The Electric Meter Saga                               

For over three years, I had been happily monitoring and recording my household electric usage by detecting how often the analog electric meter’s aluminum disk revolved. I had a blinking LED at the bottom of the meter and a synced detector at the top of the meter. Twice each revolution of the disk, there was a clear light path to the detector which would send a pulse to a UART that would send a byte through my computer’s serial port to be  recorded by a small Visual Basic 6 program I had running in the background.

In late June, SCE installed a new Smart meter at my house. They claim I can monitor my electric usage on-line but it appears  to me they have pulled that function off of their website for residential customers. Even if the site did become active, the information is in averaged one hour blocks. This is much different from the real-time graphing to which I had grown accustomed.

There are several strategies one could use to monitor electric usage. There are very good commercial products available on the web that sense the current flow above the mains in the SCE panel. One might detect small voltage drops along the main conductors that would be proportional to the current flow. I could use clamping current meters around the AC power lines that feed in though the roof.  Some folks have attempted to intercept and interpret the smart meter’s network signal. I thought about using an old CD drive’s laser, focused on the meter face to detect the LCD bar that moves in response to current usage.  Could I teach  my computer to visually read the meter using a camera? Because I wanted to know more about computer vision, I decided to take this approach.

The electric meter is about 75 feet from my backyard workshop (the doghouse) computer (modest XP sp3). There is an abandoned four-conductor unshielded telephone wire that runs around the eves of my house from the doghouse to near the meter. This is what I used with my old detection system. I found through trial and error that a USB camera stops working when USB cables are longer than about ten feet. I found a cheep RS-232 camera on the web and thought I would see if I could get that to work.