Black & Decker makes an interesting product called the Power Monitor. The monitor straps on to your hydro meter and reports the revolutions of a spinning disc or blinks of an IR LED depending which model of meter you have. It then broadcasts that reading to a handheld unit inside your house. As the fridge cycles on you can track this increase in power usage. Subtract that from the reading prior to the device powering on, and you have a rough estimate of how many watts that device uses. The Power Monitor is very simillar to the Kill-A-Watt except it monitors the entire house instead of specific devices.
There’s some benefits of the Power Monitor over other devices. It tracks the entire house, the 30 second delay on readings is almost realtime, and its affordable ($100 — would probably pay back fairly quickly). There’s also some disadvantages. It is less accurate then the Kill-A-Watt, and it has now data connection.
The Kill-A-Watt has a simillar problem, it doesn’t export the data either. This is a bit of an issue if you wanted to log the power consumption of your house. That’s where the Tweet-A-Watt comes in. What I’m attempting to do is bring this ability to the Power Monitor. How hard could it be?
The Power Monitor is a device manufactured by Blueline Innovations. It transmits a signal on a 433.92 MHz spectrum. My first attempts were to try to intercept the signal through an RF Receiver in the same frequency.
Initial attempt. Nothing. Set up an RF Transmitter, it communicated with the receiver perfectly. I was a bit stumped. This is when I checked out a session at Hacklab. There, I was schooled on using RF Scanners, spread spectrum and other RF black magic. (Many thanks to — make sure to check these guys out — Andrew Kilpatrick, Toronto Goat, and everyone else at Hacklab) We could detect the packet’s being sent, but couldn’t intercept any usable data.
It was decided that to get any useful data we must be more invasive. Warranty, out the window. We broke out the oscilloscope on the Monitor. Conveniently there’s two test probes marked on the board. This allowed us to identify the packet quite easily.
Now at least I have some confidence that we will be able to produce some results and this isn’t some wild goose chase. The next phase is to capture the data off the device. I’ll follow up shortly with the Signal Boost circuit and Arduino code used to capture the transmitted signal. More soon!