The Design of an Electronic Bicycle Monitor (EBM) Team P118: Gary Berglund Andrew Gardner Emrys Maier Ammar Mohammad

Background Electric Bicycle Components Bicycle Battery Controller Motor 2

Relevance Current interface Battery Speed Available systems Commercial ‘off the shelf’ Phone apps Electric Bicycle Monitor (EBM) Integration Weight Power efficient Used to track trips and monitor bicycle electronic systems 3

Requirements RequirementRangeAccuracy Speed0 to 99.9 mph0.05 mph Odometer0 to mi0.05 mi Trip distance0 to mi0.05 mi Trip max speed0 to 99.9 mph0.05 mph Trip average speed0 to 99.9 mph0.05 mph Trip peak current0 to 50 A100 mA Time and date100 years1 min GPS positionEarth5 m Battery voltage35 to 41 V10 mV Battery current0 to 50 A0.1 A Battery charge used20 Ah0.1 Ah Battery power delivered? Wh Record GPS track data0 to 2 GB1 record per second 4

System Block Diagram Caption for visual aid(s) 5

User Display Solution Method Decision Matrix Two Row LCDGraphics LCD Make / ModelFordata FDCC4002BInnolux AT043TN24 Display typeTextGraphics Resolution2 X 40 characters480 x 272 x 24 bpp Display area6” X.65”3.74” X 2.12” Cost$20.42$32.99 Wiring connection16 pins40 pins Bus needed8 bit parallel data24 bit parallel data Touch interfaceNoYes Hardware Milestone: 1Software Milestone: 0 Requirements from top level: Display bicycle status Requirements from other subsystems: None 6

User Display (Hardware) Needs from other subsystems: Power supply 25mA (82.5mW) main logic 22mA (613.8mW) back light Total max power: 696.3mW MCU Integrated graphics driver Four wire connection for touch sensing Solution being implemented: Graphics LCD Hardware Milestone: 1Software Milestone: 0 7

User Display (Software) Software status: Need software flow chart for GUI Solution being implemented: Graphics LCD Hardware Milestone: 1Software Milestone: 0 8

Removable Memory Solution Method Decision Matrix USB 1.1 driveSecure digital card Power consumption110mW idle mode 2.5mW suspend mode 660µW idle mode ConnectionMiniUSB portSD card connector Cost<$5 Hardware Milestone: 1Software Milestone: 0 Requirements from top level: Logged Lat/Long for post processing Using Google Maps or similar program to view route Requirements from other subsystems: None 9

Removable Memory Needs from other subsystems: MCU SPI bus Power supply 200µA (660µW) Standby 100mA (330mW) Active Solution being implemented: Secure Digital Hardware Milestone: 1Software Milestone: 0 10

Removable Memory Software status: Need software flow chart for SD functions Solution being implemented: Secure Digital Hardware Milestone: 1Software Milestone: 0 11

Case Solution Method Decision Matrix DATEC-MOBIL S A Garmin Nuvi Cost$35.09$0.00* Dimensions5.98” X 3.26” X 1.31”5.4” X 3.4” X.5” 4.3” LCD windowNo, must be modifyYes Hardware Milestone: 1Software Milestone: N/A Requirements from top level: Handlebar mounted Water resistant Requirements from other subsystems: None 12

Case (Hardware) Needs from other subsystems: All subsystems Physical constraint PCB Mounting hole coordinates match case Power supply Power button & USB connector coordinates match case Solution being implemented: Garmin Nuvi Hardware Milestone: 1Software Milestone: N/A 13

Case (Software) Software status: N/A Solution being implemented: Garmin Nuvi Hardware Milestone: 1Software Milestone: N/A 14

Battery Voltage Sensor Requirements from top level: Range of 35 to 41V Requirements from other subsystems: MCU Output 0 to 3.3V Linear relationship to battery voltage Needs from other subsystems: PSU 3.3V, Ground MCU ADC input Solution being implemented: Offset Differential Amplifier Hardware Milestone: 1Software Milestone: 0 15

Battery Voltage Sensor Solution Method Decision Matrix Voltage DividerOffset Differential Amplifier Range0V to 41V35V to 41V Accuracy40.04 mV5.86 mV Components29 Approximate Cost$2$5 Hardware Milestone: 1Software Milestone: 0 16

Battery Voltage Sensor Software status: A 10-bit ADC will be read every 1 ms and saved into a variable for the display to use Solution being implemented: Housekeeping Hardware Milestone: 1Software Milestone: 0 17

Battery Current Sensor Requirements from top level: Range of 0A to 30A Requirements from other subsystems: MCU Output 0V to 3.3V to ADC Linear relationship to measured current Needs from other subsystems: PSU 3.3V, Ground MCU ADC input Solution being implemented: Hall Effect Sensor Hardware Milestone: 1Software Milestone: 0 18

Battery Current Sensor Solution Method Decision Matrix Shunt Resistor (1 mΩ)Hall Effect Sensor ACS759 Range0 A to 31.6 A (power limited) 0 A to 50 A Accuracy30.86 mA48.83 mA Approximate Cost$5$10 Power Consumption1 W (max)123 mW Hardware Milestone: 1Software Milestone: 0 19

Battery Current Sensor Software status: A 10-bit ADC will be read every 1 ms and saved into a variable for the display to use Solution being implemented: Housekeeping Hardware Milestone: 1Software Milestone: 0 20

Wheel Speed Sensor Requirements from top level: Range of 0 to 30 mph Requirements from other subsystems: MCU Output pulse when magnet passes the sensor Needs from other subsystems: PSU 3.3V, Ground MCU Interrupt capable input Solution being implemented: Hall Effect Sensor Hardware Milestone: 1Software Milestone: 0 21

Wheel Speed Sensor Solution Method Decision Matrix Hall Effect SensorIR Reflection Sensor Dirty operationYesNo Hardware Milestone: 1Software Milestone: 0 22

Wheel Speed Sensor Software status: When a pulse is received, the wheel speed timer value is recorded and the timer is reset. The recorded timer value is used to calculate the current velocity of the bike. Solution being implemented: Interrupt Hardware Milestone: 1Software Milestone: 0 23

Power Management System Hardware Milestone: 0 Software Milestone: 0 Requirements: Interface with the existing bicycle battery voltage (35-40V typical) Provide stable, well-regulated power to each EBM subsystem Automatic shutdown at low voltage level (35V) Additional Aspirations: Avoid wasting battery power with high efficiency design Minimize complexity Objectives: 1.Identify all voltage/current needs from subsystems 2.Identify subsystem I/O software requirements 3.Develop “Power Budget” and battery charge life 4.Research specific solutions and identify component candidates 5.Design and model hardware schematic 6.Alpha test under laboratory conditions 7.Integrate into EBM subsystems and measure performance 24

Power Management System Hardware Milestone: 0 Solution Method Decision Matrix Voltage DividerLinear RegulatorDC-DC Buck Converter EfficiencyHorrible (scales)Poor (~60-70%)Excellent (~90%) RegulationHorribleExcellentGood Part CountExcellent Horrible Design ComplexityEasy Difficult Biggest DrawbackNo regulationInefficiencySwitching Noise Software Milestone: 0 Specific power supply parts have not yet been selected pending other subsystem part selection 25

Power Management System Hardware Milestone: 0 Software Milestone: 0 Requirements from top level: Step down 35-40V main battery voltage to first subsystem voltage level Needs from other subsystems: MCU: Low voltage shutdown command Subsystem power budget numbers Solution being implemented: A mix of DC-DC Buck Converters and LDO Linear Regulators Requirements from other subsystems, “Power Budget”: V_nomI_minI_nomI_maxP_minP_nomP_max VmA mW MCU (PIC) Screen Screen Backlight GPS module Voltage Sensor Current Sensor Wheel Speed Sensor Internal Memory External Memory Module

GPS Solution Method Decision Matrix A2200-AEM-506 TTFF 35s15-35s AntennaExternalInternal Number of channel48 Power consumption135.3mW + 40 mW 170mW Price$ $11.95 for antenna $39.99 Hardware Milestone: 1Software Milestone: 0 27

GPS Requirements from top level: Record latitude, longitude, and time Save them to the SD card through the MCU Use the saved data to show the path of the trip Requirements from other subsystems: None Needs from other subsystems: Power System: 5 34 mA (170 mW) MCU: I 2 C bus to send the data every one second External memory: Place to save the data Solution being implemented: Getting position and time information Hardware Milestone: 1Software Milestone: 0 28

Microcontroller Solution Method Decision Matrix PIC24FJ256DA206PIC24FJ256DA210 Pins ADC1624 SPI, I 2 C33 Program Memory128/256 EPMPNOYes Power consumption2.6 mW Price$7.20$8.14 Hardware Milestone: 1Software Milestone: 0 29

Microcontroller Requirements from top level: Analog to digital Converter (2 channel) SPI bus for SD card EPMP bus for Graphical LCD Pulse counter for speed Requirements from other subsystems: Current sensor: Analog reading of battery current Voltage sensor: Analog reading of battery voltage GPS: Position and time information LCD screen: X and Y axis of the touched place Needs from other subsystems: Power System: 800µA (2.6mW) running mode 22µA (72µW) Idle or sleep mode Solution being implemented: Microcontroller Hardware Milestone: 1Software Milestone: 0 30

Testing Will be divided into three aspects: Power system, voltage and current sensor: Power supply along with multimeter will be used Measuring the voltage and current to check requirement and accuracy Wheels speed sensor: Regular bike will be used Checking number of pulses per revolution GPS, LCD, and MCU: No external component needed Checking the results using software application GPS using google map LCD and MCU using the programming software (MPLAB X?) Heartbeat LED testing will be used after adding any component to the design 31

Project Management Meeting: Bi-weekly with Dr. Gibbs Weekly with group members Documentation Shared folder to organized documents Documents naming convention for convenient access Tasks: Divided into multiply subsystem Each subsystem include: choosing components, designing circuit schematics, PCB, and programming Overlapping responsibility to ensure general knowledge about other subsystem 32

Project Timeline (Preliminary) “Wrap Up” Plan (very early) 33

Weekly Goals Powerpoint Slide Assignments 34

Budget Currently unknown, but relevant at every step in the design process Safely assumed at less than $1000 in components No upper limit specified by sponsor Will factor into component selection 35

Conclusion/Questions 36