1. Final Project

This page has the documentation of the final project.

Full bike assembled

Electric bicycle Conversion Kit

• Document a final project masterpiece that integrates the range of units covered, answering:
• What does it do?
• Who's done what beforehand?
• What did you design?
• What sources did you use?
• What materials and components were used?
• Where did they come from?
• How much did they cost?
• What parts and systems were made?
• What processes were used?
• What questions were answered?
• What worked? What didn't?
• How was it evaluated?
• What are the implications?

The project ecompases the design and production of the conversion kit for bicycle which will be used as a mode of transport to reduce traffic jame and preserving the climate, as it will reduce the carbon footprint from fuel-powered cars.

• Project Overview
  


• Build a full conversion kit for the motorcycle.
• Design and build circuit board that include voltage regulator for microcontroller and some components that required small voltage.
• Use microcontroller to process throttle input to control the motor speed, and display battery state of charge.
• Display throttle percentage, and fault status on an OLED.
• Enable Bluetooth connectivity for real-time data monitoring via a smartphone app (optional).
• Design 3D-printed display and circuit board enclosure for handlebar mounting.
• Implement fault detection (e.g., MOSFET temperature errors, low battery) on the display.

E-Bike conversion kit controller

Motor Controller PCB for Final Project Masterpiece

What does It Do?

• Throttle-controlled motor speed
• Overcurrent protection
• Soft start and regenerative braking
• Real-time monitoring via LCD
• 5V output to power microcontroller

Who has Done What Beforehand?

• Bafang, Kelly, and VESC offer commercial motor controllers.
• Open-source projects like VESC and SimpleFOC provide firmware and hardware design examples.
• Makers on GitHub and YouTube have built brushed/BLDC motor drivers with Arduino and STM32.

What did You Design?

• Custom 1-layer motor controller PCB

• 3D-printed or CNC-cut motor mount and battery enclosure

• Motor mount

• Monitoring display box

• Circuit mounting box

What Sources did You Use?

• Datasheets: NE555G, 2SC5200, LM7805, etc.
• KiCad documentation for PCB design
• IEEE papers and YouTube for gate driver design, current control
• VESC firmware, open-source controller schematics, Elcircuits
• Fab Academy tutorials on electronics production, 3D modeling

Materials and Components used

Component	Type	Source	Est. Cost ($)
Power Transistor	2SC5200	Communica (Pty) Ltd South Africa	0.85
Voltage Regulator IC	LM7805	Communica (Pty) Ltd South Africa	0.38
Temperature Sensors	24V	Nyerekatech	3.46
Microcontroller	Seeed XIAO RP2040	Nyerekatech	7.62
Capacitors	Bulk X 10	Communica (Pty) Ltd South Africa	2.5
Resistors/Diodes	Assorted pack	Communica (Pty) Ltd South Africa	0.66
PCB	Custom fab (1-layer, FR4 copper)	From inventory
Heat Sink	Aluminum	Scrap
Battery	3.7V X 18 Li-ion	Takealot South Africa	41.04
Display	16x2 I2C / OLE	Nyerekatech	6.23
Motor	24V, 20A, 300rpm	Amazon.com	38.99
Throttle	5V output signal	Amazon.com	14.99

Parts and Systems Made

• Custom PCB (motor driver, microcontroller pcb)

• Software (monitoring, sensor feedback)

// === Include Required Libraries ===
#include                       // Core Arduino functionality
#include                          // I2C communication for OLED
#include                  // Graphics library for OLED
#include              // OLED display driver

// === OLED Display Configuration ===
#define SCREEN_WIDTH 128                  // OLED display width in pixels
#define SCREEN_HEIGHT 64                  // OLED display height in pixels
#define OLED_RESET    -1                  // No reset pin used
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// === Hardware Pin Assignments ===
const int pwmPin = 3;                     // PWM output pin for motor (connected to MOSFET gate)
const int throttlePin = A0;               // Analog input for throttle (0–1023)
const int batteryPin = 27;                // Analog input for battery voltage sensing
const int thermistorPin = D1;             // Analog input for thermistor (temperature sensing)
const int ledPin = 14;                    // LED pin for fault/status indication

// === System Thresholds and Constants ===
const float lowBatteryVoltage = 10.0;     // Minimum safe battery voltage (adjust as needed)
const float maxMosfetTemp = 80.0;         // Maximum MOSFET temperature in °C before fault

// === Thermistor Parameters ===
const float BETA = 3950.0;                // B value of thermistor
const float R0 = 10000.0;                 // Thermistor resistance at 25°C
const float T0 = 298.15;                  // 25°C in Kelvin
const float R_REF = 10000.0;              // Reference pull-up resistor

void setup() {
  // === Initialize Serial Communication ===
  Serial.begin(9600);

  // === Configure Pin Modes ===
  pinMode(pwmPin, OUTPUT);
  pinMode(batteryPin, INPUT);
  pinMode(thermistorPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW); // Start with LED off

  // === Initialize OLED Display ===
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("OLED init failed"));
    while (true); // Stop everything if OLED fails
  }

  // === Display Welcome Message ===
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(10, 20);
  display.println("Motor Controller Ready");
  display.display();
  delay(2000); // Wait for 2 seconds before starting main loop
}

void loop() {
  // === Read Throttle (0 to 1023) ===
  int throttleValue = analogRead(throttlePin);

  // === Calculate PWM Value from Throttle ===
  int pwmDuty = map(throttleValue, 0, 1023, 0, 255);  // Map to 8-bit PWM (0–255)
  analogWrite(pwmPin, pwmDuty);                       // Output PWM to motor controller

  // === Simulate Speed (for display) ===
  float speed = map(throttleValue, 0, 1023, 0, 50);   //  speed in km/h (adjust as needed)

  // === Measure Battery Voltage ===
  float adcBattery = analogRead(batteryPin);          // Read battery ADC value
  float batteryVoltage = (adcBattery / 1023.0) * 3.3 * (100.0 + 10.0) / 10.0;
  // ↑ Adjust if using a different resistor divider (here 100k:10k assumed)

  // === Read Thermistor and Calculate Temperature ===
  int adcTherm = analogRead(thermistorPin);           // Thermistor ADC read
  float resistance = R_REF * (1023.0 / adcTherm - 1.0); // Calculate thermistor resistance
  float temperature = 1.0 / (log(resistance / R0) / BETA + (1.0 / T0)) - 273.15; // °C

  // === Show All Data on OLED Display ===
  displayStatus(throttleValue, pwmDuty, batteryVoltage, temperature, speed);

  // === Print Status to Serial Monitor ===
  Serial.printf("Throttle: %d, PWM: %d, Speed: %.1f km/h, Battery: %.2f V, Temp: %.1f C\n",
                throttleValue, pwmDuty, speed, batteryVoltage, temperature);

  // === Wait for a Bit Before Next Update ===
  delay(500); // Update rate every 0.5 second
}

// === Display Normal Operating Status on OLED ===
void displayStatus(int throttle, int pwm, float voltage, float temp, float speed) {
  display.clearDisplay();                  // Clear the OLED
  display.setCursor(0, 0);                 // Reset cursor to top-left
  display.setTextColor(SSD1306_WHITE);    // Set text color
  display.setTextSize(1);                 // Set font size (small)

  // Print all values
  display.printf("Throttle: %4d\n", throttle);
  display.printf("PWM:      %3d\n", pwm);
  display.printf("Battery: %.2fV\n", voltage);
  display.printf("Temp:    %.1f C\n", temp);
  display.printf("Speed:   %.1f km/h\n", speed);

  display.display();                       // Update the OLED with new content
}


• Arduino code (C++) to control the function of the components.
>

Processes Used

Unit	Process Used
2D/3D Design	Enclosure and mount in SolidWorks
Additive Fabrication	3D printing for enclosures
Subtractive Fabrication	CNC milling for metal sheet mount
Electronics Design	KiCad schematic + PCB layout
Production	PCB milling
Embedded Programming	C++ with Arduino IDE (Xiao RP2040)
Interfacing	Throttle, sensors, OLE
System Integration	Full wiring and mechanical assembly

Questions to Be Answered

• 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?

What worked? What didn't?

• OLED display
The screen cracked that was used to display speed, temperature, battery.

How Was It Evaluated?

Evaluation Metric	Criteria
Functional Testing	Smooth throttle control, no overheating
Safety	Current limits enforced
Design Integration	Clean, compact layout; 3D-printed case
Embedded Logic	Sensor response, overvoltage/overtemp logic
Aesthetics and Packaging	Finished housing and mounted connectors
Documentation	Full BOM, schematics, code, photos, videos

Construction & Design Power & Control Technology & Safety
Assemling

• Assembling the motor
Motor is assembed on the bi using motor mount and bold and nut.

• Battery assembling
Use battery holder and box made from pespex and soldered in a series (6sx3p) and parallel to achieve 24V.

• Circuit borad assembling

> Testing

• MOSFET testing on breadboard
• Firmware testing
• Motor testing with throttle
• Motor testing without load
• FUll bike testing>

challenges

• My first Circuit board burnt due to Overcurrent on the traces, the solution was to design large trace for the high current.
• MOSFET malfunctioning, solve by changing the mulfunctioning MOSFET with new ones.
• My alternate screen did not power up, I had to re-order new screen.
• PCB milling machine not reading coordinate well, I had to learn the software controlling the machine.

Gallery

Full bike assembled

Design files
Battery holder Solidworks
Battery holder DXF
Battery holder slicing
Circuit box Solidworks
Circuit box STL
Circuit box gcode
Circuit box cover Solidworks
Circuit box cover STL
Screen cover Solidworks
Screen cover DXF
Screen box Solidworks
Screen box STL
Motor holder Solidworks
Motor holder DXF
PCB PCB project
Schematic
Battery case Solidworks
Battery case DXF