The problem seems simple enough:-
I have a thermostat that operates a 230V AC mains pump.
The thermostat is a changeover switch: The pump can either be connected to permanent live or to a switched live.
I want to add an indicator that shows which way the switch is connected i.e. is the thermostat ON or OFF?
The only way I can think of doing this is to sense the current flow in either the permanent live wire or the switched live wire to the thermostat.
Searching the internet for AC current sensing throws up possible solutions using a current transformer or Hall effect sensor.
There are the inevitable Chinese modules available on eBay - some are intended to connect to an Arduino ADC and provide a voltage proportional to current.
I don't need anything that sophisticated or complicated.
I could design something using a ZMCT103C transformer and an op amp to drive a LED but that means including a power supply.
There isn't much space available next to the thermostat and I don't want external wires if I can avoid it.
I should add that the pump has three speed settings. The current for each speed is :-
1=0.12A
2=0.27A
3=0.42A
An indicator that shows when the current is above, say 0.1A should suffice.
I did come across a suggestion below that may work, but it looks potentially dangerous!
Is there a better/safer option?