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Bonitron Air Demand
Scheduler
Design Review
Vanderbilt Senior Design
Alex Brown
Ajmer Dwivedi
Cory Haugh
February 04, 2008
Introduction

Air Demand Scheduler



Reduces peak power
consumption
Selects 1 of 2 HVAC
units to run at a time
Allows for manual control
using user overrides
Objectives






Production ready prototype
Low cost microprocessor
RS-232 I/O functionality
Identical logic
All other specifications are to remain the same
Preserve existing package
Requirements

Input Power


115VAC, 50/60Hz
Control Signals 24 VAC

Inputs



Outputs



+20 to +65 Degrees Celsius
Humidity


0 to +40 Degrees Celsius
Storage Temperature


NEMA-12 Wall Mountable w/Quick Release Door Latch (10’’ x 6’’ x 4’’)
Operating Temperature


Unit 1: Air Conditioning 1, Heat 1
Unit 2: Air Conditioning 2, Heat 2
Enclosure


Thermostat 1: Air Conditioning 1, Heat 1
Thermostat 2: Air Conditioning 2, Heat 2
Below 90%
Atmosphere

Free of Corrosive Gas and Dust
Approach




Extract existing design from previous group’s
documentation and new hardware
Replace FPGA development kit with
microcontroller
Develop PCB design partitioning circuit
components
Fabricate assemble and test design
System Diagram
PGC
Vpp
PGD
PicKit 2 Programmer
120V AC
AC Neutral
System Gnd
Chassis Gnd
Power
Conversion
5V
Gnd
PGC
Vpp
120V AC Power
Supply
PGD
Programming
Header
Vpp PGD PGC
Vcc
Gnd
RB0
Heat
Signal Gnd
A\C
Signal Gnd
ON\OFF
HVAC 1
Output Relays
RB1
Heat
Heat
Signal Gnd
A\C
Signal Gnd
ON\OFF
ON/OFF
Signal Gnd
HVAC 2
Thermostat 1
A/C
ON/OFF
Demand 1
Signal Gnd
Signal
Conversion
Heat
ON/OFF
Demand 1
RxD
RD0
Controller
TxD
RD1
Signal Gnd
Thermostat 2
A/C
RxD
RS232
Conversion
TxD
RxD
Signal Gnd
RA0
RA1
RA2
RA3
RA4
RA0
RA1
RA2
RA3
RA4
RD2
RD3
RD2
RD3
Ribbon
Cable
ON/OFF
Signal Gnd
Vcc
Gnd
Main Board
Computer
TxD
D0
D1
D2
D3
D4
LEDs (5)
D0
D1
Control Buttons (2)
Vcc
Gnd
Display Board
120V AC
AC Neutral
System Gnd
Chassis Gnd
+5V
Power
Conversion
Gnd
+18V
To Rest of Board
From Wall Socket
Power Conversion Diagram
Power Conversion Schematic
Power Conversion Requirements


Provides conditioned power to Signal
Conversion Board
Inputs


115 VAC IN
Outputs
+18 VDC (nominal) OUT
 +5 VDC OUT

Signal Conversion Diagram
Gnd
+5V
+18V
From Power Conversion
To Thermostat 1
Demand 1
Signal Gnd
Demand 1
ON/OFF
To Microcontroller
ON/OFF
Signal Gnd
Signal
Conversion
Signal Gnd
ON/OFF
Signal Gnd
Heat
Signal Gnd
A\C
Signal Gnd
To HVAC Units
ON/OFF
Heat
Signal Gnd
A\C
Signal Gnd
Signal Conversion Schematic
Signal Conversion Functional
Requirements

Inputs

Thermostats provide 24 VAC upon Demand



Outputs



2 Heat Inputs
2 Cool Inputs
Replaces thermostats to HVAC units
24 VAC sent to HVAC units via relays based on decisions
made by microcontroller, I/O Board, or user interface
Optical Isolation

Optocouplers isolate and protect microcontroller & I/O
Board from outside 24 VAC circuitry
Signal Conversion

24 VAC Input from Thermostats




If +5 VDC from microcontroller


Amplified via Darlington array to turn off relay
If 0 VDC from microcontroller


Conditioned and rectified
Electrically Isolated
Sent to microcontroller & I/O Board
Grounds output of Darlington array to turn on relay
24 VAC Output to HVAC

Sent via closed relay
Microcontroller Selection
Name
Cyclone II FPGA
HCS12
87C51
PIC16F747
Part Number
EP2C35F672C8N
MC9S12UF32
P87C51FB-4N
PIC16F747
Producer
Altera
Freescale
NXP
Microchip
Recurring Cost
$99.70
$4.20
$7.80
$3.20
Package
672-FBGA
64-LQFP
40-PDIP
40-PDIP
Programing Software
Quartus II
MGTEK MiniIDE
Third Party
Bundled with PicKit
Programing Hardware
Serial Port Cable
USB Cable
ZIF Socket + USB
PicKit 2
Programing Cost
$150.00
$100.00
$110.00
$50.00
Programing Language
VHDL
Assembly \ C
Assembly
Assembly \ C
Custom Header
Y
Y
N
Y
Timers
N
Y
Y
Y
RS-232
N
Y
Y
Y
Internal Clock
N
N
Y
Y
Non-Volatile Code
N
Y
Y
Y
Notes:
Previous groups
FPGA, used in FPGA
class at Vanderbilt
Used in
microcontrollers
class at Vanderbilt
Microcontroller currently
used in Bonitron Board
Lowest Cost to Project
Microcontroller Selection

Cyclone II FPGA
High recurring and non recurring costs
 Surface mount with 600+ pins


HCS12
Surface mount
 High non recurring costs


87C51
Third party programming software
 No C++ support

Microcontroller
Gnd
Demand 1
Demand 1
PGC
PGD
Vpp PGD PGC
Vcc
Gnd
RB0
ON\OFF
RB1
ON\OFF
RxD
RD0
Controller
TxD
TxD
RA0
RA1
RA2
RA3
RA4
RA0
RA1
RA2
RA3
RA4
To LEDs
(I/O Board)
RD2
RD3
RD2
RD3
From Buttons
(I/O Board)
RD1
RxD
To Computer (DB-9)
From Thermostats
(Signal Processing)
5V
To Relays (Signal
Processing)
From Power
Conversion
Vpp
From Programming
Header
Development Approach

Programmable microcontroller
Internal UART
 Internal timer
 Internal oscillator



Compatible with original microcontroller (40 pin
DIP)
Use PICkit 2 programmer and development kit
to code microcontroller
Development Methodology


User will write the
application program in
C or assembly code
On-board storage

RAM


Configuration retained
as long as the power is
on
Flash

Store program code in
non volatile memory
MPLAB IDE Development Software


Software provided by Microchip for programming
PIC microcontrollers
Procedure:



Write code in assembly language
Program microcontroller
Test functionality


Apply test inputs and observe outputs
Design test strategy for all possible cases
MPLAB IDE Screenshot
PICkit 2




Hardware
programmer for PIC
microcontrollers
USB programmable
Connects via 6 pin
header on PCB
Packaged with starter
kit for testing
Existing
Logic
Diagram
RS-232

Graphical user interface for control of overrides
and timers
Parallels functionality of previous override design
 Replaces variable resistors with programmable
timing capabilities


Allows user to program timers without
physically manipulating the components
Programming RS-232


GUI done using Visual Basic
Use feedback loop to perform original testing
RS-232 Hardware


Max 232 transceiver
to perform voltage
conversion between
circuitry and DB-9
Changes voltage
range from 0 - 5
VDC to ±15 VDC
Floorplan
PCB Design



Copied 90% from
previous PCB layout
Added connections for
new microcontroller and
serial port components
2-sided through hole
design allows easier trace
routing than previous
single sided board
PCB Software





Developed PCB design using PCBExpress
No License required
Order directly though the site
Extensive parts library
Ability to design custom component based on
datasheet specification
Bottom Side
Top Side
PCB Design
Approval


In order to proceed, we request your approval
of the design
Comments?
Near Term Plan
Hardware Development






Add breakpoints to existing PCB design
Obtain parts from Bonitron storeroom
Order PCB
Test circuit partitions
Assemble
Test Final product
Near Term Plan
Software Development


Develop assembly language code
Refine Visual Basic GUI
Hardware Schedule





Obtain all components by February 15th
Order PCB by February 15th
Have assembled prototype boards by March 1st
Have full board assembled by March 14th
Test till design day
Software Schedule




Complete GUI by February 22nd
Complete programming of the test board
microcontroller by March 1st
Complete programming of product ready
prototype board microcontroller by March 14th
System debug and operational testing from
March 14 until design day
Our webpage:
http://eecs.vanderbilt.edu/courses/eece295/2007-2008/Bonitron-HVAC