BLINK
Blink Turn an LED on and off every second. This example shows the simplest thing you can do with an Arduino to see physical output: it blinks the on-board LED. Hardware Required Arduino Board LED 220 ohm resistor Circuit This example uses the built-in LED that most Arduino boards have. This LED is connected to a digital pin and its number may vary from board type to board type. To make your life easier, we have a constant that is specified in every board descriptor file. This constant is LED_BUILTIN and allows you to control the built-in LED easily. Here is the correspondence between the constant and the digital pin. D13 - 101 D13 - Due D1 - Gemma D13 - Intel Edison D13 - Intel Galileo Gen2 D13 - Leonardo and Micro D13 - LilyPad D13 - LilyPad USB D13 - MEGA2560 D13 - MKR1000 D13 - Nano D13 - Pro D13 - Pro Mini D13 - UNO D13 - Yún D13 - Zero D13 - 101 If you want to light an external LED with this sketch, you need to build this circuit, where you connect o