My Project Log: The Master Blueprint for the Micro Bumper Car

Phase 1: Mechanical Framework & Gear Mastery

I kicked off the project by designing a compact, 2x2x2-inch 3D-printed chassis featuring a main tub, a top lid, a front ball caster, and a two-wheel differential drive setup. When my Pololu N20 micro gearmotors proved too long to sit horizontally end-to-end, I pivoted to a vertical motor configuration. I used a 90-degree, 1:1 bevel gear mesh to transfer power to the wheels. To prevent the wheels from sagging and stripping the gears during intense collisions, I engineered integrated structural axle tunnels and flat-bottomed pillow-block supports to anchor the axles rigidly to the chassis floor.

Phase 2: Power Architecture & Space Optimization

To maximize my remaining internal space, I chose a flat, horizontal layout on the wide-open front deck. I selected a high-capacity 1S 3.7V LiPo battery in a compact 752540 / 802540 size footprint (about 1.57 x 0.98 inches) to act as a heavy, low-lying weight over the front caster. For reverse voltage protection, I opted for a physically keyed JST-PH 2.0 connector on the battery rather than wasting space on a massive protection circuit board. To maintain a rock-steady power supply as the battery drains, I integrated a tiny Pololu 5V buck-boost voltage regulator to feed the electronics cleanly.

Phase 3: The All-In-One Brain

To keep my electronics bay clutter-free, I selected the Pololu Baby Orangutan B-328. This tiny board solves my spacing issues by combining an ATmega328P microcontroller and a dual H-bridge motor driver on a single 1.2” x 0.7” board. Because Pololu doesn’t offer an official 3D CAD file for this legacy module, I used the engineering “block-out” method to model a basic dimensional placeholder in Autodesk Inventor, allowing me to build custom plastic mounting walls and standoffs perfectly surrounding it.

Phase 4: Programming & Wireless Strategy

For the 4-player soccer tournament, I mapped out the wire paths routing power from the battery through the regulator to the brain, and then down to the N20 motor solder tabs. To flash my custom Arduino code onto the cars, I selected the Pololu USB AVR Programmer v2.1. I cleared up a major misconception here: the programmer stays on my workbench and is only plugged into the Baby Orangutan’s 6-pin ISP header (matching up the red stripe to Pin 1) for a few seconds to upload code. I only need one single programmer to update all four tournament cars, saving weight and money.

Phase 5: Wireless Control & Custom Transmitters

To wirelessly drive the car without the signal overlapping with the other three players in a match, I ruled out messy Infrared (IR) remotes. I instead explored two secure options: standard 2.4GHz hobby RC car pistol-grip controllers paired with a micro-receiver, or Bluetooth control via smartphone apps. I also mapped out a completely custom DIY option: building my own handheld transmitter from scratch using an Arduino Nano and an analog joystick module, transmitting data through the air to the robot via paired nRF24L01 2.4GHz radio transceivers for a secure, lag-free match!