GTalk fun

Someone asked me a couple months ago if it would be possible to send commands to the thermostat via email. The difficulty with that is authenticating users. Because the semester is now over and I have some weekend spare time, I decided to implement a toy with Google Talk. The screenshot bellow shows a "conversation" with my home thermostat.



With GTalk available in Gmail and on my cell phone this proves to be quite useful. Interesting extensions could use speech recognition on a cell phone to interact with an automated house.

iCal controlled thermostat

I did not know until David mentioned it to me, but the iCal on my Mac can sync with the Google Calendar (it uses CalDAV), which means iCal can control the thermostat too! Here is a screenshot: Thanks David! iCal Setup

4 minutes setup

See it here.

Smarter thermostat

At the end of last year I was looking for a replacement for my home thermostat. I wanted a smarter controller for the device that is responsible for most of my electric bill in the summer and for most of my gas bill in the winter. Since I could not find a thermostat that supported flexible scheduling, remote access without a monthly fee, reasonably priced and had a flexible interface I could use to add new features, I decided to design one that could do all this.

Most programmable thermostats have a built-in functionality that allows the creation of a daily schedule. But once programmed the thermostat cannot be adjusted remotely, so many times the thermostat might start heating or cooling hours before anyone gets home. The other impediment with programmable thermostats is that you have to use the clumsy menu on the device and learn all the cryptic codes displayed on a tiny LCD in order to program it.

My solution was to build a thermostat controller that synchronizes with a flexible calendar that I can access from the Web Browser, from my cell phone and, equally important, it is free of charge. I chose the Google Calendar and I build a tiny controller that connects to the Internet, reads commands from the calendar and applies them to the thermostat. There were quite a few communicating thermostats I could use, but the one I really liked was iT8. The one time setup for my thermostat controller is pretty simple: from my Google account I access the "Manage calendars" section and I create a new calendar. Then I copy the XML Private Address of the calendar and paste it in my thermostat controller's administration web page. That's it!

Now the controller monitors the calendar for events that have the Subject similar with "cool75", "heat85" or "off" and sends the commands to the thermostat. As expected the first command will set the thermostat setpoint to 75°F and will put it Cooling mode, while the last command will turn off the thermostat.

Having the thermostat controlled from a Google Calendar is very useful, but I also wanted to have some extra features that you don't find in regular thermostats. First, I wanted to be able to adjust the thermostat from the comfort of my desk, saving a trip downstairs, second I wanted a feature that would allow me to view the inside temperature, current set point and outside temperature. For this purpose I built a Google Gadget for iGoogle that does just that.

Now my Home tab in iGoogle makes more sense, it actually has a gadget from my house: the Thermostat.

Since I already had a nice API for the controller, I decided to add another interface to make it available in the Web Browser on my BlackBerry. This works pretty well for (unlikely) situations when my laptop is off, or when I am not at home.

Hardware

I built the thermostat controller as an Embedded system that connects directly to the Internet through my router and it also connects to the iT8 thermostat via a 3 wire cable. The really nice thing about it is that it does not require a dedicated PC for the Internet connection, everything runs on one tiny board!

Installing the iT8 itself was fairly easy and it is a nice looking thermostat.