Weird touch sensor question

[robotAtTransy]

Once, years ago, I read an article that described a rather neat (in my mind, at least) touch sensor design.   It was a ring that was mounted around the middle of a robot; the ring was made in such a way that when a contact was made with it, the software could calculate where on the ring the touch occurred.    This was not done with multiple touch switches;  it relied, instead, on the electrical characteristics of the materials that the ring was made from.   I thought it was a capacitance based system. 

However, I am unable to find the article and I am unable to find any references to such a sensor.   Maybe I dreamed it :-)  Weirder things have happened.   But, I figured there's always a chance that someone on this forum has some idea of what I am talking about. 

To recap---imagine a ring of some sort of material.   A current is running through it being measured by the software.    When something presses against the ring at a certain point, the resistance/capacitance/something changes which can then be used to determine where on the ring the contact occurred.     So, you get a 360 degree bump sensor.

any help?   anyone? 

thanks,
kenny

[jwatte]

There are "touch sliders" used for certain light dimmers that I think work similarly.

However, those sensors rely on the touch being by something like a human body. A stick of wood or metal won't work, because of the sensing technology involved (capacitive IIRC.)

Is your goal to have omnidirectional bump sensors for navigation, where you'll bump into walls, furniture, pets, etc?

[robotAtTransy]

This was an omnidirectional bump sensor; it would detect any substance.    As I researched trying desperately to find it, I realized that capacitance
was probably not the technique since all the cap. sensors I ran across were, as you said, for flesh.   :-(   Still looking.

thanks,
kenny

[Duane Degn]

I've seen this done with Soft Pots. Here's a link:
http://forums.parallax.com/showthread.php/132260-Smart-Bumper-for-Robot?p=1009763&viewfull=1#post1009763