Examples > Analog
This example shows how to read an analog input pin, map the result to a range from 0 to 255, and then use that result to set the pulsewidth modulation (PWM) of an output pin to dim or brighten an LED.
Connect one pin from your pot to 5V, the center pin to analog pin 0, and the remaining pin to ground. Next, connect a 220 ohm current limiting resistor to digital pin 9, with an LED in series. The long, positive leg (the anode) of the LED should be connected to the output from the resistor, with the shorter, negative leg (the cathode) connected to ground.
In the program below, after declaring two pin assignments (analog 0 for your potentiometer and digital 9 for your LED) and two variables,
outputValue, the only thing that you do will in the setup function is to begin serial communication.
Next, in the main loop of the code,
sensorValue is assigned to store the raw analog value coming in from the potentiometer. Because the Arduino has an
analogRead resolution of 0-1023, and an
analogWrite resolution of only 0-255, this raw data from the potentiometer needs to be scaled before using it to dim the LED.
In order to scale this value, use a function called
outputValue is assigned to equal the scaled value from the potentiometer.
map() accepts five arguments: The value to be mapped, the low range and high range of the raw data, and the low and high values for that data to be scaled too. In this case, the sensor data is mapped down from its original range of 0 to 1023 to 0 to 255.
The newly mapped sensor data is then output to the
analogOutPin dimming or brightening the LED as the potentiometer is turned. Finally, both the raw and scaled sensor values are sent to the Arduino serial window in a steady stream of data.