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Model Forum / General / Railroads / December 2004Frog 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?  SignatureBob Small > What I am looking for, is a schematic for an automatic frog power > routing module. [quoted text clipped - 17 lines] > And on a related note, does anyone have a circuit for a DCC reversing > module? Bob, what are you using to move the points? SignaturePlease change my Email address to farosenbaum1@charter.net I will not have any other Email account. The Gratiot Valley Railroad Club bi-annual train show and sale March 6, 2005, at the Macomb Community College Sports and Expo Center. Macomb County Michigan. Please visit our Web Site Click here: http://www.gvrr.org/ >> What I am looking for, is a schematic for an automatic frog power >> routing module. [quoted text clipped - 19 lines] > >Bob, what are you using to move the points? He said they're spring loaded and he's trailing through them. >>> What I am looking for, is a schematic for an automatic frog power >>> routing module. [quoted text clipped - 23 lines] > > He said they're spring loaded and he's trailing through them. 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? SignaturePlease change my Email address to farosenbaum1@charter.net I will not have any other Email account. The Gratiot Valley Railroad Club bi-annual train show and sale March 6, 2005, at the Macomb Community College Sports and Expo Center. Macomb County Michigan. Please visit our Web Site Click here: http://www.gvrr.org/ >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? 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. SignatureBob Small Scale Shops turnout machines are made so extra contacts can be installed for routing power to the frog. They sell a kit of extra contacts for this purpose. Caboose Industries also has a hand operated ground throw with contacts for routing frog power. I use them on my layout off the mainline when a switch machine isn't wanted. -- Phil Anderson Up hill slow, down hill fast, tonnage first, safety last. > >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 [quoted text clipped - 13 lines] > -- > Bob Small > Scale Shops turnout machines are made so extra contacts can be installed for > routing power to the frog. They sell a kit of extra contacts for this > purpose. > Caboose Industries also has a hand operated ground throw with contacts for > routing frog power. I use them on my layout off the mainline when a switch > machine isn't wanted. The turnout throw mechanism doesn't help if the rolling stock is forcing the turnout. > -- > Phil Anderson [quoted text clipped - 18 lines] > > -- > > Bob Small >> Scale Shops turnout machines are made so extra contacts can be installed for >> routing power to the frog. They sell a kit of extra contacts for this [quoted text clipped - 5 lines] >The turnout throw mechanism doesn't help if the rolling stock is forcing the >turnout. And the point blades will cause a short with normally wired turnouts >And the point blades will cause a short with normally wired turnouts 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. SignatureBob Small 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? >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). Interesting idea. >And on a related note, does anyone have a circuit for a DCC reversing >module? You will find one here,<http://www.merg.org.uk/resources/dcc.htm#Files%20for%20downloading> see "Auto reverse module" Keith Make friends in the hobby. Visit <http://www.grovenor.dsl.pipex.com/> Garratt photos for the big steam lovers. > What I am looking for, is a schematic for an automatic frog power > routing module. [quoted text clipped - 17 lines] > And on a related note, does anyone have a circuit for a DCC reversing > module? 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. >> 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. >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. What point motors? Don't have those on either spring switches or diamond crossings. Keith Make friends in the hobby. Visit <http://www.grovenor.dsl.pipex.com/> Garratt photos for the big steam lovers. > >> It then has some application in two areas - trailing through spring > >> loaded turnouts, and crossings. Particularly crossings, which have no [quoted text clipped - 8 lines] > What point motors? > Don't have those on either spring switches or diamond crossings. In that case, you need a double throw, end off, latching relay. Atlas make one cheap! It doesn't matter that the points aren't thrown, just that the frog polarity matches the direction of travel. >> >> It then has some application in two areas - trailing through spring >> >> loaded turnouts, and crossings. Particularly crossings, which have no [quoted text clipped - 13 lines] >It doesn't matter that the points aren't thrown, just that the frog polarity >matches the direction of travel. 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 <http://www.grovenor.dsl.pipex.com/> Garratt photos for the big steam lovers. > >> >> It then has some application in two areas - trailing through spring > >> >> loaded turnouts, and crossings. Particularly crossings, which have no [quoted text clipped - 31 lines] > snap relays, at least they can here in the UK. Any of these methods > will require metal wheels on the front of the trains. A DC power supply to the relay coil driven by an SCR fed from the contact rail would resolve that. fOn Sat, 25 Dec 2004 18:35:42 +1300, Gregory Procter <procter@ihug.co.nz> wrote: >> >> It then has some application in two areas - trailing through spring >> >> loaded turnouts, and crossings. Particularly crossings, which have no [quoted text clipped - 13 lines] >It doesn't matter that the points aren't thrown, just that the frog polarity >matches the direction of travel. 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 >>In that case, you need a double throw, end off, latching relay. Atlas make >>one cheap! >>It doesn't matter that the points aren't thrown, just that the frog polarity >>matches the direction of travel. > >It's more complicated that that. No it isn't. >The sprung blades will themselves >cause a short circuit. They won't, the sprung blades will be bonded to their adjacent stock rails as in any other 'DCC freindly' turnout. >You would a track section isolated at both >ends, at least as long as the longest locomotive, with something to [quoted text clipped - 3 lines] >2. only in it, no power before or after it >3. in it and after it, no power before it 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 <http://www.grovenor.dsl.pipex.com/> Garratt photos for the big steam lovers. > fOn Sat, 25 Dec 2004 18:35:42 +1300, Gregory Procter > <procter@ihug.co.nz> wrote: [quoted text clipped - 25 lines] > 2. only in it, no power before or after it > 3. in it and after it, no power before it 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. >It's more complicated that that. The sprung blades will themselves >cause a short circuit. No. Because the switch blades are electrically bonded to their mating stock rails (and insulated from the frog). SignatureBob Small >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. Except that there is no point motor. >Regards, >Greg.P. SignatureBob Small A light senceing circuit might be your best choice given your requirments. > What I am looking for, is a schematic for an automatic frog power > routing module. [quoted text clipped - 19 lines] > -- > Bob 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. :) Just to summarise. Thanks to everyone for their input. The requirement was to be able to switch the frog polarity electonically, without any input from the point linkage. Applications would include 1) trailling through spring loaded turnouts, and 2) crossovers. Specifically for 1) The point blades need to electrically bonded to their adjacent stock rail (as in the DCC friendly method) The polarity switching must be independent of the point blade linkage to avoid the "flick back" after each wheel passes through. So this tends to eliminate any solution where the polarity is swiched by the turnout motor, or using reed switches to detect the linkage movement. And anyway, when trailing through, the loco has already crossed the frog before getting to the turnout blades. Specifically for 2) There is no linkage. So any solution using any kind of mechanical connection, point motors, switches etc is out. It would seem that there are three possible solutions. In no particular order. a) Use a DCC autoreversing module. b) Current sensing (Twin-T) module c) Optical detectors a) I have a PSRev on order for another project, so I'll use that to test if this idea works. All the DCC autoreversing module diagrams I have seen connect both "output" wires to the track, and I am only going to connect one (to the frog). US$40 b) Need to research this one a bit more. Circuitron have a BD-2 block detector (current sensing). But I think that the "block" would have to overlap the frog in order to trigger in both directions. US$20 c) Might be the easiest to connect up. Would need 4 sensors (to detect traffic in both directions). Again Circuitron have AR-1CC. US$47 b) and c) would probably need to drive a relay as they are not designed to source/sink full loco power as they are usually intended for panel lights or signals. Of course, there is still solution d). Insulated frog! Free. SignatureBob Small |
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