DRAFT – I’m still working on this project, and the post, but here’s the basic setup and some pictures…

Overview

This project was born because our programmable thermostat was a piece of junk and the Nest is expensive (although I ended up spending about as much on supplies as I would have on a Nest. The goals were 1) to have a thermostat that could be controlled via a smartphone and 2) to keep a log of temperature and thermostat data.

The project consists of five parts

• HVAC system control hardware and temperature sensor in hallway
• Temperature sensor in living room
• Desktop application
• iPhone app
• MATLAB script to process log data

Hardware

HVAC system control hardware and temperature sensor in hallway

Arduino Uno (datasheet)
XBee 802.15.4 1.0 (XBee | Shield | Explorer USB)
Relay Shield (Wiki Page)
TMP36 Temperature Sensor (2x) (datasheet)

 
Device Data Pins
TMP36 #1 -> A0
TMP36 #2 -> A5
Control Pins for Thermostat
G Wire (Fan) -> 8
W Wire (Heat) -> 9
Y Wire (AC) -> 10
 
 

Thermometer (via Ethernet)

Arduino Mega (datasheet)
Arduino Ethernet Shield (datasheet)
TMP36 Temperature Sensor (2x) (datasheet)

Layout

 

 

 

Interface via Serial

Setting Thermostat Parameters

Goal Temperature
Delay Time
Mode

Sending Data via Serial

Temp 1
Temp 2
Goal Temp
Mode
State
Delay Time

Algorithms

Toggling HVAC On/Off

Processing Sketch

Thermostat Serial Message Parsing

Outdoor Weather via XML

Desktop Application

Status windows
Goal Temp/State/Mode control

Web-Based Control

Temperature control

Data Logging

MATLAB Data Visualization