Icarus

During the Light Tracker competition, a robot is placed at the center of large rectangular area. At each corner of the rectangle, there's a light bulb placed about 2 feet above the ground. One light bulb will then turn on, the light tracker suppose to go that corner. When the robot reaches that corner, the light bulb at that corner will be turned off, and randomly another light bulb will be turned on. The robot that reaches all four corners the fastest wins.

Hardware Design:

I designed this simple robot by using only 3 chips. They're Allegro 3966SA DC motor driver, 74HC00 quad 2-input NAND chip, and a LM339 open collector comparator. I could get away without using the comparator if the sensors I used were sensitive enough. The 2 infrared sensors I used were the only light sensors I had at the time. The sensitivity of the sensors may be adjusted using 2 pots. Icarus is powered by 4 AA NiCd batteries. They provide about 4.8V total. No voltage regulator was used. Instead, I used 5 capacitors. Below the batteries is the Tamiya Twin-Motor Gearbox. The gear box offers 6 different gear ratios. I used the lowest one since the sensors can't quite pick up the light with the faster settings. The chassis is a messed up CDR, cut to the right size. Four aluminum spacers were used to attach the circuit board to the chassis. I believe the wheels are from a Knex set.

Logic:

For the sensors, 1 means seeing a light, 0 means not. For the motors, 1 means moving forward, 0 means stop. When there's no light, Icarus spins around in place. When one of the sensors sees a light, it aligns its center with the light. When both sensors see light, it moves full speed ahead. I constructed the simple logic table below.

By using Karnaugh map, I found the logic of the left motor to be R and right motor to be R'+L or (RL')'. However, the motor runs only when the enable pin is low. So the required logics were R' and RL'. One quad NAND chip was enough to accomplish this.

Schematic:

PCB:

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