Detect sudden change in current and send signal to arduino

Question

I am trying to make a smart power socket using Arduino.

The socket should power even high power equipments at 230 Volt 50hz through a relay. I want my arduino to analyse the amount of current taken by the equipment, so that when there is a sudden drop in current taken by the equipment , the arduino will switch off the relay.

The idea is that when a charger finish charging a device ,there will be drop in current taken and so it can be turned off.Or in case of a TV when it is switched off by remote there will be a drop in current and the relay will switch off to conserve energy.

I know how t o connect and program but don't know how to detect the drop in current and send signal to aruino. It will also be fine if I can linearly decrease current and voltage so that it is compatible with arduino.

Answer 1

You need to think about the range of power you expect (when device is 'on'. If it's not orders of magnitude, them you can Use a current transformer to sense current, then a rectifier, filter, signal conditioning to get average or peak value which can be fed to the ADC.

There are also single chip solutions which will give you all the data over a serial line (see MAXQ314, for example).