The design of an electronic bicycle monitor ebm
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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. Relevance. Current interface Battery Speed Available systems Commercial ‘off the shelf’

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The Design of an Electronic Bicycle Monitor (EBM)

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The design of an electronic bicycle monitor ebm

The Design of an Electronic Bicycle Monitor (EBM)

Team P118:

Gary Berglund

Andrew Gardner

Emrys Maier

Ammar Mohammad


Background

Background

Electric Bicycle Components

Bicycle

Battery

Controller

Motor


Relevance

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


Requirements

Requirements


System block diagram

System Block Diagram

Caption for visual aid(s)


User display

  • Requirements from top level:

  • Display bicycle status

  • Requirements from other subsystems:

  • None

User Display


User display hardware

Solution being implemented: Graphics LCD

  • 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

User Display (Hardware)


User display software

Solution being implemented: Graphics LCD

  • Software status:

  • Need software flow chart for GUI

User Display (Software)


Removable memory

  • Requirements from top level:

    • Logged Lat/Long for post processing

    • Using Google Maps or similar program to view route

  • Requirements from other subsystems:

    • None

Removable Memory


Removable memory1

Solution being implemented: Secure Digital

  • Needs from other subsystems:

  • MCU

    • SPI bus

  • Power supply

    • 3.3V @ 200µA (660µW) Standby

    • 3.3V @ 100mA (330mW) Active

Removable Memory


Removable memory2

Solution being implemented: Secure Digital

  • Software status:

  • Need software flow chart for SD functions

Removable Memory


The design of an electronic bicycle monitor ebm

  • Requirements from top level:

    • Handlebar mounted

    • Water resistant

  • Requirements from other subsystems:

    • None

Case


Case hardware

Solution being implemented: Garmin Nuvi

  • Needs from other subsystems:

  • All subsystems

    • Physical constraint

    • PCB Mounting hole coordinates match case

  • Power supply

    • Power button & USB connector coordinates match case

Case (Hardware)


Case software

Solution being implemented: Garmin Nuvi

  • Software status:

  • N/A

Case (Software)


Battery voltage sensor

Solution being implemented: Offset Differential Amplifier

  • 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

Battery Voltage Sensor


Battery voltage sensor1

Battery Voltage Sensor


Battery voltage sensor2

Solution being implemented: Housekeeping

  • Software status:

  • A 10-bit ADC will be read every 1 ms and saved into a variable for the display to use

Battery Voltage Sensor


Battery current sensor

Solution being implemented: Hall Effect Sensor

  • Needs from other subsystems:

  • PSU

    • 3.3V, Ground

  • MCU

    • ADC input

  • 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

Battery Current Sensor


Battery current sensor1

Battery Current Sensor


Battery current sensor2

Solution being implemented: Housekeeping

  • Software status:

  • A 10-bit ADC will be read every 1 ms and saved into a variable for the display to use

Battery Current Sensor


Wheel speed sensor

Solution being implemented: Hall Effect Sensor

  • Needs from other subsystems:

  • PSU

    • 3.3V, Ground

  • MCU

    • Interrupt capable input

  • Requirements from top level:

    • Range of 0 to 30 mph

  • Requirements from other subsystems:

    • MCU

      • Output pulse when magnet passes the sensor

Wheel Speed Sensor


Wheel speed sensor1

Wheel Speed Sensor


Wheel speed sensor2

Solution being implemented: Interrupt

  • 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.

Wheel Speed Sensor


Power management system

Software Milestone: 0

Hardware 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:

  • Identify all voltage/current needs from subsystems

  • Identify subsystem I/O software requirements

  • Develop “Power Budget” and battery charge life

  • Research specific solutions and identify component candidates

  • Design and model hardware schematic

  • Alpha test under laboratory conditions

  • Integrate into EBM subsystems and measure performance

Power Management System


Power management system1

Software Milestone: 0

Hardware Milestone: 0

Power Management System

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


Power management system2

Software Milestone: 0

Hardware Milestone: 0

Solution being implemented: A mix of DC-DC Buck Converters and LDO Linear Regulators

  • 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

Power Management System

Requirements from other subsystems, “Power Budget”:


The design of an electronic bicycle monitor ebm

GPS


The design of an electronic bicycle monitor ebm

  • Solution being implemented:

    • Getting position and time information

GPS

  • 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

  • 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


Microcontroller

Microcontroller


Microcontroller1

Solution being implemented: Microcontroller

  • Needs from other subsystems:

  • Power System:

    • 3.3V @ 800µA (2.6mW) running mode

    • 3.3V @ 22µA (72µW) Idle or sleep mode

  • 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

Microcontroller


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

Testing


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

Project Management


Project timeline preliminary

“Wrap Up” Plan (very early)

Project Timeline (Preliminary)


Weekly goals

Powerpoint Slide Assignments

Weekly Goals


Budget

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


Conclusion questions

Conclusion/Questions


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