Passive RFID from within 4 feet?

T Chap

If not possible, anyone know what options are available for for credit card size or smaller version of active RFID?

John R.

While I beleive it is possible, you'll have to look toward "industrial" RFID type devices. The hobby orientated RFID readers are tuned to work at "near contact" distances.

If you sourced the chips, you may be able to build your own reader with a little more power that could read the "credit card" type tags at more than a couple inches. I don't know if you could get 4 feet with the 150 MHz tags or not. You may need to move up to the mid or high frequency tags.

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John R.

8 + 8 = 10

Oliver H. Bailey

YOu can get four feet on a 150 KHZ tag with a coil the size of a door. The low frequency tags are designed to only work within inches for a reason, security. Try 13.56 Mhz if you want a longer read range.

T Chap

Thanks for the info guys, that is helpful.

T Chap

Oliver, are you saying that if a user passed by a massive coil, their tag could be read? I suppose in that case that a perpetrator could have around a briefcase with a supercoil of sorts, walk up to the carrier of the tag, and read his tag without his knowledge?

Oliver H. Bailey

That is correct, however the breifcase would be very heavy. Let me illustrate. There is a company that makes a 125KHz reader that will read a pallet of tags as they move through a doorway. The reader IS the doorway. A coil goes around the doorway on the sides and the top.
The 125 KHz RFID products are also known as very low frequency devices. If you want higher range then you should go to a higher frequency such as 13.56 MHz, OR you could also use a directional antenna to increase the field in a focused direction. While that would give you additional distance, it would also be very focused so the chance of a good read dimishes.

RFID is intriguing but I have serious questions about ist's useful for applications that require a read distance of more than a couple inches.

And finally, remember that RFID is a radio wave and subject to the same environmental conditions and interuptions that any radio wave is.

There are applications where this works just fine. Radio Sahck has these mini RC cars and I stuck a 10mm glass tag on the back and use the Parallax RFID reader to determine the number a laps a certain has made. Each time through a overhead the tag is read. The reader is adjustable for different size cars and as long as it is within an inch, it always reads. These are the same tags used to identify animals.

So I hope this helps.

Oliver

T Chap

Excellent info Olver many thanks for the explanation. I am dropping the long distance attempt. [noparse]:)[/noparse]

Bean

Oliver,
Would you happen to have a link to those 10mm glass tags that work with the Parallax RFID reader ?

Bean.

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"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·

Chris Savage

Bean, the company that makes the compatible tags can be found here...The glass tags come in many sizes as well.· Take care.

http://www.cyntag.com/index.htm

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Chris Savage
Parallax Tech Support