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

Introduction Relevance to Dr. Gibbs Available systems Commercial ‘off the shelf’ Phone apps Electric Bicycle Monitor (EBM) Integration Weight Power efficient Context of use 2

Requirements Display Speed, ~20 mph max Odometer Trip Distance Maximum speed Average speed Peak current Time and Date GPS position data (latitude, longitude, altitude) Battery voltage, 35 V to 40 V Battery current, up to 30 A A·hr consumption since last charge W·hr consumption since last charge Record GPS position data for external use 3

System Block Diagram Caption for visual aid(s) 4

Mechanics Other Option Considered Standard enclosure Current status Donor case from Garmin Roadblocks Physical constants PCB limit 3 1/8” X 2 ½” SMT parts Disassembled Garmin Nuvi

Touch Display Other Option Considered Two Row LCD Current status Donor LCD from Garmin Innolux model AT043TN24 Major roadblocks Obtaining supporting documentation Implementing interface Drop-dead date: not defined yet Backup Plan Source another LCD as standby 6

Removable Memory Other options Considered USB drive USB cable Current Status SD card Type not known Roadblocks Implementing interface 7

Battery Voltage Sensor ADCMCU Battery + Reference - Amp Internal to EBM Options ADC (8-bit ~ V, 10-bit ~ V) Differential amplifier Voltage Divider 8

Battery Current Sensor External to EBM In-line with the battery positive terminal Outputs analog value for ADC directly Options Hall Effect sensor Shunt resistor Example of a Hall Effect current sensor. Image from: 9

Wheel Speed Sensor Magnetic pickup Possible Magnet Locations External to EBM Sends pulses to MCU Options Magnetic pickup Optical Roadblocks Reliability Environment Vibration 10

Power Supply Requirements 35-40V operational range Battery system provided Automatic shutdown voltage Voltage/current sensing Multiple voltage levels Display (12V?) Sensors (5V?) Microcontroller (3.3V?) Memory modules (1.8V?) GPS module (1.8V?) 11

Power Supply Options Voltage Divider Easy Minimal parts Inefficient Poor regulation Linear Regulator Small footprint Minimal parts Good regulation Inefficient DC-DC Converter Complicated Multiple parts Noisy Poor regulation Efficient 12

Power Supply Combination DC-DC step down High efficiency (~90%) Noisy LDO filter Stabilize noise Well regulated LDO step down Even better regulation Even better filtering Less efficiency (~70%) Voltage Step Down Scheme 13

GPS Specifications: Operation voltage Starting time Interference type Size Price Internal Vs. External Antenna GPS Receiver - EM

Microcontroller Inputs and outputs Interface protocol SPI, I 2 C, or UART Number of ADC bits Program memory size uC architecture 8 bit Vs. 16 bit Different Microcontrollers 15

Testing Each subsystem will be tested individually Divided into three parts: 1.Testing magnetic trigger using regular bike 2.Testing power system, voltage sensor, and current sensor using a power supply 3.Other subsystem can be tested individually without any external parts Final prototype will be tested using Dr. Gibbs’ electric bike 16

Project Management Meeting: Bi-weekly with Dr. Gibbs (every other Thursday) Weekly with group members Documentation Shared folder to organized documents (Google Drive) Document naming convention for convenient access Tasks: Divided into subsystems Each subsystem includes: choosing components, designing circuit schematics, PCB, and programming Overlapping responsibility to help with system integration 17

Project Timeline (Preliminary) “Wrap Up” Plan (very early) 18

Weekly Goals Powerpoint Slide Assignments 19

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 20

Conclusion/Questions 21