PONG in AnalogScott MorrisonNicholas HarringtonMay 13, 2009iAbstractOur team (Nick Harrington and Scott Morrison) built an analog system that dis-plays the game of PONG on a oscilloscope screen. Our game models the ball’s pathin two dimensions, including a downward acceleration due to “gravity” and realisticcollisions with the walls and paddles. Other gameplay features include the ability toreset the ball position and sounds that play at each collision.The core of our project is a simple analog computer that calculates the path of theball, including a set of comparators to detect collisions and start a new trajectory. Allof the physical constants and display parameters are adjustable, and since the collisiondetection is tied intimately to the visual output, the size of the paddles or ball can beadjusted w ith the turn of a knob.iiContents1 Introduction 12 Design Overview 12.1 Design Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Circuit Design and Analysis 23.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2 Integrators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2.1 Zero-reset Integrator . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.2.2 Arbitrary-reset Integrator . . . . . . . . . . . . . . . . . . . . . . . . 53.3 Sample and Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.4 Timing circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.4.1 Reset timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.4.2 Bounce timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.5 Comparators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.6 Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.7 Visualization and Collision Detection . . . . . . . . . . . . . . . . . . . . . . 113.7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.7.2 Visualization Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.7.3 Collision Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.7.4 Input Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.8 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Error Analysis 155 Conclusions 17iiiList of Figures1 A block diagram of the physics engine. . . . . . . . . . . . . . . . . . . . . . 22 Analog Devices ADG202A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 A simple integrator with reset-to-zero capability. . . . . . . . . . . . . . . . . 44 An integrator with two resets. . . . . . . . . . . . . . . . . . . . . . . . . . . 55 A simple sample-and-hold circuit. . . . . . . . . . . . . . . . . . . . . . . . . 66 An edge-triggered monostable timer. . . . . . . . . . . . . . . . . . . . . . . 77 Monostable timers for the bounce system. . . . . . . . . . . . . . . . . . . . 88 Voltage references for comparator bounds. . . . . . . . . . . . . . . . . . . . 99 Comparators to detect the walls and reset bounds. . . . . . . . . . . . . . . . 910 An LM386 audio amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1011 Collision Detection Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311 IntroductionOur team has taken this opportunity to recreate a classic video game: PONG. Originallyreleased in 1972, PONG became the world’s first commercially successful video game. Anearlier game based on a similar concept, “Tennis for Two”, is often described as the first elec-tronic game with a graphical display. This game was invented in 1958 by American physicistWilliam Higinbotham at Brookhaven National Laboratory, where it served as entertainmentfor visitors.Unlike Atari’s game, which was built primarily with transistor-transistor logic and pro-duced images on a pixelized television screen, our game is designed around a simplified analogcomputer. It generates vector graphics which are displayed directly on an oscilloscope screen.As such, it is inspired more directly by the techniques used by “Tennis for Two”, which wasbased on an analog computer designed for ballistic missile simulations.We chose to recreate a tennis-like game in part because of the historical significance ofgames such as Pong and Tennis for Two–but …