I'm currently playing around with a home made automation system and was wondering if anyone can tell me of a way to do the following?
Outlets do not normally draw power from appliances.
Detecting whether an outlet has power available is easy - put a two way adapter into the socket and wire a relay to a plug.
Detecting whether an appliance is drawing power is trickier. Usually that means something like a current transformer in series with the supply. However, Hall-effect devices are now very cheap and can be used as a sensor by just winding a small coil of the supply cable around one. What to use really depends on the value and range of currents that you want to detect and whether you want to measure them, set a threshold (eg whether the appliance is on standy by or running) or just detect on/off.
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