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This may seem like a silly question, but while we've all heard of touch-screens, I'm looking to build/prototype a device with a touch-surface (no screen) that can register up to four distinct points of contact (finger presses), but I have no idea what I should be searching for!

I realise a big part of touch sensing and gestures is implemented by software, but presumably there is some hardware first of all. But so far I've only found plain touch sensors, which register only that they were touched, and possibly a measure of force, rather than the kind of locational information I'm hoping for.

If what I'm looking for is a single piece of hardware (the sensor itself) then I'd love to know what the most correct term would be. Otherwise, if what I'm looking for actually needs to be constructed from several parts, then I'd love to know that too.

In addition to the general answer, I'd also appreciate any specific recommendations. My particular requirements are at least 3 finger tips registered, ideally with enough detail that I can ignore things like resting fingers. I probably need to be able to put it beneath 2-3mm of glass or perspex, and ideally I need to be able to make it curved, though if I can just make the surface on top curved then that's fine too, but likely requires a higher tolerance for surface thickness.

Lastly; if anyone reading this has a high enough reputation, then we could probably do with a touch-sensor tag, as both touchscreen and touch-panel seem more specific to a display surface.

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  • \$\begingroup\$ What you are describing is sometimes called Touch Pad. \$\endgroup\$
    – Nick Alexeev
    Feb 11, 2014 at 20:32

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Digitizer or touch screen/panel digitizer.

You can find them as replacements for small LCDs. For example, but these may not be suitable for your multi-touch requirement, and getting application information may be difficult.

They're typically laminated onto the LCD display, and can be removed safely with a controlled temperature hot-air gun (and care, they're usually very thin glass).

enter image description here

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  • \$\begingroup\$ Thanks for the response! Are digitisers always flat glass or is it possible to get curved ones? If they don't come curved, do they have any tolerance for surfaces being placed on top, for example if I wanted a curved surface could I apply it on top of the flat digitiser, then simply adapt my software to account for the change in shape? Is there a limit to how deep this top layer could be? I'm thinking for an application similar to a touch mouse. \$\endgroup\$
    – Haravikk
    Feb 13, 2014 at 20:34
  • \$\begingroup\$ Some (the plastic membrane type) are flexible (like a sheet of plastic), but that means they could fit on a surface curved in one dimension, not in two. You can put anything on top (resistive type) not much on top (capacitive type) or maybe a few mm on top (non-resistive stylus type). \$\endgroup\$
    – Spehro Pefhany
    Feb 13, 2014 at 20:40
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It's known as a "digitizer". You'll need a controller as well. For a oneoff it may be easier to remove the screen from a touchscreen device.

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Recommendations are the Semtech SX8649. It's a capacitive touch screen controller suitable for 8 buttons (cap touch pads). The data sheet even tells you how to implement them. I note that this is not for use in front of an LCD so I think it's a very applicable document: -

enter image description here

I think you should look for "capacitive touch screen controllers" if you wish to find others.

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