Modifying Peco Points for DCC

A Peco Electrofrog point modified for DCC is shown below. I have added the microswitch to the right which changes the polarity of the frog as the point changes. The microswitches were about 50c – $1 on eBay and are activated by the push rod controlled either by:
mechanical point levers
or by servos.
On this page “Point” = “Turnout”  / “Switch”       “Sleeper” = “Tie”The microswitches need to be small – these are 20mm x 10mm x 6mm thick (body size)

These were the microswitches I used but …
… the longer arms on these may have been better (can be trimmed)

The first step is to attach the microswitch in exactly the right spot as shown below.

The critical bits are:

  • I always fit the microswitch such that the electrical switch contacts are towards the “Right” rail which is always a RED wire on my layout. The centre connection  on the switch goes to the Right rail – clarified further down in the YELLOW BOX
  • the hole in the throw bar must be able to operate the lever on the microswitch (and NOT miss it!)
  • the switch needs to be positioned so that the throw bar will operate the switch (hear it “click”) when the points are thrown.
  • the switch is attached using contact cement (in my case Quick Grip). First work out which surfaces of the point and the microswitch will fit together – they need to be scraped or filed smooth for a good bond. I scrape the underside of the point with a blade and file the bottom side of the microswitch to level it (actually, I hold the microswitch and rub it back and forth on a file).

make sure you don’t get glue into the moving parts and hold it with a clamp as in the photo below.

There won’t be any wires on your switch at this stage.

The two bridging wires here need to be prised out. Check the instructions with new points or on their website.

The easiest way to lever the two short wires is with a small screwdriver.

Then put a small amount of flux on the 4 rails shown. Use something like Carr’s Red Label or DCC Concepts Flux – a non-corrosive type.

The 4 rails have had a spot of solder to “tin” the rails and on the left a piece of tinned copper wire has been soldered in place. You can buy that from electronics suppliers like Jaycar.

The rails on the left are bridged and trimmed; the wires in the middle removed; and attention moves to the frog connection on the right.

The wire provided needs to be extended to reach back to the microswitch. Use similar size tinned copper wire. Here the extra wire has been twisted around the original and will be soldered together first then run down the length of the point.

This diagram explains what is happening electrically. In my method, the switch becomes part of the point to feed the correct polarity from the Common connector on the microswitch to the frog – as shown above by the GREEN connection 3.
On my layout, an additional (Light Blue) wire from the Common connection on the microswitch is taken below the layout to be used to indicate which route is set on the panel. This means my panel LEDS show which track has power.

The extra tinned copper wire has been soldered to the point wire and is run in the least conspicuous path. I gently melt the wire into the underside of the sleeper with the soldering iron to hold it in place.

The wire from the frog terminates at the Common connection on the switch – may be labelled       “C” or “1”

The wire from the frog terminates at the Common connection on the switch – may be labelled           “C” or “1”

This rail area indicated has been tinned ready for connection …

…and this one ready for the other side.

As the run is only a few mm, bare tinned copper wire is fine.

Another view.

These wires run through the foam benchwork and connect to DCC (red & green) and the 3rd light blue wire provides a common connection (from the frog) to allow an indicator to show which way the points are set.

The LH connection is the common pole in the SPDT switch (SPDT= Single Pole Double Throw)
The middle contact connects to the red (Right rail DCC wire) and the RH contact connects to the green  Left rail .

This template locates the cut-out needed to accept the microswitch under the point.
The red lines are used to align it to the rails as the switch is off centre. In this case the point was being operated by Wire-In-Tube via the trench shown.

Having marked out the position of the recess for the microswitch, cut the underlay and foam with a sharp knife.

Routing the hole to a depth of 10-12mm with a Dremel (and vacuum cleaner).

Dremel Cutter
Ready for a test fit.

The final steps which can be done after the point is installed:

  • remove the over-centre spring IF you are using servos to control the point – this can be done from the top.
    My points are operated using servo control technology designed by the MERG UK group and built by the user. The points operate at a slow speed and can be set up using a computer interface to smoothly touch the stock rail. See MERG site.
  • leave the spring in place if you are manually switching the point.
  • notice that the sleepers near the mechanism have been thinned down from their over-scale size.
  • if servos are used, the throw bar ends can be cut off.
  • weathering will improve the realism of the installed point.

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Rick Fletcher

Born in the steam era and developed an interest in railways when given a clockwork Hornby "set". Surrounded by steam when travelling to school (by train of course) and holidays were always by steam train as we had no car. How lucky was I?

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