OT: switches

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#1
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I'm putting together an application that needs 9 push buttons going to AVR input pins. I need them to be silent and reliable as well as looking professional. I've tried several types but haven't found anything suitable yet. Any recommendations? Preferably a European supplier. TIA.

Ralph Hilton

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You have a lot of choices to make first.

Mount through a hole in a metal panel?
Mounted on PCB behind flexible panel?
Mounted on a PCB behind plastic buttons?
Keypad?
Sealed? Water resistant like a phone? Open like a PC keyboard?
How big?
How much force?
How often to be used? (100 times per hour for 10 years or twice a day for a year?)
Lighted?
What kind of marking? Logos, digits, whole sentence, pictures?

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The coolest "pushbutton" inputs I've found - and taken quite a liking to - are capacitive. No moving parts, no chance for ESD to creep in, "sealed", and all I do is use the front panel label to denote switch borders. I have been using screened front panel overlays and the things are very professional looking.

Please note - this post may not present all information available on a subject.

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refields wrote:
The coolest "pushbutton" inputs I've found - and taken quite a liking to - are capacitive. No moving parts, no chance for ESD to creep in, "sealed", and all I do is use the front panel label to denote switch borders. I have been using screened front panel overlays and the things are very professional looking.

This does sound very interesting. Where does one get this type? I did not notice it in digikey, for instance. Maybe I looked in the wrong places.

I take it that since you label the front panel to denote the borders that there are no actual borders? Maybe just no palpable borders.

Right now I use a 4x3 keypad, but I would be happy with something else too.

-Tony

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All the pre-built capacitative switches I've seen have been quite expensive. If you want capacititive switches you're probabaly best building your own with Quantum's QProx chips (http://www.qprox.com/)

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The physical part of the switch is nothing more than an electrode behind your front panel. This does restrict you though - your enclosure needs to be plastic. The border is just the practical limit to where you get activation. For my stuff the switches are separated a bit from each other so I just adjust sensitivity to get good activation and don't have to worry about crosstalk.

With a 4x3 style keypad, you'll need to trade off sensitivity and touch accuracy with electrode size.

One other issue with the capacitive switches is you lose board area to the switches or need to do the equivalent of a membrane keypad - just no physical activation.

Please note - this post may not present all information available on a subject.