i'm thinking up a way to let scientists get responses from people in brain scanners (MRI; I will write up a tutorial if I arrive at a solution and will put it here sciencestuff.xperiment.mobi). No electric devices are allowed in brain scanning machines. Past solutions rely on fibre optics (http://www.curdes.com/, http://www.pstnet.com/hardware.cfm?ID=91). Past solutions cost 1000s of dollars though!! Totally outrageous, considering that the fibre optic cables cost <30 dollars.
I'm convinced the Arduino can provide an elegant cheap alternative to these totally exploitive commercial products.
If you have experience with fibre optics, do you know what the electrical equivalent of buttons are in fibre optics? I guess that if one wanted to record from two buttons, you need 3 fibre optic cables, one to deliver light, the other two to send light down in some fashion if a mechanical button is pressed. Is this possible?
Alternatively, if the cables can be used two-way, a mechanical button could act to reflect light back down the fibre optic?
Or, a single fibre could be used with a mirror at the far end always reflecting light back down the cable. Buttons insert filters into the light. The arduino analyses the light spectrum to determine what filters have been applied.
Would much appreciate your advice on this Fed up of exploitive companies ripping off academics... grr.
I have no experience with fibre optics in medical use (we use them for muxed video streams) but the first thought was 1x sender cable with laser/IR transmitter and 1x receiver cable per switch. Switch will have a thin plastic blade that enables/blocks the light across a narrow gap in the optical cable. Arduino will poll the receivers and do something if it's state changes.
Sounds like a job for someone with a 3D printer.
IIRC, you could have different colors in fiber optic cables, and use blue for signal 1, red for signal 2, etc. It would depend on how specific your sensor and lasers are how many different combinations could be used.
However, I would imagine the obvious way of doing fiber would be out, since you don't want the electronics for the light source in the MRI room when you press the button. I could imagine two fiber optic cables per switch. The first has the laser that provides the light source. It goes to the MRI room, and then you have a physical switch that blocks or unblocks the light, and connects it up to a second fiber that runs back to the electronics lab where you have a sensor to convert it back to digital (both cables need to be shielded, particularly from each other).
I recall that pin-hole cameras can project an entire (upside down) image of a scene onto a screen. Can such 'analog' images be sent down a fibre optic wire? In which case, consider that a QR code type thing could be sent down the fibre, selected portions of that image could be blocked by 'choppers' (or more likely, some rod that is lowered into the beam when a button it pressed) and then the arduino does some nice image analysis.
Here's a fiber optic keyboard costing 8000 dollars... so it must be possible!
Fed up of exploitive companies ripping off academics... grr.