pin, value) is used to output a PWM signal.

In the function ‘pin’ is the pin number used for the PWM output. ‘value’ is a number proportional to the duty cycle of the signal.

When value is 0, then signal is always off. When value is 255, the signal is always on.

On Uno, Nano, Mini – PWM pins are 3, 5, 6, 9, 10, 11; PWM Frequency is 490 Hz (Pin 5 & 6 : 980Hz)

On Mega- PWM Pins are 2-13, 44-46; PWM Frequency is 490 Hz (Pin 4 & 13: 980Hz)

For mapping an analog input value, which ranges from 0 to 1023 to a PWM output signal, which ranges from 0 - 255, there is an inbuilt function ‘map(value, fromLow, fromHigh, toLow, toHigh)’. This function has five parameters, one parameter is the variable in which the analog value is stored, while the others are 0, 1023, 0 and 255 respectively.

Functions

The below options are Arduino functions associated with Analog signals that we will use in this tutorial:

analogRead()

analogWrite()

 

Example:

Suppose you want to use pin no. A0 to sense any analog sensor, then you will write the function as given below

analogRead (A0);

  

Experiment 1: Analog Value Read

In this experiment, we will read analog value on analog input A0.

Hardware Required

1 x Potentiometer

1 x Arduino UNO

3 x Jumper wire

 

The figure above shows how to connect a potentiometer to Arduino pin A0.

One corner terminal of POT is to be connected to the 5V of Arduino and another corner pin of POT to be connected to GND.

Connect the middle pin of POT to A0.

 

Program for Experiment #1

int inputAnalog = A0; // variable for analog input pin

int analogStatus = 0; // variable to save analog value

 

void setup()

{

Serial.begin(9600); // start the serial communication

}

 

void loop()

{

analogStatus = analogRead(inputAnalog);  //Read the analog input value and save it in the variable

Serial.println(analogStatus); //print the analog input value on serial monitor

delay (1);

}

 

Run the experiment

Connect the POT to the Arduino as shown in the picture above.

Connect the Arduino to the PC using Arduino USB cable and transfer the program to Arduino using Arduino IDE software.

USB cable is also providing the power to the Arduino board so, no need to supply separately to the Arduino.

Rotate the knob of the POT to change the voltage at pin A0.

You can see the value on the Serial communication as shown below

 

 

Experiment 2: Use PWM pin as Analog Output

This experiment will demonstrate how to use a PWM pin as Analog Output.

For mapping an analog input value, which ranges from 0 to 1023 to a PWM output signal, which ranges from 0 - 255, there is an inbuilt function ‘map(value, fromLow, fromHigh, toLow, toHigh)’. This function has five parameters, one parameter is the variable in which the analog value is stored, while the others are 0, 1023, 0 and 255 respectively.

 

Hardware Required

1 x LED

1 x 330 ohm resistor

1x Bread Board

1 x Arduino UNO

2 x jumper Wires

 

 

As you can see from the diagram above, we are now using one Arduino PWM Pin 11. An LED is connected to pin 11, through a resistor of 330 Ohm value, which is a PWM Pin.  When we write the value on PWM pin corresponding to the value brightness of the LED changes.

 

Program for Experiment #2

#define outputAnalog 11 // define constant for PWM pin

#define delay1 1000 // define constant for delay

 

void setup()

{

pinMode(outputAnalog,OUTPUT);

analogWrite(outputAnalog,0);

}

 

void loop()

{

analogWrite(outputAnalog,0);

delay(delay1);

analogWrite(outputAnalog,50);

delay(delay1);

analogWrite(outputAnalog,100);

delay(delay1);

analogWrite(outputAnalog,150);

delay(delay1);

analogWrite(outputAnalog,200);

delay(delay1);

analogWrite(outputAnalog,255);

delay(delay1);

}

Run the experiment

Connect the circuit as shown in the above diagram.

Connect the Arduino to the PC using Arduino USB cable and transfer the program to Arduino using Arduino IDE software.

USB cable is providing also providing the power to the Arduino so, no need to provide the power separately.

As program runs continuously brightness changes.