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ECE 477 Design Review Group 1  Spring 2005

ECE 477 Design Review Group 1  Spring 2005. Outline. 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

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ECE 477 Design Review Group 1  Spring 2005

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  1. ECE 477 Design Review Group 1  Spring 2005

  2. Outline • 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

  3. 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

  4. 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

  5. FIREBot Block Diagram Siren Power Supply Motor Drivers Universal Flame Detector LCD Output Wide Angle Flame Detectors Microcontroller Debug Port Narrow Angle Flame Detectors Extinguisher Trigger Servo Distance Sensors Sensor Platform Servo Push Buttons

  6. 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 • The Atmel ATMega32 • 4 PWMs, 8 Analog-To-Digital Converters, one UART • 32k FLASH, 2K SRAM, 1K EEPROM • Easily available in a PDIP Package • 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. • We have tentatively chosen the Atmel ATMega32 because of low cost and good development package. The Motorola MC9S08GT32CFB-ND is a workable alternative.

  7. 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 • Hamamatsu UVTron – UV Detector which is very sensitive but with strong discrimination. Detects a candle at 5m. • Unacceptable: Updates every 3s • 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 • IR Photodiode: Much less discrimination, also analog • Reacts some to flourescent lights, but more to flames • IR photodiode chosen to be better option since no way to get around problem of a UV photodiode under florescent lighting

  8. 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

  9. Schematic/Theory of Operation The FIREbot Electrical Schematics are built in a hierarchical structure, with blocks performing the following functions: • 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

  10. 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

  11. Power Supply Unit Top Level

  12. Switching Power Supply

  13. Linear Regulator

  14. 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

  15. Universal Flame Detector

  16. 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

  17. Wide Angle Flame Detectors

  18. 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

  19. Narrow Angle Flame Detector

  20. 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

  21. Proximity Sensors

  22. 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

  23. Microcontroller

  24. 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

  25. Servo Driver Circuit

  26. 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

  27. DC Motor Driver Circuit Top Level

  28. Half of an H-Bridge

  29. Siren Interface Sheet 20 • 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

  30. Siren

  31. 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

  32. Serial Debug Interface

  33. 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

  34. 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

  35. Character LCD Interface

  36. Preliminary PCB Layout

  37. Preliminary PCB Layout Digital Switching Power Supply

  38. Preliminary PCB Layout Digital Switching Power Supply 12V Switch

  39. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply

  40. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply Analog Flame & Proximity Sensors`

  41. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Analog Flame & Proximity Sensors`

  42. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors`

  43. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` LCD Display

  44. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` LCD Display ATMega32

  45. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` LCD Display ATMega32 Serial Debug Port

  46. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` LCD Display ATMega32 Serial Debug Port Siren

  47. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` DC Motor H-Bridges LCD Display ATMega32 Serial Debug Port Siren

  48. Preliminary PCB Layout Digital Switching Power Supply 12V Switch Servo Switching Power Supply 5V Linear Regulator Servo Motor Drivers Analog Flame & Proximity Sensors` DC Motor H-Bridges LCD Display ATMega32 Turntable Mounted PCB Serial Debug Port Siren

  49. Software Design/Development Status

  50. Software Design/Development Status

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