Domestic Appliance HIGH/LOW

Sorry for the bloody beginner's question: what is the best way to get a digital "High" from a domestic appliance that is running and a "Low" when it is switched off? Thanks in advance!

I'd start with a definition of "domestic appliance"

<I’d start with a definition of “domestic appliance”>
a “domestic appliance” is an electric device that does anything useful in your home and (critical) runs on the public power grid (220 or 110 Volts). Examples: Refrigerator, air condition, vacuum cleaner

Towarisch:
Sorry for the bloody beginner’s question: what is the best way to get a digital “High” from a domestic appliance that is running and a “Low” when it is switched off?
Thanks in advance!

Not as simple a task that one might wish for and still be safe to install and for the user of the appliance. A fundamental question is do you have or willing to gain access to the internals of the appliance to install a ‘digital on or off’ signal sensor? If so a simple small AC relay wired across the same points that the appliance uses when it’s turned on will provide a set of isolated contacts suitable for wiring to a arduino board just like a switch. If you don’t have access to the internals then you are left with monitoring the amount of AC current flowing into the appliance as a running or not running signal.
So best to talk about a specific appliance you might have in mind rather then assume that one method would work equally well for all possible appliances. A vacuum cleaner would be a challenging subject. :smiley:

Lefty