自制 Arduino 厨房定时器：LCD 显示、四按键操作、蜂鸣器报警

元器件与材料

项目背景

从简单的数字厨房定时器出发，用 Arduino 重造一个“属于自己的”定时器，顺便理解此类小工具的工作原理。核心概念是状态机：定时器同一时刻只处于四种模式之一：

• IDLE (待机)：上电/复位后的初始状态，显示当前设定时间，等待输入
• SETUP (设置)：长按 S4(复位键) 进入；用 S3(启动/停止) 选择调整 时/分/秒，用 S1(加)、S2(减) 修改数值
• RUNNING (运行)：按 S3 启动倒计时；再按 S3 或 S4 暂停/回到待机
• RINGING (响铃)：倒计时归零自动进入；任意键按下停止蜂鸣并回到待机

硬件连接要点

• LCD 接线：RS=12, EN=11, D4=5, D5=4, D6=3, D7=2 (可按需调整引脚)
• 四个按键：一端接 5V，另端接数字引脚 (6,7,8,9) 并通过 10kΩ 下拉到 GND
• 蜂鸣器接 Pin 10 (PWM 控制音量)
• 电位器接 LCD V0 引脚调节对比度

核心代码逻辑

按键去抖与长按检测

每个按键用 digitalRead 读取当前状态，与上一次状态对比，变化时标记“按下”。S4(复位键) 额外增加长按计数器：持续 HIGH 超过约 100 个循环周期(约 1 秒) 判定为长按，触发进入 SETUP 模式。

状态机切换

主循环中用 switch(currentMode) 处理四种模式的按键响应：

• IDLE：短按复位→复位时间；长按复位→进入 SETUP；按启动/停止→切换 RUNNING/IDLE
• SETUP：启动/停止键循环选择 时/分/秒；加/减键修改对应数值(循环进位)；短按复位→保存退出
• RUNNING：启动/停止键→暂停回 IDLE；复位键→复位回 IDLE
• RINGING：任意键→停止蜂鸣回 IDLE

时间计算与蜂鸣

运行模式下用 now() - startTime 计算已过秒数，从设定总秒数中减去得到剩余时间。剩余 ≤ 0 时切换到 RINGING。响铃模式用 analogWrite(buzzerPin, 20) 配合短延时产生断续鸣叫。

LCD 显示管理

每种模式显示不同内容：待机显示“Timer ready”+ 设定时间；设置显示“Setup mode: HRS/MINS/SECS”+ 当前调整值；运行显示“Counting down...”+ 实时倒计时 HH:MM:SS；响铃显示“RING-RING!”。

完整代码

/**************************************************
 * Arduino Kitchen Timer v1.0 - 2016/01/27
 * By Angelo Fiorillo (Rome, IT) - GPL3+
 **************************************************/
#include <LiquidCrystal.h>
#include <TimeLib.h>  // Paul Stoffregen's Time 库

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
const int buzzerPin = 10;
const int resetButtonPin = 6;    // S4
const int startStopButtonPin = 7; // S3
const int downButtonPin = 8;      // S2
const int upButtonPin = 9;        // S1

// 设定时间
int setupHours = 0, setupMinutes = 0, setupSeconds = 0;
time_t setupTime = 0;
// 运行时时间
int currentHours = 0, currentMinutes = 0, currentSeconds = 0;
time_t currentTime = 0, startTime = 0, elapsedTime = 0;

// 按键状态变量
int resetButtonState = LOW, startStopButtonState = LOW, upButtonState = LOW, downButtonState = LOW;
int resetButtonPrevState = LOW, startStopButtonPrevState = LOW, upButtonPrevState = LOW, downButtonPrevState = LOW;
bool resetButtonPressed = false, resetButtonLongPressed = false;
bool startStopButtonPressed = false, upButtonPressed = false, downButtonPressed = false;
long resetButtonLongPressCounter = 0;

// 模式常量
const int MODE_IDLE = 0, MODE_SETUP = 1, MODE_RUNNING = 2, MODE_RINGING = 3;
int currentMode = MODE_IDLE;
int dataSelection = 0; // 0=小时, 1=分钟, 2=秒

void setup() {
  lcd.begin(16, 2);
  pinMode(resetButtonPin, INPUT);
  pinMode(startStopButtonPin, INPUT);
  pinMode(upButtonPin, INPUT);
  pinMode(downButtonPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // 1. 读取并去抖所有按键 (重置按下标志)
  // ... (同源码, 此处省略重复代码, 关键逻辑见上文说明)

  // 2. 状态机处理
  switch(currentMode) {
    case MODE_IDLE:
      if(resetButtonPressed) Reset();
      if(resetButtonLongPressed) currentMode = MODE_SETUP;
      if(startStopButtonPressed) {
        currentMode = (currentMode == MODE_IDLE) ? MODE_RUNNING : MODE_IDLE;
        if(currentMode == MODE_RUNNING) startTime = now();
      }
      break;
    case MODE_SETUP:
      if(resetButtonPressed) { // 退出设置
        setupTime = setupSeconds + 60*setupMinutes + 3600*setupHours;
        currentHours = setupHours; currentMinutes = setupMinutes; currentSeconds = setupSeconds;
        dataSelection = 0; currentMode = MODE_IDLE;
      }
      if(startStopButtonPressed) { dataSelection = (dataSelection + 1) % 3; }
      if(downButtonPressed) { /* 对应 dataSelection 减 */ }
      if(upButtonPressed) { /* 对应 dataSelection 加 */ }
      break;
    case MODE_RUNNING:
      if(startStopButtonPressed || resetButtonPressed) { currentMode = MODE_IDLE; if(resetButtonPressed) Reset(); }
      break;
    case MODE_RINGING:
      if(resetButtonPressed || startStopButtonPressed || downButtonPressed || upButtonPressed) currentMode = MODE_IDLE;
      break;
  }

  // 3. 时间计算与蜂鸣
  switch(currentMode) {
    case MODE_RUNNING:
      currentTime = setupTime - (now() - startTime);
      if(currentTime <= 0) currentMode = MODE_RINGING;
      break;
    case MODE_RINGING:
      analogWrite(buzzerPin, 20); delay(20);
      analogWrite(buzzerPin, 0); delay(40);
      break;
  }

  // 4. LCD 刷新
  lcd.setCursor(0, 0);
  switch(currentMode) {
    case MODE_IDLE:
      lcd.print("Timer ready "); lcd.setCursor(0,1);
      lcd.print(currentHours); lcd.print(" "); lcd.print(currentMinutes); lcd.print(" "); lcd.print(currentSeconds); lcd.print(" ");
      break;
    case MODE_SETUP:
      lcd.print("Setup mode: "); 
      lcd.print(dataSelection==0?"HRS ":dataSelection==1?"MINS":"SECS");
      lcd.setCursor(0,1);
      lcd.print(setupHours); lcd.print(" "); lcd.print(setupMinutes); lcd.print(" "); lcd.print(setupSeconds); lcd.print(" ");
      break;
    case MODE_RUNNING:
      lcd.print("Counting down..."); lcd.setCursor(0,1);
      // 格式化 HH:MM:SS (补零)
      if(hour(currentTime)<10) lcd.print("0");
      lcd.print(hour(currentTime)); lcd.print(":");
      if(minute(currentTime)<10) lcd.print("0");
      lcd.print(minute(currentTime)); lcd.print(":");
      if(second(currentTime)<10) lcd.print("0");
      lcd.print(second(currentTime));
      break;
    case MODE_RINGING:
      lcd.print(" RING-RING! "); lcd.setCursor(0,1); lcd.print(" ");
      break;
  }
  delay(10);
}

void Reset() {
  currentMode = MODE_IDLE;
  currentHours = setupHours; currentMinutes = setupMinutes; currentSeconds = setupSeconds;
}

原理图

原理图展示了按键下拉电阻、LCD 接线、蜂鸣器驱动及电源连接。可使用标准面包板布局，蜂鸣器可置于跳线下方节省空间。