The Armillary Sphere

Point to your favorite celestial object!

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Inspiration

Being limited to our own views on Earth, it can be difficult to comprehend the various locations and distances of celestial objectives relative to our own positions.

Taking inspiration from 3D globe designs, we have developed an Armillary Sphere capable of visualizing to users the direction of celestial objects.

What it does

Pick a celestial object you want the laser to point to, and the servo motors and stepper motor will move accordingly. The user is thus able to visualize the relative position of the celestial object, as well as view its distance.

How we built it

  1. Idea Brainstorm - We went through many ideas to find a project both interesting but also implementing our main skill goal: successful integration of mechanical, software, and hardware subteams. When we finally decided on an armillary sphere, we first outlined our constraints (e.g. parts available, budget) and requirements (laser must move 360 degrees) in a google doc design journal.

  2. Drafting Ideas - During this phase, we listed out the potential technologies to be used as well the tasks needed to be done. We intended to make use of NASA’s Horizons API, Pyserial, Python, Arduino, custom 3D printing, and various hardware components. To ensure streamlined workflow, we separated the needed tasks into individual sectors: software API calls, hardware for controls and movement, and lastly mechanical to handle the integration of both subteams.

  3. Building - We each took charge of each of the three respective subteams in order to ensure deadlines would be met. Software handled correct API calls and data parsing needed to acquire the positions of celestial objects. Hardware handled the movement and functionality of the physical armillary sphere. Mechanical was responsible for the integration of software and hardware through 3D printing. All were combined in order to deliver the project’s functionality: pointing to various celestial objects acquired from NASA datasets.

  4. Calibration and Bug Fixing - During this minimal, yet important phase, the team ensured the project’s consistent functionality. One of hardware's biggest challenges that we solved was communication from software (given angles) to controlling the actual servo motors.

Challenges we ran into

Challenges were mainly in relation to the design of the armillary sphere. The team needed a design that could house a laser and provide for full 3D rotational capability. Additionally, as the motors only had a shaft, we had to 3D print custom gears (1-1 ratio) to ensure that the armillary sphere would move in correspondence with our hardware. Another problem was tolerancing during 3D printing -- each concentric ring had to align perfectly with each other at different heights in addition to the laser housing requiring to be nested through the rings. We put heat set inserts through the laser mount to solve this. After figuring out the right tolerance and print settings, another challenge was how to mount the servo motors, which was achieved through having standoffs and M4 bolts running through the vertical supports. Through referencing step files for motors, youtube videos, measuring with calipers, and repeated iteration, we were successfully able to design the armillary sphere.

In addition, there is difficulty in processing how to point toward celestial objects. The team realized that there must be a relative “front” and “base position” of the sphere in order to properly locate celestial objects. The NASA API call received Azimuth/Elevation coordinates in relation to true north. Thus, it is required that our sphere has a front base position that faces north in order to have accurate locational capability.

Accomplishments that we're proud of

We are really proud of our Armillary Sphere CAD. We could've done a simpler build, like an arm, but it wouldn't be as fun as our current sphere.

What we learned

  • CAD!
  • Better tolerancing with 3D printers
  • Armillary Motion

What's next for The Armillary Sphere

Many things can be done on both software and hardware sides:

Software: More robust exception handling can be implemented to handle errors when making calls to NASA API or for the user’s geolocation. In addition, even more celestial objects and their IDs can be added as options for locating.

Hardware: Better motors in replacement for servo so angle calibration is less arduous.

Mechanical: Designing a base plate needing less filament but still ensuring complete stability and reliability

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