Updated on: "Nov 15, 2010"
As a Request from a guy named "Gary in New Zealand", I designed these Two circuits for him.
These are Isolated devices that can be powered by a Battery or a 12 Volt Wall Adapter and will Monitor If power is going to an Appliance. The Status of the LED is determined: When Current is being drawn by the Load.
The Torroid Coil Shown here is a Commercial manufactured Part that he found. He sent me a sample of it so I could Design, Build and Test this design. But you can wind your own torroid.
Assuming you use this Same 280 mH Inductance Value, this circuit will work OK. Changes in Inductance "may" require a Change in the Parallel Capacitor to get best results.
You Might be able to just put a Single Wire through the Torroid Core, Or possibly you will need 2 to 4 Turns. This Depends on your AC Operating Voltage and Current.
Using Version-1, the LED stays Lit Only when "Current Is Flowing".
In Version-2, The LED Lights up When "Current Stops flowing". And a "Piezo Buzzer" can replace the LED/Resistor, to sound an Alarm, When Current flow Stops.
In Version-3, Again the LED Lights up When "Current Stops flowing". But this circuit is Much more Sensitive and will easly Monitor a 7.5 watt "Night Light" or "Chrismas Tree Bulb", Using just One Turn of wire on the Torroid.
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