HOW TO - Servo as input device

Matt Mets made this neat video about using a servo motor as an input device for keyframing a robot animation. He writes:

By reading the voltage from the center pin of the the servo's potentiometer, it can be used as an input as well as an output device. Basically, you get a bunch of extra positional sensors 'for free'. Some things that I could see this being useful for are:

1. Collision detection on unpowered arms (or even poor man's torque detection by measuring the difference between what you requested and the actual position, assuming the servo doesn't break).

2. Physical keyframing; you move the arms of the thing you are animating manually, then press a button to record that position, repeat a number of times and then have the computer play it back (see video)

3. Haptic feedback, if you can control the servo fast enough (doubtful, but worth a try).

Servo as input device for programing robot movements - Link.

Posted by Becky Stern | Feb 11, 2008 07:00 PM
DIY Projects, Electronics, Robotics | Permalink | Comments (7) | Email This | Bookmark and Share | Digg this!

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Posted by: John Ballinger on February 11, 2008 at 8:20 PM

Awesome. That is actually cool. Thanks for sharing. I am now starting to think what I could make with this? Anyway thanks for the video.
John.


Posted by: Russ Nelson on February 11, 2008 at 10:37 PM

Don't you want to measure the error output from the comparator in the servo, instead? That tells you how hard the servo is working. So if you push on it, then the software can move it in the direction of the push. Plus, you're not reverse-driving the servomotor, which can be hard on the gearing.


Posted by: broos on February 12, 2008 at 12:16 AM

I can see some potential using this for a cnc machine.
You could try to make some sort of an on the budget touch probe and use those saved data to make replica's of excisting objects!


Posted by: Hackius on February 12, 2008 at 3:03 AM

All HiTec digital servos have position reporting built in. Why would you not use that?


Posted by: worf on February 12, 2008 at 3:17 AM

great nerd.
i remember that technique once was called "teach in".
for robots.


Posted by: jean-baptiste on February 12, 2008 at 11:18 AM

maybe you can do something like Topobo http://www.youtube.com/watch?v=50JdK_K2NWk


Posted by: Matt Mets on February 12, 2008 at 11:54 PM

That Topobo toy looks awesome!


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