Circuit 04 - Potentiometers (POT)

Background

In this project, you’ll work with a potentiometer. A potentiometer is also known as a variable resistor. When it’s connected with 5 volts across its two outer pins, outputs of the middle pin will be a voltage between 0 and 5, depending on the position of the knob on the potentiometer. In this circuit, you’ll learn how to use a potentiometer to control the blinking and brightness of an LED.

Parts List

	Name	Quantity
	LED (Any colour)	1
	330Ω Resistor (Orange-Orange-Brown)	1
	Jumper Wire (Any colour)	6
	Potentiometer (POT)	1

Circuit Diagram

Breadboard Diagram

Code

Here's the code for circuit #4:

int sensorPin = A0; // The POT is connected to pin A0
int ledPin = 11;    // The LED is connected to pin 11

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // store reading from potentiometer into integer 
  // variable "sensorValue"
  int sensorValue;
  sensorValue = analogRead(sensorPin);

  // change the blink speed using "sensorValue"
  digitalWrite(ledPin, HIGH);
  delay(sensorValue);

  digitalWrite(ledPin, LOW);
  delay(sensorValue);
}

What You Should See

You should see the LED blink faster or slower in accordance with your potentiometer. If it isn't working, make sure you have assembled the circuit correctly and verified and uploaded the code to your board or see the - troubleshooting tips below.

Troubleshooting

Sporadically Working?

This is most likely due to a slightly dodgy connection with the potentiometer's pins. This can usually be conquered by holding the potentiometer down.

Not Working?

Make sure you haven't accidentally connected the potentiometer's wiper to digital pin 0 rather than analog pin A0 (the row of pins beneath the power pins).

Still Backward??

You can try operating the circuit upside down. Sometimes this helps.

Real World Application

MP3 players' volume control is an example of a potentiometer in action.

The Code Explained

Code	Explanation
int sensorPin = A0; and int ledPin = 11;	Declaring two integer (whole number) variables to remember the pin numbers.
pinMode(ledPin, OUTPUT);	Same outcome as pinMode(11, OUTPUT); from circuit #1 but now we are using a variable instead. Using a variable is a good idea if you need to change the pin used during your project.
analogRead(sensorPin);	analogRead(sensorPin) returns an integer number ranging from 0 (0 volts) to 1032 by reading the sensorPin
// single line comment	This is a comment. Text or code in the comment does not get executed in the program. Comments are usually used as places to put notes or information about the program. Use /* */ to make multi-line comments.

Digital versus Analog

If you look closely at your Arduino, you'll see some pins labeled "DIGITAL", and some labeled "ANALOG". What's the difference?

DIGITAL: Many devices, such as LEDs and pushbuttons, have only two possible states: ON and OFF, or as they're known to the Arduino, "HIGH" (5 Volts) and "LOW" (0 Volts). The digital pins on an Arduino are great at getting these signals to and from the outside world, and can even do tricks like simulated dimming (by blinking on and off really fast), and serial communications (transferring data to another device by HIGH and LOW).

ANALOG: There are a lot of things out there that aren't just ON or OFF. Temperature levels, control knobs, etc. all have a continuous range of values between HIGH and LOW. For these situations, the Arduino offers six analog inputs that translate an input voltage into a number that ranges from 0 (0 Volts) to 1023 (5 Volts). The analog pins are perfect for measuring all those "real world" values, and allow you to interface the Arduino to all kinds of things.

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Circuit 03 - Buzzers	Circuit 05 – Multiple LEDs