Wiring Turnouts
Summary: Making turnouts compatible with your DCC system isn't hard. Here are ways to improve and modify commercial turnouts. Wiring turnouts for DCC sometimes requires extra care and attention.
Overview
Here are some recommendations for wiring turnouts on a DCC layout...
- Feed track power to all routes in and out of the turnout.
- Feed track power to all metal rails in the turnout.
- Use live frog turnouts if possible.
- Feed track power to live frog using frog polarity switcher.
- Use "DCC-ready" or "DCC-friendly turnouts" if possible.
- If using PECO Electrofrogs, test metal rolling stock wheels for shorting point blades to stock blades. Consider modifying if problem occurs.
- If using PECO Insulfrogs, test metal rolling stock wheels for shorting frog rails. Consider modifying if problem occurs.
- For more information on Shinohara turnouts, see the page for Shinohara
Wiring
This diagram shows where to feed track power to a typical turnout. Basically, feed power everywhere an arrow is shown and do not rely on the metal rail joiners, they don't always make reliable electrical joints.
In particular, try to feed power to all of the separate metal rail components in each turnout (except the guard rails). If two components are already electrically bonded with with internal wires (usually on the underside) then you only need to feed one of them.
Many turnouts (Peco is an exception) have the bonding wires already installed as shown between the stock rails and the closure rails. They might not be exactly as shown on the diagram (they can be on the other side of the frog for example) but if they're not there then ideally you should add them.
Finally, if the frog is live, wire up a frog feed from a frog polarity switch or a Frog Juicer.
PECO Turnouts
PECO turnouts cause a lot of confusion but fundamentally, all PECO turnouts can be used with DCC.
There are a few reasons for the confusion. First, they come in two varieties, Insulfrog and Electrofrog. Second, even though PECO say they are "DCC-Ready", it can be argued that they are not "DCC-friendly".
A third variety, the UniFrog, is beginning to appear. This new design will replace the Insulfrog and Electrofrog in time.
For more details, see the pages dedicated to PECO Turnouts:
PECO Unifrog
PECO has introduced their new Unifrog design, which combines the Insulfrog and the Electrofrog concepts into one. See the PECO Unifrog page for more details. PECO intends to discontinue the Insulfrog and Electrofrog products over time, replacing them with the Unifrog design.
PECO Insulfrog Turnouts
PECO Insulfrog turnouts are power routing or self-isolating and therefore, it's not just good practice - you must wire all routes out of the turnout to avoid losing DCC power to a siding that is not selected.
PECO Electrofrog Turnouts
PECO Electrofrogs are simple to wire up for DCC, no special wiring is required to get them working but for the most reliable performance you should follow the recommendations above and add feeds as suggested.
Making Electrofrog Turnouts DCC Friendly
- Main article: DCC Friendly Turnout
You can also modify them to be more DCC-friendly if you encounter the problem with the back of metal wheels causing a short circuit between the blade and the stock rail.
Electrical View of a Modified PECO Electrofrog Turnout. The diagram shows the electrical view of a modified PECO Electrofrog in both the open and closed positions.
Contacts on switch rails and connections to the closure rails.
A second benefit of the modification is that it improves reliability by reducing the reliance on the mechanical contacts to carry electric current. The picture shows that the Electrofrog point rails have 3 mechanical contacts from which to get their power.
- The blade end of the switch rail physically touching the stock rail when it is closed
- A wiper contact beneath the switch rail that contacts the underside of the stock when closed.
- The pivot at the other end and of the switch rail
Before modifiying an Electrofrog as described earlier, and if you have not added a dedicated frog power feed, then the first two contacts methods are how the point rail is powered, and the third is how the frog is powered from the point rail. Therefore there is quite a bit to go wrong if things get dirty.
After modification (which then requires powering the frog), all 3 contact methods power the point rail and the frog relies on none of them. Obviously there is still the slight risk that all 3 will fail and the point rail will be unpowered but the solution (to add futher bonding wires to the point rails) is quite tricky since the wires need to flex and it is hard to solder anything to the point rails that can't be seen.