Result

You should now switch between connecting the loose end of the jumper wire to 5V and GND. When connected to 5V the on-board LED should turn on, when connected to GND the LED should turn off. Note that it will not work perfectly.

New commands

• pinMode(pinNumber, INPUT): configures the digital pin pinNumber to behave as an input.
• digitalRead( pinNumber): reads the value from the digital pin pinNumber, either HIGH or LOW.

Repetition:

• if( test ){ statements }: Checks if test is true or false. If true, the statements inside the curly brackets are executed. If false the program jumps to and executes the code after the curly brackets.
• value1 == value2: Compares value1 and value2. If the values are equal it returns true (1), if they are not equal it returns false (0). The double equal sign is called an operator.

How it works

• Two variables are declared, ledPin and inputPin. ledPin holds the value 13, and inputPin the value 5.
• In setup(), pin 13 is configured as an output and pin 5 is configured as an input.
• In loop(), pin 5’s state is read, and simultaneously checked if it is equal to HIGH.
• If the wire is connected to 5V the reading is HIGH, and the LED is turned on by writing HIGH to pin 13.
• If the wire is connected to GND the reading is LOW, and the LED is turned off by writing LOW to pin 13.
• loop() continues to loop, which means that the state on pin 5 is checked continuously.

Button

A single jumper wire might be a good way to explain the theory behind digital inputs, but it is not a reliable input for your projects. It is better to introduce you to the button. With an Arduino, you can read two different states from a button; HIGH or LOW.

In the next example you will use a TinkerKit button. TinkerKit components makes it easier for you to make circuits because they already are small circuits with the electronic components needed, such as resistors.

Example 2.8

This example does the same thing as the previous one, but instead of using a jumper wire as input, you will use a TinkerKit button.

Materials

• 1 Arduino Uno board
• 1 Education Shield
• 1 TinkerKit button
• 1 TinkerKit wire

Instructions

1. Attach the shield onto the top of the Arduino board.
2. Connect the TinkerKit button to D9 using the TinkerKit wire.
3. Upload the following code: