Arduino有數位輸出入的功能,先前有實驗過讓LED閃爍,這篇要形成基本的控制,以一個按鈕做為輸入的信號來控制LED
Jason Chin2019/9/21
當我們按鈕或是開關時,是連接電路的兩個端點,這個範例是當我們按下了按鈕,就會讓連接 Pin 13 的內建 LED 亮起來
硬體需求
- Arduino 電路板
- 按鈕開關
- 10K ohm 電阻
- 連接電線
- 麵包板
電路連接
連接到 Arduino 的線一共三條,其紅色線連接到戈人一田卜麵包板的電源,黑色線連到麵包板的地(GND),第三條線如圖的藍色線則連接到 Digital Pin 2,Push Button 如圖示的二支腳,其中一支接10K Ohms 電阻,連接到地(GND),開關的另一支腳則接到電源端(+5V)
Push 連接電阻的對面那支腳,與電阻那支腳是相通的,所以等於開關連接電阻的腳給它連接到 Digital Pin 2 去,做為開關的輸入端,也就是說當按下開關,+5V 等於輸入到 Pin 2 去,做為”開”的信號,而放開按鈕則是”關”的信號了
為什麼要有那顆 10K Ohms 電阻,其實他稱之為”提昇電阻”,為避免邏輯電路的邏輯閘,不連接時稱之為浮接 (floating) 現象,造成不是輸入”0” 也不是輸入 “1” 這種情形,所以需要提昇電阻,用來確認在”關”的時候為 “0” ,即低電位(GND)
電路圖
程式碼
說明: 程式中,用 digitalRead(buttonPin) 讀取 Digital Pin 的信號
在程式中用判斷式,判斷按鈕是否被按下,若被按下則以
digitalWrite(ledPin, HIGH) 先給 LED Pin 輸出為 “1” LED 亮起來
若按鈕沒被按下,則用 digitalWrite(ledPin, LOW) 先給 LED Pin 輸出為 “0” LED 熄滅
以下為原文的程式碼
/*
Button
Turns on and off a light emitting diode(LED) connected to digital
pin 13, when pressing a pushbutton attached to pin 2.
The circuit:
* LED attached from pin 13 to ground
* pushbutton attached to pin 2 from +5V
* 10K resistor attached to pin 2 from ground
* Note: on most Arduinos there is already an LED on the board
attached to pin 13.
created 2005
by DojoDave <http://www.0j0.org>
modified 30 Aug 2011
by Tom Igoe
This example code is in the public domain.
http://www.arduino.cc/en/Tutorial/Button
*/
// constants won’t change. They’re used here to
// set pin numbers:
const int buttonPin = 2; // the number of the pushbutton pin
const int ledPin = 13; // the number of the LED pin
// variables will change:
int buttonState = 0; // variable for reading the pushbutton status
void setup() {
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT);
}
void loop() {
// read the state of the pushbutton value:
buttonState = digitalRead(buttonPin);
// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:
digitalWrite(ledPin, HIGH);
} else {
// turn LED off:
digitalWrite(ledPin, LOW);
}
}
