Friday, July 1, 2016

My DIY Home Electricity Monitor: Collecting Parts

I've been interested in monitoring the total current input to my residence for a while now, but all of the solutions I've found don't really do what I want. Either they are tied to some remote service for operation, they collect data in some hard-to-use proprietary format, or they offer gee-whiz features while skimping on actual functionality. All of that led me to the conclusion that I needed to roll my own device.

I started by trying to figure out what I'd need:

Current loops that can be snapped around the wires in the box and aren't overly large.
Some sort of data collection device with enough intelligence to store data.
Boxes to put everything in.
Odds and ends to tie everything together (power, data lines, etc.)

Snap-On Current Loops

Current sensors are fairly easy to get, but finding ones that weren't overly large was a problem - I have a very limited amount of space in my electrical box. I also cannot undo the main coming into the residence, so small, snap-on loops were a must. I settled on these units from Seeedstudio. I purchased 100A units for the main, and 60A units for a branch panel. This particular variant was only offered in mA output, and I'm unsure as to it's output type - I assume DC but have a backup plan if not...

Precision Instrument Rectifier Board

Originally meant for an audio spectrum analyzer, this board was 1/2 of a set of 12 precision full-wave rectifiers (10 audio channels plus 2 for R and L.) That never came to be, but I have this half of the rectifier assembly. Since I plan on having 6 channels of measurement - 2 on the mains, 2 on a branch panel, and 2 on a generator input, this was perfect. Now, I just need to remember how this thing works...

A Box To Put It All In

A $5.00 hamvention purchase, these boxes came out of an old-school wired alarm system. I originally had purchased these due to the cellular modem in one of the boxes:

But it turned out to be permanently attached to a service provided by it's manufacturer. I'll set this aside for investigation at a later date, but for now it's worthless to me. However, inside one of the boxes was another board which I believe may be of use:

An Elk Products ELK-624 multi-voltage power supply and battery charger. This device kept the cellular modem and accompanying alarm box up in the case of power failures. While it didn't have a transformer, I have plenty laying around that will probably work with this. I think this unit will come into play as a UPS for the microcontroller. It's a linear supply, but I'm not too worried about it. 


Some other odds 'n ends that will probably go into the box is an AVTech Room Alert 3A device that was given to me when the original owner managed to completely destroy the firmware load and throw it into recovery mode, a Trendnet 5-port Ethernet Switch to connect the monitor, 3A, and whatever else into the network, and some power supplies. I don't know if the Rhino 5V DIN-mount power supply in the back will work yet - it's taller than the boxes I have but I may be able to work it in.

The only parts left to get are some sort of microcontroller device - I'll probably go with a Raspberry Pi 2B, simply for ease of use, some sort of ADC board to allow sensor input, and some power supplies and converters.

Off to search for more parts!