How to Find Flat Pressure Switches for a Wearable Keyboard?

[kb_designer]

Greetings everyone. Does anyone know of any flat pressure switches? I am trying to build a keyboard sewn into a shirt and have not found any suitable sensors. There are force sensors (like this one https://www.sparkfun.com/products/9375) but it would become too expensive for a full keyboard and apparently they are not very durable. I have also checked out piezo elements but as far as I know they can only detect taps, and I need to know if the user is holding down a button.

A third option is to use textile conductors (like on the peregrine glove http://theperegrine.com/product/) but that would not work for my application since it would require special gloves.

Obviously there must be a way since you can buy fabric keyboards but I don't know how they are designed?

Perhaps I could use a small capacitive surface/touchscreen on each key? (I cannot use just a single large capacitive surface for the entire keyboard because of the layout)

I could probably DIY a solution with two conductive layers and a isolation layer with a hole so that the circuit gets closed when the user holds down a button, but I don't think I could make that reliable. If possible I want to sell a few of these to friends and other fellow geeks and obviously don't want the keyboards to start failing after a while, so I think some form of piezo system would work best but I have not found any good solutions.

Any advice on this would be awsome!

 

[anorlunda]

It sounds like a membrane keyboard is a close fit. Those are typically sensing contact closure. Capacitive keyboards are also possible, but more expensive.

There are a few options listed here. Any of them could be adapted to fabric.
https://en.wikipedia.org/wiki/Computer_keyboard#Technology

But if you want to make your own invention, you'll have to evaluate yourself which technology works best for performance and cost.