Transcript ppt - Purdue College of Engineering

ECE 477 Design Review
Group 1  Spring 2005
Outline
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Project overview
Project-specific success criteria
Block diagram
Component selection rationale
Packaging design
Schematic and theory of operation
Preliminary PCB layout
Software design/development status
Project completion timeline
Questions / discussion
Project Overview
• Receive input from three types of sensors: a
universal flame detector, directional
temperature sensors, and directional
distance sensors
• Inputs processed by microcontroller
• Microcontroller drives maneuvering motors
and servos to trigger the fire extinguisher
• Sounds a siren in the presence of a fire
• Software to operate in three modes: off, “one
eye open” and patrol
Project-Specific Success Criteria
• Ability for the software to maneuver the robot on an
arbitrary indoor surface, avoiding walls or other objects
while maneuvering.
• Ability to detect a nearby fire with minimal false positives
(from non-flame heat sources) and determine the fire’s
position relative to the robot.
• Ability to maneuver the robot into position to extinguish a
fire based on data from the sensors.
• Ability to activate a fire extinguisher to extinguish a fire
when the robot is already in the correct position.
• Ability to display state information to a user through an
LCD interface
FIREBot Block Diagram
Siren
Power
Supply
Motor
Drivers
Universal
Flame
Detector
Wide Angle
Flame
Detectors
Narrow
Angle Flame
Detectors
Distance
Sensors
Push
Buttons
LCD
Output
Microcontroller
Debug
Port
Extinguisher
Trigger
Servo
Sensor
Platform
Servo
Component Selection Rationale
Microcontroller
The microcontroller must have sufficient peripherals to interface to all of the external
components as well as sufficient FLASH and SRAM to store all the code and the data
in operation. It must be inexpensive, easily available, and easy to prototype
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The Atmel ATMega32
– 4 PWMs, 8 Analog-To-Digital Converters, one UART
– 32k FLASH, 2K SRAM, 1K EEPROM
– Easily available in a PDIP Package
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The Motorola MC9S08GT32CFB
– 4 PWMs, 8 Analog-To-Digital Converters, one UART, one IR UART
– 32K FLASH and 2K SRAM.
– Also available in a DIP package.
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We have tentatively chosen the Atmel ATMega32 because of low cost and good
development package. The Motorola MC9S08GT32CFB-ND is a workable
alternative.
Component Selection Rationale
Wide Angle Flame Detector
Wide Angle Flame Detectors find flames at a long distance and at a
(relatively) wide-angle, and provide angular position location to the flame
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Hamamatsu UVTron – UV Detector which is very sensitive but with strong
discrimination. Detects a candle at 5m.
– Unacceptable: Updates every 3s
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UV Photodiode: Less sensative and less discrimination, but analog
– Very low output current
– Unacceptable: Didn’t detect flames in experiments, but reacted to
flourescent lights
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IR Photodiode: Much less discrimination, also analog
– Reacts some to flourescent lights, but more to flames
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IR photodiode chosen to be better option since no way to get around
problem of a UV photodiode under florescent lighting
Packaging Design
• Packaging carefully designed to protect delicate parts
without sacrificing operation
• Due to large amounts of heat, need a heat shield to
protect the micro and some sensors
• Structure intended to be simple, easily accessible and
easily modified
• Electronic components need to be protected from the
chemical released by fire extinguisher to put out fire
• Robot powered by an onboard rechargeable battery
• Onboard 4 lb fire extinguisher used to extinguish fires
Schematic/Theory of Operation
The FIREbot Electrical Schematics are built in a hierarchical structure, with
blocks performing the following functions:
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Power Supply
Universal Flame Detector
Wide Angle Flame Detector
Narrow Angle Flame Detector
Distance Sensors
Push Buttons
Microcontroller
Motor Drivers
Sensor Platform Driver
Extinguisher Trigger
Siren
LCD Outputs
Debug Port
Power Supply Unit
Sheet 15
• The power supply block outputs 4 voltage rails
• A 5V rail for digital components (Switching
Regulator)
• A 5V rail for analog sensors (Linear Regulator)
• A 5V rail for servos (Switching Regulator)
• A 12V rail for analog components
• Three separate 5V rails isolate the noise caused
by each type of component
• p-channel power MOSFETs used so
microcontroller can turn off all but Digital rail
Power Supply Unit Top Level
Switching Power Supply
Linear Regulator
Universal Flame Detector
Sheet 21
• Major component is the UVTron
• UVTron sensor connected to small PCB that asserts a
pulse when it detects a flame
• Open collector output of UVTron’s circuit board used to
clock a D-flip flop
• Output of D-flip flop serves as an interrupt to the
microcontroller
• Microcontroller can clear the interrupt flag with a clear
signal
• 5V digital rail used to supply all components in block,
including UVTron’s circuit board
Universal Flame Detector
Wide Angle Flame Detector
Sheet 22
• Provides interface to IR photodiodes that detect flames in a
wide field of vision at long distance
• Block physically separate from main PCB, sits on turntable
controlled by a servo to detect flames and provide angular
position
• Special circuit developed with current input inverting op-amp
along with band pass filter to amplify signal to a large
voltage and filter off noise
• Output current from IR photodiodes amplified into voltage
that can be read by a microcontroller A-to-D pin
Wide Angle Flame Detectors
Narrow Angle Flame Detector
Sheet 14
• Raytec Compact CI active infrared temperature
sensor and requiring 12V to operate
• Simple interface block
• Analog output connected to an A-to-D converter on
the microcontroller
• Output voltage proportional to surface temperature
of object in field of view
Narrow Angle Flame Detector
Proximity Sensors
Sheet 7
• Sharp GP2D120 active infrared proximity sensor
interface consists of four identical circuits
• Individual circuits incorporate a single active
infrared distance sensor
• Outputs from each distance sensor connected to
a separate A-to-D port on the microcontroller
• Analog supply rail of 5 volts used to power
circuits to isolate analog sensors from switching
noise of digital components
Proximity Sensors
Microcontroller
Sheet 12
• ATMega32 microcontroller
• 8-bit serial shift register connected to microcontroller pin
increases number of logic signals
• Active low reset pin on micro connected to standard
SPDT pushbutton switch circuit
• Capacitors used across power and ground pins for both
digital and analog circuits
• 8 MHz oscillator connected to the two oscillator pins of
microcontroller
• AVRISP interface necessary to program microcontroller
Microcontroller
Servo Motor Drivers
Sheets 8 and 19
• Extinguisher Trigger and Sensor Platform Drive
blocks identical, controlling similar servos
• Optical isolation for PWM signals
• Decoupling capacitors for power
• Dedicated 5V rail for servos to prevent noise on
other power lines
Servo Driver Circuit
DC Motor Drivers
Sheets 13 and 10
• Block responds to signals from microcontroller to
drive the two power motors of FIREBot
• PWM used to control speed of each motor
• Inputs are 8 digital signals from micro 4 for each
motor
• Signals are Forward, Reverse, Brake, and PWM
• Outputs are analog drive voltages connecting
directly to positive and negative terminals of the
power motors
• 3 parts: glue logic, H-bridges, snubbers
DC Motor Driver Circuit Top Level
Half of an H-Bridge
Siren Interface
Sheet 20
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Interfaces a 12V siren to a pin of the micro
Input is Siren_Activate signal from the micro
Output is positive and negative terminals of siren
Optically isolated Siren_Activate signal controls
gate of FET to switch positive terminal of siren.
• Activated LED is alternative to siren if necessary
Siren
Serial Debug Port Interface
Sheet 6
• Provides an RS-232 interface through which
external PC can connect to FIREBot
• Can also be used to send simple commands
• TX and RX are 5V digital signals connected
directly to micro
• TX and RX signals optically isolated from analog
circuitry
• TX and RX signals level-shifted to +/-12V logic
levels on RS-232
• Outputs to pins of DB9 serial connector
Serial Debug Interface
Push Buttons
Sheet 16
• 3-way switch provides the only user input to the
robot
• Center position indicates off mode
• Left and right positions select one of two
operating modes
• Capacitors effectively de-bounce the switch
Character LCD Interface
Sheet 9
• 20x4 Character LCD for status feedback
• LCD interface based on 74HC74 8-bit serial shift
register
• Shift register input driven by port pin on micro
• Shift register reduces number of port pins
required send data LCD from eight to one
• Other LCD control signals (i.e. LCD_STROBE)
driven directly by port pins on micro
• Potentiometer to control contrast of LCD
Character LCD Interface
Preliminary PCB Layout
Preliminary PCB Layout
Digital Switching
Power Supply
Preliminary PCB Layout
Digital Switching
Power Supply
12V
Switch
Preliminary PCB Layout
Digital Switching
Power Supply
12V
Switch
Servo Switching
Power Supply
Preliminary PCB Layout
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
12V
Switch
Servo Switching
Power Supply
Preliminary PCB Layout
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
12V
Switch
5V Linear
Regulator
Servo Switching
Power Supply
Preliminary PCB Layout
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
12V
Switch
5V Linear
Regulator
Servo Switching
Power Supply
Servo Motor Drivers
Preliminary PCB Layout
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
12V
Switch
5V Linear
Regulator
Servo Switching
Power Supply
Servo Motor Drivers
Preliminary PCB Layout
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
ATMega32
12V
Switch
5V Linear
Regulator
Servo Switching
Power Supply
Servo Motor Drivers
Preliminary PCB Layout
12V
Switch
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
5V Linear
Regulator
ATMega32
Serial Debug
Port
Servo Switching
Power Supply
Servo Motor Drivers
Preliminary PCB Layout
12V
Switch
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
5V Linear
Regulator
ATMega32
Serial Debug
Port
Siren
Servo Switching
Power Supply
Servo Motor Drivers
Preliminary PCB Layout
12V
Switch
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
5V Linear
Regulator
Servo Motor Drivers
DC Motor
H-Bridges
ATMega32
Serial Debug
Port
Servo Switching
Power Supply
Siren
Preliminary PCB Layout
12V
Switch
Digital Switching
Power Supply
Analog Flame &
Proximity Sensors`
LCD
Display
5V Linear
Regulator
Servo Motor Drivers
DC Motor
H-Bridges
ATMega32
Serial Debug
Port
Servo Switching
Power Supply
Siren
Turntable
Mounted
PCB
Software Design/Development Status
ECE477 Group 1
Spring 2005
Software Block Diagram
Control State Machine
Patrol
Mode Functions
Drive Module
Drive Motors
Approach
Mode Functions
Obstacle Module
IR Range
Sensors
Wide Angle
Flame Detector
Module
Hardware
Extinguish Mode
Functions
Universal Flame
Detector Module
Scanner Module
IR Photodiode
Circuits
Software
One-Eye-Open
Mode Functions
Narrow Angle
Flame Detector
Module
Scanner Platform
Servo
UVTron Board
Scanner
Temperature Sensor
Extinguish Module
Extinguish Servo
Software Design/Development Status
No Fire
OFF Mode
Button Pressed
Patrol Mode
OEO Mode
Button Pressed
Detect Fire
Patrol Mode
Button Pressed
Patrol Mode
Button Pressed
No Fire
OEO Mode
Button Pressed
OFF Mode
One Eye Open
Detect Fire
Mode
Approach Fire
Mode
OFF Mode
Button Pressed
OFF Mode
Button Pressed
OFF Mode
Button Pressed
OEO Mode
Button Pressed
OFF Mode
Button Pressed
Extinguish Fire
Mode
Patrol Mode
Button Pressed
ECE477 Group 1
Spring 2005
Software State Diagram
Project Completion Timeline
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Week of March 7
– Complete PCB layout
– Learn AVR development environment.
Week of March 21
– Populate PCB
– Install all sensors and parts on structure
– Begin writing hardware control state machines
Week of March 28
– Complete Writing and Verify hardware control state machines
Week of April 4
– Write and verify One-Eye-Open and Extinguish software State Machines
Week of April 11
– Write and verify Patrol Mode software state machine
Week of April 18
– Write and verify Approach Mode software state machine
Week of April 25
– Verify system functionality
Week of May 2
– Demonstrate system functionality
– Write Final documentation
Questions / Discussion