Connect with us

Simple wheelchair motor controller

Discussion in 'Sensors and Actuators' started by wizzinbya, Oct 21, 2012.

Thread Status:
Not open for further replies.
  1. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    Hi Everyone,

    I am really frustrated with the lack of information regarding the powering of a mobility vehicle after a EMP or other event that destroys the electronics. I would like to be prepared in the event of an EMP or similar type event and am thinking a simple round wire type resistor for speed control might be the answer to get my wheelchair up and running again.

    Does anyone here any ideas of a "simple" dc electric motor controller that would get my wheelchair up and running without any electronic devices which would get wiped out in the event of a solar flare or EMP?

    Thanks for any help! John
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    If this is something you are really that concerned about, get a replacement speed controller and store it in a metal box insulated from any contact with the metal box, aka line the box with something non conductive and drop the entire device in that enclosed metal box box, close the box and put in storage... Really concerned bury the box... After an EMP remove the speed controller and use...

    FYI, resistive speed control devices are horribly inefficient and can still stuffer damage from an EMP...
     
  3. donkey

    donkey

    1,286
    56
    Feb 26, 2011
    the chances of emp affecting are really that high?
     
  4. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    In a nuclear conflict, extremely rare Earth changing solar activity, or possibly an alien invasion, maybe...

    But, honestly IMO at that point there is likely going to be a lot more to worry about, or you won't be worrying at all...
     
  5. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    I cannot walk and my wheelchair is my only way to get around...I will do what ever I have to do to keep mobile. I just needed to know how to make a simple motor speed control so I can get to my back yard where I have buried my spare electronics in a faraday cage. I still would like a simple answer to the problem. Thanks, John
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    I would see how your wheelchair goes on 6V (or some other easily available fraction of the voltage it uses)

    Presuming the motor is nothing special that requires a driver, you may be able to get away with switching 6V or 12V to give yourself 2 speeds.

    Another option is to build a small PWM controller and fit inside a totally sealed diecast metal box velcroed to the wheelchair. That is likely to survive almost anything short of catastrophe. Whip it out and connect it up (hoping that your motors have survived)

    The problem is that having one significant EMP event would tent to be predictive of others. So you don't want to be too quick in pulling out your spares. Either that, or have several sets of them.
     
  7. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    You are overlooking the fact that you can't just have the parts laying around to whip something up... If those parts are not shielded when the EMP happens they very well could be destroyed or suffer damage as well... Any spare parts or assemblies need to be stored in a shielded enclosure if you want security, and that is what I suggested you do with the metal box... Steve brought up a valid point, the motors themselves very well could suffer damage as well, in fact it's quite likely they would get damaged if the EMP ended up damaging other connected components...
     
  8. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    Let me just say that I have a wheelchair with two 55 amp batteries, two permanent magnet 2 pole motors that are operated at 24 volts with an electronic controller and a joystick containing a couple of potentiometers. There is a lot of circuitry in these controllers and I would like to have the option of replacing the "electronics" with simple "electric" devices.

    My idea is to simply go from the batteries thru a ribwound or roundwire type resistor that has the capability of being tapped in several places (giving me the ability to have at least a semi-soft start up and a couple of speeds) and then to the motors. A simple electric circuit for the different taps and a multi position switch would be an easy job, but what resistor should I use and what size etc should I be looking for. Will a resistor be affected by an EMP?

    I already have spare parts buried in a Farrady Cage but I would still need to get to them so I will need a simple motor controller to get me there. I hope I am making myself clear.

    If something ever does happen, I would like to have the option of at least trying to survive and I am already a survivor of more horrors than most people could ever imagine.

    Thanks, John
     
  9. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    you tell me!
     
  10. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    OK, PWM? I was a composites engineer for General Dynamics and Gulfstream Aerospace not an electronics engineer:eek:
     
  11. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    So if that is your idea, make it and place it in a shielded box...

    One that can handle the wattage that your motors will draw, value will depend on how the motors react to the resistance, since using resistance to control the speed of motors has consequences... You likely won't get 'slow' using resistance and if you do you might not have enough torque to go up an incline or over a rough surface, or even get going from a dead stop...

    Yeah, if it's in the wrong place at the wrong time aka hooked up to a circuit (or something that acts as a antenna) that absorbs the EMP... Standing alone or insulated/grounded probably not...

    Can't get much simpler than a resitor or two and multi-position a switch, as long as they don't take a hit as well rendering them useless...

    And don't disregard Steve's advice about the motors, if your chair absorbs an EMP chances are REAL good the motors will get toasted as well...
     
  12. donkey

    donkey

    1,286
    56
    Feb 26, 2011
    would the batteries be affected by emp?
    and don't motors themselves generate a small (very small from memory) magnetic field?
    in fact I think most things generate em fields. I just can't think of the last time it affected me, I live in australia and we might have different regulations about this stuff but most likely not.
    the simplest emp is made by conecting a piece of wire to both battery terminals, this is how you make a screwdriver magnetic. in theory all circuits generate an em field and have minor protection to them.
    if you have enough of a reason to warrant it you might look at talking to the engineers of your wheelchair they might be able to tell you how likely your chair is to be harmed by emp and how powerful the emp would have to be to affect your chair.
     
  13. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Psst... Armageddon planning...

    And yeah the batteries themselves might be affected if they are hooked up to something that gets hit...

    The truth is I doubt anyone really knows the extent of what will or won't be affected in a Global Armageddon scenario as there are lots of variables to take into consideration and simulations can only predict so much...
     
    Last edited: Oct 22, 2012
  14. donkey

    donkey

    1,286
    56
    Feb 26, 2011
    well in that case I would look at going over to steam engine controlled or an old whipper snipper engine. it sounds stupid but after EMP steam engines will still work. petrol engines will need new components.. but hey there are options
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    It may be easier to harden the wheelchair against damage from EMP.

    Place the batteries and motors in a sealed metal box with minimal openings for shafts. Ensure that the shafts are electrically well connected to the metal shield.

    Do the same for the control box. Run control signals via fibre-optic from the controller to the motor.

    If you use wires to transfer signals from one to the other (even if they're in metal conduit) you risk damaging both ends if one is damaged by emp

    When the apocalypse comes, you can probably have spare controllers etc stored on the chair itself, but motors are going to be a far bigger deal to replace.

    Another option is to have a gearbox or similar so you can manually reduce the ratio between the motor and the wheels. This may allow you to run the motor at full speed (i.e. have only on/off control) but keep your speed low enough to be controllable. This assumes you have sufficient mobility to get in there and change that when the time comes.
     
  16. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    In addition to the above this assumes you have a source to actually charge the wheelchair at this point... If it was charging when hit, damage is pretty much a sure thing, if not well how long do the batteries last? When hit will the EMP damage the circuit/motors in a way that shorts the batteries and rapidly drains them?

    I guess a lot of this could be eliminated if you lived in a Faraday Cage disconnected from the grid (aka running off self sustained batteries inside the cage) and never left said cage or happened to be in it when the world changed...
     
  17. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    As I said before, I already have enough batteries, motors, controllers and joysticks to make several wheelchairs already "buried and insulated" in a Faraday Cage...I still need some sources for 1200 to 1500 watt ribwound or roundwire type resistors and maybe more specific direction in making a "SIMPLE" temporary controller that would get me going for a short time. Does anyone have a idea of cost and maybe even some resistors that would work?
    Also, how could EMP affect a ribwound or roundwire type resistor? I don't see how it could, which is why I am thinking of going in that direction.

    Thanks, John
     
    Last edited: Oct 23, 2012
  18. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    A steam powered wheelchair...if I was younger I would build one! :eek:
     
    Last edited: Oct 23, 2012
  19. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    An EMP is like an instantaneous strike of lighting but worse, this huge influx of current can pop the resistor just like any other time it's subjected to too a huge influx of current... The resistor alone will likely not be effected without something else acting as an antenna that allows the EMP to build up in the resistor, but as I said that is only a guess, who knows what will really happen...

    I don't understand why you are so reluctant to take the advice given early in this thread... Put the replacement components in a metal box and hope for the best... If you want velcro it your chair, or put in on your desk, tuck it under the seat or wrap it in aluminum foil or bury it in a metal trash can... Doesn't matter if this is a solid state motor controller or a few resistors in that box, the box should in theory provide protection more protection then the motors and batteries on the chair have...

    As for what resistors, can't say you have not provided the current necessary to drive your motors under load...
     
  20. wizzinbya

    wizzinbya

    9
    0
    Oct 21, 2012
    Please read this as I have stated: I already have enough batteries, motors, controllers and joysticks to make several wheelchairs already "buried and insulated" in a Faraday Cage.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
Loading...
Thread Status:
Not open for further replies.
Electronics Point Logo
Continue to site
Quote of the day

-