Adding position control to R2’s dome

It’s been a while since my last update because the skins have been going slow. It’s a lot of taking things apart and putting them back together again.

I finally have something worth sharing. I have been thinking of how to make R2’s dome position controlled. Up until now it has been speed controlled. Why bother you ask?

  1. I have a camera in the dome that I want to be able to aim while I am remotely monitoring it (via iPhone of course)
  2. To make R2 seem more lifelike by aiming his eyeline in a certain direction
  3. To make remote controlling it simpler

Here is a quick video I put together:

Here are the parts of the system:
– Banebots dome drive from Atomic Pickle
– Pololu.com JRK 12V12 motor controller
Softpot rotary variable resistor
Softpot actuator/wiper

The position of the dome is monitored through the softpot resistor. I had to make a small custom plate out of 1/16″ lexan that is the outline of the softpot with tabs on the side. The softpot is stuck to lexan and the lexan is screwed to the top COM8 frame ring. I drilled and tapped a hole in the dome plate so the wiper touches the ring part of the softpot.

Here are a couple pictures of the position feedback. In the first picture you can just barely see the wiper white tip touching the softpot.

In this picture you can see the tan softpot ring and wires hanging off the middle of the top frame ring.

The wiring is pretty simple but the software to configure the JRK 12V12 motor controller is pretty extensive.

You may notice the dome seems a bit sluggish. This is due to a few reasons.

  1. The dome slips when changing directions due to the o-ring slipping on the Rockler bearing.
  2. I have not optimized the setup of the motor controller yet. I need to tune the system to optimize the performance a bit.
  3. The motor controller is not turned up to full power yet (450/600). I wanted to play it safe at first and avoid burning it out.
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3 Responses to “Adding position control to R2’s dome”

  1. Björn Giesler Says:

    This is awesome. I just ordered the same components (softpot and wiper) for my droid; this is much simpler than the optical encoder solution I first had in mind. Thanks for the inspiration!

  2. Tommy Says:

    Exactly what seriously influenced you to publish “Adding position control to R2’s dome Glenn’s Astromech Weblog”?

    I personallyreally enjoyed reading the post! Many thanks
    -Preston

    • ggpipe Says:

      The purpose was to allow R2 to follow people faces with its eye. The position control was the mechanical aspect of it and the other part is a camera behind the eye that does vision processing to detect and track peoples faces.

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