On Sat, 01 Feb 2014 17:19:56 -0600, 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.

Do your A to D conversion at the 3rd or higher harmonic of line frequency
(higher really is better), square, and average. Then take the square
root, and you have RMS.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com