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The Rotating Globe Using Atmel Mega163




Introduction

For years scientists and scholars alike have been plagued by one common obstacle which, until now, has proven to be impossible to overcome.  How do you find the country you want on a globe?  Sure, the easy answer is to just use the longitude and latitude coordinates, but really, that’s quite confusing.  Some may even say to just do a web search to take a look at the country, but this really doesn’t have the convenience we’re looking for, and could potentially take hours or even days to finally get an answer.  This is why we’ve developed a globe that will spin and point to 1 out of a possible 11 countries you wish to see.  This may not appeal to some, but we feel that for a generally useless gadget that can possibly make a difference in about a dozen peoples’ lives, nothing can beat “The Rotating Globe”.

The Rotating Globe Using Atmel Mega163

The general concept is simple.  We asked a friend to name the first gadget that came to mind and he said, “I want a globe that will spin to any country I want”.   So, we delivered.  Using an Atmel microcontroller, and few motors, and a lot of scotch tape, we make one of the greatest contributions to educational technology ever invented by make a globe that will, indeed, spin to any country you want.  The result is a system that is both educational and mildly amusing.

Spring 2002 Gmouse

High Level Design and Objectives

The user can either enter a country’s ID number or a longitude and latitude value into the keypad and the globe rotates to the desired country.  The country’s name, longitude, and latitude are then displayed on the LCD screen.  One motor rotates the globe to the correct longitude and the other motor moves a pointer to the correct latitude.  The microcontroller stores the present location of the globe and steps the motors the shortest distance possible.

 

We decided to sacrifice motor strength for stepping accuracy.  Consequently, a pointer is used to indicate latitude instead of spinning the globe because the stepper motor is not strong enough to spin both the mass of the globe and the other stepper motor.  The axis of the globe was placed at perpendicular angle to minimize the amount of mass the motor needed to move.  A slow stepping speed was also used to ensure that the momentum of the spinning globe does not cause a skipped step.

Summary of Operation

After powering on, the first operation is to calibrate the machine.  By pressing ‘0’ followed by a ‘#’, the machine enters a calibrate mode which allows the user to give the globe an accurate starting place.  Generally, the pointer will move up to the equator, and the user can manually turn the globe so that the pointer is on the Prime Meridian.

Once the machine is calibrated, the user had two options: either enter a country code, or a specific latitude or longitude.  If a country is desired, the number entered must be one of the codes already programmed, followed by a ‘#’.  Numbers entered that are followed by a ‘A’, ‘B’, ‘D’, or ‘*’ will cause the globe to spin and/or point to the corresponding latitude or longitude entered.  We assume the user will only enter valid coordinates.

 

For more detail: The Rotating Globe

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