Common return wiring on Gaugemaster D controller

[RichardEyre]

I originally set my layout up with common return wiring as per the diagrams on Brian Lambert's website, but got odd results. It appears that the 12V DC and 16V AC share a winding, and cannot be used for common return.

 

However, does anyone know if the 16V AC connectors share a winding with either of the controlled outputs? I can remove the 12V DC from common return very easily, but I'd rather keep it for the 16V AC if possible (Tortoises with steering diodes).

 

The documentation says the controlled outputs support common return, and the accessories don't, but doesn't mention combining the controlled with the uncontrolled.

 

Thanks in advance, Ric

[Brian]

Hi

Taken from the Model D leaflet....

 

The “16v AC Accessories” terminals are for use with point motors and other AC electrical accessories, but are not suitable for Common Return wiring with the DC outputs.

This means one of the two windings on the dual wound transformer is used to power both the 12 volt dc controlled and 16 volt ac uncontrolled outputs.

Therefore the ac output cannot be used with a single wire common return system that also has the track (Controlled) returns on it too.

[RichardEyre]

Hi Brian,

 

That's what I read, but wasn't sure if it meant only between the 2 accessory outputs, with the 2 controlled handled separately. Thanks for clarifying that for me.

 

Ric

[Kenton]

I don't understand what you were thinking.

Mixing DC and AC is never going to work!

Common return is used to describe both AC and DC circuits but NOT a combination of them.

The AC "common" return isn't really a common return circuit where transformer windings are connected. It is simply used to describe a circuit where one side of the AC is wired on a continuous run to each element (in your case point motor - ?Peco solenoids?) and the other side of the element is switched.

True common return is where one rail is wired common to both transformers and the other side of the two transformers are switched into the other rail. Both are DC circuits and are switched as either one controller or the other - never both.

[RichardEyre]

I see no difference between having 2 controllers supplying 2 isolated sections of track with different voltages, and supplying a combination of lights/motors/track.

 

Surely it's the PD between the 2 sides of the output that's important, not what's happening over any particular piece of the return wire? If you can have 1 controller forwards and 1 controller reverse over a common return, why not an AC source too? That's basically as if someone were switching a track controller from forward to reverse 50 times a second, and from your description there's no reason that wouldn't work (aside from the obvious physical restrictions).

 

From Brian's explanation above (I'm sure he will correct me if I'm wrong) I believe that mixing AC and DC on common return will work, except that my controller used shared windings for some of the outputs.

 

For the record, my motors are Tortoises, wired with a single wire supplying half wave DC from the AC supply (via a pair of diodes).

[Brian]

Not sure what you're meaning Kenton??

You can Common return ac and dc on the same single wire, so long as all the power supplies or windings on a dual/triple wound transformer supplying the power are totally separate.

 

So for example... a common return wire of suitable wire gauge size, can have Controller 1 rails rtn, Controller 2 rails rtn, Controller 3 rails rtn (and so on) and then have all the ac fed point motors returns and any dc powered lighting return too. So long as each supply is totally separate.

The problem arises, as a short circuit, when two items share a power supply (Such as with the GM Model D) and then these outputs cannot be common connected.

[kevinlms]

I originally set my layout up with common return wiring as per the diagrams on Brian Lambert's website, but got odd results. It appears that the 12V DC and 16V AC share a winding, and cannot be used for common return.

 

However, does anyone know if the 16V AC connectors share a winding with either of the controlled outputs? I can remove the 12V DC from common return very easily, but I'd rather keep it for the 16V AC if possible (Tortoises with steering diodes).

 

The documentation says the controlled outputs support common return, and the accessories don't, but doesn't mention combining the controlled with the uncontrolled.

 

Thanks in advance, Ric

 

 

Simple answer.

 

If you have common return on the output side (connected to the track), you cannot share transformer windings between controllers or accessories as these are also common returns, in other words - you must have a seperate power supply for each device you're trying to power.

 

Kevin Martin

[Kenton]

Not sure what you're meaning Kenton??

You can Common return ac and dc on the same single wire, so long as all the power supplies or windings on a dual/triple wound transformer supplying the power are totally separate.

 

So for example... a common return wire of suitable wire gauge size, can have Controller 1 rails rtn, Controller 2 rails rtn, Controller 3 rails rtn (and so on) and then have all the ac fed point motors returns and any dc powered lighting return too.  So long as each supply is totally separate.

The problem arises, as a short circuit, when two items share a power supply (Such as with the GM Model D) and then these outputs cannot be common connected.

Simply, I was always taught not to mix DC and AC.

 

I accept your superior knowledge on these things but just cannot see a justification for doing so. Even more so when it results in a problem. Layout wiring is complicated enough for most people (often made more so it seems). I would continue to advocate keeping your DC track supply bus separate from the accessory bus.