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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.
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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We developed this switch when working with a little boy who had Spinal Muscular Atrophy (SMA). The only movement he could make was moving one finger about 3-5 mm. He had practically no muscle tone at all. He normally laid on his side and used a ventilator to help him breathe. We tried all the commercial switches we had (a sizable amount), but he couldn't use any of them. The membrane switches (very light pressure required) were unusable because he couldn't generate enough pressure to use them. Some of the other switches, such as the beam breakers, worked but hampered his breathing because they rested on his ribcage (he had no intercostal muscle control), so they couldn't be used because of the difficulty in mounting them and the interference with his breathing. He was able to use the aluminum foil switch easily to turn toys on and off. It was fantastically light, activated with bare amounts of pressure, molded its shape to his chest, did not impair breathing, and succeeded where $600 switches had failed in the previous evaluation.
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10x for the great contribution.
BTW - do you have an idea how to make a spindle switch that turns on with centrifugal force?
My first thought would be to look at a couple technologies:
Tilt Sensor (anti cheating) for pinball machines
http://electronics.howstuffworks.com/pinball-machine4.htm
Steam flyball governor
http://www.history.rochester.edu/steam/thurston/1878/chapter3.html
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.