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 issued buzz, the number of adjustable doorbell design, The number of rings. (With PROTUES8.1 simulation circuit)