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I want to build a device using an Arduino or similar that would allow me to detect when particular objects were in a box (things like a TV remote for example). My thought was that I could use rfid tags on the objects and then put a reader in a box to detect them. Maybe line the walls of the box with metal or other radio wave inhibiting material to ensure items weren't sitting next to the box but were indeed in the box.

Been doing some research and 2 issues I'm trying to overcome:

1) Distance seems to be an issue with this approach using the rfid readers I have found so far at reasonable costs (lower freq). I would like the box to be at least a foot sq and most of the cheaper readers only read an inch or two.

2) Another issue appears to be that the inexpensive low frequency rfid readers can only detect a single rfid and not multiple at once. I want to be able to have multiple different objects in the box and be able to distinguish between them.

Wanted to get your opinion of any other ideas on how I could accomplish my project or if I'm on the right track help refine my thinking a bit.

Thanks, Jason

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  • \$\begingroup\$ NTAG compatible knock-off readers should be able to read 4 tags at once, but getting one that reaches more than NFC distance will be hard now that NFC is hyping so hard. There used to be a 13.54MHz TI test kit with a small optional amp-board that reached about 1m distance, but I think that totalled at €130, so that's probably not what you consider affordable. Anyway, what you want is possible and 13.54MHz should be affordable enough from a none-main-brand, but finding it with >10cm distance will be hard. Also think about looking up loop antenna design practices. That's also a steep curve @ 1st \$\endgroup\$ – Asmyldof Feb 29 '16 at 18:40
  • \$\begingroup\$ As you mentioned to use metal casing to shield it, your reading range is also shortened, because the reflected signal create more noise. \$\endgroup\$ – Ben May 6 '18 at 1:13
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I think, after a preparation, measuring the weight of box solves the problem. If the weights of different kinds are forcibly approximated to different primary numbers, you can distinguish the kind and quantity of them mathematically.

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