What switches for cab control?

[Pete the Elaner]

I am planning a layout which will have 4 circuits which I want independently controlled.

I was thinking of using 4 controllers, being able to switch each controller to each circuit. I was thinking of using rotary switches but the standard electronic ones are only rated at 300mA. I have done some research into higher-rated ones but they the only ones I can find are about £30 each & I dread to think how big they are.

Does anyone have any recommendations? I could use a bank of toggle switches for each section but I would prefer something more elegant.

[cpman46]

Might I suggest one possible solution is to use the rotary switches to control 12V dc DPDT relays to switch the controller outputs if you are worried about the curent carrying capacity of the switches. A typical type 47 relay has contacts rated at 2A. In normal operation I would expect to be changing over controllers when their outputs were set to zero and therefore not switching any appreciable current.

Just a thought, no doubt there will be many other equally valid suggestions.

Regards

Mike

[dhjgreen]

The 300mA rating will likely be at 250 volts to minimise arcing. As you will not be drawing any current when you switch, you will be OK. Make sure you buy "break before make" to avoid connecting two controllers together momentarily.

[34theletterbetweenB&D]

... I would prefer something more elegant.

 You can do it manual telephone exchange style with a plug board. First sectioned layout I ever saw the operating side of was so equipped, and it was mighty efficient.

 

Include the beauteous young lady  as seen in GPO informational films of the 1920s to make the connections and say "You are now connected, go ahead driver" and you will be at the apogee of elegance.

[kevinlms]

I would agree with the advice already offered. It is bad railway practice to switch a cab on while power is on at the controller and a train on the track, causing the 'startled rabbit' effect'. So I wouldn't worry about it too much.

 

The switches are fairly robust & you shouldn't damage the switches, unless you have very old models, with magnets that are shot. In that case, you will have lots of other problems, especially heat related, further damaging the motor!

[Gordon H]

If using just rotary switches you should also bear in mind that you may be briefly switching sections between controllers that are already in use, e.g  if you are using Controller 1, and want to change to Controller 3, you have to go through the Controller 2 position to get there.

A bank of 'Radio Buttons' per section would avoid this situation, but is a somewhat cumbersome solution - and they not so easy to get hold of these days.

Personally, I would use a relay based method similar to the one I produced a while ago for the Abingdon club.

[Dunsignalling]

It is bad practice to use a rotary (or other) section switch to isolate a loco or train.  

 

The classic reason for not doing so is that, at a terminus, where an arriving train is subsequently to leave having had another loco attached to the other end, the "arrived" locos have to be isolated by other means than the section switch in order to prevent them following it out.

 

Switching a section between multiple cabs using rotary switch will inevitably cause momentary connection of controllers that may be in use elsewhere. So long as the layout is designed with isolating sections and dead ends in the right places, there should be no chance of powering up a loco by accident.

 

As a matter of design, in order to save unnecessary wiring, consider which cabs will need to control any particular section. In the case of one large layout I know, there are six cabs but no section can be switched to more than three of them - the others wouldn't be used even if they were connected. 

 

John

[Pete the Elaner]

Thank you for all the responses. I had not considered that the current limit would regard arcing so it sounds like the rotaries may be ok as long as the power is off. I could use another switch to turn the circuit on & off.

I actually used rotaries on an older layout of mine, ignorant of the fact they were rated at 300mA & never had an issue. I never switched a live circuit though.

 

It is not for my layout so I want to keep it as simple as possible in case something goes wrong, so although I had thought of relays I am also mindful that they are potentially another level of complexity.

[Chimer]

Apologies if I'm misreading your original post and you know this already, but remember what you need to be able to do is select which controller is linked to a circuit, not which circuit is linked to a controller - because you may want two circuits driven by the same controller in order to pass a train from one to the other, while you definitely don't want two controllers trying to drive the same circuit.  So it's four controllers and one circuit wired to each switch .........

 

Cheers

 

Chris

[DCB]

I use some old open frame rotaries which I bought from Hardings in Cheltenham high street 25 years or so ago, these are break before make and I have 3 pole 4 way,  and 2 pole 6 way in use. They cope with up to 2 amps when banking with an On Track 2 amp controller and two tired H/D mechs.

 

I also use some Maplin rotaries apparently rated at 0.3 amps for 20 plus years without issues in a terminus station but where power is much lower, 1 loco at a tine usually.

 

I have the layout set up so I can control 90% of it from any one of 4 controllers. two of these have wander lead controllers, only the hidden siding loco yard cannot be operated by anything but its own controller.

 

The layout was intended for 3 or more operators but I often find myself operating alone which is where the flexibility is invaluable. 

 

The interference between controllers when switching can be minimised by choosing positions for the circuits, so you don't switch across a circuit  powered up.  My up main switches are wired Shunt-Off-Down-Up with "Up" straight up and the Down  Shunt-Off-Up-Down with "Down" straight up so all switches normally point straight up.  Any of 4 controllers can be connected to "Up" or "Down"

 

An off position on a rotary is really essential if you want to prevent stray trains moving, I made the mistake of not providing them.

 

I would suggest a trip to your friendly local electronics supplies shop where there are probably dusty boxes full of open frame rotary switches, twin wafer quad wafer all sorts. Probably dead cheap.  Hardings are.

[Pete the Elaner]

Apologies if I'm misreading your original post and you know this already, but remember what you need to be able to do is select which controller is linked to a circuit, not which circuit is linked to a controller - because you may want two circuits driven by the same controller in order to pass a train from one to the other, while you definitely don't want two controllers trying to drive the same circuit.  So it's four controllers and one circuit wired to each switch .........

 

Cheers

 

Chris

Good point & well worth mentioning.

Having read my original post, it seems to have been a little vague in this respect. I always intended to place the switch on the track circuit & not the other way around.