The Relay have normally open contact and normally closed contact ,common pole, when you not setup the electric circuit , the common pole contact with normally closed contact , , the MCU s pin connect with the conctrol pin of the Relay through triode,when mcu s io provide low level, the Relay will work ,when normally open contact pole connect with GND, normally closed contact with 12V,it will produce a wave of Rectangular



继电器有常开触点和常闭触点，普通极了，当你没有安装电路，与常闭触点接触普通杆接触，单片机的引脚连接，通过三极管继电器的控制引脚，当单片机的IO提供低电平，继电器工作，当常开接触极接GND，12V常闭触点，它将产生一个矩形波；-We want to get the Rectangular wave,the　method is that　Use MCU to control the Relay,

The Relay　have　normally open contact and normally closed contact ,common pole,

when you not setup the electric circuit　, the common pole　contact with　normally closed contact ,

the MCU s pin connect with the conctrol pin of the Relay through triode,when　mcu　s io provide　low level,

the Relay will work ,when normally open contact pole connect with GND, normally closed contact with 12V,it will produce a wave of Rectangular