MechBase Line Following Rover

Step 1: Baseplate

Set down the 32×32 baseplate on your work surface. Orient it so the longer side runs left to right in front of you.

Step 2: Main Frame Rails

Take two 2730 bricks (1×10 with holes). These form the two parallel rails of the chassis frame.

Rear rail: Place one brick horizontally near the rear third of the baseplate. The Technic holes should face upward.

Front rail: Place the second brick parallel to the first, about 8 studs (64mm) forward. The two rails should be evenly spaced.

Press both bricks firmly onto the baseplate studs.

Step 3: Cross Braces

Take two 3701 bricks (1×4 with holes). These connect the rails at each end, forming a rigid rectangular frame.

Rear cross brace: Place one brick perpendicular to the long rails at the rear end.

Front cross brace: Place the second brick the same way at the front end.

Insert 2780 pins at each corner. Push each pin down through the overlapping Technic holes. Use 4 pins total.

Step 4: Axle Mount Brackets

Take four 3701 bricks (1×4 with holes). These form the axle mount brackets that extend outward from each rail.

Rear mounts (2 bricks): At each end of the rear cross brace, place a 3701 extending outward from the frame edge.

Front mounts (2 bricks): Repeat at the front cross brace.

Lock each with a 2780 pin through the overlapping hole. Use 4 pins total.

Step 5: Rear Drive Axle

Take the 3737 axle (10L, 8mm diameter, ~80mm long).

Slide the axle horizontally through the rear axle mount brackets. Center it so it extends about 8mm past each mount bracket for wheel clearance.

Lock in place: Insert 32062 (2L Notched) axles into adjacent holes on each side. Notch faces UP to prevent axle from sliding out.

Step 6: Front Caster Axle

Take the 32073 axle (5L, 8mm diameter, ~40mm long). Shorter than rear — intentional since front is passive.

Slide through front axle mount brackets. Lock with two 32062 (2L Notched) axles, notches facing UP.

Step 7: Wheel Installation

On each axle end: slide a 4265c (Bush ½ Smooth) onto the axle first as spacer, then press the 56908 wheel onto the axle past the bushing.

Repeat for all 4 wheels. Order: bushing → wheel

Step 8: Motor Mount Brackets

Take two 3894 bricks (1×6 with holes). These provide motor mounting positions alongside the rear axle.

Place each brick parallel to the long rails, positioned just outside the rear axle mounts.

Lock each with a 2780 pin where it overlaps the long rail.

Step 9: Mount Motors

Each TT Micro Motor (37mm):

• Diameter: 37mm (~4.6 Technic studs)
• Output: 3mm round shaft, protruding ~8mm from gearbox
• Voltage: 3-6V DC nominal (run at 7.4V from LiPo via Adafruit HAT)

Mounting: Position each motor so its output shaft aligns with the rear axle. Use the Adafruit TT motor coupler (product 3810) to connect the 3mm motor shaft to the 8mm Technic axle. Secure with zip ties to the 3894 brackets.

Step 10: Electronics Platform

Build a raised platform in the center of the chassis using four 3024 bricks (2×4) stacked for airflow underneath.

Use zip ties to secure the Pi Zero 2 W to the platform. The Adafruit Dual Motor HAT stacks directly on top of the Pi's GPIO header.

Step 11: IR Sensor Array Mount

Take three 3701 bricks (1×4 with holes). These form the front mount for the IR sensor array.

Place them side-by-side at the front of the chassis, extending forward past the front axle. This positions the sensors to look at the ground ahead.

Mount the three TCRT5000 IR sensors on a breadboard, then attach the breadboard to the Technic brackets using zip ties. Sensors should face downward, ~10mm above the ground.

Step 12: Battery Mount

Take one 3024 brick (2×4). Place it at the rear of the chassis as a battery anchor point.

Secure the 2S LiPo 7.4V 2200mAh battery in the rear corner, away from spinning wheels. Use velcro straps or zip ties.

Power routing:

• Battery(+) → Motor Driver VMOT
• Battery(-) → Motor Driver GND → Pi GPIO GND
• Buck converter → Pi 5V via USB-C (if needed)

1. Install dependencies

sudo apt update
sudo apt install -y python3-pip
pip3 install adafruit-circuitpython-motorkeeper adafruit-blinka

2. Create project folder

mkdir ~/mechbase && cd ~/mechbase

3. Save line_follower.py

import time
import board
import busio
import digitalio
from adafruit_motor import stepper

# Initialize I2C and motor HAT
i2c = busio.I2C(board.SCL, board.SDA)
motor_hat = stepper.MotorHAT(i2c)

# Motor setup
left_motor = motor_hat.motor1
right_motor = motor_hat.motor2

# IR sensors (digital mode)
ir_left = digitalio.DigitalInOut(board.D17)
ir_center = digitalio.DigitalInOut(board.D27)
ir_right = digitalio.DigitalInOut(board.D22)

def read_sensors():
    # Read IR sensor array, return list of boolean values
    return [
        not ir_left.value,
        not ir_center.value,
        not ir_right.value
    ]

def follow_line():
    sensors = read_sensors()
    
    if sensors[1]:  # Center on line
        left_motor.throttle = 0.5
        right_motor.throttle = 0.5
    elif sensors[0]:  # Line on left, turn left
        left_motor.throttle = 0.3
        right_motor.throttle = 0.5
    elif sensors[2]:  # Line on right, turn right
        left_motor.throttle = 0.5
        right_motor.throttle = 0.3
    else:  # Lost line, stop
        left_motor.throttle = 0
        right_motor.throttle = 0

# Main loop
print("Line Following Rover - Starting")
try:
    while True:
        follow_line()
        time.sleep(0.05)
except KeyboardInterrupt:
    print("Stopping")
    left_motor.throttle = 0
    right_motor.throttle = 0

4. Run it

python3 line_follower.py