Got a solenoid/switch question...

[Kayin]

I need to build a setup, small as possible, to actuate 4 solenoids attached to 4 touch switches. It would also need to display an LED to show a switch was depressed and one to show the actuation of the solenoid (so as to be self-diagnosing, and to provide feedback for damaged nerves.)

This setup is going on a French horn to let me play again with my adducted left hand after a pair of accidents in the past 12 months. So it needs to be battery powered and small, and as lightweight as possible. If I need exact weights of valves and such, I can get them for a friend who's donating horn expertise (he's a well-known custom builder, and married to a good friend of mine.)

Anyone know where to start or what I'm looking for? As it's rotary motion, let me know if I'm barking at the wrong tree...

[Trace]

I'm thinking:

A servo directly mounted on the valve

As far as touch switches, Two pieces of copper, one bent slightly up over the other that you could press to contact the other

[Kayin]

You think like me, but the LEDs? I'm losing all tactile sensation, I need the feedback...

[d_stilgar]

Do you want it to feel like the original experience as much as possible, that is, same hand shape and motion of the fingers, but requiring less strength? Or do you need something with tactile feedback, but new shape, design, etc to compensate for a lack of mobility/agility in the hand?

[Kayin]

The latter. My thumb drew up, and I have a lot less strength in the hand-which may drop to next to nothing.

http://www.servocity.com/html/hs-50_ultra-micro__feather_.html Anyone think these might work?

[d_stilgar]

I feel that servos are going to be too loud and too slow for playing. Your best bet is going to be using solenoids. I would design the solenoids to attach to a horn and press the levers linearly as normal. They would be attached to switches near the horn to activate them.

Depending on your dexterity and strength you will have to decide what kind of switches to use and where to place them. You are still going to need to hold the horn up and the transition will probably be easiest if the end result is similar enough to using a horn like you used to. I imagine the device being able to be removed or added to any horn, and only moving your left hand position a little up and to the left of the original place.

For switches I was thinking maybe modified electronic triggers from paintball guns? Maybe that's not very good. You could switch the thumb valve switch to your pinky if your thumb can't do it and then the triggers could all be in a row.

[Kayin]

I was told the same thing by Felix Cantesanu of Cantesanu Horns.

I'm considering a truly custom horn to allow for best placement of the servos and the wiring, batteries, and all necessary to do this. I've even identified a few good candidates, and there's some good cheap horns available that would be excellent donors to the cause on Ebay.

I'll draw up some sketches and post them tomorrow. It would take a LOT of work, but I do have some friends helping me with the horn side.

I've even been told it was possible to get a grant to do this. Lord knows I'd still stay cheap for failure's sake...

[Trace]

Kayin, some pictures are availible at http://thebestcasescenario.com/trace/horn

[Kayin]

Awesome, Trace. That design is even a lot like the ones I'm looking at...

[x88x]

I'm with d_stiglar, I think servos will be too slow and noisy. I would use rotary solenoids mounted directly on the valves. For the switches, if you want touch switches you'll probably want to have the touch switches control a very small voltage that switches transistors. That way you don't have the full voltage that the solenoids would require passing through the generally much more delicate touch switches (or your fingers, depending on switch design). It would be simple to run an LED or whatever to turn on when the solenoid is on to provide feedback. How far gone is your tactile sensation? Would, say, pager vibrators on each finger do anything to help or would that just needlessly complicate things? For the switches, especially if you're expecting even further strength loss in the hand, I would go with either touch switches or feather switches. Feather switches would have the benefit of having a noticeable movement when they activate, though that maybe be an additional problem if you have any dexterity degradation.