The Design of an Electronic Bicycle Monitor (EBM)

The Design of an Electronic Bicycle Monitor (EBM)

Team P118:Gary Berglund

Andrew GardnerEmrys 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

RequirementsRequirement Range Accuracy

Speed 0 to 99.9 mph 0.05 mph

Odometer 0 to 99999.9 mi 0.05 mi

Trip distance 0 to 999.9 mi 0.05 mi

Trip max speed 0 to 99.9 mph 0.05 mph

Trip average speed 0 to 99.9 mph 0.05 mph

Trip peak current 0 to 50 A 100 mA

Time and date 100 years 1 min

GPS position Earth 5 m

Battery voltage 35 to 41 V 10 mV

Battery current 0 to 50 A 0.1 A

Battery charge used 20 Ah 0.1 Ah

Battery power delivered ? Wh ? Wh

Record GPS track data 0 to 2 GB 1 record per second

4

System Block Diagram

Caption for visual aid(s)

5

User Display

Solution Method Decision Matrix

Two Row LCD Graphics LCD

Make / Model Fordata FDCC4002B Innolux AT043TN24

Display type Text Graphics

Resolution 2 X 40 characters 480 x 272 x 24 bpp

Display area 6” X .65” 3.74” X 2.12”

Cost $20.42 $32.99

Wiring connection 16 pins 40 pins

Bus needed 8 bit parallel data 24 bit parallel data

Touch interface No Yes

Hardware Milestone: 1 Software Milestone: 0

Requirements from top level:• Display bicycle statusRequirements from other subsystems:• None

6

User Display (Hardware)

Needs from other subsystems:• Power supply

• 3.3V @ 25mA (82.5mW) main logic• 27.9V @ 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


7

User Display (Software)

Software status:• Need software flow chart for GUI

Solution being implemented: Graphics LCD


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Removable Memory


USB 1.1 drive Secure digital card

Power consumption 110mW idle mode2.5mW suspend mode

660µW idle mode

Connection MiniUSB port SD card connector

Cost <$5 <$5


Requirements from top level:• Logged Lat/Long for post processing• Using Google Maps or similar program to view route

Requirements from other subsystems:• None

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Removable Memory

Needs from other subsystems:• MCU

• SPI bus• Power supply

• 3.3V @ 200µA (660µW) Standby• 3.3V @ 100mA (330mW) Active

Solution being implemented: Secure Digital


10

Removable Memory

Software status:• Need software flow chart for SD functions

Solution being implemented: Secure Digital


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Case


DATEC-MOBIL S A9073109

Garmin Nuvi

Cost $35.09 $0.00*

Dimensions 5.98” X 3.26” X 1.31” 5.4” X 3.4” X .5”

4.3” LCD window No, must be modify Yes

Hardware Milestone: 1 Software 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


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Case (Software)

Software status:• N/A

Solution being implemented: Garmin Nuvi


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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


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Voltage Divider Offset Differential Amplifier

Range 0V to 41V 35V to 41V

Accuracy 40.04 mV 5.86 mV

Components 2 9

Approximate Cost $2 $5


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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


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Battery Current Sensor

Requirements from top level:• Range of 0A to 30A


• Output 0V to 3.3V to ADC• Linear relationship to measured

current



• ADC input

Solution being implemented: Hall Effect Sensor


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Shunt Resistor (1 mΩ) Hall Effect SensorACS759

Range 0 A to 31.6 A(power limited)

0 A to 50 A

Accuracy 30.86 mA 48.83 mA

Approximate Cost $5 $10

Power Consumption 1 W (max) 123 mW


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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


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Wheel Speed Sensor

Requirements from top level:• Range of 0 to 30 mph


• Output pulse when magnet passes the sensor



• Interrupt capable input

Solution being implemented: Hall Effect Sensor


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Wheel Speed Sensor


Hall Effect Sensor IR Reflection Sensor

Dirty operation Yes No


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


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Power Management SystemHardware 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 subsystems2. Identify subsystem I/O software requirements3. Develop “Power Budget” and battery charge life4. Research specific solutions and identify component candidates5. Design and model hardware schematic6. Alpha test under laboratory conditions7. Integrate into EBM subsystems and measure performance

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Power Management SystemHardware Milestone: 0


Voltage Divider Linear Regulator DC-DC Buck Converter

Efficiency Horrible (scales) Poor (~60-70%) Excellent (~90%)

Regulation Horrible Excellent Good

Part Count Excellent Excellent Horrible

Design Complexity Easy Easy Difficult

Biggest Drawback No regulation Inefficiency Switching Noise

Software Milestone: 0

• Specific power supply parts have not yet been selected pending other subsystem part selection

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Power Management SystemHardware 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_nom I_min I_nom I_max P_min P_nom P_max V mA mA mA mW mW mW

MCU (PIC) 3.3 - 100 - - 330 -Screen 3.3 - 17 25 - 56.1 82.5Screen Backlight 27.9 20 - 22 558 - 613.8GPS module 3.3 12 20 100 39.6 66 330Voltage Sensor - - - - - - -Current Sensor - - - - - - -Wheel Speed Sensor - - - - - - -Internal Memory - - - - - - -External Memory Module - - - - - - -

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GPS


A2200-A EM-506

TTFF 35s 15-35s

Antenna External Internal

Number of channel 48 48

Power consumption 135.3mW + 40 mW

170mW

Price $13.60 + $11.95 for antenna

$39.99


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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 tripRequirements from other subsystems:

• None

Needs from other subsystems:• Power System:

• 5 V @ 34 mA (170 mW)

• MCU:• I2C bus to send the data every one

second

• External memory:• Place to save the data

Solution being implemented: • Getting position and time information


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Microcontroller


PIC24FJ256DA206 PIC24FJ256DA210

Pins 64 100

ADC 16 24

SPI, I2C 3 3

Program Memory 128/256 128/256

EPMP NO Yes

Power consumption 2.6 mW 2.6 mW

Price $7.20 $8.14


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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:

• 3.3V @ 800µA (2.6mW) running mode• 3.3V @ 22µA (72µW) Idle or sleep

mode

Solution being implemented: Microcontroller


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TestingWill be divided into three aspects:• Power system, voltage and current sensor:

• Power supply along with multimeter will be usedMeasuring 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 mapLCD and MCU using the programming software (MPLAB X?)

Heartbeat LED testing will be used after adding any component to the design

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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

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Project Timeline (Preliminary)

Tasks 7-Apr 9-Apr 9-Apr 14-Apr 14-Apr 16-Apr

Complete block diagram GRB GRBUpdate tasks/wrap up plan ATG ATG ATG ATGSelect slideshow format/develop slides for Preliminary_v1 All

Merge Slideshow ATGA3: SDP Plan - Prelim - v1 due by 12 noon allWeigh component options (decide uC, V&I sensor, PSU parts, display, memory, GPS) all allSDPPv1 Plan, and revised powerpoint slides due by 12 noon

SDPPv2 Plan due by unknownPower Supply

Identify voltage and current requirements ATG ATGSelect controller ATGProgram interface to MCUAlpha Testing

DisplayIdentify communication standard GRB GRBPower requirements GRB GRBSchematic interface GRB GRBAlpha Testing

External SensorsVoltage Sensor EEM EEM

“Wrap Up” Plan (very early)

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Weekly GoalsPowerpoint Slide Assignments

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Topic # Slide Est. Time (mins) StudentIntro 1 Title Slide 0 Emrys

2 Introduction / relevance / background 1 Emrys3 Requirements / specifications (Overall) 1 Emrys

Design Overview 4 System Block Diagram 2 Richard5 Mechanics 1 Richard6 Display / Touch input 1 Richard7 Removable storage 1 Richard8 Battery voltage sensor 0.5 Emrys9 Battery current sensor 0.5 Emrys

10 Wheel position sensor 0.5 Emrys11 PSU requirements 0.5 Andy12 PSU options 0.5 Andy13 PSU choice 0.5 Andy14 GPS 1 Ammar15 MCU / internal memory 1 Ammar16 Test methods 1 Ammar

Project Management 17 Management Plan 1 Ammar18 Timeline 0.5 Andy19 Weekly Goals 0.5 Andy

Budget 20 Budget 0.5 AndyConclusion 21 Conclusion 0.5 Andy

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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

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Conclusion/Questions

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