Mike Brinker

Midterm

Entrances and Exits. The simple stuff. How to cross the gap/bridge/platform. Is it locked? Yes it is. Is it closed? Yes it is. How do I go through/pass?

The ZML door has a keypad lock on it. It also has an imbedded card reader and simple key lock. So let's add a fourth to the mix. I propose to use RFID to open the Zemeckis Immersive lab door for me so that I barely even need to think before crossing the gap. I also want an LCD readout that greets me as I walk in, recognizing me as I go through (hello basic stamp!). The following is a diagram of the setup. Just think about it...transponder: 71 dollars, RFID tag (think mobile speedpass): 5 bucks, LCD readout screen: 30 dollars, transponder antennae: 250 dollars
Being able to open the Zemeckis door without having to punch in a code...priceless.

Transponder module (reader)

keyring tag (like Mobile Speed Pass)

I am still trying to figure out ways of boosting my 13.56 Mhz RFID transponder read range to farther than 4 inches. According to a few sites, you can increase the range farther by adding a larger diameter antennae to your transponder (tag?). 4 inches is with a 2 inch diameter antenna. However expensive that antennae may be is still beyond me at this point. The antennaes I have seen for some tags are made of metal and coiled around the tag quite a few times. Would that hold up for the transponder as well? I don't know. More research is required.

The following is a mathmatical formula for read ranges and antennae, but unfortuneatly, it's too high freq for me (I'm at 13 megahertz, this is like 800)
http://www.maxstream.net/support/white-papers/the-power-of-sensitivity.pdf

More general info on wireless frequency
http://www.emsys.net/sfedg/presentations/Wireless%2017%20April%202001.PDF

Here we go, a desciption

"Influence of the Transmitted Power on the Reading Range:

The antenna's working range is dependent on the antenna itself, the reader, the
transponder and the level of the output power of the reader (adjustable). because the transponder gets its energy from the magnetic field produced by the antenna and that the field intensity decreases at higher distances, the radiated transmitting power has strong influence on the range."

Measured example: Label, 45 x 76 mm, over the center of the antenna,
oriented parallel to the antenna

pulled from here.

Shibby, the transponder that I found from Digi-Key is the TI S4100 model for 71 bucks. Problem is, the transponder is only rated for 200 mW for the HF side of things. I need something with about 4 or 5 watts of power. Back to the drawing board.

Well maybe not, here is another bit of info for actually figuring out the coil dimensions on both the reader and tag, as well as the distance/range. This looks more promising...maybe...