Introduction

Traditional Slot Car Operation

Traditional slot cars run on a track with two lanes, and users compete with each other by racing around the track with small electric cars. The players control the speed of their cars by squeezing a trigger on a handheld gun. The trigger operates a potentiometer which varies the voltage to two rails along the length of each lane of the track. Sliding pickups on the bottom of the car close the circuit through a dc motor, which drives the car forward.

In this situation, the user provides feedback to the potentiometer by sensing the car's speed visually and adjusting the position of the potentiometer to try to make his car go faster than his opponent without spinning out or flying off the track.

Automated Slot Car Operation

In this project, one of the two human users was replaced with a Motorola MC68HC11-E9 microprocessor unit (MCU), which controls the car using pulse width modulation (PWM) of the voltage from a constant dc power source.

Closed-loop feedback was achieved with infrared photodetectors mounted in the track, which send pulses to the processor at various points along its length as the car passes them. Based on the timing of these pulses, the car slows down in the corners and speeds up in the straight-aways.

A liquid crystal display (LCD) provides information to the user including real-time speed and lap times, as well as startup instructions and winner/loser results. Relative speed is also displayed with arrays of light emitting diodes {LEDs} for each car.

Difficulty level may be selected from low, medium, and high, which allows users to practice and increase the difficulty as they improve their skills. As the difficulty increases, the duty cycle is increased and the computer controlled car goes faster, making it harder to beat.

Ryan Krauss / Lisa Ellis / Joe Frankel
For problems or questions regarding this web contact [Joe Frankel].
Last updated: 11/25/02.