Mousetrap

Mousetrap is my 3rd and most serious attempt at a competitive MicroSumo. My 2nd attempt, Sprite, was too constrained by the controller board size to do what I really wanted, so I designed the MEGAbitty controller. At under 1" square, this controller freed me from having to design the bot around the controller.

Mousetrap started with sketches and eventually 3D CAD models using ProDesktop Express (free!). CAD allowed me to find the optimal gearbox mounting angle to leave enough room for the battery pack while still allowing the bot to fold in half. The folding action reduces the bot to a 5cm cube, as required at the start of a MicroSumo match.

From the 3D models, I generated flat patterns for the three chassis pieces, which were laser cut and scored via www.filener.com from mystery plastic. The plastic is very resilient and can withstand hundreds of bending cycles before breaking. Mousetrap depends on this resilience for its hinge. The plastic also laser cuts well, and glues nicely with acrylic cement. Unfortunately, its surplus, and so far, unidentifiable.

A simple latch holds the robot in the folded position and is released when the bot's wheels start turning. A latex band pulls the unlatched top half down and NdFeB magnets (black disks in the pictures of Mousetrap folded up) hold it open. It's important that the robot opens quickly so a competitor can't get underneath it; also the line sensors don't point downward until the bot opens. Mousetrap lives up to its name by quickly springing open with a nice "snap!"

Mousetrap has plenty of power with TechMax "#1A" motor/gearboxes overdriven to 6V, and the large wheels give it enough speed to cross the ring in under a second. MEGAbitty Line Sensors keep the robot in the ring, and a Sharp distance sensor provides long range object detection. Short-range sensors on either side allow for evasive maneuvering away from side attacks. Eventually there will be a short-range rear sensor as well.

The MEGAbitty Controller is based on an Atmel Mega8 AVR and all of the sumo code is programmed in C using CodeVision.