You can also use a potentiometer or other variable resistor to change the brightness of an LED.

Using Arduino IDE and a pot to read analog voltage and display that on the serial monitor.

/*

ReadAnalogVoltage

Reads an analog input on pin 0, converts it to voltage, and prints the result to the serial monitor.

The graphical representation is available using serial plotter (Tools > Serial Plotter menu)

Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

This example code is in the public domain.

*/

// the setup routine runs once when you press reset:

void setup() {

// initialize serial communication at 9600 bits per second:

Serial.begin(9600);

}

// the loop routine runs over and over again forever:

void loop() {

// read the input on analog pin 0:

int sensorValue = analogRead(A0);

// Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):

float voltage = sensorValue * (5.0 / 1023.0);

// print out the value you read:

Serial.println(voltage);

}

USING Max MSP and Jitter to read and display output to an LED