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Finding a switch
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Please be positive and constructive with your questions and comments.

Finding a switch

by bradenraden on Fri Oct 15, 2010 1:08 pm

I'm looking for some advice on a switch. It will end up being embedded in a soft gelatin or silicone "foot", next to an LED. It needs to fit in a pretty small spot, under about 5mm*15mm*30mm.

I tried out this switch http://www.radioshack.com/product/index.jsp?productId=3190382, but that failed. Well, the second one failed after I melted the first one with my amazing soldering skills. It failed because the switch needs to be "activatable" from many angles, and it needs to be very sensitive. And it took many tries and different angles to get it to activate. Users will be squishing the LED embedded in the "toe" to get it to go out. Think squeezing your thumbnail to make it turn white. Or one of those toys that you squeeze the hand to make music play.

The only thought I've had is putting an air bubble in there and somehow attaching an air pressure activated switch, but I've been unable to find a switch to suit my needs.

Anyone have any advice to offer?
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Re: Finding a switch

by adafruit_support_bill on Fri Oct 15, 2010 1:19 pm

QTC 'pills' would be my first choice. They are rubber disks that conduct electricity under pressure: http://www.msa.ac.uk/~fraser/wiringpg/files/p001v004.pdf
Zoflex is also a good option. It is available in a variety of shapes and sensitivities. http://cnmat.berkeley.edu/resource/zoflex_conductive_rubber

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Re: Finding a switch

by bradenraden on Fri Oct 15, 2010 4:37 pm

Thanks for the leads!
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Re: Finding a switch

by chatham on Sat Oct 16, 2010 3:07 pm

I don't know if this would be the most reliable solution out there, but it's just a thought. Would it work if you made a cavity inside the foot, then put a piece of foil or metal along the top and the bottom of the cavity, then attached wires to them? That way, when the foot is stepped on, the metal touches, and when the foot isn't stepped on, the silicone has enough resilience that the pocket opens back up, separating the metal? I guess the biggest concern would be whether or not the silicone cavity would reliably open back up when you stopped stepping on it...

Just a thought! I make no claims to the robustness of this idea! But I did make Dance Dance Revolution pads years ago that used metal plates held separate by weather stripping as pressure plate switches years ago, and they were pretty robust...
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Re: Finding a switch

by bradenraden on Mon Oct 18, 2010 8:51 am

That sounds like a fun solution. I'm not the best at mold-making and casting so it would probably take several tries to get it right.
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Re: Finding a switch

by chatham on Mon Oct 18, 2010 2:36 pm

Just another quick fabrication thought - you could make the switch first, as a smaller unit out of your silicone, then once you get that working well, take a working unit and cast it inside the full foot.
OpenChord.org - Open Source kits to let you play Guitar Hero with a real guitar, or build your own Wii/PS3/USB controllers.

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Re: Finding a switch

by richms on Tue Oct 19, 2010 1:30 am

how about making it hollow and check the pressure?

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