1. 按键控制

1.1 认识按键

• 目的：控制电动机或其他电气设备运行，常用来连通或断开，控制电路
  

1.2 工作原理

• 原理：K1、K2、K3、K4【开关量】与数字引脚相连，通过对按键操作，展现为电平的高低
  • 不按的情况，K1连接R1，与VCC相连，表现为高电平
  • 按下键时，K1直接与GND相连，表现为低电平
    

1.3 Arduino代码展示

//定义按键
int k1 = 8;
int k2 = 9;
int k3 = 10;
int k4 = 11;void setup(){Serial.begin(9600);pinMode(k1, INPUT);pinMode(k2, INPUT);pinMode(k3, INPUT);pinMode(k4, INPUT);
}void loop(){if(!digitalRead(k1))	//按下k1，digitalRead返回值为低电平【即返回为0】，取反为1，打印出“k1被按下”Serial.println("K1 is pressed");if(!digitalRead(k2))Serial.println("K2 is pressed");if(!digitalRead(k3))Serial.println("K3 is pressed");if(!digitalRead(k4))Serial.println("K4 is pressed");delay(100);
}

1.4 原理图

• k1被按下时，看窗口监视器输出什么
  
• 一下输出3个的“K1 is pressed”的原因是程序的抖动

1.5 实现去抖【消抖动延时】

int k1 = 8, k2 = 9, k3 = 10, k4 = 11; //定义按键
int key = 0; //定义键值
int key1 = 0；void setup(){Serial.begin(9600);pinMode(k1, INPUT_PULLUP);pinMode(k2, INPUT_PULLUP);pinMode(k3, INPUT_PULLUP);pinMode(k4, INPUT_PULLUP);
}void read_key(){if(!digitalRead(k1) || !digitalRead(k2) || !digitalRead(k3) || !digitalRead(k4)){ //同时读取4个按键值，只要有一个按键被按下，则显示为低电平，取反之后为1，条件为真，执行程序delay(25); //消抖动延时if(!digitalRead(k1) || !digitalRead(k2) || !digitalRead(k3) || !digitalRead(k4)){ //再次读取键值，确认是否有按键if(!digitalRead(k1)) key = 1; //记录按下的键值if(!digitalRead(k2)) key = 2;if(!digitalRead(k3)) key = 3;if(!digitalRead(k4)) key = 4;}else key = 0;}if(key1 != key) //只要这个键一直按着不松开，则认为按一个键。屏蔽标准键盘输入的联机问题，不会认为按许多键key1 = key;else key = 0;
}void loop(){ //主函数，先查询有无按键，有按键的话在屏幕显示结果read_key(); //调用读取按键的函数if(!key){Serial.print("K");Serial.print(key);Serial.println(" is pressed");key = 0; //再初始化为0，方面下次循环}
}

2. 蜂鸣器控制

2.1 认识蜂鸣器

• 蜂鸣器是一种一体化结构的电子讯响器，采用直流电压供电，主要用于电子产品中作发生器件。
  

2.2 分类

• 按结构
  • 压电蜂鸣器
  • 电磁蜂鸣器
• 按有无振荡源
  • 有源蜂鸣器
  • 无源蜂鸣器

  a为有源蜂鸣器，b为无源蜂鸣器

2.3 工作原理

1. 有源蜂鸣器

• 有源蜂鸣器内部含有振荡电路，主要是通过供应直流电，将恒定直流电转化为一定频率的脉冲信号，从而实现磁场交变，带动钼片振动发声。

2. 无源蜂鸣器

• 内部不带震荡源，所以加直流电，磁路恒定，钼片不能振动发声。只有加方波的理想信号，频率不同，震荡出来声音也不同。

2.4 连线

• 蜂鸣器共连两条线，正极连接到数字8口，负极连接到GND插口中。
  
  

2.5 Arduino代码展示

int buzzer = 8; //定义控制蜂鸣器的数字IO脚，另一脚连接到GND上void setup(){pinMode(buzzer, OUTPUT); //设置数字IO模式，OUTPUT为输出//Arduino输送信号控制蜂鸣器响不响，所以定义为OUTPUT
}void loop(){unsigned char i, j; //定义变量while(1){for(i = 0; i < 80; i ++){ //输出一个频率的声音digitalWrite(buzzer, HIGH); //发声音delay(1); //延迟1msdigitalWrite(buzzer, LOW); //不发声音delay(1); //延迟1ms}for(i = 0; i < 100; i ++){ //输出另一个频率的声音digitalWrite(buzzer, HIGH);delay(2); //延迟2msdigitalWrite(buzzer, LOW);delay(2);}}
}

3. PWM模拟量输出

亮度发生渐变的三色灯——“呼吸灯”，实现灯的变化

3.2 Arduino代码展示

const int red = 3;
const int green = 4;
const int blue = 5;
//3、4、5属于PWM引脚void setup(){set pins 2 through 13 as outputs:{pinMode(red, OUTPUT);pinMode(green, OUTPUT);pinMode(blue, OUTPUT);}
}void loop(){//低--->高变化【白色形成】for(int brightness = 0; brightness < 255; brightness ++){ //0 ~ 255，红绿蓝同步逐渐发生变化analogWrite(red, brightness); analogWrite(green, brightness);analogWrite(blue, brightness);delay(3);}//高--->低变化【白色褪色】for(int brightness = 255; brightness >= 0; brightness --){analogWrite(red, brightness); analogWrite(green, brightness);analogWrite(blue, brightness);delay(3);}//显示红色for(int brightness = 255; brightness >= 0; brightness --){analogWrite(red, brightness); //analogWrite(green, brightness);//analogWrite(blue, brightness);delay(3);}//显示绿色for(int brightness = 255; brightness >= 0; brightness --){//analogWrite(red, brightness); analogWrite(green, brightness);//analogWrite(blue, brightness);delay(3);}//显示蓝色for(int brightness = 255; brightness >= 0; brightness --){//analogWrite(red, brightness); //analogWrite(green, brightness);analogWrite(blue, brightness);delay(3);}//显示红绿的混色for(int brightness = 255; brightness >= 0; brightness --){analogWrite(red, brightness); analogWrite(green, brightness);//analogWrite(blue, brightness);delay(3);}//显示红蓝混色for(int brightness = 255; brightness >= 0; brightness --){analogWrite(red, brightness); //analogWrite(green, brightness);analogWrite(blue, brightness);delay(3);}//显示绿蓝混色for(int brightness = 255; brightness >= 0; brightness --){//analogWrite(red, brightness); analogWrite(green, brightness);analogWrite(blue, brightness);delay(3);}
}

4. 湿温度测量

4.1 认识器件

• 用来粗略测试现场环境的湿温度，多为DHT11湿温度传感器。温湿度是模拟信号，但模块经过处理转换成数字信号通过单总线输出。
  

4.2 传感器接口

• VCC — 电源引脚5V
• GND — 电源引脚GND
• DAT — 数字引脚 2
  
  
  

4.3 Arduino代码展示【封装库】

#include "dht11.h" //封装库的头文件dht11 DHT11; //构造函数封装实例化#define DHT11PIN 2 //定义引脚void setup(){Serial.begin(9600); //串口通信Serial.println("DHT11 TEST PROGRAM");Serial.print("LIBRARY VERSION");Serial.println(DHT11LIB_VERSION);Serial.println();
}void loop(){Serial.println("\\n");int chk = DHT11.read(DHT11PIN); //返回值为chkSerial.print("Read sensor: ");switch(chk){case DHTLIB_OKSerial.println("OK");break;case DHTLIB_ERROR_CHECKSUMSerial.println("Checksum error");break;case DHTBIL_ERROR_TIMEOUTSerial.println("Time out error");break;default:Serial.println("Unknown error");break;}Serial.print("Humidity(%): "); //打印湿度Serial.print((float)DHT11.humidity, 2); //显示两位小数Serial.print("Temperature(oC): "); //打印温度Serial.print((float)DHT11.temperature, 2);Serial.print("Temperature(oF): "); //打印温度Serial.print(Fahrenheit(DHT11.temperature), 2);Serial.print("Temperature(K): "); //打印温度Serial.print(Kelvin(DHT11.temperature), 2);Serial.print("Dew Point(oC): "); //打印Serial.print(dewPoint(DHT11.temperature, DHT11.humidity));Serial.print("Dew PointFast(oC): "); //打印Serial.print(dewPoint(DHT11.temperature, DHT11.humidity));delay(2000);}
}