Atlas Custom Line turnouts and DCC : LUSENET : Wiring for DCC : One Thread

Attempting to make Atlas track Switches DCC friendly. When frog is insulated and I want to connect it to a track bus wire through a lamp and relay contacts, does it matter which track bus it's connected to with respect to the position of the switch points, polarity wise? In other words, with DCC being a basic square wave would FROG polarity matter?


Phil Euper

-- Phil Euper (, March 11, 1999



Absolutly matters. The DCC signal is square wave - in opposite conjuction with the other rail. (One side up - the other down). This is a balanced transmission. You have to switch the frog polarity to always be the opposite junction from the opposing stock rail route. Having a tail light bulb in series to the frog connection is good saftey - but the lead through the bulb to the frog must switch polarity. It is exactly the same synchronization issue of the balanced polarity that causes shorts on reversing loops with DCC and has to accomodated with either a reversing booster or a module designed for that purpose. In these cases, gaps on both sides are required to detect and allow for the sensening. The frog has to be treated in a similiar way. -ed mccamey-

-- Ed McCamey (, March 11, 1999.

Wiring of the metal insulated frog is the same for DCC as it is for DC. You still need to switch the electrical connection of the frog to match that of the point rails. I've never found a need to have the frogs electrified. Any loco with all wheel pick-up will continue to be powered as it rolls over an insulated frog. There is a definate advantage of using the Atlas turn-outs. The two point rails are insulated from each other and electrically connected to their respective stock rails. So they are always powered at the right polarity regardless of turn-out position. You don't need any insulated rail joints unless there is a reversing loop. But the electrical connection is through the point rail pivot. Tighten this joint before permanently installing the turn-out. If you do put insulated rail joiners at the stub end(s) of the turn-out (for power district or occupation detection), provide a power feed to the turn- out rails leading to the frog so the points don't have to carry current. (Atlas has improved that connection on code 83.)

-- Don Vollrath (, March 24, 1999.

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