利用单片机为主控芯片，通过检测按键是否按下来启动定时门铃，利用定时器控制蜂鸣器发出叮咚，此设计的门铃次数可调节，通过数码管显示调节的响铃次数与响铃时剩余的响铃次数。（附有PROTUES8.1仿真电路）-Using the MCU as the main control chip, by detecting whether the button is pressed to start the timer doorbell, the use of timer control buzzer issue