Arduino PMW

PWM stands for Pulse Width Modulation. Arduino uses this powerful PWM technique for controlling analog circuits with its digital outputs. Digital control uses to be only turn on (full 5v) or off (0v) in the binary format, and this on/off pattern can generate a square wave signal. For example if you want a LED to be half bright, you can either reduce the current across the LED into half or using this the more flexible PWM technique by sending 50% duty cycle square wave signal to the LED.

This simple Arduino tutorial is created to demonstrate how to dim a LED by using this PWM technique from Arduino.

On the Uno and similar boards, pins 5 and 6 have a frequency of approximately 980 Hz. Pins 3 and 11 on the Leonardo also run at 980 Hz.

On most Arduino boards (those with the ATmega168 or ATmega328), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 - 13 and 44 - 46. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11.

The Arduino Due supports analogWrite() on pins 2 through 13, plus pins DAC0 and DAC1. Unlike the PWM pins, DAC0 and DAC1 are Digital to Analog converters, and act as true analog outputs.

What you need for this tutorial?

• Any of the Arduino Board (Arduino UNO will be used in this example)
• 1 x Potentiometer,
• 1 x 22oΩ resistor, (or any resistor that suits your LED)
• 1 x LED (any color based on your mood),
• 1 x Breadboard.

Connect your circuit as the below diagram.

I am using digital pin 3 as the PWM output in this example or you can use any pin that marked with PWM (if you are Arduino UNO, PIN 3, 5, 6, 9, 10 and 11 support PWM).

Arduino Code:

int inputPin = A0;  // set input pin for the potentiometer
int inputValue = 0; // potentiometer input variable
int ledPin = 3;     // set output pin for the LED

void setup() {
     // declare the ledPin as an OUTPUT:
     pinMode(ledPin, OUTPUT);
}

void loop() {
     // read the value from the potentiometer:
     inputValue = analogRead(inputPin);

     // send the square wave signal to the LED:
     analogWrite(ledPin, inputValue/4);
}

analogRead() will always return the range between 0 to 1023 from the analog device (the potentiometer in this case), but the analogWrite() function only supports the range from 0 to 255. e.g. analogWrite(127) always send a 50% duty cycle to the LED, analogWrite(255) is a full 100% duty cycle (full brightness) and analogWrite(0) is always off.

You can test out this tutorial by turning the potentiometer, the brightness of the LED changes ranging from completely off to the full brightness as you turn the potentiometer.