What is analogRead() function in Arduino??

What is the analog read function, how to use analogRead() functions, and what does analogRead function read values are some questions that may arise while programming an Arduino.

Hello guys! Today we going to see about the analogRead() function in Arduino so let’s begin.

What is analogRead() function??

analogRead is used to read analog voltages from 0 to 5v and convert them into digital integer values from 0 to 1023. The analogRead function is similar to the digitalRead function as it takes only one argument inside the function, the analogRead function reads analog values as input. analogRead function returns integer value from 0 to 1023, unlike in digitalRead it return only values 0 or 1 means HIGH or LOW (5v or 0v).analogRead reads a scale between value between 0 and 1023.

what is analogRead in Arduino

Analog reads values are used to read analog values from sensors like temperature sensors, resistance, voltage, and current. analogRead function reads the value from analog input pins A0-A5 of Arduino and feds to onboard analog to digital (ADC) converter to give digital values range between 0 to 1023. ADC can measure 1024 (2^10) as ADC is of 10-bit.

analogread Arduino

What is the difference between digitalRead and analogRead??

digitalRead() reads current status of digital pin whether its HIGH or LOW in form of 0 & 1 means 0v & 5v(1 - HIGH & 0 – LOW).  digitalRead() returns one values whether 0 or 1 which represents 0v and 5v. digitalRead() is used by digital pin (0-13) of Arduino.

analogRead() reads Analog voltage from 0v to 5v. analogRead() returns integer values from 0 to 1023. analogRead() returns values from 0 to 1023 which represents 0v to 5v. analogRead() uses an analog pin from A0-A5 as input and fed it to ADC to convert it to give integer values.

pinMode(A0, INPUT);

Reading analog voltages through the analog pin A1 and store into variables.

int readvalue = analogRead(A0);

That value is stored in variable name readvalue is the value between 0 to 1023.

Serial.print(“Analog value :“);


Arduino analog read

Simple Example of analogRead using potentiometer and Arduino

Code - 

int potentiometer_pin = A0;
int potnetiometer_value;
void setup() {

void loop() 
 potnetiometer_value = analogRead(potentiometer_pin);

Output - 

analogRead output

How to read voltages in Arduino using analogRead()??

To understand how the analogRead function works first we need to know the basics of ohm’s law.

ohm's law formula

In the above circuit, we know that current flows from higher potential toward a lower potential mean from positive terminal to negative terminal. But electron flows on the opposite side from the negative side toward the positive side. Opposite charges electrons are repelled by negative charge batteries hence it moves towards the positive charge of batteries.

According to ohm’s law


Where V is a voltage in volts, I is the current in Amp flowing in a circuit & R is the resistance in Ohms offered by the circuit.

So I = V/R and R= V/I

ohm's law equation

For example, consider a voltage of 5v and resistor of 330Ω

I= V/R = 5/330 = 15.15 mA

So we got the current flowing in a circuit as I = 15.15 mA

What if you have more than one resistor?

From above we have current I = 15.15 mA, Resistor R1 = 330Ω & Resistor R2 = 100Ω

So total Resistor

 Rs = R1+R2 = 330Ω + 100Ω = 430Ω

reading voltage using Arduino

So total Current

I = V/Rs = 5v/430Ω = 11.63 mA

V1 = IR1 = 11.63 x 330 = 3.4v

V2 = IR2 = 11.63 x 100 = 1.16v

By Reading voltage by Arduino

Slope (m) = (y2 – y1/ x2 - x1)

Slope (m) = (5 – 0 / 1023 – 0)

(m) = 5 / 1023

y – y1 = m(x - x1)

y = (5 / 1023) * (x)

y = voltage & x = value from sensor

Voltage (v) = 5.0/1023.0 * value from sensor

X represents values read by Arduino read pin from the potentiometer

Y represents the output voltage

Arduino with LDR to read voltage using analogRead()

This image is created using fritzing

Connect the ground pin of the LDR sensor to the ground pin of Arduino, the VCC pin to 5v, and the Signal pin to A1. Also, connect the positive lead of LED to Arduino pin 6.

Code - 

int LDR_pin = A1;
int Sensor_value;
int LED_pin = 6;
float voltage;
void setup() 
void loop() 
 Sensor_value = analogRead(LDR_pin); 
  voltage = (5.0/1023.0)* Sensor_value;


Arduino with a potentiometer to read Analog voltage using analogRead()

10k ohm potentiometer

Potentiometers are variable resistors having three pins terminal. The first pin is where we connect Vcc, the last pin is where we connect to the ground and at the middle pin we connect the signal pin.

To understand potentiometers we will look at how potentiometers work.

rotary potentiometer

When we move the slider (B) upside towards point A, then the voltage at the reading pin (Analog pin) will be 5v. When we move the slider (B) towards the downside the read pin which is the analog pin will read 0v and when the slider is between point A and point C, the read pin will read 2.5v. Equivalent circuit to get more analysis.

How does Potentiometer work??

b10k potentiometer

R Total = 10k

R Total will change according to pot value in my case its 10K

a potentiometer

If we move the slider left side in an anti-clockwise direction the value of R2 will be 0, R2=0

R Total = R1 + 0

R Total = R1 = 10k

If we move the slider right side in the clockwise direction the value of R1 will be 0, R1=0

R Total = 0 + R2

R Total = R2 = 10k

If we move the slider in middle between R1 resistor and R2 resistor then.

R Total = R1 + R2 = 5k + 5k = 10k

V = IR, I = V/R

I = 5/10k = .5mA

Current I = .5mA

Voltage (V) = I x R2

If R2 = 0, then Voltage (V) = .5 x 0 = 0

If R2 = 10k, then Voltage (V) = .5 x 10k = 5v

potentiometer Arduino

Code -
int potentiometer_pin = A0;
int potnetiometer_value;
float voltage;
void setup() {
void loop() 
 potnetiometer_value = analogRead(potentiometer_pin);
 voltage = (5.0/1023.0)* potnetiometer_value;

Output - 

Now we used the serial monitor to observe the output. To open up the serial monitor, click on Tools > Serial Monitor or use the shortcut (SHIFT + CONTROL + M)You can see when there is the value of voltage increases and decreases according to the rotation of knob of potentiometer”. the rotation of the knob can be the clockwise or anti-clockwise direction.

Conclusion –

Today we learn about the analogRead() function in Arduino, where to use the analogRead function, how to use the analogRead function, the syntax and parameters of the analogRead function, the difference between digital read and analogRead, read voltages in Arduino & Arduino with the potentiometer to read Analog voltage.

"I hope you find this IoT blog very helpful to you. In the upcoming lesson, we will see more about IoT sensors till then bye. See you all in my next blog."

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