Ehvac: Wireless Modular Multi-Zone hvac controller Group b javier Arias Ryan Kastovich Genaro Moore Michael Trampler



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University of Central Florida

2012


eHVAC: Wireless Modular Multi-Zone HVAC Controller

Group B

Javier Arias

Ryan Kastovich

Genaro Moore

Michael Trampler

Table of Contents



Section 1: Executive Summary 4

Section 2: Project Description 6

2.1 Project Motivation and Goals 6

2.2 Objectives 7

2.3 Project Requirements and Specifications 7

2.4 Division of Labor 8

Section 3: Research 11

3.1 Research Methods 11

3.2 Main Control Unit (MCU) 12

3.2.1 System Control Module 12

3.2.1.1 Safety Controls 13

3.2.1.2 Real Time Clock (RTC) 15

3.2.1.3 Heat Pump Control 16

3.2.1.4 Fan Control 18

3.2.1.5 Vent Control 19

3.2.2 System UI & Intelligence Module 22

3.2.2.1 Operating System 23

3.2.2.2 HTTP Server 24

3.2.2.3 Common Gateway Interface (CGI) 25

3.2.2.4 Database (DB) 26

3.2.2.5 Beyond Hardware: The Cloud & The Google App Engine Platform 28

3.2.2.6 Python Vs. Java Vs. C 29

Table 3.2.2.6-1 Comparing Languages 31

3.2.2.7 MVC Framework: How it all comes together 31

3.2.2.7.1 Comparison of MVC Frameworks 32

3.2.3 Comparison of System Modules 34

3.2.3.1 Comparison of System Control Modules 34

3.2.3.2 Comparison of System UI & Intelligence Solutions 36

3.2.4 System Control and System UI & Intelligence Interface 38

3.2.5 Interfacing the MCU with the RSM(s) 41

Table 3.2.5-1 General characteristics of TI CC2520 Zigbee® Transceiver [67]. 42

Table 3.2.5-2 General Characteristics of TI CC2500 Transceiver [67]. 43

Table 3.2.5-3 General Characteristics of TI CC1101 Transceiver [67]. 43

3.2.6 Interfacing with the outside world (LAN + Internet) 44

3.3 Power 46

3.3.1 System Control 46

3.3.2 Remote Sensing Module 46

3.4 Thermostat (Remote Sensor Module - RSM) 49

3.4.1 Functions 50

3.4.1.1 Temperature measurement 50

3.4.1.2 CO2 Monitoring 52

3.4.1.3 VOC Monitoring 54

3.4.1.4 Humidity Monitoring 55

3.4.1.5 Zone Control 58

3.4.2 Hardware 59

3.4.2.1 Microcontroller Hardware 59

3.4.2.2 Input/ Output Hardware 60

Section 4: Design Specifications 62

4.1 System UI & Intelligence 62

4.1.1 Software 62

4.1.1.1 Platform 62

4.1.1.2 Programming Language 63

4.1.1.3 MVC Framework 64

4.1.1.4 Database Structure 64

4.1.2 Web Application Layout 68

4.1.3 Web Application Variable Definitions 77

4.2 Main Control Unit/ System Control 82

4.2.1 Hardware 82

4.2.1.1 System Control Module Microcontroller & Communications 82

4.2.1.2 Damper Control 84

4.2.1.3 Fan Control 86

4.2.1.4 Compressor Control 86

4.2.1.5 Power 87

4.2.2 Software 88

4.2.2.1 Damper Control 88

4.2.2.2 Heat Pump Control 89

4.2.2.3 Fan Control 91

4.2.2.4 Safety Sensors 92

4.2.3 RSM Interface 92

4.2.4 Web Application Interface 93

4.3.1 Hardware 93

4.3.1.1 Input/ Output 93

4.3.1.2 Physical Dimensions 95

4.3.1.3 Power Supply 97

4.3.1.4 Sensor Schematic 97

4.3.1.5 Micro Controller Schematic 98

4.3.1.6 Wireless Hardware 99

4.3.2 Software 101

4.3.2.1 Sensor Subroutine 102

4.3.2.2 Wireless TX Subroutine 104

4.3.2.3 Wireless RX Subroutine 107

4.3.2.4 Input Subroutine 109

4.3.2.5 Display Subroutine 110

Section 5: Prototyping 115

5.1 Thermostat Prototyping 115

5.2 System UI & Intelligence Prototyping 116

5.3 System Control Prototyping 117

Section 6: Testing 119

6.1 Testing Criteria 119

6.2 Remote Sensor Module Testing 120

6.2.1 Human-Machine Interface Testing 120

6.2.2 Sensor Testing 121

6.2.3 Wireless Connectivity 122

6.3 System UI & Intelligence Module Testing 123

6.3.1 Web Application Access 123

6.3.2 Page Links and Settings 124

6.3.3 Temperature and Humidity Readout 126

6.3.4 Simultaneous Load 127

6.3.5 Control Mechanisms 128

6.3.6 Data Logging 130

6.4 System Control Module 131

6.4.1 Wireless Connectivity 131

6.4.2 Test Damper Control 132

Section 7: Administrative Content 138

7.1 Milestone Discussion 138

7.2 Finance Discussion 139

Table 7.2-1 MCU Parts 139

Table 7.2-2 RSM Parts 140

Section 8: Appendices 141

Appendix A: Copyright Permissions 141

Pending 144

Appendix B: Datasheets 146

Appendix C: Extraneous Figures 147

Appendix D: Acronyms 147

Appendix E: Bibliography 149


Table of Figures


Table of Tables



Section 1: Executive Summary

Today, there are an increasing number of households running HVAC (heating, ventilation, and air-conditioning) control systems 24/7. While many of these systems might be designed to be as efficient as possible, it does not mean that they are smart enough to accommodate the needs of the user(s) in every possible usage scenario combination. For example, not every room in a house needs to be set at the same temperature at all times, especially once everyone has gone to bed. So at night, there are usually no occupants in the kitchen, living room, or dining room which are still being cooled or heated. Then, a multi-zone system was introduced to help fulfill the extra needs of consumers. With this new innovative system, users were given the ability to dictate individual temperatures to different “zones,” whether they be bedrooms and living rooms, or different floors of an office building. The user could control the HVAC to cool and/or heat only the room’s occupied, turning off the zones vacant through installed dampeners to control air flow. To give an example let’s say there are two zones for an HVAC system, if one zone is vacant, then the user could turn one zone off directing all the air flow to the occupied zone which will then be cooled or heated faster. So with this system installed, power consumption will decrease which results in a cut in energy costs.


HVAC systems are designed to maintain a desired temperature set point. Unfortunately this system creates a large temperature gradient between the inside of the domicile and the natural weather. As per thermodynamics the larger the temperature gradient between two areas the quicker thermal energy transfers through the substrate which separates them. For example in the summer, the outside temperature can hit +90 degrees Fahrenheit while the set point for most HVAC systems will usually be between 65 and 80 degrees. This causes a large temperature gradient and reduces the effectiveness of the insulation provided by walls and purpose built insulation material. If the temperature gradient were to be reduced to a negligible value then thermal energy would stop flowing into the domicile. Our system’s main goal is to reduce the temperature gradient between the interior of the domicile and the exterior during the hottest part of the day. This will greatly reduce the amount of time the heat pump’s compressor will run which in turn will greatly reduce the energy it consumes. It is generally accepted that the heat pump is one of the largest energy draws in a domicile; therefore reducing its energy draw should be one of the easiest ways to reduce energy waste.
To reinforce this projects energy saving applications, here’s another example of how this system will help. On a regular day in typical households worldwide, people have air conditioning units that run throughout the day while no one is home. If consideration is taken on how much energy is being wasted on a vacant house, the reality is that on a yearly basis this amount is astronomical. The advantage of the HVAC system would be the ability to shutdown the main system when no one is home. It would accomplish this task with a host of sensors tied together which would recognize if someone was home, and if by chance they were not, a self-shutdown sequence would initiate. This in itself would save tons of energy and would lower the cost of running a system in a consumer’s home/zone.
This system will be designed such that a consumer will be able to utilize the multi-zone controllers all while keeping the power consumption low, as well as being eco-friendly and leaving a small footprint. Although the power consumption will be low, there won’t be any drop off in precision levels, customizability, or aesthetics. Multiple remote sensor modules (RSM) will be implemented so the user will be able to control temperature and humidity in certain zones through an aesthetically pleasing interface. The web app will come with preset modes with which a user can employ to run throughout the day to further decrease power consumption. But if those preset modes do not adequately meet the requirements of the user, he/she will be able to program the RSM to meet his/her own needs. This system will also feature internet connectivity for the convenience of control anywhere there's internet access. The web interface will give the user the control features of an RSM, while the user is away.




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