Simple wheelchair motor controller

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...

 

the chances of emp affecting are really that high?

 

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...

 

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...

 

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...

 

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.

 

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...

 

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

 

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...

 

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...