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So I've started working on a small project (small at the moment) and I'm seeing some issues in my prototype plans, and I need your help with this.

Short answer: I need a led touchscreen with NFC capabilities. I made a figurine (kind of those you see for games like Skylanders,...). It has a built-in NFC plate that is setup correctly. Now my problem is, when I place that figurine on the screen, I need to exactly know where it has been placed. This could be done really quickly if there was only one figurine, not even an NFC tag needed if the touchscreen can detect the figure.

Now the problem is, I need to know which figurine has been placed on the screen, and on which location. Kind of a live feedback of where everything is actually. Is this duable in any way?

I was thinking of a think touchscreen and then 40-50 NFC tags underneath it to cover everything but I don't feel like that is a good idea. And it will not be very acurate.

Trisma
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  • you maybe able to use an IR touch screen, to detect where the figure is, on 2 edges there are emitters, and on the opposite, there are detectors. forming a grid on the screen. – jsolarski Jan 03 '20 at 21:11
  • Seems interesting, never heard of IR touch screen. But how would it work with the figurines then? Do they have to emit any kind of IR signals? – Trisma Jan 03 '20 at 21:28
  • What size are the screen and figurines? What’s the budget? Do the figurines move? How many figurines would be on the screen at the same time? How quick do you need detection to be? How accurate do you need the position to be? – jcaron Jan 03 '20 at 22:37
  • Also, do you need the orientation of the figure as well? – jcaron Jan 03 '20 at 22:48
  • @jcaron The size I'm using right now is a 26 square screen. Budget is not set at the moment but I have people who can help me financing if needed. So there can be a lot of figurines. Let's say the max would be 30 at the same time. And yes they move, detection should be nearly instantly if possible. And accuracy can deviate a little bit but should also be as precise as possible – Trisma Jan 03 '20 at 23:58
  • 26 square? A square with 26 cm sides? 26 inch sides? 26 cm diagonal? 26 inch diagonal? 26 square inches? For the rest you need to be a lot more precise. In terms of budget there are solutions in the 10K+ range for instance. What’s “nearly instantly”? One second? One tenth? What’s the accuracy requirement? 10 cm? 1 cm? 1 mm? Solutions may be very different... – jcaron Jan 04 '20 at 00:05
  • Sorry for not being that precise. It's a 26 inch diagonal screen in a square format (4:3). I would say as low as possible for the price of course, 10K would be overkill for the project. It should at least be accurate with a max difference of 2-3 cm or something – Trisma Jan 04 '20 at 09:12
  • @Trisma they are used in POSs and other places where people have gloves on. in there with the nfc to detect which figure, and the screen to telll them where it is. here is a commerical example https://youtu.be/nA89-16wJ54 – jsolarski Jan 05 '20 at 00:50

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NFC is an inherently narrowband medium, and thus doesn't allow for exact remote location.

40-50 NFC tags does sound like it could work, but then your figurines would need to be NFC readers – that's a lot of complexity for a figurine.

Conversely, you could put 40-50 NFC readers beneath your screen, but I doubt that's a financially viable option.

I don't know whether NFC is a great approach here. Maybe keep the identification NFC-based, but simply use an e.g. resistive touchscreen and pressure – the moment a new NFC tag becomes visible to single reader that observes the whole table, you look for a pressure point. You know that this must be the new figurine, entering the game. The rest is just tracking the positions that you already know.

Honestly, this isn't a small project – localization of multiple objects on centimeter scale is a hard problem that industrial automation still is fighting with. I'd honestly probably go with a camera mounted across the screen, looking at the tops of your figurines, and some optical object recognition.

Marcus Müller
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  • Thanks for your great answer. I already figured out that that much nfc readers would be way too hard. Could there maybe be a way to place different touch dots underneath the figurine (I mean buy that that the base of the figurine would be a simplified QR code or something). A camera isn't an option in what I'm trying to do. That way NFC wouldn't be necessary at all, but I don't know if it is a good idea – Trisma Jan 03 '20 at 21:37
  • I don't really understand what you mean – a QR code **is** read by a camera – Marcus Müller Jan 03 '20 at 21:46
  • Sorry that wasn't really clear. I mean that I could create a 4x4 grid for the base of each figurine. Each spot on that grid (so 4x4, 16 spots) can be : a touch sensitive surface or just a normal surface. That way I can figure out where the items are (maybe). But are there screens that can handle that much points? – Trisma Jan 03 '20 at 21:49
  • How can a touch sensity figure bottom figure out the figurine's position? This is getting really confusing... – Marcus Müller Jan 03 '20 at 21:50
  • Lets say you have a small grid, a 2x2 one. Lets also say that the 4 spots in the grid are covered with touch sensitive elements (I think it's just rubber, or the material used for phone styluses). The screen will detect those 4 individual dots and the software can than determine what figurine it is (since each figure will have his unique dots on the grid pattern) – Trisma Jan 03 '20 at 21:54
  • Add on message above : I don't think that my idea isn't any good. But isn't there any other way? Even with those 50 nfc readers underneath it? And they have to be very precisly... – Trisma Jan 03 '20 at 22:07
  • You can find NFC readers for a few euros a piece. But many screens have metallic components which would be a problem. – jcaron Jan 03 '20 at 22:40
  • @Trisma you're confusing *touch sensitive* with *detectable by touch sensing*. That's like confusing *seeing* with *visible*! Ok, but really, your "solution" just makes the problem harder from a touch sensing perspective. Don't think you're going to get far with that... – Marcus Müller Jan 03 '20 at 22:41
  • Really, this sounds so much like a optical problem: **why** are cameras impossible in your situation? – Marcus Müller Jan 03 '20 at 22:42
  • I think OP’s idea is that the figure would have a touch surface with a mix of surfaces that are detectable as touches by the touch screen and others that aren’t. So by detecting the number and relative position of those touches (like multiple fingers on a screen), one would be able to detect the figurine, its position and orientation. Capacitive touch screens routinely detect 10 touches, some probably go a bit further. With 3 “touches” per figurine (with different angles to recognise them), it would work with at least 3 figurines. – jcaron Jan 03 '20 at 23:09
  • @jcaron it would indeed be a problem if the screen blocks the information, but there are a lot of screens in my town (and public transport) where there is nfc under the screen – Trisma Jan 03 '20 at 23:55
  • @MarcusMüller It's because you should just be able to take the screen, plug it in and use it. Only the screen and nothing else. – Trisma Jan 03 '20 at 23:55
  • @Trisma I’d be curious to see “a lot of screens” with NFC under the screen (as in you place your card on the screen and the card is read there) with a decent size screen. Card payment terminals with a small 2 or 3” screen don’t count, the reader is most probably not where you think it is. – jcaron Jan 04 '20 at 00:08
  • In all busses there are 10 inch screens with nfc, and there are some vending machines with big led screens and you can just place your card anywhere on the screen. Don't really know how they do it but it doesn't solve the problem to locate the figurine – Trisma Jan 04 '20 at 09:14
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    Off topic, but I’d be curious to know where those are (or if you have pictures/references for those), as under-screen NFC is really not that common (especially “anywhere” on the screen”). Back to your topic, Iiyama have 30-point 32” screens and 40-point 43” screens, but that’s still quite a long shot from detecting **and** recognising 30 figurines. You’ll probably have to combine different technologies, like RFID/NFC to recognise and touch to have the position. Do you need the figurines’ orientation? – jcaron Jan 04 '20 at 22:26
  • @jcaron I'll come back on this later. I'll try to combine a giant nfc reader under the screen along with a simple touchscreen. It will work differently as intended, but it should work. Update to come – Trisma Jan 08 '20 at 14:09