DC controllers switching

Mike Smith wrote: [...]

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.

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:

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

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.

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.

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

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!)

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