In the embedded world, controlling a single LED is "Hello World" code, which we learned in first chapter. Now, as we are familiar with the concepts of LED, we can start to control multiple LEDs with Arduino. Here, we will start by making a simple traffic light module.
As we all know, a traffic light is made up of three LEDs: red, yellow, and green. To make this project, we need red, green, and yellow LEDs, strip wires, and a few 255 Ω resistors.
In the previous chapter, in our "Hello World" program, we connected an LED directly with pin 13. Here, we will connect red, yellow, and green LEDs with pins 9, 10, and 11 respectively. In the case of pin 13, it has an in-built pull up resistor. Pull up resistors are used to limit the current supplied to an LED. We can't give current of more than a few mA to LEDs. But, with pin 13, current is itself limited in Arduino by the internal pull up resistor. If we want to connect to pins other than 13...
