How does this Electric Floor work?

[xanhast]

How does this "Electric Floor" work?

Hi,

I was day dreaming, thinking about how to power a moving (model)vehicle. I thought about monorails, dodgems and about how to power dodgems using only a single surface.

I then looked up the http://en.wikipedia.org/wiki/Bumper_car" and read, with no citation:

A newer method uses alternating strips of metal across the floor separated by insulating spacers, and no ceiling grid. The alternating strips carry the supply current, and the bumper cars are large enough so that the vehicle body can always cover at least two strips at anyone time. An array of brushes under the car make random contact with whatever strip is below, and the voltage polarity on each contact is sorted out to always provide a correct and complete circuit to operate the vehicle.

How do you design that last part?


Extra:
I was curious and looked around some more and found that the (coincidently local) dodgems seen http://www.flickr.com/photos/newporteye/5130627965/" .

Thanks for your help.

 

[davenn]

Hi There

Assuming we are referring to DC voltage supply from the strips to the dodgem car sorting out the polarity is easy. One common way is to use a bridge rectifier it doesn't matter what polarity the DC is applied to the AC terminals the rectifier will always produce +DC on the + terminal and -DC (0V) on the negative terminal

its a method many of us use in portable equip in the field, powered off batteries, where it could be easy to accidentally reverse the DC supply connections

Dave

 

[Fish4Fun]

I would assume you would need at least four brushes to assure you were always in contact with both supply rails. The following diagram would use two diodes per brush to achieve a DC signal to the motor regardless if the rails were AC or DC.

Fish

 

[xanhast]

That's what I was after, thanks Dave.

Yes Fish, though 3 brushes would be suffice?

How do you think they made this safe? Wouldn't you get a heck of a shock if you fell on this?

 

[SirAskalot]

Fish: You probably want to switch polarity on one row of diodes.

xanhast: Not quite sure but I guess the voltage is relative low.

 

[Fish4Fun]

Yes Fish, though 3 brushes would be suffice?

How do you think they made this safe? Wouldn't you get a heck of a shock if you fell on this?

You would have to work out the geometry; I would guess that it could be done with three, but I am sure it can be done with 4 :-)

As far as "Safe"...hrmmm, not entirely sure the old ones were safe, LOL. The "old ones" used the floor for one leg (I would assume ground) and the roof for the other (eliminating the need for geometry AND rectifiers). I would guess that the "new ones" using the floor in your picture, simply use relatively low voltage DC (12V to 48V), and that the source is turned off when people are on the track (and not in the cars).

Fish

 

[Fish4Fun]

SirAskalot,

Good Catch, LOL. I fixed it.

Fish

 

[ixlr8nz]

Hi guys,

Sorry to bring up an old topic but was just wondering what happens if one of the brushes shorts out the + and - at the same time?

This system could actually be used on small table top size rc car tracks etc (then you wouldn't need batteries). It might be possible to use copper tape like many wooden slot car tracks use to deliver the power rather than steel.

Thanks
Mike

 

[AlephZero]

Sorry to bring up an old topic but was just wondering what happens if one of the brushes shorts out the + and - at the same time?

Read the description carefully:

A newer method uses alternating strips of metal across the floor separated by insulating spacers ...

 

[ixlr8nz]

That is correct but in reality the spacers are about an inch wide and are there to stop each of the plates from shorting on themselves (going off the pictures I can see.) I'm sure the brushes are fairly big in comparison to carry the current (of course I haven't seen any so am not 100% sure). My question still stands.

thanks
Mike

 

[Tinselworm]

Hello, I am new on here but I have worked on these go karts and dodgems since they opened in 2010. the floor system is all run from a single transformer, so that the go karts and dodgems share a voltage of 54v between them, and an amperage of 800A, which is quite high but essentially safe to touch with dry hands, as most of us have accidentally done at one time.
They will short if a contact is sustained between the 2, and are powerful enough to do this damage...
http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc6/163183_502179968604_781353604_6049727_4777406_n.jpg
the floor runs one strip as positive (54v) then the next strip earthed, then positive, etc... The brushes are roughly 1.5 inches wide but are rounded as so that only a small amount is in contact with the surface of the track at one time, they are seen arranged on the bottom of the kart in this picture.
http://a2.sphotos.ak.fbcdn.net/hphotos-ak-snc6/165752_10150094403158605_781353604_6123052_967004_n.jpg
the insulating strips are the same width as the contactors, and in some cases will create a bridge between the 2 sides but it will only ever be momentary, and some sparks will appear, this probably happens to every kart and every dodgem on every race at least once.
A dead short will make the track cut off after 60ms, and it will not turn back on until the short is cleared. The go karts and dodgems both have the current leading into inverters, the karts have 2 of these, and they will invert the current from DC into AC for the motors. Each go kart runs the AC current directly through a magnetic switch, which allows the voltage to be immediately cut off if a short is applied, this is through a low voltage input for the magnet which activates when the kart is on, but when an over/under current or short is detected, the Curtis controller cuts off the power and the magnet will drop, this is set by the Controllers to be activated whenever the track shorts out, so that no damage can be done to a go kart when the track comes back on. Due to the current being so high, it is carried through cables of 3/4" diameter. There is actually a very small tabletop copy of the dodgems, hidden by the go kart tracks that is fully working, and available to play, it runs on the same system.

I hope I have been of use.

Tinselworm.

 

[sophiecentaur]

Hello, I am new on here but I have worked on these go karts and dodgems since they opened in 2010. the floor system is all run from a single transformer, so that the go karts and dodgems share a voltage of 54v between them, and an amperage of 800A, which is quite high but essentially safe to touch with dry hands, as most of us have accidentally done at one time.
They will short if a contact is sustained between the 2, and are powerful enough to do this damage...

the floor runs one strip as positive (54v) then the next strip earthed, then positive, etc... The brushes are roughly 1.5 inches wide but are rounded as so that only a small amount is in contact with the surface of the track at one time, they are seen arranged on the bottom of the kart in this picture.

the insulating strips are the same width as the contactors, and in some cases will create a bridge between the 2 sides but it will only ever be momentary, and some sparks will appear, this probably happens to every kart and every dodgem on every race at least once.
A dead short will make the track cut off after 60ms, and it will not turn back on until the short is cleared. The go karts and dodgems both have the current leading into inverters, the karts have 2 of these, and they will invert the current from DC into AC for the motors. Each go kart runs the AC current directly through a magnetic switch, which allows the voltage to be immediately cut off if a short is applied, this is through a low voltage input for the magnet which activates when the kart is on, but when an over/under current or short is detected, the Curtis controller cuts off the power and the magnet will drop, this is set by the Controllers to be activated whenever the track shorts out, so that no damage can be done to a go kart when the track comes back on. Due to the current being so high, it is carried through cables of 3/4" diameter. There is actually a very small tabletop copy of the dodgems, hidden by the go kart tracks that is fully working, and available to play, it runs on the same system.

I hope I have been of use.

Tinselworm.

Thanks. Those pictures plus your info have 'short circuited' a lot of 'potential' BS!

 

[ixlr8nz]

Thanks very much for the reply and photos - awesome job.