The EnerJar - PIC power meter

The **broken link removed** looks like a fun and useful project. It's the winner of the **broken link removed**. Schematics and source code can be found at the **broken link removed** site.

Pretty neat, I've got one of those energy meters I bought from Canadian Tire. Another neat project but too dangerous to build a kit around was the X10 controller (one of Microchips app notes)
I thought about it once, would have called it the Python. Fun part would be the high speed ICD isolation.
**broken link removed**
https://www.codinghorror.com/blog/archives/000353.html

Kill-A-Watt is truly a great toy.

The EnerJar's missing detail is the power supply. Really you need a transformer which defeats the cheapness factor. There are some other ways to do it though. What most people think is to use a resistor off the main line to feed a cap and zener but the power dissipated in the resistor is silly. Even at 30mA to drive the LED display and PIC and that's like 3.5W.

Displaying the phase, power factor, and line freq is really nice.
Harmonic content is even nicer!

One thing to remember is the ground isn't ground, it's AC neutral. As such if you want to hook it up through a serial port to the computer or whatever then you need an optoisolator or something.