Build Mater the Friendly Robot Tow Truck! (Inspired by Disney and Pixar's Cars)

Say hello to Mater, the cheerful, chatty, and clumsy tow truck robot who’s always ready to lend a hook! Inspired by Pixar’s Mater and built on the smart framework of the KABANDHA pet robot by aphla, this robot combines personality, mobility, and fun in a single interactive package. Whether you want a helpful tow bot or a funny friend rolling around your workspace, Mater is your guy!

Built with dual Arduino Nanos, expressive OLED eyes, a servo-controlled tow hook, and a Bluetooth remote control system, this robot is ideal for both students and hobbyists who want to create an emotional support robot with real-world motion.

Electronics:

1. 2 × Arduino Nano (one for motion, one for interaction)
2. 1 × DRV8833 Motor Driver
3. 1 × 7.4V LiPo Battery
4. 1 × Servo Motor (for the tow hook)
5. 4 × N20 Motors with wheels
6. 1 × HC-05 Bluetooth Module
7. 1 × OLED Display (128x64)
8. Breadboard or perfboard
9. Male/Female header pins
10. Assorted jumper wires

Hardware:

1. 5mm Sunboard sheets (chassis and canopy)
2. Hot glue, super glue
3. Hobby knife, ruler, screwdriver
4. Tow hook element (can be bent wire or custom 3D print)

Tools:

1. Soldering iron & paste
2. Wire stripper & cutter
3. Cutting mat
4. Computer with Arduino IDE

Mater isn't just a toy Robo — he's a character. He moves on four wheels, shows expressions using an OLED screen, responds to commands through Bluetooth, and can tow small items with his servo-powered hook. Unlike standard robots, Mater is designed with emotion and interaction in mind. Whether you want him to assist, entertain, or follow you around, he delivers personality in every movement.

Start by cutting sunboard pieces using a hobby knife:

1. Base: 10cm × 6cm
2. Height: 8cm
3. Rear slot for the servo (2cm × 2cm)

Build the structure using hot glue for strength and super glue for fine seams. Add a rounded front to resemble a classic truck hood. Make sure the internal space is enough for wiring and mounting both Arduinos and components. It doesn’t have to be perfect – Mater loves being a bit scrappy!

Use 4 N20 motors—two on each side—for omnidirectional movement. Securely glue them to the underside of the chassis. Align them evenly to ensure the robot rolls smoothly and doesn't tilt. Slide wheels onto the shafts and test spin manually to check for resistance. Add support near the edges to stabilize the weight of the battery and servo.

Wire your two Arduino Nanos as follows:

1. Nano 1 controls the motors via the DRV8833 motor driver and servo for the tow hook.
2. Nano 2 handles Bluetooth (HC-05) communication and OLED eye animations.

[Note: By using two microcontrollers, we can efficiently manage both the motor and communication tasks at the same time, ensuring Mater has smooth movement and interactive capabilities.]

Mount the components on a perfboard or breadboard for easy access. Power both Arduinos using a 7.4V LiPo battery through voltage regulators if necessary. Keep the wiring tidy with cable ties or adhesive pads to avoid short circuits or entanglement during motion.

Open the Arduino IDE, install the required libraries:

1. Servo.h
2. Adafruit_GFX
3. Adafruit_SSD1306

Upload:

1. Motor and tow hook control code to Nano 1
2. OLED eye animation and Bluetooth code to Nano 2

Make sure to select the correct COM ports for each Nano and upload them one at a time. You can even add different eye "moods" for Mater by editing the OLED frame logic.

🔗 [Here's the code link 👈]

Connect the SG90 servo motor to a plastic or wire hook and mount it into the rear slot of the chassis. This hook is Mater’s signature move!

Program it to raise/lower using Bluetooth commands ('W' for up and 'w' for down). You can use this to lift paperclips, tiny cars, or candy. Be sure the servo horn has enough clearance to rotate without obstruction.

Mount the OLED display on the front “face” of Mater. Use cartoon-style expressions such as blinking, winking, or looking around. These give Mater his quirky character and make him feel alive.

Customize expressions depending on actions:

1. Moving forward = wide excited eyes
2. Tow mode = focused narrowed eyes
3. Idle = sleepy blink

This is where your personality can shine through the robot.

Download the “Bluetooth RC Car” app by ANDI.co on Android. Pair it with your HC-05 module (default password: 1234 or 0000).

Use the app’s interface to:

1. F – Forward
2. B – Backward
3. L – Turn Left
4. R – Turn Right
5. S – Stop
6. W / w – Raise/Lower Tow Hook

Test responsiveness and fine-tune motor PWM values if speed needs balancing.

Place all internal components securely, double-check wiring, and fasten the battery with a strap or Velcro. Power up the bot, connect via Bluetooth, and drive it around. If it wobbles, adjust weight distribution or wheel grip.

You can decorate Mater with stickers, paint, or even voice module support for catchphrases like "I’m happier than a tornado in a trailer park!"

You've just brought Mater to life — a friendly, expressive tow-truck robot buddy with his own personality and usefulness. Whether you're a student entering the Robot Friends Contest or a maker trying out expressive robotics, this project is both fun and rewarding.