Getting Started with Thermostat

Projects General Guidance
1

Howdy,
I am a total newbie to arduino and I need advice on the ideas in regard of my idea.
I would like to built a thermostat for my home HVAC using arduino.
The requirements are:
WiFi access to set the temperature
Temperature sensor in a different room that the thermostat
Usage of the 24V power supply as the standard Honeywell thermostat uses
LCD display and push buttons to set temperature at the unit
Outside temperature sensor (as I want to set the inside temp in relationship to the outside temp)

Basically it should be like the Nest, just with a sensor in a different room and an outside sensor.

I googled, but I only found the solution from AirQ http://dev.airqnetworks.com/

2

To be honest this is not the kind of projects beginners do!!!

That sounds like a good project for a well-experienced Electronics Engineer. However that does not mean it can not be done.

You need to learn different parts of dealing with Arduino such as:

1.Using a thermistor/temperature sensor and you'd learn that by following the tutorial here:
http://oomlout.com/a/products/ardx
click on CIRC-10
now for you to practice that project you need an Arduino which I presume u already got and the following parts:
Breadboard
Jumper wires
Circuit layout found here -> http://www.ardx.org/src/circ/CIRC10-3dexploded-445.png
Temp Sensor part # TP36
Once you've done this project you will be very good in dealing with temp sensors.

2.Using voltage regulators.
shown here -> 5v from 9v battery using 7805 Voltage regulator IC - YouTube
except in your case you want the 7809 or its other variants so you can turn your 24 Volts into 9 Volts that can feed the Arduino.
Or a simpler solution would be to use a stand alone power adaptor for the arduino Ranging between 7 to 12 Volts.

3.Monitor and Controls like this:

I dunno about Wifi cause I have not tried it yet.

Good luck.

3

Thanks for the feedback.
So far I have not bought anything.

I was thinking of starting with something like this: http://www.ebay.com/itm/Arduino-Mega-2560-Starter-Kit-Deluxe-genuine-huge-value-compare-anywhere-/181021640547?pt=LH_DefaultDomain_0&hash=item2a25bb0763

4

Hello , I can help on the temperature sensing and lcd but have not dealt with WiFi.

I always use ntc 10k sensors and a 10k resistor as voltage divider and works pretty nice with accuracy of +/-0.5 celcius. Considering cost $0.3 total makes not care for accuracy..

5

Hello,

for temperature sensing you can also take a LM35. It works directly on 5V and you don't need additional components as long as your temperature isn't under +2°C. The output voltage goes linear with temperature and is scaled directly in °C. You can look at my blog:

This post is about connecting the LM35 and a special problem that can occur with long wires.

Elektrix

6

Thanks for the feedback.
Before pursuing my Adrustat I will need to better understand my HVAC.

I looked at the wires 2 days ago and learned:

  • that I have more wires than expected
  • my system uses a Heatpump
  • I have a 3zone control unit, of which just 1 zone is used
  • I don't need to use a control unit and could wire the outside unit directly to a T-stat
  • the drain pipe sensor was not connected
  • my drain pipe was clogged

Now I have wet carpet and moisture damage in my laminate floors...