Builders guide robot pacman.pdf

Since the beacon signal needs to cover 360 degrees but each emitter only has a60-degree transmission angle, we arranged 6 emitters into a circle to form the IRbeacon. Both IR beacon and IR receivers are positioned on the top of the robotsabove the wall, so they are not obstructed as the robots move around the maze.5.4 Contact SensorThe contact sensor on both Pac-Man and Ghost uses a simple pull-down circuit tonotify the microprocessor upon collision of the two robots. The circuitry is asshown below in Figure 28. The contact sensor is designed to be a ringsurrounding the base of the robots. The circular shape was chosen to provide anall-around, large surface area for contact. The ring is constructed with a flexibleplastic support with brass strips mounted on it. The conductive strips on the tworings are designed to be offset, so the contact would be detected by both robots.The contact sensor is shown below in Figure 28.5.5 LCD displayFigure 28. Contact SensorThe number of dots collected, as well as the number of times contacts are madeare shown on the top layer of Pac-Man by an LCD display. Each time a dot iscollected, the microcontroller will increment the dot count on the LCD display.The last two digits belong to the dot count, and the first digit is the contact count.Originally we intended to use LED 7-segment displays; however, due to currentconsideration, we changed our design to the less current intensive LCDtechnology. Upon testing, we discovered that the segments on the LCD displayfades quickly if we simply supply DC power to the segment pin. The solution isto use a square wave to drive the display segments allowing the LCD to dischargeduring the off period. Testing also shows that the frequency of the square wave21