need help in the selection of sensors

[Muneeb]

selection of sensors

i have to do a project home automation using microcontroller
it will control 3 home appliances a 500w bulb, electric fan, refrigrator
i want the device to respond back whether it is working or not
please tell me about sensors type for this purpose and the name by which
they are available in the market
thanks

 

[artem]

The simplest way is to use ccurrent transformer connected sequentially with your devices .
Trasformer output side must be rectified and detected with Schmidt trigger and converted to TTL level .

 

[GrandAlf]

You may have a problem with the fridge as the load switches on and off via the thermostat. Temp sensor would not be much use either as the fridge would have defrosted before reporting a fault. You could check for available power at the stat via an AC opto, but probably not much point. With bulbs of course you could use an LDR or phototransistor etc, cheaper than a transformer.