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|   February 10, 2009 at 10:05 AM

Are EM4102 cards compatible with EM4001? Will this reader read an EM4102 tag?

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|   July 26, 2009 at 10:28 AM

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|   April  6, 2009 at 1:13 AM

Can anyone confirm if this will read HID Indala cards?

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|   July  6, 2009 at 1:42 PM

What happens if you leave a card within its proximity? Will it continuously trigger and send the ID? or do you need to prod the reader to read a tag (if one is avaliable)?

Is it ok to leave RFID tags "powered" for long periods of time?

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|   July 16, 2009 at 6:59 AM

not a problem from my experience. the reader only reads once, and then if you want to read again, you'll need to cycle the power or reset the reader.

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|   October  5, 2009 at 7:49 PM

great sensor. I was able to read cards through a notebook and a stack of paper.

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|   October  6, 2009 at 6:57 PM

This is a great piece of code and hookup diagram for the ID-20 and ID-12. The reader is great, one known issue is that the serial line (D0, pin 9) needs to be disconnected from Arduino RX in order to upload a new sketch to the board or else the upload will fail.

Reader has a range of about 8cm using the ID cards sparkfun sells. The thicker plastic key fobs are reading at about 6cm. With a case on this it should still have a great read range.

If you tie the Reset line to 5v+ as the datasheet says you will have to wait a maybe a second after moving the card out of range to read the same card again. If you connect the Reset line to a digital pin on an arduino you can bring the pin HIGH, read the card, then bring it LOW after a successful read. Looping this will let you continually scan cards in range and/or scan cards faster.

Make sure to use a transistor or a resistor on the LED/BZ output so you dont kill the pin.

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|   October  6, 2009 at 6:59 PM

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|   November 12, 2009 at 3:14 PM

When using the Reset line to re-read a transponder, wait at least 200ms after bringing the reset line high, then read, and then bring it back low.

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|   November 29, 2009 at 10:09 PM

I'm looking for an RFID reader, and my choice is between the the ID20 and the Parallax serial rfid reader http://www.parallax.com/Store/Accessories/Communication/tabid/161/ProductID/114/Default.aspx?SortField=ProductName,ProductName I am looking for one that will read tags through a door, which is 2" solid wood, but with thinner inset panels that are about 3/4". I could definitely fit either reader over one of these panels. Is it feasible to have a keychain-type RFID tag be readable through the door, and which reader would be best suited for this application?

Thanks a lot!!

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|   December  3, 2009 at 2:51 AM

I have been experimenting with tags that have about 1" diameter antennas. I was able to read the tags through a 1.5" solid piece of wood. In fact, it read the tag 3.5" away from the face of this reader.

I found the tags on a different site, which I will not post, since this is Sparkfun's site. A quick Google can lead you to a myriad of different tags. Make sure your encoding matches though.

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|   December  3, 2009 at 4:37 PM

Thanks! It looks like this is the reader I'll go with.

And I'm going to at least start with the credit card shaped tags here at Sparkfun, and see where that gets me.

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|   January 14, 2010 at 9:23 PM

After having tested this for awhile, I am satisfied with the range. With no obstruction, the credit-card sized tags from SparkFun can be read from about 5-6 inches directly in front of or behind the reader, and from about 2 inches around the sides. Nonmetallic obstructions (stacks of paper, wood, etc.) have little effect on the range. The cards can be read through one layer of aluminum foil from about 1 inch, and not at all through more layers, not surprisingly...

This works perfectly behind the door it was intended for, so I'm happy :)

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|   December 15, 2009 at 2:02 PM

Is it possible to hook up a self build antenna to this RFID module?

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|   January 12, 2010 at 10:50 PM

Yes! The datasheet has some general guidelines to follow when building an external antenna. They even provide a website on the theory behind loop antennas.

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|   January 13, 2010 at 8:16 AM

is it possible to write a tag? i mean, can i write data to the tag with this?

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|   January 15, 2010 at 0:25 AM

No, you would need an ID-20RW (or WR, the datasheet uses them interchangeably) to write to tags. Even then, the datasheet talks about using a different card format, the Temec Q5555.

I don't know whether the Temec format is compatible with the EM4001/2 or not.