Objectives:
 Learn how a button works
 Be able to wire and program a button to make LEDs flash
By the end of this session:
 You will know how to write a program and connect a
button to change the ways that LEDs flash, as well as
how to use ‘IF’ statements.
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Arduino Uno
Breadboard
Jumper Wires
LEDs
Resistors
When the button is pressed, a connection is made
between the two legs of the device, this can be detected by the Arduino and can be used to provide an
input and to affect the way that a program runs.
Buttons
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1)
Insert the button and resistor into the
breadboard as in the diagram. Make sure that
there is a black stripe on the resistor!
2)
Connect a wire between the leg of
the button and the GND pin on the
Arduino
3)
Connect a wire between the
other leg of the button and the
‘9’ pin and, then connect a
wire between the other leg of
the resistor and the 5V pin, as
in the diagram
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1)
Plug the USB cable into the Arduino and Computer, then open the Arduino
Program.
2)
Visit the website—http://bit.ly/1woHjXc—and copy and paste the
‘Button template program’ into the Arduino window.
3)
The program sets ‘button’
(pin 9) as an INPUT in the
setup function.
It then enters the loop and
saves the value read from
the button into a variable
called buttonState. This is 1
if the button is not pressed,
or 0 if the button is pressed.
The final part checks to see if
the buttonState value is 0
(pressed), then it turns the built-in LED on, else it turns the built in LED
off.
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4)
Upload the program by clicking on the upload button.
5)
Your LED should turn on when you press the button and then turn off as
soon as you let go.
Now, add the following lines of code, to make the LED flash when you hold
the button down.
6)
Upload the program by clicking on the upload button.
7)
The LED should flash when you press the button.
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8)
Try connecting another button to the breadboard as shown in the
diagram,
then
add
the
following
lines
of
code:
You will see that the green wire has been added to connect the two
buttons together, but since the first button’s leg was connected to GND,
both LED’s legs become connected to GND. The blue wire was added to
connect the button to pin 8 on the Arduino.
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9)
We need to tell the program that we have added another button.
Firstly, we need to give it a
name and make a variable
for its value to be
stored
We need to tell it that
’newButton’ is an input
We then need to save the
button state
Finally, make the LED flash,
only when both the
buttons are pressed.
10)
Upload the program by clicking on the upload button.
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11)
You should see the LEDs flashing only when you press both buttons. This is
because the if statement means, if the first button is pressed (==0) AND the
second one is also pressed (==0), then flash the lights.
Extension task
If you finish all of these steps, try making the LED flash when either button is
pressed, or make it flash all the time, but when the buttons are pressed,
they flash faster.
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