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X-Band Motion Detector — Parallax Forums

X-Band Motion Detector

ultegraultegra Posts: 6
edited 2014-07-15 23:59 in Accessories
Hi, I am using your sensor "X-Band Motion Detector". It works perfectly in Arduino Uno but when it is close a UHF RFID reader, the detector detects a motion constantly. The reader works on the following frequency range: 865-868 Mhz. How could I solve this interference? Gracias!

Comments

  • RS_JimRS_Jim Posts: 1,764
    edited 2014-07-09 09:44
    A quick guess would be to physically separate them. The square law says if you double the distance you get 1/4 the signal. Maybe a simple separation increase would solve the problem.
    Jim
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2014-07-09 15:26
    Another option might be related to sensitivity...have you tried adjusting the sensitivity down on the X-Band to the lowest setting that still works for your application? Does this improve the situation?
  • ultegraultegra Posts: 6
    edited 2014-07-09 23:27
    RS_Jim wrote: »
    A quick guess would be to physically separate them. The square law says if you double the distance you get 1/4 the signal. Maybe a simple separation increase would solve the problem.
    Jim

    Hi Jim, thanks for your answer. The problem is that the detector and the RFID reader must be close together and in addition, the reader must work at 30 dBm.
  • ultegraultegra Posts: 6
    edited 2014-07-09 23:35
    Chris Savage wrote: »
    Another option might be related to sensitivity...have you tried adjusting the sensitivity down on the X-Band to the lowest setting that still works for your application? Does this improve the situation?

    Hi Chris and thanks for your answer. I tried but it does not improve the problem. Any other possible solution?
  • kwinnkwinn Posts: 8,697
    edited 2014-07-10 07:45
    You can try changing the orientation of the two units in relation to each other.
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2014-07-10 15:01
    Can you leave the RFID reader off until motion is detected, and then blank out the motion detector for a time to allow the RFID reader to work? A redundant sensor, such as the OMRON D6T thermal body heat array could detect the continued presence of someone in the area.
  • ultegraultegra Posts: 6
    edited 2014-07-15 00:58
    RS_Jim wrote: »
    A quick guess would be to physically separate them. The square law says if you double the distance you get 1/4 the signal. Maybe a simple separation increase would solve the problem.
    Jim

    Hi RS_Jim,
    yes but I can not change the orientation, just try to separate a bit but does not work. Thanks.
  • ultegraultegra Posts: 6
    edited 2014-07-15 01:20
    Tracy Allen wrote: »
    Can you leave the RFID reader off until motion is detected, and then blank out the motion detector for a time to allow the RFID reader to work? A redundant sensor, such as the OMRON D6T thermal body heat array could detect the continued presence of someone in the area.

    Hi Tracy Allen,
    It is a good solutions but I still have interference problems. The complete equipment consists of: RFID UHF (that is off) and Arduino Uno and GPRS Shield (both turned on). The maximum distance that can separate X-Band Detector between Arduino Uno and GPRS module is two feet. The detector must work to maximum sensitivity and in these conditions still have interference problems.
  • xanaduxanadu Posts: 3,347
    edited 2014-07-15 13:17
    Seems odd that an RFID receiver on such a low freq would emit something picked up in the x band.

    Have you tried electrically isolating the two sensors?
  • ultegraultegra Posts: 6
    edited 2014-07-15 23:50
    xanadu wrote: »
    Seems odd that an RFID receiver on such a low freq would emit something picked up in the x band.

    Have you tried electrically isolating the two sensors?

    Hi Xanadu and thanks for your answer.
    I do not know it. Do you know any link where I can learn to do it?
  • xanaduxanadu Posts: 3,347
    edited 2014-07-15 23:59
    Two separate power supplies for the offending devices. They can share the same ground since there is IO between them. It's not pretty, but we need to troubleshoot the issue as quickly as possible. The ground should be monitored as well, do you have access to a scope?
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