Junkyard Battle Racers is a project which was designed and built for CSU’s mechatronics class by Alex Zenk, Katie Johnson, Floyd Bundrant, and Jacob Gover. It is essentially a real-life version of Mario Kart complete with power-ups, speed boosts, and IR laser tag guns. When a power-up pod is run over, an IR proximity sensor built into the bottom of the kart detects that a power-up has been acquired. At that point, a random power-up is assigned. Full digital sound effects are played on on-board speakers and an LCD screen built into the wheel notifies the player of which power-up has been acquired (Speed Boost, Shield, EMP Blaster, or Death Beam Gun). The player can then activate the power-up whenever it is most beneficial.

The karts’ gas pedal is not mechanically attached to the engine throttle. Instead, the gas pedal pulls on a spring loaded slide potentiometer in a custom 3D printed enclosure which sits behind the driver. This allows the pedal position to be read by a microcontroller. The microcontroller then tells a small servo motor attached to the engine throttle which position to go to based on the gas pedal position. In normal driving mode, flooring the gas pedal corresponds to roughly 50% of the kart’s full throttle ability. When a speed boost is activated, the “floored” position is remapped to 100% throttle for 15 seconds, and sound effects are played.

Unlike the drive-by-wire system, the brake pedal works differently. For safety reasons, the brake pedal is mechanically attached to the braking system, but features a secondary mechanism that can also actuate the brakes if signaled to do so by the on-board microcontroller. This means the driver always has the ability to hit the brakes, but the brakes can be actuated automatically if the kart is hit by a power-up. The kart also features a mechanical kill switch in reach of the driver and kill relay which kills the motor in case the battery dies for added safety measures.

When either the EMP Blaster or Death Beam Gun power-ups are acquired, the driver obtains the ability to shoot the opponents kart with an attached laser-tag gun. The laser-tag gun was custom designed and 3D printed. Immediately after the power-up is obtained, the IR blaster begins emitting a unique hex code. This code tells the opponents kart when you have locked on to them by triggering a “warning” sound effect on their kart. This is to allow your opponent a chance to use a shield power-up should she have one. Once the trigger is pulled the IR gun emits a different hex code depending on the power-up you are shooting. The opponents kart is able to read this data and trigger the corresponding sequence. An EMP hit, sets the opponents kart to 0 throttle for 15 seconds, allowing them to only coast. A Death Beam hit sets the opponents throttle to 0 and actuates the brakes, bringing them to a complete stop for several seconds. Both hit sequences also trigger custom sound effects and LCD messages.