Applications and Implications

• Custom PCB (motor driver, microcontroller pcb)
• firmware (monitoring, sensor feedback)
• Enclosure (3D printed or CNC-milled)
• Motor mount

• Will it use PWM for motor speed control?
• Will it support both brushed and BLDC motors?
• Can the microcontroller handle real-time monitoring and control?
• What kind of failsafe and recovery strategy will be implemented?

The following section catalogs all tasks completed to date, tasks still pending, current system status, unresolved questions, and an estimated timeline. This helps keep the project on schedule and provides transparency for collaborators or evaluators.

Completed Tasks

• ✓ Designed the Motor Controller Schematic
  

  • Utilized KiCad to create a complete schematic, including IRFZ44, resistors, IN4007 diode, throttle input conditioning circuitry, brake switch interface, DC‐DC 24->5 V converter, microcontroller (Xiao RP2040), and connectors (battery, 3‐pin for throttle,brake,display, pins for the sensors).

• ✓ PCB Layout Validation & Fabrication
  

  • Converted schematic to PCB layout in KiCad, paid particular attention to high‐current traces (10 mm width), thermal relief for MOSFETs, and distance between high‐power nets to prevent arcing.
  • Routed ground planes, added thermal vias under MOSFET pads, and created silkscreen annotations for component placement.
  • Exported Gerber and drill files, and submitted to PCB fabrication service (1 layer copper).

• ✓ PCB Assembly
  

  • After PCB production, hand‐soldered MOSFETs, DC‐DC converter module, microcontroller, and all (resistors, capacitors).
  • Confirmed solder quality with X‐ray refracted light, tested continuity of power rails and gate‐drive nets.

• ✓ Initial Firmware Development
  

  • Wrote C++ firmware on Arduino IDE targeting XIAO RP2040.   – ADC reading of throttle (0–5 V) with 10‐bit resolution, mapped to 8‐bit PWM duty cycle.
    – Brake switch interrupt (pin change) to override throttle and cut PWM instantly.
    – UART serial logging (9600 baud) for real‐time telemetry: throttle value, current sense reading, temperature reading, battery voltage reading.
  

• ✓ Static Bench Testing
  

  • Connected PCB to a lab power supply (24 V @ 5 A limit), resistive load to simulate motor current draw.
  • Verified that as throttle turns from 0 to 5 V, PWM duty smoothly increases and output voltage follows setpoint.
  • Measured current by reading voltage drop on 0.01 Ω sense resistor through differential amplifier → ADC; confirmed linear scaling.

• ✓ Overload Protection
  

  • Calibrated the op‐amp‐based current sensor: measured known loads, adjusted gain resistors to map 0–30 A to 0–5 V range.
  • Added software limit: if sensed current > 25 A for > 100 ms, cut PWM to 0 and issue fault code over serial. Confirmed with short‐circuit test (~5 Ω load) that fault triggers as expected.

• ✓ Connect OLED display and battery
  

  • Connect and enclosures the display in the 3D printed screen enclosure.
  • connect battery cells in series and parallel to achieve required voltage (24V).

• ✓ Fine-Tune PWM Frequency & Duty Cycle Modulation
  

  • Evaluate effect of different PWM frequencies (10 kHz–50 kHz) on motor noise and efficiency. Adjust Timer1 prescaler and TOP value in firmware.
  • Implement a two‐stage current limit: soft limit at 20 A (reduce duty linearly) and hard limit at 30 A (trigger fault).

• ✓ Real‐World Motor & Battery Testing
  

  • Connect PCB to an actual 250 W hub motor and 24V Li‐ion pack.
  • Record performance metrics: acceleration response, steady‐state speed under various loads, current draw at full throttle, and temperature rise over 10 minutes of constant duty.

• ✓ Throttle Response Curve Improvement
  

  • Implement software mapping (e.g., exponential curve) so that initial throttle movements result in gentle acceleration and higher turns yield steeper power. Add a configurable dead zone (0–10% throttle ignored) to avoid jerky starts.

• ✓ Enclosure Design & Packaging
  

  • Use CAD software (SolidWorks) to model a custom plastic enclosure that houses the PCB, DC‐DC converter, and connectors.
  • Provide ventilation/heat sinks for MOSFETs, rubber gaskets for waterproofing, and mounting flanges to bolt the enclosure to the bike frame. 3D print a prototype for fit validation.

• ✓ Complete Documentation & Demo Video
  

  • Compile all photos, CAD screenshots, test logs, and firmware code into a coherent project report and step-by-step assembly guide.
  • Capture a 2–3 minute video showing the fully assembled e-bike running outdoors: demonstrate acceleration, braking. Narrate the key technical points and safety features.

• ✓ Final Presentation Slides & video
  

  • Prepare a concise slide deck (10–12 slides) summarizing problem statement, system architecture, design challenges, test results, final performance, and next steps.
  • Design an 24×36″ poster for showcasing at symposiums or maker fairs. Include diagrams, charts (e.g., efficiency vs. load), and key takeaways.

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• ⧗ Temperature Sensing & Thermal Protection
  

  • Position negative‐temperature‐coefficient (NTC) thermistors on MOSFET heatsink or inside battery pack. Add conditioning circuitry (pull‐up resistor + lowpass RC) to ADC inputs.
  • In firmware, continuously monitor temperature; if > 70 °C, ramp down PWM; if > 80 °C, cut off and flag overheat.

• Throttle -> PWM Mapping: The firmware’s linear mapping of throttle voltage (0–5 V) to PWM duty (0–100%) is stable and reproducible. No visible jitter at low speeds.
• MOSFET Switching: IRFP44 switch cleanly at 20 kHz with minimal switching losses (measured ~2 W per MOSFET at 15 A load).
• Serial Telemetry: Real‐time data (throttle, current, temperature, voltage) prints reliably to terminal at 9600 baud. Useful for debugging and logging.