125khz RFID antenna

Discussion in 'Wireless & RF Design' started by brianmay27, Mar 3, 2014.

  1. brianmay27

    Thread Starter New Member

    Oct 7, 2011
    Hey all,

    Im currently working on a project involving my motorcycle and a RFID authentication. Since space is so limited I want to have all the controllers at the rear of the bike and have the RFID antenna at the front. I was thinking for a simple proof of concept and to keep things simple I would use the parallax (http://www.parallax.com/product/28140) rfid reader and chop of the embedded antenna and hook up my own.

    I am fluent coding and basic hardware protocols but when it comes to AC waveforms all my knowledge goes out the door. Anyway I want to know if I make a coil using magnetic wire, will I need to use a coaxial cable to travel from front to end to ensure as little interference or could I get away running the strains of mag wire? Again no idea what im talking about so if its improbable than lmk.

    Any suggestions would be great!

    Thanks in advance
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    at 125 khz, you will not have a real antenna, the size would be prohibitive. the best you can hope for is an inductive pickup. a coil on a ferite bar would work fine. check amidon associates for ferite antenna material.
  3. WBahn


    Mar 31, 2012
    What is it that you are trying to achieve? How far away from the antenna coil (which is really one side of an air-core transformer when all is said and done) will the RFID tags be that you want to read?
  4. brianmay27

    Thread Starter New Member

    Oct 7, 2011
    Ok, good to know. So I would wrap the coil around the cast iron handle bar and that should work as an inductive pickup? Will this work if the RFID is above the handlebar or will it only work if it is at the end of the handlebar?

    So lets see if I can make a visual..


    So if this stays as it is, the # at the left is the end of the handlebar, the = is the iron handlebar and the right # is the junction box. The 0 would represent where the coil would be. and the ___ is the plastic grip.

    Anyway I have a rfid chip implanted in my hand. Range is currently an issue but I have tested using a standard rfid reader it can read though my glove and some plastic.

    Thanks for the info so far. I hope I have not just made it more confusing.
  5. geoffers

    Active Member

    Oct 25, 2010
    Someone may correct me on this? But I think if you wrap your coil around a iron tube, the coil will try to induce a current in the tube and drasticly reduce the rfid range if not stop it working completly?

    I'm curious, are you making a dead mans handle or such like in case you fall off:)

    Cheers Geoff,
    Ps I like rfid and bikes!
  6. aleza84

    New Member

    Mar 26, 2014
    Any idea on how to calculate/make a RFID 125khz pcb antenna, I've seen some commercial ones... would like to make one.