D3为继电器工作指示灯，说明5V电压处于正常状态。

D2为继电器吸合指示灯，说明继电器处于吸合状态(继电器线圈两端有电压)。

C1为继电器并联的电容，继电器释放后线圈两端电压往下滑，可防止吸合频率过高影响寿命。

D1为继电器反向并联的二极管，可防止继电器释放后，产生很高的电压峰值，击穿对静电敏感的器件。

R3,R1为继电器的工作、吸合指示灯，可防止电压高击穿电源指示灯。

Q1为PNP三极管，用于对单片机的I/O口的电流进行放大。

R2为三极管基极串联的电阻，防止输入的信号过强。

RL1为5V继电器，L1为220V白炽灯，可连接AC 220V 10A或DC 30V 10A控制用电器。

1HZ方波信号源可直接改为单片机的I/O口，控制强电接通或断开。-D3 relay work light, indicating 5V voltage in a normal state.

D2 is a relay indicator, indicating the relay is attracted state (at both ends of the relay coil voltage).

Parallel capacitor C1 relay, the voltage across the relay coil is released sliding, pull prevents excessive frequency affect life expectancy.

D1 relay antiparallel diodes prevent the relay after the release to generate a high voltage peak, the breakdown of static sensitive devices.

R3, R1 is working relay, pull the indicator to prevent high breakdown voltage power indicator.

Q1 is a PNP transistor, for MCU I/O port of the current amplification.

R2 is a resistor in series with the transistor base, to prevent the input signal is too strong.

RL1 is 5V relay, L1 is 220V incandescent, or can be connected to AC 220V 10A DC 30V 10A control appliances.

1HZ square wave signal source directly to the microcontroller s I/O port, control the strong power on or off.