Power Monitor

Hi there! I am brand new to this so please forgive.
I would like to verify that a remote water pump is drawing current. I tried threading its N wire through a small toroid with around 50 turns of enamelled copper wire hoping the current drawn by the pump would induce a small current in the winding, enough to light an LED. It gave 25mV... So I made a coil former out of 2 plastic washers and a plastic spacer and wound many hundred turns of 40 SWG (0.12mm) copper wire on. It gives 25mV... I don't want to insert a resistor into the mains lead, so any other ideas? Many thanks, Stuart55.

Stuart55 said:

like to verify that a remote water pump is drawing current.

don't want to insert a resistor into the mains lead

Click to expand...

The mains lead is a resistor.

The resistance of #14 AWG is 2.6 milliohms/foot.
At 5A pump current this wire would give 13 millivolts/foot and with enough feet it could be used as a current sensor to give enough voltage drop to turn on a xsistor or certainly enough to activate an opamp comparator.
You need to power this circuitry with a wall 'former or battery.

If you tweek a GFI unit they can be modified to switch on a relay and light up about any size bulb you want!