I've just read an interesting bit about how much more engaging kids
found a QRIO robot when it reacted to touches on its head, arms, and
hands. Here's a video:
And here's the story:
My question is: how do its touch sensors work? Its head and arms look
like hard plastic or metal. Could be that they have panels floating on
microswitches, but I wonder if it's something else, like capacitance
sensors or some such. Anyone have any ideas?
These should be fairly self-discoverable using a Yahoo or Google search.
Most work using a resistive pad and rubber that is semi-confuctive (like
the kind used in remote control buttons), but others use a capacitor
For homebrew, a lot of people have created large area pressure sensitive
plates using anti-static foam. A sheet switch is the same, except that
it has a Schmitt trigger or comparator to create a definite on/off
transition, rather than an analog reading.
One would think, but my google-fu is failing me today. "Pressure
sensitive rubber" comes up with a lot of hits, but all at the research
or patent stage -- and I know from past experience that there is a lot
of fairly useless nonsense among the patent records, and a lot of
research articles that never lead to useful devices (though you'd have
to spend a fair amount of time studying each one to figure out why).
A search for "sheet switch" produces similar results. The same term is
apparently used for a lot of not-quite-the-same things, that operate on
So my question wasn't so much "how might this work" -- since you're
right, Google provides many answers to that -- but rather, "how DOES
this actually work, in the Qrio robot?" I find it instructive to see
how real, working robots solve problems, as opposed to things in the lab
or patent office that might or might not work under real-world
But apparently nobody here knows exactly what Qrio is using, which is
fine. I just thought it worth a shot; I'm used to others knowing a lot
more about robotics than me. :)
Yeah, I've considered that too. But that's more of a pressure sensor
than a touch sensor; it wouldn't be likely to register gentle touches,
but would instead require a respectable squeeze.
Sometimes you have to get creative. So you start with terms like
'pressure sensing rubber,' then note that some of the links talk about
conductive rubber, so you follow those, and eventually you get to some
pretty standard technologies related to detecting "touch" by creating a
flexible conductive rubber over a matrix of contact points to create
individual small switches. Lo and behold, you see some of the
manufacturers of these products call them membrane switches, and you can
use that phrase for further searches, and so on.
From there, you see some of these work by resitance, some capacitance,
and I'm sure some might work using some more esoteric approaches, like
optical or even acoustic. (I can imagine a touch matrix using deformable
fiber optics and a small laser to create a coherent light source. Maybe
someone has already thought of this, maybe not, but that's what the
Mother of Invention is all about.) If you're wanting to recreate such a
"skin" yourself obviously the lower cost approaches (e.g. resistance)
will be preferable.
Google may return the patents hits first but only because some of those
sites have been good at spamming Google's database. Be sure to try some
of the other search engines, as not all spam techniques work equally on
all the engines.