I want to control several (model) fairground dodgem cars remotely but there are only the same 2 connectors to each dodgem ie one from the roof wiper arm and one via the floor and wheels. I have thought of a mix of AC and DC but my knowledge is limited to that giving only 2 circuits which don't interfere with each other. I think Hornby railways used to use something like I require. Suggestions anybody, please ? I'm looking for 3 circuits minimum, 4 circuits maximum.

 

Bumper cars are controlled by foot pedals in each car.
You need to build a wireless power controller for each car that overrides the foot pedal.

 

There is no electrical control of steering. I assume you might want to steer the car. An entire electro-mechanical system would have to be developed.

 

Welcome to the all about circuits general forum.
This is a new area of discussion, Dodgem cars are a new area. What is a bit unclear to me is if these are different models of full size dodgem cars or scale models, and how many is that "several" quantity?
Assuming that the requirement is for controlling all of the cars at the same time, and that each control will provide 4 circuits of ON/OFF , a wired-wireless scheme can allow control of a fair sized fleet.
That would consist of multiple 4-channel transmitter and receiver pairs, each with a separate carrier frequency, each having it's signal fed to the roof connection. This would require a high-current rated RF choke in the roof power feed line. That can be a rather simple circuit to present a higher impedance to RF.
The actual control connections to each car would be a different discussion.

 

Are you saying you want to send a control signal over the power connections? There are ways to do this, but bumper cars power would be incredibly noisy, make this near impossible. A wireless remote would be far easier.

 

Many thanks for all the replies which clearly suggest some form of wireless control is needed. By the way, this is only a model, not the real thing - and a Meccano model (if any of you are familiar with that system).

I would still like to have some practical details for a circuit which allows AC and DC to be put in and then separated (rectifier sort of thing) - eg what component values are needed for capacitors, and so on. This could control the steering for 2 dodgems separately and each car could carry a battery for motor drive on all the time - it's only a game !

 

Many thanks for all the replies which clearly suggest some form of wireless control is needed. By the way, this is only a model, not the real thing - and a Meccano model (if any of you are familiar with that system).

I would still like to have some practical details for a circuit which allows AC and DC to be put in and then separated (rectifier sort of thing) - eg what component values are needed for capacitors, and so on. This could control the steering for 2 dodgems separately and each car could carry a battery for motor drive on all the time - it's only a game !

The separation is why I suggested a series choke coil, which can be just a few turns of the power conductor in a coil. Then coupling via a small value capacitor. Evidently my explanation was not adequate. THERE IS NO NEED FOR ANY RECTIFIER to keep any RF out of the power circuits. Just look at the example of a 2-element L-C low-pass filter. Consider the frequency difference, mains frequency for the power, and several megahertz for the control signal.

 

Thanks MisterBill2 - I'll have a go at that! It keeps this 94 year old CEng (mostly mechanical) learning a bit more about electronics .... of which there weren't any when I qualified - they were electrics in those days.

 

Moel railways use a system known as DCC (Digital Command Control - https://en.wikipedia.org/wiki/Digital_Command_Control) which allows control of speed and direction and other functions such as sound using only the two wire power feed.

 

Thank you AlbertHall for the DCC note and more importantly, taking the trouble to find and send me the wikipedia pages. Quite a lot to think about !

 

OK, one thing that I neglected to say was that in the situation of an AC signal on a DC line, the AC signal is always a much smaller amplitude than the DC power. Often it is very small, perhaps ten millivolts on a DC line that may be 24 volts or more. So usually the AC portion does not affect the operation of the DC load devices. The AC signal is usually a much higher frequency than the noise present on the DC lines and it is coupled to the detection system with small value capacitors so that any noise does not interfere.
It may, or not, be similar to the DCC system mentioned above, except that in the past it was not digital.

 

DCC uses a square wave going from positive to negative, perhaps ±14V for model railway. The widths of the positive and negative sections encode the digital control information. It is around 5-10 kHz.

https://en.wikipedia.org/wiki/File:DCCsig.png

 

DCC uses a square wave going from positive to negative, perhaps ±14V for model railway. The widths of the positive and negative sections encode the digital control information. It is around 5-10 kHz.

https://en.wikipedia.org/wiki/File:DCCsig.png

K, now that I know what DCC is, what I am describing is not at all similar, except for being a control system over the power wires. So no other similarity at all..

 

Many thanks MisterBill. I am now getting lots of info and will report any (satisfactory) circuits I may be able to devise.