Tesla

Source: The Oatmeal

This is a very little project to grab the data from on OWL-CM160 and generate RRD graph. The way the OWL device communicates and the reverse engineering of the USB frame came from Philippe Cornet's Eagle-Owl project.

A lot of Eagle-Owl code has been removed/changed but all the meaning part are from the original project. I did this fork since my need are really simple, I only wanted to generate RRD graph, no need for sqlite nor javascript.

The RRD database currently hold:

• 60 entry points per hour
• 48 entry points per day (One per half hour)
• 14 per week (Two per day, averaged with 720 entries each; representing 12h)
• 30 per month (One for each day, averaged with 1440 entries; representing 24h)
• 52 per year (One per week, averaged with 10080 entries; representing 1 week)
• The last value

In order to graph, you can uses scripts in the tools directory which call rrdtool to generate the graph. You can obviously uses any tools you want to graph this results, rrd can also exports as XML or JSON.

OWL-CM160

This little guy here will measure the current passing through a wire with an amperometric clamp. It is not the most precise method in the world, but it'll do the job for many of us that rent a place and can't change easily the circuit breaker.

With this device, and a little software, you can track your electrical consumption which let you find out some habits of yours or if you have a device that sucks way more that it should (an old frigdge, a lamp, ...).

Requirements

You should have librrd4, libusb and cmake installed on your system.

This should do the trick for a Debian/Ubuntu distribution:

$ sudo apt-get install librrd-dev libusb-dev cmake

On Arch Linux:

$ sudo pacman -S rrdtool libusb-compat cmake

Install

Pretty standard:

$ mkdir -p build; cd build
$ cmake .. && make
$ sudo make install

Start

You need to change the default path in the init script (the tesla file at the root of this repo).

This path is were the graph will be generated.

To install the init script, you only need to do:

$ sudo cp tesla /etc/init.d/tesla
$ sudo update-rc.d tesla defaults
$ sudo /etc/init.d/tesla start

To install the systemd service file:

$ sudo cp tesla.service /etc/systemd/system
$ sudo systemctl enable tesla
$ sudo systemctl start tesla

That's it.

As soon as you plug the device in your machine, it will read the data and populate its RRD database.

Debugging

If you feel like debugging, it's easy with cmake, just compile a debug build and add -Wall if you want.

Enjoy and send your patches in!

$ cd build/
$ cmake -DCMAKE_BUILD_TYPE=Debug -DCMAKE_C_FLAGS_DEBUG=-Wall ..