Button-Activated LED Fade

This code allows you to increase the brightness of an LED by holding down a button. Release the button to allow the light to dim to nothing.


/* * Use a button to increase the brightness of an LED using analogWrite(). * When the button is released, the brightness descends. * Use the constrain function to keep the brightness between 0 and 255 * Remember analogWrite() only works on pins 3,5,6,9,10,11 */ int brightness; //brightness of the LED void setup() { pinMode(5, OUTPUT); //LED pinMode(12, INPUT_PULLUP); //button } void loop() { brightness = constrain(brightness, 0, 255); //constrain brightness between 0 and 255 analogWrite(5, brightness); //write 'brightness' to the LED delay(5); //pause at each brightness level if (digitalRead(12) == LOW) { //if the button is pressed brightness = brightness + 1; //increase the value of 'brightness' by 1 } else { //otherwise (if button not pressed) brightness = brightness - 1;//decrease brightness by one } } // (c) 2017 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense


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Read the Code Walkthrough Text (click to open)


New Concept: Digital Versus Analog

Some things in the world are very much 'on' or 'off', like a light switch or a car engine. In code, you can think of those types of things as 'digital'. Other things, like a dimmer switch or car's tire speed, are measured on a spectrum. They still have an 'off' position and a 'maximum' position, but there are many small steps between those extremes. These things are 'analog' in code. 

With Maker Board, analogWrite() has a range of outputs from 0 to 255. The analogRead() function has a scale of 0-1023 where it can take readings.


If you're having trouble, try to run a program that can help you find the answer.

1. What is the range of the analogWrite() function?

2. What are the arguments needed by the constrain function?