Point frogs and electrical issues
This page is under development. A helpful graphic will eventually be provided.
Frogs are the 'vee' shaped part of a railway point where individual rails cross. This presents a challenge for normal two-rail model railway electrical design because the powered rails of every section of track must have opposite electrical polarity, and yet if the frog is powered it needs to provide positive polarity for one route and negative polarity for the other route. PECO addresses this challenge with in two main solutions and one combined solution.
Correct turnout wiring varies by turnout type and whether the layout electrics are DC or DCC.
'Insulfrog' turnouts
Frogs
The PECO Insulfrog solution has plastic frogs that impose no electrical polarity issue. This means that rolling stock wheels riding over the frog cannot collect power. Short-wheelbase locomotives, or individual wheels or bogies on wagons may lose power entirely when traversing this unpowered frog.
Availability
PECO OO9 / HOn30 / HOe collection 'Insulfrog' turnouts:
Rail power
Insulfrog points can be used to switch power to connected (through or diverging, otherwise unpowered tracks on or off. This allows locomotives on DC layouts to be selectively turned on (driven by the controller) or off (isolated from the controller). Alternatively the connected tracks may be independently powered. Similarly, a DCC locomotive can be selectively turned on or off even if not commanded to move. Insulfrog point closure
Insulfrog points do not need insulated joiners. Power can be provided by joiners connecting to adjacent tracks.
'Electrofrog' turnouts
Frogs
The other main solution is to make the frog conductive like ordinary rail but electrically isolated with an attached wire which can receive the correct polarity provided by an external switching system that supplies the correct polarity according to the selected route.
Availability
PECO OO9 / HOn30 / HOe (9 mm gauge) collection 'Electrofrog' points:
PECO HOm (12 mm gauge) collection 'Electrofrog' turnouts:
Rail power
Electrofrog points power can be provided by joiners connecting to adjacent tracks, except the frog and frog rails which must be electrically isolated and powered by a switched polarity device. Electrofrog' point frogs extend to and must be electrically isolated from adjacent track with insulated rail joiners.
'Unifrog' turnouts
A combined solution is a convertible hybrid of 'Insulfrog' and 'Electrofrog' solutions. This is further explained in this PECO TV 'Demystifying Unifrog' video. Unifrog points have an isolated frog that may be powered by a switched polarity device, insulated from the live frog rails.
Availability
PECO HOn3 (10.5 mm gauge) collection 'Unifrog' turnouts:
Rail power
Unifrog points have short conductive frogs that are isolated from the adjacent tracks. They can be left unpowered, in which case they will perform like Insulfrogs, or powered with a polarity switching system as is an Electrofrog. Whereas Electrofrog points must be electrically insulated from adjacent track sections, the short Unifrog 'vee' is immediately isolated from the remainder of the turnout and each rail connection to all three adjoining track sections can be conductive.
Micro Engineering Company points
The turnouts in the Micro Engineering Company HOn3 (10.5 mm gauge) collection are equivalent to PECO 'Electrofrog' turnouts in that the frog is conductive and isolated from the frog rails. A conductive contact pad is provided underneath the frog of the turnout that can be connected to a polarity switching system. (Unlike PECO Electrofrog and Unifrog turnouts, no frog wire is provided.)