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Gentlemen,

I'm working on a rather large layout.  I have two switches that I would like to run "automatic" non derailing using twin coil switch machines.  Is it a problem to allow the wheels of a long train to constantly activate that coil in that manner?  If so, does anyone make a unit that will allow that switch to activate say, once per minute (while allowing for a manual override momentary switch)?  Keep in mind that I am an art and scenery guy.  So if you send me some circuit to build...well...

I had several capacitor discharge units that were supposed to work for this.  But these did nothing to control the amount of times the switch activated and when it did, it seemed too powerful.  I set these units aside as dangerous as they created arc marks on the truck I was using to test with.

Thanks,

Troy

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If your capacitive switch machines were causing burn marks in the wheels, they have no inrush protection, it's easy to prevent that with a low value current limiting resistor.

You don't mention the make/model of the twin coil switch machine, but if it's the Atlas switch machine, do NOT let it be continuously energized unless you like swapping them out regularly!

I have a drawer full of old "in the box" NJ Switch machines.  The arcing was being caused by the so called capacitor discharge units.  Now removed.  Am I being over cautious on this?  Once a set of wheel hit the insulated track to through the machine, it actually only throws once.  But would a long train in the block keep power to the coil and burn it out?  Or is that only if the switch machine would continue to throw causing arc build up at the points?

My thought was a small time delay switch, but I can't seem to find a low voltage AC unit.  I found some 110V that can be set up to several minutes.  But they don't list  a minimum voltage to work.  Do you think 18 volts would be to low?  And again, maybe I'm over thinking this.

Troy, I assume you have short insulated rail sections you're using to throw the switch machine for non-derailing operation.  If you wire these sections directly to the coil, you will burn it out after a while.  Here is how to wire your NJI machines so that the switch machine only gets momentary power to throw the switch.

The NJI machine has 6 thin spring metal bands with contacts at the ends of them.  You only want to use the inner 4 contacts for non-derailing as shown below.

Slide1

Note that with the switch thrown in one direction, the contacts away from the machine (call them A and B) are closed and the contacts next to the machine (call them C and D) are open.

Slide2

With the switch thrown the other way, the contacts next to the machine (C and D) are closed and the contacts away from the machine (A and B) are open.  You can bend the ends of the contact bars A and D to make sure you get this opening and closing action.

Slide3

To make it work, the wire from one of your insulated rails goes to a contact strip B and a wire goes from contact strip A to one of the outside terminals on the coil.  The wire from the other insulated rails goes to a contact strip C and a wire goes from contact strip D to the other outside terminal on the coil.  An A/C hot switch machine power wire goes to the center terminal on the switch machine coils.  You can also see this wiring in the first photo above.  The two capacitors are optional to decrease arcing in the contacts but they are a pain to solder into place and are not needed to make this work.

Slide4

Troubleshooting:

1) If the switch machine doesn't throw when you roll a car across the insulated rails, reverse the connections of the insulated rail wires to the contacts.  In the photo, if the copper wire was connected to contact B as shown, unsolder it and connect it to contact C.  Move the silver wire to contact B.

2) If the switch throws the wrong way when you roll a car across the insulated rails (making it a derailing switch instead of a non-derailing switch), reverse the connections from the contacts to the machine coils.  In the first photo, swap the positions of the silver and copper wires that connect to the outside terminals of the coils.

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@Crazy J RR posted:

I am kind of surprised no one has made a "delayed" circuit for sale.  Something where you can "dial up" a time (say up to a minute) before the switch will receive power again.

Well, when you think about it, an arbitrary delay like that would likely be a significant drawback unless you have a very fixed operating cycle.  I have trouble imagining a scenario in normal running where I would tolerate the non-derailing failing unless a minute went by since the last activation!

I have a large number of Ross switches equipped with DZ1000 machines w/DZ 1002 controllers.  Here's an exchange I just had with Dennis Zander who manufactures these machines:

Dennis,

I've wired a number of switches for automatic non-derailing. After one of these switches has been automatically thrown, is the switch electromagnet still drawing current? Said switch seems to remain  "quiet", even when a car is sitting on the triggering, insulated approach rail. This question occurred to me when I wired them and appeared today, in a slightly different context, on the OGR Forum.

Hal

Hi,

The switch machine motor has power removed when the final position is reached.

Dennis

So, no possibility of frying one of these, even if a train sits on the control rail indefinitely.

Hal

Well, when you think about it, an arbitrary delay like that would likely be a significant drawback unless you have a very fixed operating cycle.  I have trouble imagining a scenario in normal running where I would tolerate the non-derailing failing unless a minute went by since the last activation!

John,

Wonder if OP was thinking of letting coils cool off between activations.  But you are right, you would have to mentally keep track of how long has lapsed for each switch before activating again. OWW my head hurts thinking of this for a large layout!

But after a few derailments (at the farthest inaccessible places, of course), I am sure the OP will move onto "plan B" or "plan C"

@Crazy J RR posted:

...

I am kind of surprised no one has made a "delayed" circuit for sale.  Something where you can "dial up" a time (say up to a minute) before the switch will receive power again.

Another approach would be a timed circuit where you "dial up" a time (say up to 5 seconds) of how long to apply power for a given trigger.  So train hits derailing trigger and circuit fires for the short time it takes to operate the switch-machine.  Then it turns off and sits idle until the trigger goes away (i.e., the entire consist passes thru).  When the trigger goes away the circuit re-arms ready for the next train...which could be 1 second later.

It sounded like his major issue was the inrush current, which is an easily fixed issue.  I think resolving the issue with the CD unit would be the path of least resistance.  There are a number of designs of CD units, not all of them switch the cap current through the wheels, so one of those might be more appropriate for the job.  The CD unit is the simplest way to do this, at least IMO, so I'm trying not to throw out the baby, I think he's still alive.

I have a ton of NJ switch machines on my layout.  I drive them with 14 VAC.  I use 28  volt center tap transformers which provides two 14 volt taps.  The transformers source plenty of amps to provide the switch machine inrush current.  No need for capacitance discharge units.  You can wire the non-derailing using the NJ leaf contacts as Rob described above.  Frankly IMHO the leaf contacts are a PITA.  I use the NJ leaf contacts to control the coil on a relay which handles the switch machine coil high currents, latching which eliminates switch machine burnout and signaling.

Well, I "benchworked" the set-up described by Rob.  It was a bit of a challenge getting the contacts in the right position (and I have to say I'm concerned about the long term positioning on those) but it worked like a champ!  I will only need to set up these on four turnouts.  This will be for "bull" sessions when running trains, sippin' some Cap'n Morgan and telling fish stories.  Otherwise, this 30X50 double deck monster (50+ turnouts so far) is intended for hands on operation.  But when the Cap'n flows and the BS flies, those key points need to work by themselves!

Thanks boys!

@Crazy J RR posted:

Well, I "benchworked" the set-up described by Rob.  It was a bit of a challenge getting the contacts in the right position (and I have to say I'm concerned about the long term positioning on those) but it worked like a champ!  I will only need to set up these on four turnouts.  This will be for "bull" sessions when running trains, sippin' some Cap'n Morgan and telling fish stories.  Otherwise, this 30X50 double deck monster (50+ turnouts so far) is intended for hands on operation.  But when the Cap'n flows and the BS flies, those key points need to work by themselves!

Thanks boys!

If it's reliable operation you're looking for on only 4 turnouts, I would recommend ditching the NJ turnouts.  Your experience and suspicions about the NJ leaf spring contacts are well founded based on my experience.  Tortoise switch machines would be the choice for reliable under layout mount.

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