1. ECE 477 Design Review Team 12  Spring 2006 EricDaniel Atandra Sriharsha Aasenda Silva Burman Vengapaty

2. Outline Project overviewProject overview Project-specific success criteriaProject-specific success criteria Block diagramBlock diagram Component selection rationaleComponent selection rationale Packaging designPackaging design Schematic and theory of operationSchematic and theory of operation PCB layoutPCB layout Software design/development statusSoftware design/development status Project completion timelineProject completion timeline Questions / discussionQuestions / discussion

3. Project Overview Maximum Power Point Tracker (MPPT) : DC to DC converter that converts the input voltage from a solar cell array to the output voltage of a battery pack.DC to DC converter that converts the input voltage from a solar cell array to the output voltage of a battery pack. Optimum “power point” alongOptimum “power point” along current vs. voltage curve that produces power for solar array. Our tracking algorithm will provideOur tracking algorithm will provide control of the DC to DC converter in order to achieve this power point. Relay data to the telemetry unit on the solar car via the CAN bus.Relay data to the telemetry unit on the solar car via the CAN bus.

4. Project-Specific Success Criteria An ability to measure pertinent voltages and currents within an accuracy of 2% over the range of possible values [0-8A and 0- 70V]An ability to measure pertinent voltages and currents within an accuracy of 2% over the range of possible values [0-8A and 0- 70V] An ability to send I-V and temperature data to other peripherals via the CAN.An ability to send I-V and temperature data to other peripherals via the CAN. An ability to switch to a "debug" mode (when an RS-232 cable is connected) in which the I-V curve is continuously scanned.An ability to switch to a "debug" mode (when an RS-232 cable is connected) in which the I-V curve is continuously scanned. An ability to maintain the maximum power point of the solar array under standardized artificial light conditions through a high powered halogen lampAn ability to maintain the maximum power point of the solar array under standardized artificial light conditions through a high powered halogen lamp An ability to disconnect the solar array in response to a CAN command.An ability to disconnect the solar array in response to a CAN command.

5. Block Diagram Micro Controller Power Block Analog Block CAN Transceiver Serial Communication (Debugging) Programming Port Clock CAN Address Outputs 2 4 5 2 3 2 5 5

6. Microcontroller - PIC18F2680(SOG.050/28/WB.420/L.700) Power Supply - MAX1684(SOG.025/WG.244/L.200) Op Amp - MCP6001/2/4(SOG.050/14/WB.224/L.350) CAN Transceiver - MCP2551(SOG.050/14/WB.244/L.200) Component Selection Rationale Microcontroller Pin Count CANRAM(bytes)Flash(bytes)Cost MC68HC08AZ6064Yes2KBn/a16.00 PIC18F268028Yes156832K12.00 AT90CAN3264Yes2K32K16.00

7. Packaging Design The packaging would have the following dimensions:The packaging would have the following dimensions: Width = 5.210”, Length = 5.300”,Height = 2.750” Enclosed within a 0.125” thick Foam CoreEnclosed within a 0.125” thick Foam Core Fiberglass packaging with nearly 0.250” spacing on both sides Includes 80mm x 80mm x 10 mmIncludes 80mm x 80mm x 10 mm ventilation enclosure

8. Schematic/Theory of Operation Main Block: Microcontroller and oscillator Microcontroller and oscillator Power Supply Power Supply Overvoltage Protection Overvoltage Protection Headers Headers CAN Interface CAN Interface SPI Shift Register and diagnostic LEDs SPI Shift Register and diagnostic LEDs Analog Block: Voltage translators and filters Voltage translators and filters Current sensing insight Current sensing insight Output current sense Output current sense Input current sense Input current sense

9. Main Schematic

10. Microcontroller and oscillator Crystal runs at 10Mhz.Crystal runs at 10Mhz. Microcontroller’s PLL can multiply that frequency by 4 time – 40Mhz.Microcontroller’s PLL can multiply that frequency by 4 time – 40Mhz. For power saving condition, microcontroller can run at 10Mhz.For power saving condition, microcontroller can run at 10Mhz. Microcontroller is interfaced with 5 analog inputs.Microcontroller is interfaced with 5 analog inputs. It drives 3 Mosfets.It drives 3 Mosfets. It uses several communication ports.It uses several communication ports. It uses a shift register for additional I/Os.It uses a shift register for additional I/Os.

11. Power Supply 5V supply is used to supply microcontroller and peripherals.5V supply is used to supply microcontroller and peripherals. Expected to operate at 90% efficiency, between 30mA to 400mA.Expected to operate at 90% efficiency, between 30mA to 400mA. 4.096V supply is used as analog inputs reference voltage.4.096V supply is used as analog inputs reference voltage. All amplifier also are supplied by this voltage regulator.All amplifier also are supplied by this voltage regulator.

12. Overvoltage Protection Disconnects solar array from power board if voltage at battery exceeds 70V.Disconnects solar array from power board if voltage at battery exceeds 70V. Comparator’s OUT goes to 0V if Vbat ≥ 70V.Comparator’s OUT goes to 0V if Vbat ≥ 70V. Mosfet’s source is connected to a BJT’s base, which requires 5V to turn ON.Mosfet’s source is connected to a BJT’s base, which requires 5V to turn ON. RELAY_CONTROL is disregarded in that case.RELAY_CONTROL is disregarded in that case.

13. Headers FAN_SUPPLY turns external fan on or off through the FAN_SUPPLY signal.FAN_SUPPLY turns external fan on or off through the FAN_SUPPLY signal. Serial Connector is primarily used for debugging.Serial Connector is primarily used for debugging. Programming board is used primarily for programming.Programming board is used primarily for programming. Header pin 1 is pulled up. This is because it’s connected to nMCLR, which is a low-active external reset for the microcontroller.Header pin 1 is pulled up. This is because it’s connected to nMCLR, which is a low-active external reset for the microcontroller.

14. CAN Transceiver translates voltage level for the CAN line.CAN Transceiver translates voltage level for the CAN line. RS value changes the slew-rate for the CAN line. RS=4.7KΩ is for rather fast slew-rate, which can be adjusted afterwards.RS value changes the slew-rate for the CAN line. RS=4.7KΩ is for rather fast slew-rate, which can be adjusted afterwards. CAN Connectors are connected in a parallel manner with the remaining 7 MPPT boards in the solar car.CAN Connectors are connected in a parallel manner with the remaining 7 MPPT boards in the solar car. CABLE_DETECT is connected to microcontroller to alert it in case of connectors being unconnected.CABLE_DETECT is connected to microcontroller to alert it in case of connectors being unconnected. CAN Interface CAN Address Setup simply inputs CAN address to the microcontroller.CAN Address Setup simply inputs CAN address to the microcontroller.

15. SPI Shift Register and Diagnostic LEDs SPI Shift Register accommodate extra I/Os that would otherwise require a larger microcontroller.SPI Shift Register accommodate extra I/Os that would otherwise require a larger microcontroller. Diagnostic LEDs provide a visual insight to the MPPT operation.Diagnostic LEDs provide a visual insight to the MPPT operation.

16. Analog Inputs

17. INPUT_V_SENSE Summing amplifier to translate 70V to 4.096VSumming amplifier to translate 70V to 4.096V 2 nd order Butterworth low-pass filter with cut- off frequency of 20 Hz2 nd order Butterworth low-pass filter with cut- off frequency of 20 Hz

18. Solar Array Solar Car Batteries GND DC/DC Converter Power board current direction Input current senseOutput current sense Input voltage sense Output voltage sense Current sense rationale

19. INPUT_I_SENSE Summing amplifier to translate -[0 to 8]A to [0.1024 to (4.096 - 0.1024)] VSumming amplifier to translate -[0 to 8]A to [0.1024 to (4.096 - 0.1024)] V

20. OUTPUT_I_SENSE Summing amplifier to translate [0 to 8]A into [0.1024 to (4.096 - 0.1024)] VSumming amplifier to translate [0 to 8]A into [0.1024 to (4.096 - 0.1024)] V

21. PCB Layout Constraints 1.Size (no more that 1.8” tall by 3.0” wide) 2.Accurate analog conversion 3.Need for high-speed signal integrity

22. PCB Layout Placement Priorities 1.Power 2.Digital 3.Analog 4.Everything Else

23. PCB Layout Routing Priorities 1.Power 2.Clock Signals and CAN 3.Analog 4.Digital (shift register, etc) 5.Everything Else (LEDs, switches, etc.)

24. PCB Layout First Attempt - Ratsnest

25. PCB Layout First Attempt - Combined

26. PCB Layout Second Attempt - Ratsnest

27. PCB Layout Second Attempt - Combined

28. PCB Layout Second Attempt – Top Layer

29. PCB Layout Second Attempt – Bottom Layer

30. Software Design/Development Status Researched CANOpen protocolResearched CANOpen protocol Researched PIC18F2680 programming related featuresResearched PIC18F2680 programming related features Consulted with the other two solar teams to decide upon how to handle the object dictionaryConsulted with the other two solar teams to decide upon how to handle the object dictionary Object Dictionary CAN Open Application I/O CAN

31. Software Design/Development Status MPPT Algorithm:MPPT Algorithm: –Find the initial MPP at startup –Every 50 ms check the points to the left and the right of the MPP and adjust the MPP accordingly –Re-sweep the IV curve every minute to acquire the proper MPP in case of a imperfect IV curve

32. Project Completion Timeline TaskStartFinishDuration Finalized Schematic and PCB 03/02/0603/10/06 9 d Prototype Design on Eval. Board 03/02/0603/22/06 21 d Implementation of MPPT algorithm and CANOpen protocol 03/02/0603/24/06 23 d Hardware and software integrated 03/24/0604/14/06 22 d Debugging and troubleshooting 04/14/0604/21/06 8 d

33. Questions / Discussion