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A Humanitarian Engineering Problem
zrosener asks: "A have a friend who has ALS (Stephen Hawking's ailment), a particularly nasty disease in which her motor neurons deteriorate over time, slowly waylaying her. She is in pretty bad shape now, and her movement is restricted to moving her eyes, and very limited (1 inch in each direction) hand movement. She has very light bell that she uses to wake up her husband when she needs assistance, but as her strength wanes it is becoming less and less effective. She is afraid at night now that if something were to go wrong she would not be able to rouse her husband. My challenge to you is to design a noise-making-husband-alerting device cheaply and quickly assembled from strip mall parts (Radioshack, Walmart, etc.) that she could use with her extremely restricted movement. Buttons are out of the questions, as are anything that requires gripping. Analog answers are encouraged too! Please email all suggestions or post them."
Possibly even easier, depending on teh reliability of her muscle control, is a pair of finger cymbals. Each is connected to one side of the wire - tap them together, on it goes.
I used to work at Dynavox -- they make augmentative communication devices for people who have ALS among other ailments.
While most people accessed the devices (made them talk) by touching the touch panel, some people used sip/puff or optical switches (among other types of switches) to activate the devices.
The tash mercury switch bottom of this page might be an option, also look into proximity switches.
Take a piezo buzzer or Sonaralert (if you want something LOUD) and wire it to a standard-issue microswitch. You can get microswitches with actuators that are a short piece of metal about the size of a ball-point-pen clip. Actuation force can be VERY tiny (grams) with motion as little as 1/8 to 1/4 inch.
Some versions with cat-whisker actuators are also avaiable, just a bit of wire sticking straight up that you give a push in any direction. You can build something similar out of a couple of paper clips if you want REAL cheap.
You could add a latch/time circuit so you wouldn't have to keep the switch depressed, ie: a quick press would sound the alarm for some set period of time.
There are also preassembled photosensors with a light source and sensor and a gap between the two, stick a finger between them and it triggers, zero force required.
I've also seen the microswitch thing work as a blink/squint sensor. You stick the wire actuator to the skin above/below the eye and a good squint will trigger it.
One last idea, shine a low-power IR led at the corner of the eye, read the reflection brightness with a photocell. Now looking to that side causes the colored part of the eye to reduce the reflected light, triggering the sensor.
The biggest problem with running something off the eyebrow or eye look/blink is usually preventing it from going off by accident, or if the person goes to sleep.
There are also devices that actuate by sucking/blowing on a straw or pushing with the toung or chin...though these don't work so well if you're on a respirator.
Milo from Kangaroo Koncepts
I have seen those buttons often in elevators here in Europe, they don't need any pressure, just touching them makes a difference of potential, between the button and ground and activates a very simple circuit with an Operational Amplifier and a transistor. The only drawback is that they don't work with globes or with dielectric matherials. (Skin is obviously ok). So I think those are cheap and easy to get. In order to be useful: a buzzer should be attached to the switch ( a domestic buzzer will do ) or to a electrical switch if the buzzer exceeds the amperage of the presureless switch. I think it would be interesting to make it able to use a battery just in case the lights go off and she has to call for assistance. Assembling the parts shouldn't be difficult. I hope it helps. Pedro Larroy
I suggest a portable biofeedback monitor. My GF uses one for muscle problems. They have a light, relatively small sensor that can be taped to the skin. When the muscle underneath is tensed, the alarm goes off - and the trigger level is widely adjustable.
The device she uses is walkman sized and cost about $500 from a company in Canada. The brand name is Myotrac.
Any working muscle will do and the thing is very sensitive, with gain as well as level controls. And very easy to use. Google turns up lots of hits, here's the manufacturers URL: http://www.thoughttechnology.com/myotrac.htm
As a bonus, the engineers answer the phone and will gladly discuss your intended use.