Customization & Hardware Extensions

EVDrive is designed from the ground up on open-hardware and open-architecture principles. Rather than providing a locked-down commercial toy or an opaque black box, EVDrive empowers students, makers, and educators to learn real-world engineering through mechanical design, rapid prototyping, sensor integration, and embedded programming.

1. Mechanical Architecture & 3D Prototyping

Building a mobile robot teaches students how mechanical tolerances, material properties, and weight distribution directly impact vehicle dynamics and sensor accuracy:

Physical Dimensions & Footprint

Baseline Dimensions: The standard chassis measures 240mm long by 140mm wide, providing a stable low-center-of-gravity platform that easily navigates classroom floors, tabletops, and lab tracks.
Low Mass & High Rigidity: 3D printed in PETG or Tough PLA with 35%–45% infill, the frame dampens stepper motor vibration while maintaining dimensional accuracy under acceleration.

Flexible Power Architecture

Battery Compatibility: Operates smoothly with standard rechargeable NiMH AA battery packs, alkaline cells, or external DC power supplies via onboard buck/boost converters.
Onboard Safety: High-current P-channel MOSFETs and quick-blow fuses safeguard the board against accidental reverse battery connections or short circuits during student lab work.

Open-Source CAD Ecosystem

Full Parametric Models: RH Circuits provides complete, unrestricted 3D .STEP and .STL CAD models on the Chassis Downloads Page.
Learn Real CAD: Students can open the STEP files directly in industry-standard CAD suites (Autodesk Fusion 360, SolidWorks, or Onshape) to inspect geometry, modify mounting brackets, and export custom 3D prints.

2. Chassis Mounting Grid & Architecture

The EVDrive chassis includes a pre-drilled M3 mounting grid engineered specifically for rapid prototyping and hardware expansion:

Front Mounting Holes: Located on the front cross-member for screwing in modular front bumpers, sensor brackets, or mechanical microswitch end-effectors.
Rear Mounting Points: Dedicated mounting holes at the rear of the chassis for securing pointer dowels, optical benchmark flags, or wheelie bars.
Lateral Side Holes: Running down both left and right sides of the chassis bed. Used for mounting trim counterweights to balance mass distribution, securing custom battery cradles, or attaching line-following sensor arrays.
Top Standoff Mounting Holes: 4 elevated M3 standoff mounting points positioned above the electronics. Screwing on the Top Deck Plate provides an elevated mounting surface for optical sights, tactile pushbuttons, and status displays.

3. Designing Custom Attachments & Sensor Modules

A. Modular Front Push Bumper & End-Effectors

For robotics projects involving object manipulation, obstacle avoidance, or maze exploration:

Screw-in Front Mount: The bumper screws directly into the chassis front M3 holes with two to four screws. This modular design makes it easy to iterate on geometries between test sessions.
Custom End-Effectors: Learners can design grippers, curved pushers, or bumper pads tailored to specific robotics challenges.
Bumper Microswitch Integration: You can mount a small snap-action limit switch to the bumper face connected to expansion GPIO 21 on header J6 to detect physical contact in software.

B. Optical Sighting & Visual Alignment Jigs

Aligning your vehicle accurately on a start line prevents angle deviations that magnify over distance runs:

Non-laser optical scopes: A standard crosshair optical tube or non-magnified sight mounted to the chassis top deck plate.
Mechanical alignment jigs: A machined straightedge, 3D-printed guide square, or alignment fence referenced against the wheels to align the chassis with a floor reference line.
Design Your Own Bracket: We encourage learners to design and 3D print their own custom mounting bracket or alignment jig tailored to their specific optics and workflow.

C. Extra Sensors (GPIO Header `J6`)

The board breaks out 8 extra digital/analog pins (GPIO 21, 35, 36, 37, 38, 45, 47, 48) along with +3V3 and GND:

Front Bumper Microswitch: Mount a limit switch on your bumper bracket to detect the moment the car makes contact with an obstacle.
Ultrasonic Distance Sensor: Connect an HC-SR04 ultrasonic sensor to measure distances to walls or dynamic obstacles.
Infrared Line Tracking: Mount an array of reflectance sensors beneath the front cross-member for autonomous line-following algorithms.

cpp

// Example: Reading a front microswitch bumper on GPIO 21
const int PIN_BUMPER = 21;

void setupBumper() {
  pinMode(PIN_BUMPER, INPUT_PULLUP);
}

bool hasMadeContact() {
  return digitalRead(PIN_BUMPER) == LOW; // Switch triggers on contact
}

D. Auxiliary Motors or Servos

If your project includes an active steering mechanism, an actuated gripper, or a pan-tilt sensor head, you can drive hobby servos or small DC motors using the expansion GPIO header (with hardware PWM) or auxiliary power terminals.

E. Custom Input and Display (On-Device UI)

Instead of relying solely on a connected computer or wireless telemetry, you can connect an I2C OLED display (such as an SSD1306), pushbuttons, or a rotary encoder directly to the expansion header J6 to input parameters on the car itself. A custom 3D-printed enclosure keeps the controls neatly integrated.

4. Hands-On Coding & Project Architecture

Treat the code snippets in these docs as modular building blocks. A core goal of EVDrive is helping students master real programming concepts rather than relying on pre-packaged turnkey firmware:

Understand Every Subsystem: Build your sketch step-by-step, starting with basic stepper pulse generation.
Master Closed-Loop Feedback: Incorporate gyro-based heading correction to keep your robot driving straight.
Implement Real Odometry: Integrate the AS5600 magnetic encoders to calculate real physical displacement in meters.
Design State Machines: Organize your code into structured autonomous states (e.g., IDLE, ACCEL, CRUISE, DECEL, STOPPED).

This modular architecture gives learners a deep, lasting foundation in embedded systems, motion control, and robotics programming.