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Comments on What type of button is this on a remote control

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What type of button is this on a remote control

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The remote control of my TV has two kinds of buttons. There are "normal" ones for the digits etc. which work by bringing a conductive material on the underside of the button in contact with the board of the remote control to establish contact.

And then there are these round silver buttons in the centre for the remote. One pushes their curved surface down to bring it into contact with, presumably, a contact below (not visible from the outside).

Photo of the board of the remote control. In the centre are 9 round silver buttons

How is this later type of button called? I don't need a specific part name or number, just a general category name would be helpful.

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It is interesting to see how they deposited these carbon electrodes over solder mask and copper traces both under the button foil switches and membrane switches alike which offer more tactile feel. Both offer capacitance changes to non-conductive switches. The membrane switches are mounted on their own clear insulator laminate.

All sensors are configured in a matrix for typical scanning mode typically by a single IC interfaced to a low-budget uC.

The advantage of capacitance switches are better reliability and silent operation except for the sealed membranes which give better tactile feel. Using an audio range signal the sensor IC easily detect the reflection of signals when the gap is reduced < 1mm with programmable sensitivity.

How they chose the need for tactile membranes over the printed fingers must have been based on the frequency of fast operations to reduce false negative operations with the benefit of tactile response.

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Not necessarily capacitive switches. (2 comments)
Not necessarily capacitive switches.
Olin Lathrop‭ wrote 9 months ago

You are assuming the domed buttons are capacitive switches. Maybe they are, but I wouldn't rule out that they are simple mechanical contacts. In all the products I've worked on that had these kinds of domed buttons, they were just switches. The on-resistance was up to about 200 Ω or so. I connected them between ground and a microcontroller pin with internal weak pullup, with debouncing in the firmware.

TonyStewart‭ wrote 9 months ago · edited 9 months ago

My assumptions were based on analyzing the photo of the transparent substrate that the membrane switches were bonded to without any conductive traces. Yet on the same side below them was the carbon printed traces connecting the domed membranes beneath the clear substrate. It is true that membrane switches can be conductive but in this case I see no tracks. Perhaps they were if the clear substrate has holes under them to make contact.

I could be wrong, but then maybe not. https://dgniceonetech.medium.com/features-and-advantages-of-capacitive-membrane-switches-db1933d1f74b

It's hard to analyze a 3D layout on a 2D photo.