Peco electrofrog switch...

[Flatrat]

Okay, I've done something idiotic and not sure where i went wrong. I built a basic loop with one Peco electrofrog swt. [simple loop with one switch and the train runs fine until I throw the switch] the train won't run when I throw the switch. I have two feeders to the loop but didn't run one to the turnout. Where did I screw up?

[nkalanaga]

No insulating joiners?  The problem is simple, but not obvious.  The frog is live, and the rails beyond the frog switch polarity with the frog.  Suppose the frog is positive when the train is going round the loop.  When the switch is thrown, the frog becomes negative, but the rail beyond it is still fed by the original positive feeder.  Thus, a short circuit.

The solution, for a simple loop, is equally simple.  You need an insulating joiner beyond the frog.  For simplicity in wiring, I'd put one in both rails of the main line.  Electrically, you'll then have a switch with two dead-end tracks beyond the frog, and no shorts, unless you try to run a loco through the closed switch.  But you wouldn't do that, would you?

One of the basic rules of wiring with power-routing turnouts is that power cannot be fed from the frog end of the turnout.  For more complicated layouts this can get tricky, and in some cases, can result in dead sections of track.  All of the insulating joints are there, but someone missed a section that needs a feeder.

[Flatrat]

Okay. I apologize for being so obtuse and...well never mind. But it sounds like, from what you post that if I put insulating joiners, going into the switch from the mainline my short circuit will go away. Correct?

[GaryHinshaw]

It depends on what you mean by "going into the switch".  Here is a diagram from Wiring for DCC that might help with how to think about it:



As nkalanaga said, with these Peco Electrofrog turnouts, the (green) frog rails are power-routed along with the frog.  If you have feeders on either of the diverging routes - and you don't have insulating joints on the end of the frog rails as shown - you will get a short.  In particular, if you have feeders on the main route, it will short when the turnout is lined for the diverging route (frog rails blue), and vice-versa for feeders on the diverging route.  If you have feeders on both routes, it will always short!  The solution is insulated joiners on the frog rails, but you then need to make sure the rails beyond the frog rails get power somehow.

HTH,
Gary

[Flatrat]

Oops. [Duh]

A diagram is worth a thousand words. Thanks

Scott

[altohorn25]

It wasn't a dumb question.  The first ntrak module I built (quite a few years ago) I used the peco electrofrogs without knowing about the power-routing and it took me forever to get it running.  Once I cut gaps in the rails (as per the diagram), everything suddenly worked.

Nate

[Flatrat]

Thanks everyone. the diagram made it clear. After studying it for a moment or two I figured just cutting the inside mainline rail just past the frog would solve my problem. It worked fine, trains are running around just great and now I can back up into the siding without having to run feeders to it. As long as I don't run over the closed switch there should never be a short.

[nkalanaga]

I agree, it wasn't a dumb question.  This problem has been perplexing people as long as 2-rail power supplies have been used.  Model magazines used to run articles every few months on how to wire turnouts. Then manufacturers started making insulated-frog turnouts...

Incidentally, it doesn't matter what type of power one uses, DC, AC, DCC, they're all wired the same.