spdt, dpdt???

[bwchaney]

 I have a seb dcc digitrax system.  I wish to turn off power to individual staging tracks.  all my searches have turned up numerous confusing answers.  My straightforward questions are:   do i single gap the staging track or double gap? and which switch do i need to power the track after gapping.  sp or dp,.  thanks in advance bwchaney

[graphitehemi]

I would gap BOTH rails to cut off all power using a DPST switch.... altho I'm not sure why you would need to do turn off power to your staging tracks anyways using DCC.

[bwchaney]

 my sound engines tend to not shut down and if i could turn off power to the staging track i would not have to mute the engines when they are not in use.

[IRONROOSTER]

 In electric switches the P refers to the number of  Poles or internal switches.  D is double so a DPST has two internal switches and can turn 2 wires on and off, S would be single for 1 wire.  The T refers to the number of throws.  In a Single throw the connection is on/off such as DPST.  In A Double throw the conection is from one wire to a second wire.  So a DPDT switches the incoming wires between 2 sets of outgoing wires.  There's also a center off option for some double throws so the toggle has 3 postions the middle or center position makes no connections.

So to turn on/off both rails you would use a DPST - Double Pole Single Throw.  If you single gap you would use a SPST - Single Pole Single Throw to turn on/off one rail.  (Note you can always use a switch with more throws or poles than you need and just leave some connections unused.).

While single gapping can work I, personally, favor double gapping as I think it helps prevent mistakes that lead to shorts especially when making future changes/additions.

Enjoy

Paul

[selector]

I also double gap in these circumstances, except that I use such a setup for my programming track that doubles as the lead to my turntable from a turnout.

I agree with the DPST in this case, although you could achieve your aims by using an SPST and only severing the power to one rail...it would still be effective.

Lastly, is there no CV setting in your sound decoder that will make it go dormant after so many minutes have passed without a packet being sent to it? My QSI's, Tsunamis, and LokSound decoders all seem to shut themselves down after a while where I haven't commanded them to do anything.  They still get full track voltage, and must draw a micro-amp while they sleep, but that's all.  Essentially, they don't exist for a system capable of delivering anything over 1 amp.

-Crandell

[bwchaney]

I thought for ease it would be easier to cut off the power to the track rather than mess with cv's.  thanks to all for their replies.  bwchaney

[nbrodar]

 I gap a single rail and use SPST pushbuttons to control my staging and engine storage tracks.  Why...I don't like leaving decoders sitting around hot if I don't have to. I also still have some locomotives without decoders, so I can turn off the engine tracks and still have them as display units.  It's also a safety thing, so someone doesn't accidentally grab a locomotive and either crash into the wall, or turntable pit.

Nick

[bwchaney]

 exactly; thanks nick and all

[tbdanny]

One thing I've done on my layout - if you feel up for it - is having a light sensor at the 'entrance' of the staging track, hooked into a timer.  The light sensor trips the timer, which holds the staging track on long enough to drive the train in, then times out and cuts power automatically - and yes, I'm using DCC

[wjstix]

selector

I also double gap in these circumstances, except that I use such a setup for my programming track that doubles as the lead to my turntable from a turnout.

I agree with the DPST in this case, although you could achieve your aims by using an SPST and only severing the power to one rail...it would still be effective.

Lastly, is there no CV setting in your sound decoder that will make it go dormant after so many minutes have passed without a packet being sent to it? My QSI's, Tsunamis, and LokSound decoders all seem to shut themselves down after a while where I haven't commanded them to do anything.  They still get full track voltage, and must draw a micro-amp while they sleep, but that's all.  Essentially, they don't exist for a system capable of delivering anything over 1 amp.

-Crandell

I've always been a "double-gapper" myself, but I suspect in a lot of situations I could have gotten by with single gaps. I would think double gaps would keep each section more isolated in case of a short due to a derailment.

I'm not sure about the CV to shut down sound after so long, but I think every sound decoder has a CV you can set so that the sound doesn't turn on until you call up the engine's ID number. I know all of my Soundtraxx, QSI and Tsunami sound and power decoders have that option, and my MRC "Sounder" sound only one does too.