Can DCC Circuit Breakers be used with DC?

[Dungrange]

I'm currently building what will be a continuous run DCC layout in my attic.  I'm planning to include a couple of DCC Circuit Breakers (possibly the DCC Specialities PSX) between my DCC command station (the 5A Sig-na-trak ACE2) and the track bus(es).  However, I'd also like to be able to unplug the DCC Command Station and plug in a DC controller for testing, running in and just to be able to run some locomotives that I'll probably never convert to DCC.

 

My question is therefore could I pass the 0 - 12V DC voltage through a PSX without damaging it, or when looking to connect up a DC controller, would I also have to also disconnect all DCC Circuit Breakers?

 

I'd plan to include a switch to ensure that it wouldn't be possible to have both DC and DCC connected to the layout simultaneously, but whilst a DPDT switch would suffice if it was placed between the Command Station and the circuit breakers, I'd need a 4PDT, or 6PDT switch if I was to adopt the same approach with two or three PSX boards adding an extra two poles for each PSX.

 

I wouldn't be looking for the PSX's to work under DC (because I'd probably only be feeding 0.5A to the layout), just that they wouldn't be damaged.

 

Any thoughts?

 

Edited August 8, 2020 by Dungrange

[RFS]

As this is your own layout, are you likely to be the only operator? I first built my loft-based layout with 2 PSX circuit breakers. This meant that whenever there was a problem with one half, the other half kept running. I found I couldn't manage with an issue on one half and deal with the other half still running. Might be different with a club or exhibition layout with multiple operators though.

 

So I've dispensed with the circuit breakers, and any fault stops the whole layout when the Lenz command station trips. Power to the sections is through DPDT switches so if I have an unexplained fault I can isolate individual sections to narrow it down.

 

Would this work for you? 

 

The PSX circuit breakers use DCC power and I'm not sure they would like DC power, especially as when you stop a loco power goes off altogether.

[Dungrange]

1 hour ago, RFS said:

As this is your own layout, are you likely to be the only operator?

 

Most of the time I will be the only operator.  However, the layout will be able to be dismantled and could, at least in theory, be taken to an exhibition, where I'd probably have two or possibly could accommodate three operators.

 

I was primarily looking at including a Circuit Breaker so that I can have a separate Accessory Bus, so that overrunning a set of points and causing a short wont shut down the Command Station and the Accessory Bus.  However, I take your point about the difficulty of leaving something running whilst dealing with an incident, so a single PSX may be more appropriate than two or three.

 

1 hour ago, RFS said:

The PSX circuit breakers use DCC power and I'm not sure they would like DC power, especially as when you stop a loco power goes off altogether.

 

Okay, I think this answers my question.  Looking at the instructions again, I see you are correct - there is no separate power supply to the board, so the electronics on it must be powered from the DCC Input on terminals J1-3 and J1-4.  Consequently, it doesn't seem like a good idea to vary the voltage across these terminals, so if I want to be able to connect a DC controller, it looks as though the Circuit Breaker (or Breakers) need to be disconnected as well as the Command Station.  That also points to minimising the number of PSX boards, as high current multi-pole switches seem to be rather expensive.

[47137]

This has got me thinking about my own layout. Right now I have no circuit breakers and one short always stops the whole layout. As the layout grows and it becomes suitable for two operators, I think two PSX boards would be good for me - one for each end of the railway. Essentially, one PSX for the track under the auspices of each operator.

 

I also run DC from time to time. I would look to 4-pole changeover relays to isolate the PSX boards. One relay per PSX.

 

What controls the relays would depend on my imagination and enthusiasm at the time, but I suppose something local able to detect the presence of the DCC bus signal would be good.

 

- Richard.

 

Edit: there is a note here on the PSX instructions, "Not for DC, Analog"

https://www.dccconcepts.com/wp-content/uploads/2017/08/DCC-Specialities-PSX.pdf

Edited August 9, 2020 by 47137
Added link

[WIMorrison]

if a layout is large enough to warrant 2 operators then I suggest that it should also have separate power busses for the track and accessory operation. Especially given that 2 operators on DCC are much more liable to overrun a turnout set incorrectly by the other operator. The separate accessory bus will facilitate resetting the turnout correctly by either operator.

[Dungrange]

2 hours ago, 47137 said:

Edit: there is a note here on the PSX instructions, "Not for DC, Analog"

https://www.dccconcepts.com/wp-content/uploads/2017/08/DCC-Specialities-PSX.pdf

 

Doh!  Thanks for pointing out the obvious.  I did read the instructions on that link previously, but never noticed the rather obvious "Not for DC, Analogue" in a box at the top of the page!!  That therefore confirms that if I want to accommodate the ability to run DC, then these would need to be disconnected first.

 

I haven't started track laying yet, so it will be a while before I actually get to wiring anything other than droppers, but I need to think about how the grander wiring scheme will look sooner or later.