DC controllers switching

Am I missing something here - I am helping a chap build a layout, he has
purchased a Morley Vortrak Zero Nine 4-track controller with built in CDU
and plain 12v accessory outputs, which is way more than he is ever likely to
need. This unit provides straight DC 0-12V at up to 1.1A per circuit, no
feedback. The unit comes with two hand-held 'walkabout' type controllers
however these will not be used in this case as (for medical reasons) the
chap will be sitting in the centre of the layout.
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The layout is two ovals, one high the other low, with an incline connecting
the two. This allows trains to be left orbiting on the upper deck whilst
shubnting takes place below.
I was planning on using a track diagram on a bit of cut-down computer case
with DPDT switches to select between controllers for individual sections and
prepared a drawing based on that - However he tells me there is a warning
included in the paper work saying that 'at no time should two controllers be
connected together' or bad things happen.
I looked at the drawing and realised that if, or rather when, he switches
one section to one controller and the next to another controller the engine
will bridge the gap, connecting the two together.
I never had a problem with the old GF/Gaugemasters I use, and at some point
I may have done exactly that.
Anyone think this is an issue? Is there some aspect of switching that I
have been missing?
Regards
Mike
Reply to
Mike Smith
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IMO the warning implies that the unit contains a single power supply, with the output going to two controlled circuits. If that is indeed so, it is the _worst_ possible way to provide multiple controlled outputs for a model railway, as it practically guarantees that the plus and minus side of the single power supply circuit will be connected directly (as in your example.) IMO, such powerpacks shouldn't be allowed. Even with only an amp or so of nominal output, if the fuses are slow acting it's possible to cause a minor fire, which could of course turn into a major one.
You could use some combination of fancy wiring, diode logic or relays to prevent what you fear. Eg, you could put an engine-length block between operating blocks, and wire it such that if both controllers try to connect to it, it goes dead.
But it's much simpler to just get two truly independent controllers. Train-set powerpacks are just fine for this. Just use the AC output, and incorporate a diode bridge in the handheld controller, or crank the controlled DC output to max and leave it there. Any handheld DC control unit will work with any DC supply of suitable voltage.
If the Vortrak unit is truly one power supply with divided outputs, I strongly suggest returning it, and replacing it with two smaller controllers, or with a truly dual unit (such as the Gaugemaster).
HTH wolf k.
Reply to
Wolf K
I'd drop the makers a line and ask. Include your wiring plan for a section of the layout, and illustrate the problem you are concerned about. The makers are producing a high cost product which implies decent support levels.
The makers say they are using separate transformers for each controller, so there shouldn't be a problem of a common earth arrangement. Therefore, I can't see what the issue would be for the controllers. The loco under the influence of two controllers may change speed. But I'm not an electrician !
- Nigel
Mike Smith wrote:
Reply to
Nigel Cliffe
Thanks - Over the years I must have done this at some point with my old GF controlers, and never had a problem, but the fact they added a separate sheet of paper with a specific warning worried me a bit.
Regards
Mike
Reply to
Mike Smith
I have two dual MRC280 transformer/controllers, and I have no problem having two controllers (from different units) connected in parallel while I'm in the process of switching over. If the controllers are set to the same position, it doesn't affect the speed of the loco; a parallel connection doesn't change the voltage.
Reply to
MartinS
As the controllers mentioned have a soft start ( presumably an AC dither superimposed on the baseline DC) then the makers may be concerned for the worst case -- total reversal of polarities -- which possibly could cause componant failure. I have read of the need to "return to maker" - albeit with good swift turnaround times - for short circuit damage.
If this is the case then it is a controller unsuited for normal mortals.
I have used 6 controllers ( I have to work solo) with hand over sections involving parallel power transitions using H&M without problems although I must confess to repairing and even modifying them after component failures , this was usually the off micro switch of the output control.
Reply to
Sailor
Maybe I'm miss the point here, but wouldn't old fashioned "Cab Control" solve this problem?
I use two different controllers, but since each section on the layout can be switched to either unit, there's never any need to hand - off from one to the other.
DC
Reply to
dc
When setting a route which involves section changing and maybe 3 controllers there will always be a point when pickups straddle two units. With normal controllers of reasonable sophistication each will shut down on overcurrent if the two have any polarity problems! This, in my view is a good safety feature.Even cab control works in the same way unless you have a system which requires one loco supervision only.
I begin to think that with DCC chips reverting to default or other addresses when frogs spark or X914 motors go off like rockets ignoring all the pleading from the acc/decell settings that dc revisited could be a real possibility. (At least the new Hornby 37 and the bachmann 37 behave nicely and restore the faith!)
Reply to
Sailor
Yes the problem is somewhat inevitable, if one section is switched to one controller and the adjoining section to another as the loco crosses the gap it connects the two together, it was just the warning they included that worried me, currently on-site with a job but will e-mail the makers before going over to finish the wiring for him (he's busy with scenery at the mo).
Rehards Mike
Reply to
Mike Smith

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