Cobalt iP digital frog switch function

[peter _murray]

I am running a DCC system using elink and Railmaster. I am thinking of using the frog swich function on the cobalt to liven/deaden a section of track to avoid running some points the wrong way. I have isolated the "b" track and intend using the frog switch to remove power from it when the point is in the wrong direction. My question is, when I do this both tracks will have the same "polarity". I dont think this will cause any problems but wish to check with beter heads than mine before I ruin a decoder or worse.

[Chrissaf]

I assume that your operational method rationale is along the lines of:

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"When the point is set the wrong way against the loco, the frog switching puts the same DCC phase on both rails in the isolated section to prevent locos continuing to run into the incorrectly switched point."

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If you do that, then as soon as the loco starts to cross over the insulated joint onto the isolated section, the loco will come to a stop (as you intend). But not because both rails are at the same DCC phase, but because at the instance of crossing the insulated joint you will get a 'short circuit' that will trip the controller and the whole layout will come to a standstill. The same as what probably would have happened if the loco had just run into the point.

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/media/tinymce_upload/fa51f772bea89fd1f9657b7a9d680f45.jpg

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So to prevent the short happening, you would have to manually stop the loco prior to the isolated section so that it doesn't cross the joint. This needs manual intervention which kinda circumvents the rationale for putting the isolated section there in the first place.

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The Cobalt has a mechanical changeover switch as well as a 'frog' switch. Why not use the 'changeover' switch instead......so that instead of making the 'B' rail the same phase (as it would using the 'frog' switch) you make the 'B' rail open circuit without any DCC phase. That will bring the loco to a standstill, but without creating a 'short circuit' condition.

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/media/tinymce_upload/5285e8bff4080391fdaf82b74f633bc9.jpg

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M = represents the Cobalt point motor.

[peter _murray]

Thank you for your input. A very obvious problem that should have occurred to me. Guess I will have to revert to a previous solution of using the switch to drive a DTDS relay to run both the track power off/ on and relevant signal lights. A lot more wiring and effort but tried and trusted. Thanks Peter

[Chrissaf]

If you are using the existing Cobalt metallic changeover contacts for signals. Then what about using those contacts (rather than a switch) to operate the DPDT (Double Pole Double Throw) relay and move the signals PLUS the isolated section onto the DPDT contacts.

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I am assuming that DTDS is a typo.