Hints & Tips

Modifying Peco Electrofrog turnouts

After many experiments at modifying turnouts on my layout for better operation and mixed results, I have recently put in place my own version of the Allan Gartner (see his site) modification for all the turnouts in the new extension of my layout. This modification offers a better electrical continuity over the turnouts and prevents accidental short circuits between the stock rails and the point rails. This modification improves the turnout operation in all cases but is especially suited for DCC operation.

The modification consists in completely insulating the frog part of the turnout and repowering it through a latching relay controlled in parallel with the switch motor (Peco twin-coil motor).

Insulating the frog

The figure below shows a modified turnout (N scale Code 80 Peco Electrofrog turnout) :

The frog insulation is done in two steps :

  1. by cutting both closure rails where indicated. This is done using a cutting disk in a Dremel rotating tool (or similar). The gap created is then filled by a small piece of styrene of proper thickness glued with ACC. After the glue has completely cured, this piece is filed to shape.
  2. by insulating both frog rails from adjacent track, using insulating rail joiners.

Important notes :

  1. When cutting closure rails, a worn disk (of small diameter) should be used so as to avoid cutting or notching the stock rails, at the same time (especially for N scale turnouts).
  2. Due to the overall diameter of the rotating tool, you may need to make the cut at an angle. This is not a problem as long as the frog is completely insulated.
  3. Cutting the rails with a cutting disk generates a good amount of heat that can damage the plastic parts of the turnout. It is recommended to use some sort of heat sink to evacuate the heat. The best is to cover the whole turnout (except the small area where you are working) with a damp cloth. This is very efficient and avoids any surprise. The same technique is to be used when soldering wires to the rails (for subsequent operations).

(Re)connecting everything

Closure rails (and point rails themselves) are only powered through the contacts between the points and the stock rails. These contacts are unreliable and degrade over time. For a reliable operation, it is necessary to connect them to the adjacent stock rails. This is done as follows :

  1. At mid-point between the frog and the point rails, remove the plastic part of the turnout, under the rails, between two ties. This will show up the bottom of the rails.
  2. Prepare two wires long enough to go to the relay underside and stripped to gap the distance between the stock rail and the closure rail. Solder them under the turnout on both the stock rail and the closure rail. This has to be done on both sides of the tunout, separately. You'll end up with both closure rails connected each to the adjacent stock rail, plus two lengths of wire to be connected to the relay located underside.

While you have the soldering iron in hand, solder a third wire (again long enough to go to the relay underside) to the side of the frog guardrail.

Don't forget to put in place the "heat sink", as described above for all these operations so as to protect the plastic parts of the turnout from heat.

The most difficult part of the operation is done. At this point, you may want to paint the visible wires a black color so as to hide them. Drill holes in your roadbed for the three wires and install your turnout with its motor.

The hidden side of things...

The figure below shows how everything is installed and wired under the the roadbed :

On the right is the Peco switch motor with an auxiliary contact installed on top (for turnout position feedback). This is installed the usual way. Regarding Peco motors (PL10) supply, I recommend a Capacitor Discharge Unit able to provide a good pulse to switch these motors needing several Amps for proper operation. Also the wiring must be done with heavy wire (#18 min.) so as to minimize votage drops.

On the left is the latching relay used to switch the frog polarity, depending on the turnout position. These relays require only a pulse to be operated and can be wired in parallel with the switch motor as they have two coils, just like any solenoid motor. Just make sure the relay coils have a voltage rating compatible with your switch machine operating voltage and you wire them with the proper polarity (the coils are polarized). In my case, the switch machines are operated with a 30 volt pulse (more or less) and I choosed 24 volt relays that can whithstand up to 40 volts. They are Omron type G6AK relays, available at many electronics suppliers. These relays have two contacts that I wired in parallel so as to withstand the short-circuit current of my Digitrax booster (5 Amps), each contact being rated at 3 amps.

For my own use, I made some small PCB's for mounting the relays (and also a pair of terminal boards to ease wiring). The figure at right shows the top wiew (component side) of one of those PCB's (no scale). For people interested in making their own PCB's, I can send an artwork at scale 1:1. Note that the coils of the relay being polarized, it is necessary to respect some rules : The "plus" is the common (center terminal) while the controls are "minus" (left and right terminals) on the "control" terminal board (the bottom one). The relay boards are attached to the subroadbed using double sided adhesive foam tape.

At this point, what's left is to connect the switch motors to their controls, to wire the "control" side of the relays in parallel with the switch motor and to connect the relay contacts to the wires coming from the frog and both stock rails (see above picture for details).

For the techies, the figure at left summarizes the complete wiring.

Now, everything is complete ! It may appear complicated at first. But I can assure you it is not and it is much more complicated to explain that to do. I need no more than 10 minutes to modify any turnout. So, believe me, go ahead ! you won't regret it. It's really worth the effort : you'll get a true reliable operation and no more stalling on your turnouts.

It should be noted however that this modification will not prevent short circuits on your turnouts if you send a train in the wrong direction (the frog will not be at the right polarity). If you cannot prevent this situation, the best solution is to install a car taillight bulb between the relay and the frog, so as to limit the current.

Good luck.

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Page created by Jean-Louis Simonet
Last update : 05/12/2003
© 2003, Jean-Louis Simonet