RFID Document management

[Emyr]

My workplace produces a lot of documents and the staff are constantly searching for a particular client's lovely cardboard files.

I had an idea whereby I'd stick one of those 3cmx3cm RFID labels to each file (like they do in bookshop/newsagents), then find the files by keying the client name into a PDA-size thing, some client-server magic to fetch the tag/file ID, then waving the PDA past the shelf until it beeps.

I think I need a range of up to 50cm air + up to 50cm paper (filing cabinets are something I can worry about in a later version).
It needs to be cheap enough for my non-geek boss to say yes; If I can get the tag price below £0.50 each I think it'll be a winner.

Any hints? I know the <£20 125KHz modules used in some Arduino projects have a range of about 10cm so I think I'll be using the 13.56MHz items.

[alm]

That's certainly creative, but based on the RFID equipment I've seen, I don't think it's feasible. The small antenna's usually need almost contact (max. 10cm or so). I've seen readers with an antenna of about 30cm x 30cm, they had a range of about 30cm or so. And antenna's of about 150cm x 60cm, they had a range of about half a meter or so. I'm not claiming this is was all state-of-the-art equipment, but it was the best we could get a few years ago, and cost certainly more than 20 GBP (between €150 and €20000). This was all at 13.56MHz.

You are trying to create a magnetic field, so you can't just use a directional parabolic antenna. Another complication is that the tag would have very little surface area when scanned from the back of the document, which would decrease the range even further. UHF technology would have the range, but is a lot more bulky, the tags are probably more expensive, and it's not very directional. You'd also need a fairly smart reader that's able to read multiple tags at once, the simple readers that you see at libraries will produce garbage when multiple tags are in range.

Unless there has been a breakthrough in RFID technology in the past few years, I don't think it's possible to do this with anything remotely PDA-sized.

[Emyr]

I think the tags would mostly be end-on, so that may have an effect on the received power.

How about a range of 30cm? If the tag is at the edge of the file furthest from the reader, this is as far as it could probably be. I think the only reason some of the shelves are two files deep is because it's too much hassle to work out if the deeper ones are ready for archiving yet...

850MHz+ systems seem to have ranges of 3m or more, I guess they'd be big bucks too if anyone listed their prices 

[joelby]

Can you put all of the documents into an electronic document management system?

[Emyr]

We threw together a system where we could upload scanned mail to a web-system for the boss's 3 week cruise but I don't think the firm is quite ready for me to inflict complete computerisation upon them (although it has been discussed, as a pipedream). Part of the problem is that most of the staff were already out of school before PCs became "affordable", and are struggling to play catchup.