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RFID tracking and positioning project
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marrogant View Drop Down
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Posts: 7 		Post Options Post Options   Quote marrogant Quote  Post ReplyReply Direct Link To This Post Topic: RFID tracking and positioning project
    Posted: 12 January 2007 at 7:38am

Oh! Great idea! So you think it would work to have RFID tags implanted in the fingers of the people doing the scheduling?!

Joking aside, I actually do think that given all the constraints, an RFID array would be easier than an optical system... With optical, I'd need an array of webcams and have to ensure the careful placement of the post-its/cards in the grid, keeping a clear line-of-sight (and not sure how I'd be able to get those post-its close to the bottom of the wall), and having uniform lighting... too many variables to control.

Maybe RFID tags are not the entire solution, but  part of it. Is there a contact-based ID system? Each grid cell would have a small metal surface, and the tags (I'm thinking we might be able to move from post-its to a laminated card) would transmit their ID upon contact... A sort of RFID without the RF (except maybe using RF to power the tags).

This would eliminate the need to cycle through each of the readers and/or to use signal strengths to calculate location of the tags.

m
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amal View Drop Down
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Posts: 1528 		Post Options Post Options   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2007 at 7:50am

Hmm, yeah... with a crazy large grid like that it might be difficult. However, the virtual soccor game I played used one camera and projector, and the surface was really large. I think this system is much more flexible than it might first appear.

However, you might be on the right track with contact-based ID. I'm not sure how spendy these systems are, but they would work perfectly in your situation. The system is called iButton.

http://www.maxim-ic.com/products/ibutton/ibuttons/

http://www.maxim-ic.com/products/ibutton/

As you put it, it works like RFID, but without the RF. It's basically a one-wire ID system where you touch the iButton to a receiver and you're set. It's specially made for stuff like this and I can't believe I didn't think of it before.

I'm not sure what this link is to, but it might be a cheap and easy to use software development package for the iButton.
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marrogant View Drop Down
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Posts: 7 		Post Options Post Options   Quote marrogant Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2007 at 8:17am

Wow! Just reading up on OneWire now. VERY exciting. Thank you !!!

 
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Posts: 1528 		Post Options Post Options   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2007 at 8:19am

No prob, glad to be of help ;)

Many key tracking applications used in property management offices use iButton technology to keep track of which apartment and house keys are in which secure slot. Call around to a local property management company and see if they use the "KeyTrack" system. Most places hate the system, but its not because of the iButton technology, its because of the crappy KeyTrack software. Either way, you should be able to go there and check out the iButton system first hand.

Also, I checked the prices and it is very cheap. You can get iButtons for around $2 a piece and the reader devices are under $50 each. I have no idea what it would cost to put together a multiplexer to handle hundreds or thousands of receivers, but it sounds like a fun project. If you can, post pictures of your current grid... I'd love to see what it looks like!



Edited by amal - 12 January 2007 at 8:22am
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vadim View Drop Down
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Posts: 5 		Post Options Post Options   Quote vadim Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 8:01am

Hello everybody.

I'm currently doing a similar research. And looking for a cheap indoor system that will allow to track direction (only direction - like compass) to the specified passive RFID tag with a handheld device/reader.

Do anyone know the system that already suits my needs? Or do i have to develop new one?
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Posts: 1528 		Post Options Post Options   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 8:14am
Since passive tags don't emit anything (they are dead until energized by the reader), you won't be able to get a bearing on them unless you put the reader within range of the tag, and by then you'll probably know right where it is anyways.

If you're looking for a simple direction finding solution, I'm sure there are other IR or RF devices that can help you that do not fall under the RFID umbrella. I hate to be a broken record on this fact, but the last two letters in RFID stand for identification, and that's the primary purpose of RFID... not radio-direction finding. Do you need to ID something once you find it's direction? If so, perhaps your direction solution could incorporate RFID into it, but those RFID components of the solution will most likely not be involved in the direction finding aspect.
Amal ;)
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Posts: 5 		Post Options Post Options   Quote vadim Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 8:48am

Yes, i need to find a specific tag by ID, so RFID.
Plus i need a very cheap and small solution (there will be quite many tags) - that's why passive ones.

As far as i know, passive tags work within a 4-7 meters range from reader - that's ok for me.

Do you know any system for that?
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Posts: 1528 		Post Options Post Options   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 8:53am
Originally posted by vadim

As far as i know, passive tags work within a 4-7 meters range from reader - that's ok for me.


Tag read range depends heavily on the type of reader and antenna you are using, as well as the frequency used by the tags. Low frequency (125KHz-140KHz) tags and high frequency (13.56MHz) tags really have limited ranges between 5cm to 1 meter at best. The only passive tags I know of that work at longer ranges are UHF tags, and the reader equipment for those tags is not cheap, nor is it small enough to be hand held/mobile. I think you're going to have to look at another option for your direction finding. You can still use cheap passive tags to ID the tagged object once you locate it.


Edited by amal - 15 February 2007 at 8:53am
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Posts: 5 		Post Options Post Options   Quote vadim Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 9:02am

It's some sort of library system (finding a specific book on the shelves) and the problem is that i have too many tags within a 4-7 meters range.
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Posts: 1528 		Post Options Post Options   Quote amal Quote  Post ReplyReply Direct Link To This Post Posted: 15 February 2007 at 9:09am
Ahh I see... are the shelves themselves setup with reader antennas (fixed system), or do you have some kind of handheld unit? What types of tags does the system use? What frequency does it use?

I'm sure its possible within the realm of physics to find the direction of the tags being read, however finding a reader device with either the antenna design to allow that to happen or the internal circuitry to determine direction that would allow for that will be difficult at best. The closest thing I can think of is the RFID-Radar TrolleyScan product, but you'd have to replace your entire library system and use their tags and fixed reader products.
Amal ;)
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