Builders guide robot pacman.pdf

5.0 SensorsSeveral different types of sensors are used to achieve the following functionalities in thePac-Man project:1) Wall detection – Pac-Man and Ghost should be able to maneuver around themaze without hitting or scraping the walls, and meanwhile detect openings in themaze. Given the configuration of the robots and the maze, this functionalityrequires distance sensors that have good resolution within a 15 cm range.2) Dot counting – The “Dots” in the Pac-Man game is realized by the floormounted LEDs in the maze. Pac-Man should be able to distinguish between thebare floor and an LED light source as it passes over them even when it is notcentered within the track. As in the computer game, the dots disappear after eatenby Pac-Man. Our LEDs should also turn off immediately after it has beendetected.3) Pac-Man location tracking – Ghost should be able to locate Pac-Man from agive distance within the maze. This functionality requires sensors that have awide detection angle (approximately 45 degrees) and a long detection range(approximately 120 cm).4) Contact - When Pac-Man and Ghost physically make contact, both robotsshould be able to detect the event.Given the above functional requirements, the following sensor designs are investigated aspossible solutions.5.1 Wall detectionWe first considered the Sharp GP2d12 IR ranger module (Figure 21), which isequipped with an infrared transmitter and receiver pair. Several features makesGP2D12 an attractive candidate – 1) Small packaging (0.75in x 0.5in) whichhelps keep the size of our robot under control, 2) GP2D12’s analog output (0.25Vto 2.45V) is easily interfaced with the PIC microcontroller’s internal A-Dconverter, and 3) high immunity to ambient light.16