### Intelligent switch

The idea of this assembly is to get the automatic shutdown of a series of devices, by detecting the shutdown of the main equipment (Master). For example, if we connect the CPU of our PC to the main socket of this circuit, and the rest of the devices (monitor, printer, scanner, etc.) to the auxiliary socket; when disconnecting the CPU the power of the whole set would be disconnected ... even that of the control circuit itself. In this way there would be no equipment consuming in Standby mode, and the total consumption would be zero.

Operating principle

The circuit is based on the voltage transfer provided by one of the two coils of an EMI filter, to the passage of the current by the other winding. This assembly works as a current transformer, delivering a voltage in the secondary winding, proportional to the current circulating through the primary. In this case, the voltage transfer is not linear with the power, since it will depend on the type of load that we connect in the 'Master' socket. If the load behaves as a pure resistance, the voltage transfer will be less than if it had a reactive component.

For more details to build this Intelligent switch, you can access on my Web page:

http://j-rpm.com/2019/04/interruptor-inteligente/

YouTube video: