Arduino based thermostat

Piwoslaw · 10-13-11, 06:53 AM

As of today I am the proud owner of an Arduino Duemilanove

Woohoo!

One of the things I'd like to do with it is to replace our thermostat. Not that the one we have is bad (it's saved us a LOT on heating bills since I installed it 3 or 4 years ago), but there are a few things I'd like to change. Some of these things are available in more expensive models, others could be worked around with a second or third t-stat, but I'd like to keep it simple and cheap, plus I like the challenge

I'm sure that I'm not the only one who would like to have a thermostat tailored to her/his house and individual heating&cooling needs, so I started this thread so that we could all pitch in our wants, ideas and expertise to get this project going. I'll start by describing what my t-stat does, then vaguely what I'd like it to do. I'd like others to do the same to give ideas about functions I may not have thought of. Any help with algorithms or even arduino code is very welcome.

My thermostat has only two programmable temperatures - night and day - with resolution 0.25°C. The programs are broken into 24 one-hour intervals, and only three programs are user-adjustable. There are also a few programs hardwired into the unit (always day temp, always night temp, always above 7°C, etc.). The program we use most is day from '0900' to '2100', night from 2100 to 0900. If I want to change the temperature, for example the house will be empty between 1700 and 2000, then I can press the 'night' button and it will hold night temperature until the next change in the program's settings, or I can set the night temp for X hours, after which the t-stat resumes whichever temperature the program now calls for.
This is better than a basic t-stat, manual or analog, but doesn't always allow me to fine tune it the way I want, so here is my wishlist:

Temperature changes more often than every hour. Every 15 minutes should be better.
More temperatures, not just two for night and day.
Inputs from more rooms.
'Intelligent coasting'. The t-stat will do nothing if there is a temperature change within 15 minutes that would turn the boiler off. That way the boiler doesn't run for only a few minutes when the heat wouldn't make its way to the house.

Bonus question: I know that certain high-end thermostats measure outdoor temperature, but how is that information used while heating/cooling?

EDIT: This just crossed my mind for something more advanced: A sensor to monitor whether the sun is shining, then adjust the set on-time accordingly.
Also, measure humidity and adjust heating/cooling to perceived temperature (heat index).

10-13-11, 06:53 AM	#1
Piwoslaw Super Moderator Join Date: May 2009 Location: Warsaw, Poland Posts: 961 Thanks: 188 Thanked 110 Times in 86 Posts	Arduino based thermostat As of today I am the proud owner of an Arduino Duemilanove Woohoo! One of the things I'd like to do with it is to replace our thermostat. Not that the one we have is bad (it's saved us a LOT on heating bills since I installed it 3 or 4 years ago), but there are a few things I'd like to change. Some of these things are available in more expensive models, others could be worked around with a second or third t-stat, but I'd like to keep it simple and cheap, plus I like the challenge I'm sure that I'm not the only one who would like to have a thermostat tailored to her/his house and individual heating&cooling needs, so I started this thread so that we could all pitch in our wants, ideas and expertise to get this project going. I'll start by describing what my t-stat does, then vaguely what I'd like it to do. I'd like others to do the same to give ideas about functions I may not have thought of. Any help with algorithms or even arduino code is very welcome. My thermostat has only two programmable temperatures - night and day - with resolution 0.25°C. The programs are broken into 24 one-hour intervals, and only three programs are user-adjustable. There are also a few programs hardwired into the unit (always day temp, always night temp, always above 7°C, etc.). The program we use most is day from '0900' to '2100', night from 2100 to 0900. If I want to change the temperature, for example the house will be empty between 1700 and 2000, then I can press the 'night' button and it will hold night temperature until the next change in the program's settings, or I can set the night temp for X hours, after which the t-stat resumes whichever temperature the program now calls for. This is better than a basic t-stat, manual or analog, but doesn't always allow me to fine tune it the way I want, so here is my wishlist: Temperature changes more often than every hour. Every 15 minutes should be better. More temperatures, not just two for night and day. Inputs from more rooms. 'Intelligent coasting'. The t-stat will do nothing if there is a temperature change within 15 minutes that would turn the boiler off. That way the boiler doesn't run for only a few minutes when the heat wouldn't make its way to the house. Bonus question: I know that certain high-end thermostats measure outdoor temperature, but how is that information used while heating/cooling? EDIT: This just crossed my mind for something more advanced: A sensor to monitor whether the sun is shining, then adjust the set on-time accordingly. Also, measure humidity and adjust heating/cooling to perceived temperature (heat index). __________________ Ecorenovation - the bottomless piggy bank that tries to tame the energy hog. Last edited by Piwoslaw; 10-13-11 at 08:45 AM..