Picture of Foil Capability Switch
In Assistive Technology, one of the major areas that is considered for people with significant disabilities is switch access.  Using a capability switch or accessibility switch, someone can control their environment, play with a toy, use a computer, or communicate.  All manner of switches are available commercially - switches that work on mouth pressure, fingers, muscle twitching, pulling, pushing, etc.

The problem is that special needs are - by definition - special.  You do not have to work in this field long before you encounter a client whose needs can not be met by an existing product. 

The foil switch allows for rapid customization of switch access.  It allows for prototyping abilities not found in commercial products.  The therapist can quickly (in the field) evaluate many different sites for switch access and experiment with various ranges of motion.  It also means that a therapist can make a switch custom-tailored to an individual.   The user can become the switch.

The foil switch activates with an extremely light touch, which is great for clients with low muscle tone.  It is also very cheap to make - it costs about $1 for a switch (some commercial switches cost hundreds, but most are under $100 USD).   It follows a "make once, use many" approach - once the wiring harness is made, it can be reused again and again and be instantly customized by changing the shape of the aluminum foil.

Over the years, it has proven itself to be an extremely versatile tool and we have used it with many clients, both adults and children.

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swildman1 year ago
I have a very different comment. I think it AMAZING what you do for these people. I always feel so bad for people with disabilities that can't express what they are feeling or thinking or what they desire. You give them a voice! I think that's amazing!!! Thank you!
I feel the same way too. My brother is autistic, but he is learning.
Dylon12412 months ago
what is this supposed to do? Just use an arduino
shadowwynd (author)  Dylon12412 months ago
This allows someone with limited movement to turn something off or on. It is just a switch. By itself - it does nothing. Paired with the right technology, it allows someone with very weak muscles to communicate, to use a computer, to change channels on a TV, to play with a toy, or use ....... whatever (including, I suppose, an Arduino). The advantage is it is incredibly cheap and incredibly versatile. There are many switches on the market that cost $$ or $$$ and do not work as well as this for certain people.
silvaticus1 year ago
Thank you for this! I work at an ICF-MR. Customization balanced with cost is always an issue. I will using this!
billbillt1 year ago
great work
Kiteman1 year ago
Since you wrote this, conductive thread and paint have become more widespread - have you thought of incorporating those in your custom switches?
shadowwynd (author)  Kiteman1 year ago
I have tried conductive thread a couple times. It works for some people and some instances. We tried conductive thread with a glove (touch fingers together, etc.). The aluminum foil worked better in that case.

I haven't used conductive paint yet. I have tried using graphite (pencil lead) on some things before with mixed results.
RooMooJoo1 year ago
Great idea! I was using micro-switches, which can't always be put to purpose in certain situations.
juiceman742 years ago
I had my 6 graders make games and type writer application with similar switches.  We used Picoboards (I bought individual boards for $70).
10x for the great contribution.

BTW - do you have an idea how to make a spindle switch that turns on with centrifugal force?
use a top that light up?
what kind of top? I didn't understand you.

Thanks for the reply.
kids toy that lights up on spinning similar to or a duplication of a tilt switch. ballbearing is in a slide as it spins the force pushes the ball bearing into the end (cup) and it shorts the edges ligting up the top.

you could do same I guess.

short plastic tube seal one end at switched end embed two (or six every other one is half th eswitch , so no matter how the ball goes in it works) wires either side of tube mounted at upward angle , as it spins ball moves up shorts the leads, like a mercury switch.OR Use two pieces of printed circuit board in shape of a Vee at the action end and it should work quite nicely

If it has to work in any position while spinning it must be spring loaded so the ball can move freely ONLY when spun.

Duncan used to make tops that lit only when spinning , if the top has an on off switch and is not spin activated the switch won't work. Those switch quite a bit of rotational speed to function.
shadowwynd (author)  juiceman742 years ago
I assume (you could do it the opposite way also) when stopped, no contact between conductors.  When rotating with enough force, contact is made between conductors.

My first thought would be to look at a couple technologies:

Tilt Sensor (anti cheating) for pinball machines

Steam flyball governor

In the first, gravity normally separates the contacts when the machine is upright, contact is made when tilted.  In the second, the governor is placed on a rotating shaft.  The balls get further apart the faster the shaft goes. 

If the direction of shaft rotation is perpendicular to gravity, a couple options come to mind.

First, you could make the pinball tilt sensor, but connect the plumb bob to a vertical rotating shaft with a spring.  Use a slip ring to transmit electricity to a collar that is soldered to the spring.The spring will be partially mounted on the vertical shaft.  When the shaft is stopped, the spring will hang straight down due to gravity.  When the shaft is in motion, the weight will move sideways, the spring will bend sideways, the spring will contact the ring, thus closing the circuit.

You could also make something similar on the edge of a flywheel.  A contact spring bends outwards when the wheel is spinning and touches a contact plate, then returns to an upright position when stopped.

If you can find a glass-tube mercury tilt switch (from old A/C control units, etc.) that would make an easy tilt switch also.

You could have a weight (non-conductive) attached to a spring in a tube or track.  When the rotation is stopped, the weight is near the center.  When rotating, the weight slides down the track and presses a button (commercial switch).

You could have a piece of metal in a nonconductive track, attached with a spring to the center of the rotating object.  When there is no rotation, the spring keeps the metal near the center.  When rotating, the metal slides down the track and bridges two contacts, OR the metal weight is electrified and thus is the other contact.

These would also work if you had a horizontal rotating shaft, but you would need to make sure the spring is stiff enough that it does not touch due to gravity, only rotation.

Shadowynd, Thanks for the interesting ideas.

I'm in the direction of the more simpler suggestions you gave. In the attached picture I've drawn my idea. I still need to check it out.

Kid's toys use a spring that bends with force with spin and creates contact with another meta which short circuit.
What is the idea behind the horizontal rotation shaft?

centerfugal switch.jpg
glue conductive foam to a non conductive glove, then hook a wire to each finger, if you use resistors in series with each finger and all are different you could make a circuit that does yes/no maybe, or on off up down etc. If the client can use the fingers you got it all 4 in parallel gives a fifth ohm rating and the "reciever" can dope them out, and activate different things.

if you like complete digital use a source for 4 different square freqs and a reciever to see them , and outputted to various devices.
foobear3 years ago
very interesting