PIC monitoring of an AC pump

Hi all:
I want to monitor the loading of an AC pump.....120VAC around 12amps.
Using a PIC. The intention is to decide if it is loaded or overloaded using the 12Amps as the trip.

I figure using a toroid (with the 120V line looped thru it) into a resistive load and then rectified by a schottky into a smoothing cap and then into biasing a 2n3904 on/off as an input drive to a digital input should do the trick.

Am I missing anything here?

Some hysteresis. Near the trip point, your proposed circuit will trip on-off AC cycle by AC cycle.

Make sure you have a burden resistor on that toroid

f open-circuited with current flowing in the primary the transformer secondary will attempt to continue driving current into what is effectively an infinite impedance. This will produce a high and potentially dangerous voltage across the open secondary [1]

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You'll get some variance using a transistor, an op amp comparator would give you good accuracy.
A proprietry current transformer would make things easier if you can get one.

dr pepper said:

You'll get some variance using a transistor, an op amp comparator would give you good accuracy.
A proprietry current transformer would make things easier if you can get one.

Click to expand...

Speaking of which, has anyone used Pearson or Ion Physics CTs? Any suggestion as to which is the better product?