Portable Thermostat

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Portable Thermostat

• Midterm Presentation

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Team Advisor

• Dr. Marion Hagler
• hagler_at_ece.msstate.edu
• http//www.ece.msstate.edu/hagler

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Team Members

• Adnan Mulkana
• Hardware
• Remote Programming
• RF
• RS-232
• User Interface
• Documentation

• Joseph Baugh
• Presenting
• Hardware
• Base Programming
• RF
• RS-232
• HVAC Interface
• Documentation

• Brian Chapman Team Leader
• Hardware
• Board Design
• Power
• Temperature Sensor
• HVAC Interface
• Documentation

• Gray Williams
• Visual Basic (GUI)
• User interface
• RS-232
• RF
• HVAC Interface
• Documentation

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Problem Statement

• Traditional Thermostat
• Stationary
• Problems
• Temperature measured at a single location
• The elderly and disabled have to go from the
  bedroom or living room to the thermostats
  central location to adjust it.

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System Overview
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Elements of Design

• Semester Emphasis
• Packaging
• HVAC Interface
• System Cost
• Connectivity
• OS Compatibility

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Remote Module

• Temperature Sensor
• Thermistor
• Range 50ºF to 90 ºF
• User Interface
• 8X2 LCD
• Joystick input
• Microcontroller
• PIC16F873
• RF Module
• Maxstream 9XStream

User Interface
Temperature Sensor
PIC
RF Module
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Remote Packaging

• Vented
• User Interface
• LCD
• Joystick / Switch
• Target Size
• 7.5 L x 3.5 W
• Similar to TI-89
• Weight
• 8 oz.

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Remote PCB
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Remote Revisions

• Replaced PIC16F877 with PIC16F873
• Less space
• Cheaper
• Replaced 8X1 LCD with 8X2 LCD
• Displays more detailed information
• Smaller and lighter
• Replaced mode and temperature buttons with
  joystick
• Simplified user interface
• Cheaper

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Base Module

• Microcontroller
• PIC16F873
• RS-232
• Used to connect base to PC
• HVAC Interface
• Controls HVAC system
• 5-wire interface

PIC
RF
RS-232
Temp. Sensor
HVAC
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Base Packaging

• Wall-mountable
• Vented
• Accessible from back and front
• HVAC Interface
• PCB sized to fit pre-fabricated packaging
• Serpac 052

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Base PCB
Thermistor
HVAC
RS-232
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Base Revisions

• Replaced PIC16F877 with PIC16F873
• Less space
• Cheaper
• Replaced MAX232 with MAX233
• Removed four electrolytic capacitors
• MAX3100
• Removed crystal and two capacitors

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PC Module

• Interface for base
• Displays HVAC state and temperatures
• Used to set base when remote is not present
• Anticipator
• Over-Current Protection
• Compatible with Windows 95, 98, ME, 2000, XP

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Cost
Remote

• Costs conducted for purchasing in single
  quantities
• Total Cost 167.43
• Maximum Cost 200.00

Base
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Work Completed

• New Components Added and Tested
• Communication
• OS Compatibility
• Power Supplies
• Attempted switching supply for remote
• Used diodes to regulate battery voltage
• PCBs Ordered
• Chose Base Package

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Future Work

• Verify PCBs
• Packaging
• Modify base packaging
• Fabricate remote packaging
• Test System
• Update Software

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Questions
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(No Transcript)
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Temperature Sensor

• Uses thermistor to measure temperature
• Measures temperatures ranging from 50ºF to 90 ºF
• Outputs values ranging from 0V to 5V
• Same temperature sensor used on base

User Interface
Temperature Sensor
PIC
RF Module
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User Interface

• Displays and receives information from user
• Joystick control allows temperature control and
  mode selection
• 8X2 LCD displays mode, ambient temperature, and
  desired temperature

User Interface
Temperature Sensor
PIC
RF Module
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PIC

• PIC 16F873
• 28 pins
• 10-bit ADC
• Onboard UART

• Receives inputs from the user interface and
  applies them.
• Sends mode, ambient temperature, and desired
  temperature to LCD
• 10-bit ADC converts thermistor voltage into
  temperature value
• Sends messages to the base, via the RF

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RF Module

• Maxstream 9X
• Uses RS-232 (serial port) protocol to receive
  information from PIC
• Sends information to base

User Interface
Temperature Sensor
PIC
RF Module
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MAX3100
MAX 3100
PIC
RS-232

• External UART
• SPI Interface
• Used to interface with Maxstream 9X (RF)

RF
Temp. Sensor
HVAC
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PIC
MAX 3100
PIC
RS-232

• Receives inputs RF and relays them to the PC
• Receives inputs from PC and applies them to the
  HVAC
• Interfaces with the HVAC system
• 10-bit ADC converts thermistor voltage into
  temperature value

RF
Temp. Sensor
HVAC
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RS-232
MAX 3100
PIC
RS-232

• Serial Port
• Used to connect the base to the PC
• Compatible with most PCs
• MAX233
• RS-232 voltage converter
• Used to convert CMOS voltage levels (0V, 5V) to
  RS-232 voltage levels (-12V, 12V)

RF
Temp. Sensor
HVAC
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HVAC Interface

• Controls HVAC system
• Designed for 5-wire interface
• Compatible with 4-wire systems.
• Not compatible with heat pumps.

• Relays
• Must switch 24V, 1.2A.
• Capable of switching xxxV, x.xA.
• FET
• Used to power relays
• Current constraint on PIC outputs.

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Elements of Design

• User interfaces
• Base
• Remote
• Construct a low-weight remote
• Accurate temperature sensor
• Connect to existing 5-wire HVAC interfaces
• Account for high-current problems with rapid
  switching
• Provide anticipator settings
• Communication between remote, base, and PC
• Produce a total system costing no more than 200

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Hardware Layout

• Remote
• Measures remote temperatures and transmits
  commands to base.
• Base
• Measures local temperature and connects remote,
  PC, and HVAC.
• PC
• Serves as base interface and sends command to the
  base.

Remote
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Remote Module
Remote
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Base Module
Base
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PC Module
PC
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Power - Remote
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Power - Base

• Many HVAC systems do not support power-stealing
  thermostats.
• The 5-wire HVAC interface does not enable
  hardwiring.
• Base will receive power from an adapter.

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RS-232
RS-232

• Serial Port
• Connection from the PC to the base
• Present on most PCs

BASIC
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Flowchart