1. Arduino learning notebook -- Button experience (VOL. 1)
1. Arduino learning notebook -- Button experience
www.juvtamll.com ( a company supply PCB Prototyping, PCBA service, sell modules.)
The button is a commonly used key, normally
used to connect or disconnect the circuit, so as to control the the motor or
other equipment.
The buttons have a variety of appearance.
This experiment is used for this kind of miniature keypad, 6mm, as shown below.
Look at the back of the button, it has 4
pins.
When the button not be pushed, No. 1 and 2 are
connected, 3 and 4 are connected.
When the button is pressed down, all the
pins will be connected.
We use button to control the led.
The general situation is install the button
series in the led circuit, however, it’s too simple.
We use the indirect way, the button judge output
voltage from the circuit. If the voltage is greater than 4.88 V, output high
level to the LED circuit, whereas output low level. Using logical judgment to light
or off the LED, this control method is used widely.
The connection method is shown below.
A part of button is connected to 5V pin,
the other side is connected to analog pin 5. LED long pins in series 220 Ω
resistance connecting pin 7, short pins to GND.
Upload the following code to the arduino
control panel to see the effect.
[code]
1. int key = 7; / / set the digital IO pin
of the LED
2. void setup ()
3. {
4. pinMode (key, the OUTPUT); / / set
digital IO pin to output mode
5.}
6. void loop ()
7. {
8. int I; / / define variable
9. while (1)
10. {
11. i = analogRead (5); / / read the voltage
from analog pin 5
12. if (i > 1000) / / if the voltage
value is greater than 1000 (i.e. 4.88 V)
13. digitalWrite (key, HIGH); / / set the
seventh pin for high level and light led
14. else
15. digitalWrite (key, LOW); / / set the
seventh pin for low level and extinguish led lights
16.}
17.}
The experiment uses analogRead() function
to read the values of the analog interface.
Divide the input voltage of 0-5v into 1024
copies, each of which is approximately 0.0049 V and its value is between 0 and
1023.
If the value is greater than 1000, output
high level to LED, the corresponding voltage will be greater than 4.88 V.
The scope and resolution of the analogRead
() command can be modified by using the analogReference () command.
At the beginning of this experiment, the
standard of judgment was 512, which is 2.5 V.
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