Analog Inputs
So far we have dealt only with digital inputs, which have two values: off and on, or 0 and 1. There’s another class of inputs - analog inputs have a smooth range between two values - “off” and “full blast.” Some familiar analog controls include the volume knob on your radio, or the dimmer switch on household lights.
The Arduino has special pins for analog inputs that convert voltages between 0V and 5V to numbers between 0 and 1024. There are 8 analog pins in total, A0 through A7, that run down the left side of your Arduino. Before we explore how to read values from analog sensors, let’s take a close look at one particular type of sensor.