Frog power routing

What I am looking for, is a schematic for an automatic frog power routing module. Something like the DCC automatic reversing modules, but with only three wires. One to the frog, and one to each of the rails (that are insulated from the frog). The idea is that (assuming the frog is the "wrong" polarity) the module will detect the short, and then flip the frog feed. Basically an electronic equivalent of a SPDT switch mechanically connected to the turnout linkage.

Ideally, there is no connection (in any form, ie slide switches, reed switchs, haal effect ic) to the turnout control mechanism. It then has some application in two areas - trailing through spring loaded turnouts, and crossings. Particularly crossings, which have no moving parts, but still require polarity changing the acute frogs. Ideally the module would be totally solid state, and encased in epoxy.

And on a related note, does anyone have a circuit for a DCC reversing module?

Reply to
Robert Small
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Bob, what are you using to move the points?

Reply to
Frank A. Rosenbaum

Interesting idea.

You will find one here, see "Auto reverse module"

Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Reply to
Keith Norgrove

He said they're spring loaded and he's trailing through them.

Reply to
Christopher A. Lee

Thanks, I missed that on the first read.

If there is an automatic circuit for the spring loaded points, wouldn't it keep switching on and off between the trucks of each car as the points return to their normal position?

Reply to
Frank A. Rosenbaum

As the resident Luddite, might I suggest cutting a 1/4" isolated rail section in the common rail of each track from the turnout which would complete the solenoid circuit of the point motor to throw the turnout to the correct route? The frog would then be the correct polarity for the wheels to roll through.

Regards, Greg.P.

Reply to
Gregory Procter

What point motors? Don't have those on either spring switches or diamond crossings.

Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Reply to
Keith Norgrove

No. Because there is no correlation between the position of the turnout switchblades, and the polarity of the frog.

When trailing through, the switchblades will flip back and forth, but because the frog polarity is determined solely by some electronic means, it (the frog polarity) does not change.

If the frog polarity was switched by the turnout linkage, then, yes, it would change. And this is why I am needing a solution which does not have any mechanical positional input.

Reply to
Robert Small

Except that there is no point motor.

Reply to
Robert Small

Quite, In those pre-electronic days 40 years ago we used such methods on an exhibition layout I worked on. We started with your suggestion but found that contact was unreliable and the current needed for solenoids caused excessive sparking fairly quickly making the contact even worse. We changed to wire wipers contacting the back of the flange which much improved things but still not good enougfh to get through a days show reliably. We then changed the solenoid for a pair of telephone relays with 1000ohm coils, set up with a stick contact on one fed through the back contact of the other. Hence a pulse on the one wiper would pick the first relay which then held in, a pulse on the second relay would cut the feed to the first relay dropping it. If you want to try it I see no reason why a set up like this can't be used with dcc, it can run off the dcc track power with a rectifier to power the relays, appropriate relays can be had for less than Atlas snap relays, at least they can here in the UK. Any of these methods will require metal wheels on the front of the trains.

Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Reply to
Keith Norgrove

It's more complicated that that. The sprung blades will themselves cause a short circuit. You would a track section isolated at both ends, at least as long as the longest locomotive, with something to sequence power to

  1. Before it and in it, no power after it.
  2. only in it, no power before or after it
  3. in it and after it, no power before it
Reply to
Christopher A. Lee

And the point blades will cause a short with normally wired turnouts

Reply to
Christopher A. Lee

Reply to
Chuck Kimbrough

Isn't it amazing how many idiots don't know what you are trying to do? The only way that you can get the frog power right is to detect a train before it gets to the turnout. In that regard, there are many ways of doing it from a photodetector sensing that the light is severly decreased by the train going over (point the detector at an overhead light for best results), to a contact that the wheel hits and shorts it to something else, including the track, to electronically detecting when current is being drawn from that particular track (Twin-T and it's derivatives of sensing current) and so forth. Personally, I'd go with the photodetector design (there are several on the web that work) as this won't affect the voltage on the track and is quite foolproof in its operation. The outputs of the two detectors will probably best drive a relay or switch machine motor to actually control the polarity of the frog itself.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Reply to
Bob May

No it isn't.

They won't, the sprung blades will be bonded to their adjacent stock rails as in any other 'DCC freindly' turnout.

No you don't, you just need something to change the polarity of the frog before the train reaches it, several suitable triggers have been suggested. An alternative is an electronic unit to switch the frog instantly as the short occurs, which was where this discussion started. It should be fairly easy to adapt a DCC reverse loop module to do this. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Reply to
Keith Norgrove

A DC power supply to the relay coil driven by an SCR fed from the contact rail would resolve that.

Reply to
Gregory Procter

We're back to a point motor driving the points in that case - yeah, I overlooked the points causing a short! =8^O

Regards, Greg.P.

Reply to
Gregory Procter

What's normal?

There are two ways to wire the point blades.

One has them both electrically the same, and polarity switched with the frog (and this is what you call normal). In this case, yes, there is a short if a wheel touches the back of the open blade.

The other way has each switch blade electrically tied to its mating stock rail (and isolated from the frog). In this case, the open blade and the stock rail are the same polarity, so there is no short potential. It also means that you can have much less point throw, since if a wheel back touches the open switch blade, there is no short. For the DCC crowd, this is the "DCC friendly" version.

I believe that some vendors offer one kind, others the other, and some both. I build my own.

Reply to
Robert Small

No. Because the switch blades are electrically bonded to their mating stock rails (and insulated from the frog).

Reply to
Robert Small

Sorry to be of little help here but sure glad I switched to 3-rail a few years ago. I don't miss the days of reverse loops and switch polarity very much. AC operation sure makes things simple. Kinda like me. :)

Reply to
Corelane

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