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HVAC Project

May 17th, 2009 Marc

The HVAC Writeup is complete and now posted in the projects section. Feel free to discuss/ask about it here. I read all your responses and will reply to your questions! Leave you email if you’d like.

HVACMonitor: Web-Enabled Thermostat


  1. jason
    May 17th, 2009 at 20:16 | #1

    Great project. Looking forward to schematics, and parts list, ect………….

    • May 19th, 2009 at 00:50 | #2

      Thanks Jason!
      I’ve updated with the EagleCAD files, take a look!
      I’ll be putting the full write-up online soon, along with code & schematics.

      Thanks for the interest!

      Btw, how did you find out about my project?

  2. May 19th, 2009 at 21:21 | #3

    Very nice project. I’m thinking of building something similar. I have a question - how difficult would it be to run this off of 24V relay voltage?

    • May 19th, 2009 at 21:44 | #4


      Great Question! It was part of the original plan to get this running off the 24Vac system (That’s why there’s an extra screw terminal on the board, just below the R labeled one), however time constraints forced me to let that idea go. A simple diode bridge and a voltage regulator would have this leech power from the HVAC wiring; like all thermostats do. Simply bridging power from the R terminal and the Common of the transformer would work.

      All the wiring needed is available. Just a matter of integrating it on the board.

      Thanks for bringing it up, It’s going onto the 2nd revision of the board, along with merging both boards into 1 design.


  3. May 20th, 2009 at 09:40 | #5

    Hey Marc,

    Sweet project. I was just thinking about using something like this for my house. Instead of remote monitoring and control, I would use it to add some automatic heating control. It would interface to a weather website and get the predicted weather and determine if the heat should be turned on.

    I thought of this when I got out of the shower and noticed the heat was on. It was probably 50-60 degrees out at that time, and it is supposed to get into the mid 70’s today. So in a couple hours, the outside temp would be greater than inside and it was probably inefficient for the heat to be on at that time.

    I guess a programable thermostat could also work, but that idea would be alittle smarter.


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