Automatic control of multiple trains through ground triggers and floating grounds ?

[cruikshank]

OK, I've posted alot about this club layout we are working on.  We are controlling stop tracks, through trigger tracks, essentially completing the circuit to ground via the train wheels, thus starting the engine that is stopped in an isolated track.  So far so good.  It basically works, but tonight we ran into a problem.  We are using a Lionel ZW, the new one.  The mainline is fed off of post one, controlled through a trainmaster RC control.  Pardon me if I get that wrong, but I was "N" scale, not a Lionel guy, before I got into this club.  The stop tracks have their center rail powered through post # 2 at aproximately 14 volts, so that they will get a boost to pull out, when they are triggered to go.  This works also.  The problem is we appeared to have a floating ground or something.  On certain stop tracks the voltage does not go to zero, but we are getting about 2-3 VAC, when there should be nothing.  I know many people who use stop and trigger tracks, use relays and drop the center rail out, but since a circuit flows from one terminal, back to another, what is wrong with dropping out the ground or outside rail if you will instead?  Is there something I'm not seeing?  All of the stop tracks that have the +14 VAC on them are isolated at both outside, and the center rail.  One outside rail has the trigger wire that goes back to the trigger track to complete the ground circuit.  This layout is rather large 30 x 55, and has lots of track and switches, but we did use good practices,  minimum 14 gauge Bus, much of it 10 gauge, terminal strips, all wires labled, scotch lock connections etc.  Thanks in advance for any feedback.  I do have another question that I'll ask in another post.  Dave

[lionelsoni]

There's nothing wrong with the concept.  I use it on my elevated track to sequence two trains on the same loop.  When the "trigger track" is unoccupied, its insulated outside rail is connected only to the outside rails of the "stop track", so there should be no source of voltage across a train in the stop track.  This is true no matter what transformer you are using.  So I would suspect that something is not wired the way we think it is.

Is there anything other than the stop track connected to the insulated rail of the trigger track, like an accessory or a anti-derailing turnout's control rail?  If there were such an accessory, powered from a voltage source different from that of the stop track, you would see the voltage difference at the stop track, but probably not when the stopped train is present.  The few volts that you report might just be the difference between the stop track's 14 volts and the accessory voltage.

[chuck]

Did you calibrate the ZW?  There is a procedure in the manual to do this, page 14. If you don't run into any of the issues outlined  in the previous post, try the callibrate procedure.

[ADCX Rob]

Bob Nelson hit it right on.

There's a little current bleeding through a bulb or coil somewhere - probably a turnout.

Rob

[cruikshank]

Thanks for the replies.  All of the switches are currently manual or spring loaded so no switch motors or bulbs. There is one accessorie currently attached , a signal bridge, so I'll look at that.  Also there are some long wire runs, perhaps the resistance of the wire from the long run, is enough to cause the voltage potential I'm reading.  The first thing I'm going to do, next time I'm there, the layout is 40 miles away, is to make sure every track in the vacinity is attached to the 10 gauge ground bus.  Thanks,  Dave

There is enough voltage there that when an older F3 is sitting there, supposed to be stopped, it buzzes, but doesn't run.   We are running a control block, withing a control block as a fail safe to avoid cornfield meets.  This has happened when trains get out of time or sync, or if somehow a train blows through a stop track.   Dave 

 

[chuck]

The new ZW is an electronic power supply.  If you don't callibrate it, the handles may not be set to zero volts.