ECE 477 Design Review Team 4  Fall 2012

1. ECE 477 Design Review Team 4  Fall 2012 Paste a photo of team members here, annotated with names of team members.

2. Project Overview • Automated Coffee Roaster • Popcorn popper • Includes heating elements and fan • Automatic roasting added • User interface • Optically tracks bean color • Monitors heat with IR Thermometer • Listens for relevant cracks with microphone

3. Project-Specific Success Criteria • An ability to achieve different levels of roasting based on user input • An ability to detect the temperature of the beans • An ability to monitor the color of the beans • An ability to interact with the user through a GUI • An ability to shut off the device if unusual conditions (high temperatures, unusual color, abnormally long time) are detected

4. Heat Coils Power Supply Fan Relay 1 Relay 2 7805 Voltage Rectifier Vcc PD5 PD4 ATmega 168 LM386 Pre-Amp Rotary Encoder PA0 PD1-3 Microphone Reset PC0 / PC1 Reset PD0 LED I2C Bus Hacrocam Board Infrared Thermometer LCD Display Block Diagram

5. Component Selection Rationale • ATmega 168 • Atmel recommended for home appliances • 16KB self-programming flash program memory • 512-byte EEPROM • Compatible with Arduino software stack • Hacrocam • Open source • Mounted microcontroller that is also compatible with Arduino software stack

6. Component Selection Rationale • IR Thermometer (MLX90614KSF-ACF) • -70°C – 380°C detection range • 10 degree field of view, trig verified • Compensated temperature gradient • LCD Display (NHD-C220BiZ) • Simple communication method • Transflective • Resists wide temperature range

7. Component Selection Rationale • Microphone • Highly directional • Very cheap • LED • White light to not bias color • Lid will be covered with high-heat spray and aluminum to isolate light

8. Component Selection Rationale • AC Relays (Heating Coils) • 240 V @ 12 A (only need 10A) • Fast switching (40 ms transition) • Activation voltage of minimum 4V • Solid State • DC Relay (Fan) • 30 V @ 2A • Solid State

9. Packaging Design • As simple as possible, but homely • External build quality of the Nesco product • Operational similarity, simplicity, and homely of Engadget product • More functionality than both, better component placement • Minimal exterior components

10. Theory of Operation (Heat Dissipation) • All components are high heat rated • Camera will be behind acrylic heat shield • Microphone will have metal mesh windscreen • All electronics besides sensors will be below heating chamber • Fans and ventilation ducts will further cool all electronics

11. Theory of Operation (Power) • Wall voltage will run the heating coils directly • Wall voltage will be transformed to 25.2 VAC and then rectified to run the fan. • Also transformed to 12.6 VAC, rectified, and sent through a 7805 voltage regulator to power the microcontroller at 5V

12. Theory of Operation (I2C) • Two microcontrollers • The Hacrocam, IR Thermometer, and LCD screen will be accessed via I2C bus. • Hacrocam will use self-mounted micro to average picture color before sending data. • Base microcontroller will track and average the last 2-3 IR temperature readings. • LCD screen will be used to communicate with the user.

13. Theory of Operation (User Interaction) • Rotary encoder will allow the user to scroll through and select roasting options • Reset will allow the user to cancel the roasting at any time • Microphone will establish a “noise floor” to monitor base number of peaks in the area • Will listen to number of peaks for every other half second to determine if the beans are cracking

14. Schematic/Theory of Operation

15. Schematic/Theory of Operation: Power Circuit

16. Schematic/Theory of Operation: Relay Circuits

17. Schematic/Theory of Operation: LED Circuit

18. Schematic/Theory of Operation: I2C Circuit

19. Schematic/Theory of Operation: Microphone/Amplifier Circuit

20. Schematic/Theory of Operation: Reset Circuit

21. Schematic/Theory of Operation: Oscillator Circuit

22. Schematic/Theory of Operation: Microcontroller Decoupling Capacitors

23. Power Mic Analog IO uC and Digital IO

24. General Consideration • Acid Traps, no acute angles • Signal Bounce, no right angles • Signals in different layers should pass perpendicularly if possible • Analog and Digital need separate grounds (star routing) • Ground Fill in real PCB

25. PCB Layout: Solid State Relays • Control signals need minimal amounts of current: ~30mA. Standard 10mil trace will suffice • SSR1: Mounted on the PCB, will have to pass 1.7A of 20VDC for the fan. This will need to have >50mil traces and molex connectors, plus etxra space between traces • SSR2: Mounted separately from PCB

27. PCB Layout: I2C • 100KHz operation; noise, impedance, and signal length possible concerns (rated to ~1m) • Rule of thumb: <1/10 of wavelength, transmission line effects not a concern • I2C fall time is about 100ns = 5MHz • Wavelength@5MHz = ~100meters • We're well under 10 meters, not concerned

28. PCB Layout: Power Supply • Conversion: 12.6VAC -> ~12VDC -> 5VDC • As with SSR, needs to be relatively isolated • 7805 will need heatsink, so some keepout area will be needed Header pins are rated at 1A each, should be sufficient for power supply

30. PCB Layout: Microcontroller • All voltage pairs have decoupling caps, need to be placed nearby • Want to attempt to keep uC and headers away from switching noise of amplifier and transistors • Crystal and associated caps are slammed up against the microcontroller

32. Software • ATMEGA • Arduino software stack • Open-source, higher level Processing language • Included libraries for I2C • Hacrocam • Interfaces with Arduino Software • Programmable through serial interface • Extra SRAM for additional processing routines • Color averaging done on-chip

33. Basic Software Execution

34. Project Completion Timeline

35. Questions / Discussion