利用51单片机的定时功能设定热水器的开关时间，以便控制器能够在设定的开关时刻通过单片机的输出端口控制输出继电器的动作，进而控制热水器的启闭。以最简单的硬件电路实现最有效的定时控制。-51 single use water heater timer function to set the switching time, so that the controller can set the switch point by the microcontroller output port control output relay action, then control the water heater open and close. The most simple hardware circuit to achieve the most effective timing control.