Model Railway Point controller

[Twix41]

Hi all

I have an idea for a model railway point controller, i have a rather large railway layout, which has 30+ point motors, i want to build a small hand controller that i can move around and plug in where i want to be working from. It will have push to make buttons, and as small a cable as possible to connect it to the layout, i'm thinking some kind of logic/micro processor circuit in the controller, then thats sent down the connecting wire, and the reverse process under the layout which controls the point motors. Is this possible? am i barking up the wrong tree? any help would be gratefully apreciated

 

[ben7]

You can have switches that are numbered, and they can activated by entering the switch # and which direction you want it to be set at.

Have you used microcontrollers before?

Happy model railroading!

-Ben

 

[crutschow]

If you are not familiar with microprocessors, then you could use two free-running UARTS to transfer an 8-bit word serially from one in the controller to the one in your layout using three wires (1 bit, power and ground). You could select the switch number with two thumb-wheel HEX switches on the controller. Since you only need 5 bits for 32 switch points, the remaining three bits can be used for other control purposes, such as selecting/energizing the desired motor direction.

At the receive end you could used the 5 bits to control the address of a multiplexer to select the motor you want to control. You could have two parallel multiplexers controlled by the same address, each selecting one direction of the same motor. You would, of course, need an amp at each mux output to drive the selected motor and direction (two amps for each motor). Pushing the direction button on the controller would then send a pulse through the appropriate mux to the appropriate motor amp.

You could eliminate the UARTs if you can tolerate a 9-wire cable (7 bits, power and ground) to send the bits in parallel.

Does all this make sense?

 

[Twix41]

Thanks for the quick replys so far, i have a basic understanding of electronics, i did a college course a while back and a year at uni, my Dad also works on the layout, and as he's getting on a bit the idea of trying to remember 30+ different point motor numbers would be a little daunting i think, thats why I would prefer to have a small diagram of the layout on the controller, and each point motor have 2 push buttons to send the motor one way or the other.

crutschow, your suggestion of just 3 wires is what i'm looking for, i think i may have to look into UARTS a bit and see whats involved

 

[crutschow]

Thanks for the quick replys so far, i have a basic understanding of electronics, i did a college course a while back and a year at uni, my Dad also works on the layout, and as he's getting on a bit the idea of trying to remember 30+ different point motor numbers would be a little daunting i think, thats why I would prefer to have a small diagram of the layout on the controller, and each point motor have 2 push buttons to send the motor one way or the other.

That would require 60+ push buttons on the controller, which would seem to require a rather larger controller.

60+ push buttons would also require a decoder to reduce the 60+ wires down to the 6-bits to send on the UART, which is significant added complexity.

I would suggest staying with the thumb-wheel switches to select the motor, and add a small diagram with switch number versus motor location.

I did think of a way to use two BCD encoded thumb-wheel switch (0-9 each) which is easier to work with then HEX. 6-bits will select 40 (0-39) motor locations, with two bits remaining for motor direction. You can decode this signal at the layout using BCD to Decimal Decoders such as a CD4028.

 

[Twix41]

Thanks crutschow, I get the idea, just need to research a bit to work out whats needed to get this circuit working

 

[4pyros]

Twix41; Old school would be a diode matrix to select routes and the right points would move. New school is DCC. Andy

 

[mbarazeen]

what about tone encoding & multiplexing?
like you press a botton to arm all motors, it will send a common tone,(motor side controller will wait for the next comming series of tones)
then you press FWD or REV button of a particular motor so your mutiplexer will send a series of 8 bit tone that will be recognized at the correct end and will be responded to unarm (by different common tone) all other motors.(system goes to standby)
received signal will be processed by the particular end

may be an old idea

 

[4pyros]

Still simpler to do routes instead of 60 switches on a controler. Andy