On 2014-02-01, RogerN wrote:

I have main propane heat but I also have some of the electric oil filled
radiators. I like the oil filled radiators for cold spots and to give
temperature adjustment to individual rooms.

The problem is that the heaters use up most of the power available on the
circuit. We quit using a heater that was plugged in to the same circuit as
the kitchen, every time we'd run the microwave, toaster, or other high
current appliance, it would kick the breaker out.

So it seems like a good project to use a current transformer to measure amp
draw on the breaker and automatically turn off the heater when the amps draw
is too high. I don't care much for the thermostats on the oil filled
radiators, it seems to more control the temperature of the heater, not so
much the room temperature. So I'm thinking an microcontroller, use the
analog inputs to read temperature and amps, and a digital output for a solid
state relay to the heater.

Anyone here mess with signal conditioning for current transformers? Seems
that I need a "precision rectifier" circuit and a capacitor to charge up to
the peak, then scale to RMS amps.

RogerN



I did exactly that for two sump pumps. Two are too big for one circuit
and there is no way to split them into separate circuits (they are
hooked up to the building that I do not own).

What you need is called a "current sensing relay" and they are
available. You need to use a current sensing relay and a contactor to
turn the heater no and off.

i