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ECE 477 Design Review Group 2 Fall 2005 From Left: Jeffrey Alvin, Ricky Kannothra, Valentinos Zachariou, Michael Dorsey Outline • • • • • • • • • • Project overview Project-specific success criteria Block diagram Component selection rationale Packaging design Schematic and theory of operation PCB layout Software design/development status Project completion timeline Questions / discussion Project Overview • User will program a specific area to patrol • The robot will move up and down the area on a motorized wheelbase looking for trash (red, empty aluminum cans) with a mounted camera • When trash is found, a series of servo motors with a metal shovel attached will pick up the trash and dispose in attached trashcan • Two ultrasonic sensors used to avoid obstacles and identify when trashcan is full • Continue these actions until it has reached the end of the specified area (notify with LCD) Project-Specific Success Criteria • Ability to identify red, empty aluminum cans for pickup • Ability to pick up identified object(s) • Ability to automatically traverse the pickup zone, a rectangular grid • Ability to detect a “basket full” condition • Ability to set operation mode using a keypad and display system status using a LCD display Block Diagram Power Supply Keypad LCD Compass Microcontroller Ultrasonic Sensor (trashcan) Servo Motors (shovel attached) Wheelbase Ultrasonic Sensor (avoidance) Camera Component Selection Rationale Microcontroller Must have a suitable processing speed to be able to handle the feed from the CMUcam2+ camera, at least 90kb Flash and 2-3kb SRAM for storing code, at least 8 PWM modules, at least 2 UART modules, ADC, excess I/O pins, low cost and easily attainable. Atmel ATMEGA128L - 8-16 Mhz, 8 PWM modules, 2 UART modules - 1 ADC, 53 I/O pins - 128kb Flash, 4k EEPROM, 4k SRAM - Free development board, free samples online Rabbit 3000 - 55 Mhz, 4 PWM modules, no ADC, 56 I/O pins - 1 Mb memory space - expensive development board Decided on the Atmel ATMEGA128L based on the modules available and meets our basic needs for processor speed and memory. Also, a free development board helps. Packaging Design Top Top View View Side View Side View Schematic/Theory of Operation The T.R.A.P. electrical schematic consists of the following blocks • • • • • • • • • • 5 V, Regulated Power Supply 7.2 V, Unregulated Power Supply Microcontroller Servo Motor control H-Bridge control LCD Keypad Compass Ultrasonic Sensors Camera 5V, Regulated Power Supply • Accepts 7.2V from a NiMH battery connected through an on/off switch • Outputs 5V, regulated using a switching voltage regulator. • Connects to an analog to digital converter on the microcontroller, through a voltage divider, to help monitor and prevent deep discharge of the battery. • Provides visible warning for low charge, using a red LED. 5V, Regulated Power Supply 7.2 V, Unregulated Power Supply • Direct unregulated connection of a 7.2V NiMH battery through an on/off switch. • Connects to an analog to digital converter on the microcontroller, through a voltage divider, to help prevent deep discharge of the battery. • Powers the servo motors and part of the Hbridge circuit. 7.2 V, Unregulated Power Supply Microcontroller • ATmega128L – 8AI microcontroller • Active low reset pin of the microcontroller connected to three sources of reset. • Reset button on the keypad through a 74HC03 Nand gate. • Standard ASPDT push button circuit • MCP809 reset circuit. • Decoupling capacitors connected across every power and ground pin. • AVRISP interface required to program the microcontroller from the PCB board Microcontroller Microcontroller Microcontroller Microcontroller Microcontroller Microcontroller Servo Motor control H-Bridge control • H – Bridge controls 2 pairs of motors • The motors in each pair are connected in parallel and rotate together as one motor • Each motor has its own 100uF capacitor connected across its terminals • H – Bridge contains a large 330uF capacitor in parallel with two more 103uF capacitors to maintain constant current flow to the motors at all times H-Bridge control CMU camera & LCD Keypad • • • • Scan Type Keypad Current flows in through Pins 1 – 4 Current flows out through Pins 5 – 8 When a key is pressed the keypad connects one pin from pins 1 – 4 to one pin from pins 5 – 6 Keypad Compass Ultrasonic Sensors PCB Layout PCB Top Layer PCB Bottom Layer Power Supply with Voltage Regulator Microcontroller Layout Decoupling Capacitors For Microcontroller Three sources of Reset Headers to Peripherals Second Power Supply Software Design/Development Status START Initialization error Error Initialization Pause TrashDisposal Turnaround Camera alert Compass alert Main Completed dimensions Basketfull Keypad input Finish Reposition Avoidance Project Completion Timeline • Oct 16-22: Complete testing of individual components/interfacing with microcontroller • Oct 23-29: Write: initialization, error, pause, finish, basketfull • Oct 30-Nov 5: Write: turnaround, trash disposal, avoidance, reposition • Nov 6-12: Write: MAIN • Nov 13-19: Combine all functions and debug • Nov 20-26: Debug - (Thanksgiving) • Nov 27-Dec 3: Final Testing • Dec 5-9: Presentation Questions / Discussion