Programmable Thermostat

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Programmable Thermostat
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Team Members

• Team Leader
• Jessie Thomas
• Team Members
• Bobby Herron
• Zach Mullins
• Andrew Gertig
• Faculty Advisor
• Dr. R. S. Winton

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Project Tasks
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Problems and Solutions

• High Energy Consumption
• Lack of Precision
• Materials

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What will it do?

• Interface with a pre-existing HVAC setup
• Perform functions of normal thermostat
• Allow user to set a program
• Run the user set program
• Keep the time and the day of the week
• Be able to be reset to factory settings

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What will it look like?
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Initial Problems

• LCD screen
• Not enough programs

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Solution
First Design Second Design
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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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Voltage Rectifier and Regulator Circuit
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Voltage Rectifier Output
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Voltage Regulator Output
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Testing

• Some problems with back-up power

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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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Thermistor

• Means of measuring temperature
• Sends information to the PIC allowing proper
  operation of the thermostat

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Thermistor Resistance Test

• I Vout / Ruser
• Ruser 10k
• Vtherm Vref Vout
• Vref 5V
• Rtherm Vtherm / I

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Testing

• Initial Testing - working
• Analog-to-Digital Conversion with 16F877 - not
  complete

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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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Keypad and Switches

• Digital output
• Analog output

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Testing

• Problem Buttons are too sensitive
• Solution More delay time and grounds for buttons

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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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Microcontroller

• PIC16F877
• Center of operations
• Interfaces every aspect of thermostat

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Testing

• Not Enough Memory
• Solutions External memory or another
  microprocessor

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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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LCD

• Optrex America Inc.
• DMC-16202N-LY-AME
• 16 x 2 Character Display
• Allows user to see how thermostat is operating
• Allows user to program thermostat (with help of
  user buttons)

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LCD Screen
Fan Status
Program Number
System Status
Day of the Week
Temperature
AM or PM
Temperature Units
Time
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Testing

• LCD working properly
• Backlight not tested yet

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Main Components
Power
Microcontroller
LCD
Backup Power
Temperature Sensor
Relays
User Buttons
Switches
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Relays

• Needed to turn on HVAC relays
• Compact 1-Amp SPST Reed Relay 5VDC
• Currently using three (heat, cool, fan)

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Testing

• Problem Relays stick sometimes
• Solution Relays with higher voltage rating

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Software

• Use Case Scenarios
• Information Model
• User Interface

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Use Cases
Turn Program On or Off
Change Program Number
Press Reset but Walk Away
Change System Mode (Heating, Cooling, Off)
Push Fwd or Back Buttons
Change Temperature Setting (Up or Down Button)
Change Fan Mode (On or Auto)
Enter Program Mode But Walk Away (Does Not Exit)
Enter Program Mode, and Exit Correctly (2 ways
of doing this)
Reset Factory Setting (Push Reset, then Fwd)
Sunny Day
Rainy Day
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User Interface
Main checks for programs and inputs
Program Menu allows the user to setup programs
Start Menu gets initial information from the
user
Reset Menu allows the user to reset information
setup in the start menu
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Testing

• Menus are working correctly
• Main program has not been tested because of the
  lack of memory

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Acknowledgements

• Dr. Winton
• The ECE Shop Personnel
• Microchip
• Dr. Picone
• Mr. Bill Buchanan

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Questions?