EMI or random radio interfearance

Discussion in 'General Electronics Chat' started by rp mccann, Jul 29, 2014.

  1. rp mccann

    Thread Starter New Member

    Jul 29, 2014
    Please excuse a possible dumb question, I have just discovered this wonderful and informative site, in fact I haven't left it for over 2 hours until I just joined, but here goes.

    I seem to remember a few newspaper artistic here in the US (New York specifically) where a few mobility chairs suddenly darted out into traffic, causing accidents and injury. The conclusion was in one case, a taxi radio transmission, and the others had to do with police radios being used, causing some type of EMF (I assume). These were with "home made" controller circuits

    Is this no longer a problem that occurred, or is the solution being built into the circuits shown (just not identified)?

    I used to be a electronic repair tech for 37 years from tubes to surface mount until a hit and run car accident left me in my limited mobility, so I am now real slow in attempting to build projects again, but both of my scooters now appear to have bad controllers (a Rascal and a Golden) and I cannot afford to pay for repair out of pocket, and wish to build, but with safety for myself and others are a big concern.

    thank yo for your time and efforts with this great site, and my assistance I can be given (peace of mind) over the question. I currently live north of Seattle WA USA, and am getting so tired of just looking out the window

    I hope I have posted this in the correct area, I am referring to Electronic Mobility Chairs for those of us who have problems walking now a days, if this is the wrong location, please forgive my ignorance.
    Last edited: Jul 29, 2014
  2. mitko89


    Sep 20, 2012
    I'm not one of the seniors of the forum, but would like to welcome you.
    As far as I understand from your post you wish to build control circuit for your scooter?
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Sorry to tell you that even an experienced person generally pays more $$$ to build a single unit then to buy the equivalent device.

    Have you checked Amazon? EBay? Alibaba?
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Welcome to the forum!
    I agree with Ernie re the cost. Since you are concerned with safety (rightly so) there is also the problem that you might not be able to get insurance for a scooter with a home-built controller with no proven safety-standards compliance.
    If your present controllers are repairable you could consider 'hardening' them against interference.
  5. AlphaDesign888

    New Member

    Jul 27, 2014
    Yeah and that is what has killed the industry. I can buy an awesome power supply for $75 but I can build an mediocre one for $200.

    Where's the incentive for normal people anymore?
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    The "un intended acceleration" issue has been controversial for a long time. Whether it is a scooter or a Camry or even an old Audi 5000, some people want to blame the electronics or the EMI while others believe it is the operator putting his foot on the accelerator instead of the brake. In the case of scooters in NYC, why only there? Are those radios only sold in NYC?
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
    sometimes, the manufacturers seem to forget all about the outside world. a few ferite beads, bypass caps and shielding go a long way toward making things resistant to rf. lets face it, theres rf everywhere these days, from cell phones to radar, the potential for "unintended operation" is pretty high. in the old days, people would just blame the nearest ham operator for all problems with their blender or whatever. now things are supposed to be resistant to rf, but if the manufacturer cuts a few corners, strange things happen.
  8. Papabravo


    Feb 24, 2006
    Those claims of radio interference are based on exactly zero evidence. You have a motor and some motor driver circuitry and some switches. None of this has any obvious connection to RF circuitry and unintentional activation seems highly dubious. Extraordinary claims require extraordinary proof.
    GopherT likes this.
  9. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Papabravo likes this.
  10. alfacliff

    Well-Known Member

    Dec 13, 2013
    I have personally seen electronic devices affected by rf. the quality assurance people here survey the ovens with a bunch of thremocouples connected to a high dollar chart recorder, anyone walking y with a portable radio or a forklift with a mobile radio that happens to transmit near the oven makes the tempratures jump at least 10 degrees. cars these days aarent simple electrical devices, they are very computerized. even the gas pedals now arent connected to anything but a potentiometer then to the computer. a servo actually sets the speedl car electronics are notoriously unshielded, just barely enough to get past the necessary tests.
  11. Papabravo


    Feb 24, 2006
    All of this is true enough, but so far no causal connection has been established between the existence of an EM field and the specific response involved in propelling a motorized vehicle in an unintended direction. Just because extraneous signals are coupled into a system does not allow you to conclude that a specific response will be affected. What is required is to establish the level and method of signal coupling and a specific response. It would be desirable, but not essential if the result could be repeatable.

    You can do this experiment yourself beginning with an unlicensed FRS radio ($39.00/pair at Radio Shack). These are low power FM walkie-talkies. If you can make the scooter move I would be greatly surprised. If not then the next step is to enlist the aid of a local ham who may be able to help with higher power radios and different transmission modes. Again I will be surprised if the experiment yields positive results.
    Last edited: Jul 30, 2014
  12. shortbus

    AAC Fanatic!

    Sep 30, 2009
    Maybe the people injured were wealthy Grandparents. And the kids/grandkids hacked the scooter with a RC circuit, to help granny along. So they can get the will read sooner?:)
  13. crutschow


    Mar 14, 2008
    Other than buying a new controller, the other option is to try and repair the ones you have, especially since you have worked as a repair tech. The big problem is getting a schematic of course, since the companies are usually reluctant to divulge that data.
    Have you tried searching for info on the two controllers that you have?
    What's you level of understanding of electronic circuit operation?