Common return using two different types of controllers?

[Clive Mortimore]

1 hour ago, kevinlms said:

But the Model D specifically says that it is suitable for Common Return. I think your information is well out of date.

The information related to transformers in parallel. The OP states two different makes of controller with two transformers.  Common return places the sections of track in parallel, therefore the controllers are also in parallel as they are all wired to a common return. The controllers are in series from the transformers and the sections of track, which in turn puts the output from the transformers in parallel.

 

And common return is still harder to fault find than separate fed sections.

[Sol]

Output of controllers are two wires- one goes to the common rail & the other via cab/section switches to the other rail & normal cab control does not allow two controllers to connect to the same piece of track so they can't be in parallel.

To be in parallel, both controller outputs must have both outputs joined, so where Clive, where do you get that concept? Did you read those links I provided?

 

[Sol]

7 minutes ago, Clive Mortimore said:

The information related to transformers in parallel. The OP states two different makes of controller with two transformers.  Common return places the sections of track in parallel, therefore the controllers are also in parallel as they are all wired to a common return. The controllers are in series from the transformers and the sections of track, which in turn puts the output from the transformers in parallel.

 

And common return is still harder to fault find than separate fed sections.

 

 

and your last sentence is not true - I spent many years working with common return in the course of my employment using 3 different DC voltages  ( -ve & +ve with respect to the common earth/return ) and   low &  high frequency AC.... no problems...

[Crosland]

3 hours ago, Clive Mortimore said:

Oh yeah!

 

 

Go back a few post , the bloke who designed Gaugemaster controllers said "do not use common return". Why? There must be something he knows about them which the experts are not clocking on to.

 

It's "experts" against one guy from GM. I know where my money is going

 

[Crosland]

1 hour ago, Clive Mortimore said:

The information related to transformers in parallel. The OP states two different makes of controller with two transformers.  Common return places the sections of track in parallel, therefore the controllers are also in parallel as they are all wired to a common return. The controllers are in series from the transformers and the sections of track, which in turn puts the output from the transformers in parallel.

 

And common return is still harder to fault find than separate fed sections.

 

You clearly do not understand what common return is. As I (and others) said up thread there is ONE connection between the one side of each of the btwo transformers, i.e., the COMMON. The other sides of the transforems are NOT connected together. The transformers are NOT wired together in parallel.

 

Edit:

The only time they can be connected is if you drive a loco over an isolating gap between track sections that are fed from different controllers. This is a transient state during operating, VERY, VERY different to deliberately wiring two transformers in parallel.

Edited July 26, 2019 by Crosland

[kevinlms]

47 minutes ago, Clive Mortimore said:

The information related to transformers in parallel. The OP states two different makes of controller with two transformers.  Common return places the sections of track in parallel, therefore the controllers are also in parallel as they are all wired to a common return. The controllers are in series from the transformers and the sections of track, which in turn puts the output from the transformers in parallel.

 

And common return is still harder to fault find than separate fed sections.

Obviously your mind is made up and think Common Return is a parallel connection.

 

Almost as bad as someone else who thinks LEDs, don't need resistors!

[Clive Mortimore]

Sol showed links to common return....if they didn't show parallel what did they show?

 

Common return in cars goes back to the same power source. If the engine is running and you touch that wire that should be earthed...."wow you bu88er"!!!!!!

 

The diagram as published by Gaugemaster shows what could happen if you have one controller unplugged, it potentially becomes dangerous.

 

 

[Clive Mortimore]

55 minutes ago, Crosland said:

 

It's "experts" against one guy from GM. I know where my money is going

 

So you have made a living from model railway controllers.....'king hell I am standing up for the worse boss I ever had. 

 

 

I am so glad you all have demonstrated with a working model that I am wrong.

 

Wire up a layout with two transformers in common return, leave one unplugged, bridge two sections wired up to the two different transformers with a loco and hold the plug of the unplugged one, then apply the power.....I can't wait to see the video.

[Crosland]

1 minute ago, Clive Mortimore said:

Wire up a layout with two transformers in common return, leave one unplugged, bridge two sections wired up to the two different transformers with a loco and hold the plug of the unplugged one, then apply the power.....I can't wait to see the video.

 

I think what you mean is bridge two sections wired to two controllers powered by the two transformers. Note that a transformer is a very specific item used to transform one AC voltage to another. It does nothing on DC, other than get warm.

 

My controllers are electronic. The AC from one transformer is rectified to DC and simply cannot be connected to the secondary side of the unpowered transformer. Feeding DC from the track through an unpowered controller is simply not going to result in any lethal voltages. It might damage the controller, but that's unlikely.

 

I doubt many people use bare transformers (no controller) to power the track these days. Please show an example of a layout that is wired so. When was GM's advice actually written?

[Sol]

6 minutes ago, Clive Mortimore said:

So you have made a living from model railway controllers.....'king hell I am standing up for the worse boss I ever had. 

 

 

I am so glad you all have demonstrated with a working model that I am wrong.

 

Wire up a layout with two transformers in common return, leave one unplugged, bridge two sections wired up to the two different transformers with a loco and hold the plug of the unplugged one, then apply the power.....I can't wait to see the video.

 

Er..  how is the DC from the controllers that has a common connection, not the transformers which provide AC to the controllers, going to be converted back to AC into one transformer that is unplugged ?

 

And why would you have one transformer unplugged? Aren't all of your power supplies connected up so only one mains switch is needed to get them all working?

[Crosland]

13 minutes ago, Clive Mortimore said:

Common return in cars goes back to the same power source.

 

And is not common return. To have a common return you need more than one supply sharing the return path, i.e., having a return path in common .

 

Car wiring was commonly referred to as common positive or common  negative. All modern cars are common negative to indicate that the negative side of the battery is connected to the chassis.

[Sol]

Clive, a simple drawing to show the common so how does the DC from controller get converted back to AC on the other transformer?

[Pete the Elaner]

4 hours ago, Sol said:

 If the designer is still alive ( and reading your words Clive which I have underlined, he is )  so why not ask him what is wrong with Common return.

As I have said, it was used in telephone exchanges and many others situations in real life with Mother Earth as the common.

It is fine when used in appropriate situations by people who understand where & why they can use it, but how do they know the end user will understand?

Many modellers do not know & have no interest in learning. As long as their trains run, they do not care.

 

Instead of explaining what it is & where it can be used, it is much easier to recommend not to use it.

Edited July 26, 2019 by Pete the Elaner
Missed a 'not'...which changes the meaning somewhat

[Clive Mortimore]

39 minutes ago, Sol said:

 

Er..  how is the DC from the controllers that has a common connection, not the transformers which provide AC to the controllers, going to be converted back to AC into one transformer that is unplugged ?

 

And why would you have one transformer unplugged? Aren't all of your power supplies connected up so only one mains switch is needed to get them all working?

Two answers

 

First relates to the OP two controllers from different manufacturers, take the moulded on plug off and lose your warranty. Or do you take the plugs off and wire everything on the one plug? 

 

Second, people who would leave one unplugged and use the other one on the same common return are the same people I use to nurse, those who who would amputate a finger closing a door, fall off their ladder through the greenhouse, electrocute themselves putting up the new light fitting, ride a motor-cycle without a crash helmet........

[sharris]

2 hours ago, Clive Mortimore said:

The diagram as published by Gaugemaster shows what could happen if you have one controller unplugged, it potentially becomes dangerous.

 

the Gaugemaster diagram shows what happens if you connect the Auxilliary AC output on one controller to the Auxilliary AC output on a second controller (presumable in a rather dubious and foolhardy attempt to double the available AC current) - the auxilliary AC outputs come straight from the output windings of the transformer, so with the diagram as shown one transformer steps 240V ac down to 12V ac, while the second transformer steps the 12V ac up to 240V ac, putting a dangerous potential across the pins of a mains plug. 

 

Looking at the various 'reverse engineered' schematics of Gaugemaster controllers (it's the internet, so I can't vouch for their accuracy as I've not seen a genuine article), the general idea appears to be: 

 

Mains ---> Transformer -(a)--> Bridge rectifier ---> Potential divider pot ---> Darlington emitter follower ---> Direction switch ---> Track. 

 

with auxilliary ac output at (a).  There are a few other bits scattered around (LEDs, current cut-outs, etc. and in some versions a capacitor circuit for simulated braking).

 

Once you get past the bridge rectifier, and further past the speed control circuit it is hard to see how you can 'reverse energise' the transformer from the track outputs even if you accidentally bridge track sections (common return or not) powered by different controllers. 

Edited July 26, 2019 by sharris

[Nigelcliffe]

Clive,

 

this discussion is going nowhere because you seem to be misunderstanding, or misrepresenting something.

 

Taking Sol's diagram above, showing two transformers, connected to two DC controllers, connected to the rails, with one common return path.    Plug in one transformer to the mains.   No matter what you do on the tracks, connecting any combination of wires from the DC controllers, connecting any of the rails, there is no path to get mains to flow out of the plug of the second transformer.  You can handle the mains plug of the second transformer, hold the two mains pins in each hand, and nothing comes out of it.   

The reason being the rectifier stages in the DC controllers, there is no mechanism to get AC out from those back to the unpowered transformer. 

 

 

And, it is no different to your choice to switch both power feeds.  Modify Sol's drawing to add a section break in both rails, rather than one rail.  That would appear to represent your wiring arrangement (independent to both rails).   Now place a loco over the track breaks.   There is no electrical difference to the loco over the twin breaks compared to a loco over a single break (Sol's original diagram).  Both equally safe, electrically identical.

 

 

(  This is fundamentally different to connecting two transformer AC outputs together in parallel, which can be lethal.   Discussed earlier in thread.   
I can see why someone at a company which supplies uncased AC transformers, and cased AC-output transformers might get concerned about any common wiring because of a risk that someone decides to connect the output of AC transformers together (don't do it, its very dangerous).   But, that is creating general advice to avoid a single serious failure type.  ).

 

 

If you and others find switching both wires makes things better for you - be it understanding where wires go, fault finding, whatever -  that's fine, keep on doing it.  But there is nothing unsafe about common return DC wiring on layouts. 

 

 

 

- Nigel

 

 

 

[kevinlms]

I did come across a dangerous piece of wiring at an exhibition here in Oz (I didn't notice it, until it was being dismantled at the end of the exhibition!).

 

The builder had used an IEC extension lead to carry power between two modules. However on the main module, he used a male plug and a female socket, on the 2nd module. This is an absolute no, no and so I explained to the owner, why it was such a bad idea. (Two sets of live pins - OK when put together, but potentially lethal when being assembled).

 

The owner agreed that he'd done the wrong thing and the next time I saw it, it had been rectified.

 

It is important for those holding exhibitions, to ensure mains wiring has been done correctly (PAT Testing is best) on ALL exhibits. Better to have a static layout, than one which is dangerous. The owner probably won't be happy, but the choice has to made.

1/ Make it safe.

2/ A static layout.

3/ Take it home!

[AndyID]

3 hours ago, Clive Mortimore said:

Two answers

 

First relates to the OP two controllers from different manufacturers, take the moulded on plug off and lose your warranty. Or do you take the plugs off and wire everything on the one plug? 

 

Second, people who would leave one unplugged and use the other one on the same common return are the same people I use to nurse, those who who would amputate a finger closing a door, fall off their ladder through the greenhouse, electrocute themselves putting up the new light fitting, ride a motor-cycle without a crash helmet........

 

Clive,

 

That's just a lot of scaremongering nonsense. Now you are completely wrong.

 

It's been explained repeatedly in this thread that there is no electrocution hazard associated with interconnecting the outputs of two controllers. Either you have no idea what you are talking about or you are deliberately spreading fear, uncertainty and doubt.

 

Please stop.

 

Andy

[Clive Mortimore]

2 hours ago, AndyID said:

 

Clive,

 

That's just a lot of scaremongering nonsense. Now you are completely wrong.

 

It's been explained repeatedly in this thread that there is no electrocution hazard associated with interconnecting the outputs of two controllers. Either you have no idea what you are talking about or you are deliberately spreading fear, uncertainty and doubt.

 

Please stop.

 

Andy

I have a layout to finish, and some modelling to do.......something looking at your and your mates  contributions seems very lacking. 

[Denbridge]

10 hours ago, kevinlms said:

But the Model D specifically says that it is suitable for Common Return. I think your information is well out of date.

My last layout incorporated 8 gaugemaster controllers on a common return wiring system which performed faultlessly for 8 years until circumstances forced its dismantling.  Most of that layout is now incorporated into another huge layout with more gaugemaster controls and still with common return wiring. Whenever I visit it still runs impeccably. 

[AndyID]

1 hour ago, Clive Mortimore said:

I have a layout to finish, and some modelling to do.......something looking at your and your mates  contributions seems very lacking. 

 

Don't let us keep you

[Sol]

9 hours ago, Clive Mortimore said:

Two answers

 

First relates to the OP two controllers from different manufacturers, take the moulded on plug off and lose your warranty. Or do you take the plugs off and wire everything on the one plug?    Yes I take plugs off and join all onto one mains power  connection - 5 different power supplies after rectification  - DCC traction power, 2 different DC voltages for relays, CDU supply & a 12 vDC supply for LEDs, etc that all use the same common return.

 

Second, people who would leave one unplugged and use the other one on the same common return are the same people I use to nurse, those who who would amputate a finger closing a door, fall off their ladder through the greenhouse, electrocute themselves putting up the new light fitting, ride a motor-cycle without a crash helmet........

 

[Sol]

10 hours ago, Sol said:

 

Er..  how is the DC from the controllers that has a common connection, not the transformers which provide AC to the controllers, going to be converted back to AC into one transformer that is unplugged ?

 

And why would you have one transformer unplugged? Aren't all of your power supplies connected up so only one mains switch is needed to get them all working?

 

 

Clive, while you "answered" the latter two questions - you missed answering the first which I have now highlighted

 

and my modelling has many options & it includes Internet forums

[Clive Mortimore]

A man who rewires five mains leads into one plug is lecturing me. 

[Sol]

6 minutes ago, Clive Mortimore said:

A man who rewires five mains leads into one plug is lecturing me. 

 

I did not say I wired them all into one plug - I use mains power terminal connection strips and protected from any accidental contact - power box to hold all supplies.

The terminal connection strips are the same as found in bed lamps and portable heaters, etc.