How To Control The Intensity of Led using Potentiometer/PWM

Introduction

In This tutorial, We are going to show how You can control The intensity or Brightness of LED Using Potentiometer/PWM

You will learn how to Dynamically make the LED fade-in/out when you rotate the potentiometer knob.

How To Control The Intensity of Led using Potentiometer/PWM -Components Required

Circuit Diagram

Steps to build the circuit:

As a best practice, we’ll start with the ground (GND). It’s very important to make a common ground for all components. To do this, we will first plug a black wire (black is convention for GND) between a GND pin of the Arduino and the “minus” line on the breadboard. From this “minus” line, then we will be able to connect all other grounds, which will make things easier to manage.

Add the LED:

Connect the shorter leg of the LED to the ground. You can directly plug this leg into the “minus” line of the breadboard, or add a small black wire.
Plug the other (longer) leg of the LED to an independent line on the breadboard.
From this leg, add a 220 Ohm resistor to yet another line.
Add a wire between the other side of the resistor and a PWM-compatible digital pin (so we can control the brightness). Here on Arduino UNO you can choose between pins 3, 5, 6, 9, 10, and 11 – you can recognize PWM compatibility with the “~” next to the pin number.

Add the Potentiometer:

Plug the 3 legs of the potentiometer to 3 different lines on the breadboard.
Connect the extreme left (or right) leg to GND.
Connect the other extreme leg to 5V on the Arduino.
Add a wire between the middle pin and an analog pin.

Arduino’s code to control LED brightness with the potentiometer

In this application, what we want to do is simple: when we turn the knob up (for example turning clockwise), we want the LED brightness to increase.

The minimum knob position will correspond to the minimum brightness – LED turned off. And the maximum position will correspond to the maximum brightness – LED with full intensity, same as if you used digitalWrite() with HIGH.

You Can use This Code

/****************************************************************************************************
Description: Control Led Intensity using Potentiometer/PWM
Website: www.Iduino.co.in
E-mail: support@Iduino.co.in
Modified BY: IDUINO
****************************************************************************************************/
#define LED_PIN 11
#define POTENTIOMETER_PIN A1
void setup()
{
  pinMode(LED_PIN, OUTPUT);
}
void loop()
{
  int potentiometerValue = analogRead(POTENTIOMETER_PIN);
  int brightness = potentiometerValue / 4;
  analogWrite(LED_PIN, brightness);
}

Code Explanation

#define LED_PIN 11
#define POTENTIOMETER_PIN A1

“#define” is used to Pre-define the values in the program

LED_PIN Defined for digital Pin 11 in code

POTENTIOMETER_PIN Defined for Analog Pin A1

One for the LED pin, one for the potentiometer. This way, we can modify the circuit at any moment, all we’ll need to do in the code is to modify those 2 lines.

void setup()
{
  pinMode(LED_PIN, OUTPUT);
}

void setup()

In the void setup(), we need to initialize the mode for the pins we want to use:

The LED is a component we control, so we use pinMode() with OUTPUT.
The potentiometer is a component we read from, so its mode is INPUT. However, for analog pins, no need to use pinMode() as those pins are already in INPUT mode!

pinMode, LED_PIN Defined as output for providing output to your project

Read potentiometer value

int potentiometerValue = analogRead(POTENTIOMETER_PIN);

We enter the void loop(), and the first thing we do is to read the potentiometer value.

To do that we use the analogRead() function, which takes one parameter: the pin number to read from. We store the value inside an integer variable. This value will be in the range 0-1023. In other words, this is a 10 bit number: 2^10 = 1024.

This number corresponds to the voltage we read on the analog pin. The higher the voltage, the higher this number. For 0V you get 0, and for 5V you get 1023.

Compute LED brightness (option 1)

int brightness = potentiometerValue / 4;

In order to control the LED brightness, we are going to use the analogWrite() function on the LED pin (later on). This analogWrite() function takes a byte value, or in other words, a number between 0 and 255.

So, before we use this function, we need to make sure the value is in the correct range. And as I really like simplicity, you can see that, roughly, 1024 is 255 multiplied by 4 (not exactly this value but this is a good enough approximate for what we need to do). So, if we want to put a value from the range 0-1023 to the range 0-255, we can just divide by 4.

Nothing fancy here, it’s very simple and it works.

Compute LED brightness with map (option 2)

int brightness = map(potentiometerValue, 0, 1023, 0, 255);

To do the same thing, you could also use the Arduino map() function which can put a number into a different range.

With this line and the 5 arguments in the function, what we’re saying is: take the potentiometer Value from the range 0-1023, to the range 0-255.

Using map() is great whenever you need to do operations like this, and it works for any integer range.

Apply brightness setting to LED

analogWrite(LED_PIN, brightness);

So now we have computed the brightness to apply to the LED. This brightness variable is an integer number between 0 and 255. Exactly what we need for the analogWrite() function.

analogWrite() takes 2 arguments: the pin to apply the voltage to, and then a byte number between 0-255.

Note: this is only going to work on PWM compatible pins. So if you see that the LED is just fully powered off/on when you run this program, this is probably because the digital pin you’ve chosen is not PWM compatible.

So, what’s going to happen here: the value 0-255 will be translated into a voltage. 0V for 0, 5V for 255, and proportional values in between.

After this instruction, the void loop() exits and is called again, so we directly apply the new potentiometer value to the LED brightness. The update frequency is very high here, so you when you turn the potentiometer knob, you will immediately see the LED brightness change.