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Andrew Phillips, Ben Laskowski, Shannon Abrell, Rob Swanson.

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Presentation on theme: "Andrew Phillips, Ben Laskowski, Shannon Abrell, Rob Swanson."— Presentation transcript:

1 Andrew Phillips, Ben Laskowski, Shannon Abrell, Rob Swanson

2  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

3 eV-TEK, or Telemetry for Electric Karts, is a tool for collecting and transmitting electric go-kart parameters in a race situation. The collected data can help the driver and pit crew optimize vehicle performance and ultimately win races.

4  An ability to report the approximate number of laps remaining on a given battery charge  An ability to detect and report cell voltage anomalies  An ability to sense and display kart speed  An ability to track the number of laps completed  An ability to log and display vehicle telemetry data


6  Op-Amps – LM324  Operates from single 5v supply  Low supply currents (700μA per amplifier)  Low cost  Current sense amp – INA148  Inputs need not be referenced to circuit ground  Large common-mode input voltage range  External ADC – MCP3204  Needed extra ADC channels  This IC inexpensive and meets speed/resolution needs

7  Battery Management Micro – PIC18F4423  13 ADC channels w/ 12-bit resolution  Easily obtained  Mature technology (few silicon errata items)  Main Micro – PIC32MX575F256L  6 UARTs, product familiarity  Wireless – XBee Pro 900MHz  6 mile range, sufficient data transfer speed

8  Main Packaging  Aluminum  Aerodynamic  Sits in front of driver on roll cage  Detachable faceplate holds main board  Driver displays  Wiring connection at rear

9  Battery Management  Stand-alone package  Plastic case provides electric isolation  Slots for battery leads and serial line to main controller

10  Voltage Follower  Acts to increase input impedance of ADC channels  Allows the use of large divider resistor values for low current drain

11  Battery Micro  Digitizes and scales battery voltages via simple code  Integrates current flow over time to obtain battery charge

12  External ADC  Used to increase number of ADC channels available  Interfaces to battery microcontroller over SPI

13  Main microc0ntroller  Can run up to 80MHz = 80MIPS  Collects and processes data from battery packs and sensors; logs; transmits to pit area

14  Power supply  Converts 12V to 5V and 3.3V  High-efficiency switchmode regulator for 12->5V conversion  Linear LDO for 5->3.3V  Maximum power dissipation ~2.4W  Large copper pours on PCB for heatsinking

15  Optical isolation  Battery monitors float with respect to main control board  1kV of isolation provided; we require ~50V of isolation  Servo motors also isolated “just in case”  Side benefit: 3.3V 5V conversion

16  XBee module  Appears as serial port to PIC32  Hardware flow control pins used to minimize risk of buffer overflow

17  LED Drivers  TLC5917  Similar to 74HC595 but includes constant- current output drivers  Ease PCB routing – 3 wire bus instead of 13

18  USB-Serial converter  Makes USB appear as UART for PIC32  Eases software, PCB layout  Mature product, most errata fixed by manufacturer

19  DataFlash IC  2MB EEPROM-like device for data logging  Simple SPI interface; faster and more versatile than SD card  Data made available for download via USB interface

20  Voltage followers  Mostly uninterrupted ground plane for noise rejection  Decoupling capacitor very close to op-amps – vital for stability

21  Current monitor  Completely uninterrupted ground plane  Voltage reference IC and decoupling caps very close to op-amp

22  Digital components  Separated from analog components  As many extra micro pins as practical padded out  Decoupling capacitors as close as practical to each power pin

23  Power supply  Linear LDO regulator  Expected power dissipation ~100mW  Bulk capacitor located nearby for stability

24  Microcontroller  Decoupling capacitors located physically and electrically close to chip  Every pin is padded out for debugging and/or expansion  Pads provided for precision oscillator module, though it should not be required

25  Power supply  Switching regulator is on top of continuous ground plane, and high dI/dt nodes are very short  Linear regulator has many vias to copper plane for heatsinking  Sufficient capacitance nearby for low ripple

26  Optical Isolation  Physically separate from most other critical interfaces  Keepout areas near battery connectors – physical isolation is several times what is required

27  Xbee  Antenna connection is as far from other components as possible  Capacitor located nearby to provide current pulses during RX->TX mode switches

28  LED Drivers  Located directly underneath 7-segment LED modules for compactness

29  USB UART  Trace length from USB connector is minimized to preserve differential nature of bus  Decoupling capacitors located as close as possible

30  EEPROM  Located under PIC32 for layout convenience and to minimize length of high-speed SPI traces  Decoupling capacitor nearby

31  Battery monitors  Software is essentially done  Need mechanism to calibrate measurements ▪ Preliminary tests indicate this will be easy  Roughly 400 lines of well-commented assembly code

32  Main controller  Began reading up on various microcontroller features (DMA, interrupt mechanism)  Installed and began experimenting with C compiler  Simple programs compile successfully

33 ItemExpected Completion Week Order all remaining components8 Complete design and order main PCB9 Complete battery monitor software10 Assembly of battery monitor boards10 Complete battery monitor packaging11 Main board software complete13 Assembly of main board13 Complete main package enclosure14 Final integration15

34 Questions / Discussion

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