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Topic: anyone know details on 125 kHz RFID reader? (Read 2 times) previous topic - next topic

markB

I stumbled across some additional data, while searching for priority1 ...can't remember where.
It was suggested a larger coil could do what I wanted, and Robert suggested
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In you're case you'll be looking at a 30-35 cm coil. 
I'm thinking about 50 turns, with 0.25mm wire. Just add or remove turns until the coil resonates at 134khz. You'll want the coil voltage to be sitting at about 300v peak to peak.


His other coil details are here http://www.priority1design.com.au/rfid_coil_antenna.html

You seem to be on the right track, and I suspect you will have more luck with the ID-2, as I have read they are very good.
Some other details I found here http://www.wethepeoplewillnotbechipped.com/main/viewpage.php?page_id=79 which use a ferrite rod.

Let me know how you get on m(dot)beckett(at)amuri(dot)net
Thanks
Mark

Grumpy_Mike

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I do not see any commercial RFID parts on it, just an AVR, a counter/divider and an amplifier.  Consequently it's not possible to look at the chip manufacturers specs.

A lot of commercial RFID readers don't either. I used to design them for a living.

It is just a matter of winding a coil with the right resonant frequency. This does not have to be 125KHz but something either side of it. The response is symmetrical so you can go up or down. I would go for something like 130KHz to maximize the range. Tune it by either taking turns off the coil or adding / subtracting capacitance. If you do the latter you have to know if the reader has a parallel LC tuned circuit or a series one, so you know how to add more capacatance.

gardner

#7
Jun 09, 2011, 05:49 pm Last Edit: Jun 09, 2011, 05:55 pm by gardner Reason: 1
Thanks Mike.


If you do the latter you have to know if the reader has a parallel LC tuned circuit or a series one, so you know how to add more capacitance.


This is kinda where things fall down with the RDM reader -- they just don't give you much to go on, to get your coil design right.  I'm looking forward to getting my hands on the ID-2 since they do spell out this aspect of the design.  Unfortunately they appear to be back ordered.

...and thanks Mark.


Quote
In you're case you'll be looking at a 30-35 cm coil.
...
You'll want the coil voltage to be sitting at about 300v peak to peak.



Can you mention which reader circuit Robert is referring to here?  EM4095 or U2270B something else?  I'm not above wiring up my own reader using one of these chips, but I am not keen on ordering them all the way from Oz.

markB

I brought a RFIDRW-E-232 and it uses the EM4095 in more of less the same configuration as the datasheet.

They could be available closer to your home.

Mark

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