Wiring switches independent of track power under DCS

I too have K-Line low-profile O27 switches in both 27" and 42".  What I offer here may or may not be comparable, but it might help.

I power my rails (thru my TIU) using an MRC Dual 27.  I has fixed output ports, + and -.  That's 14V and I use it to power the switches.  The ground from the trannie goes to an AIU and then off to the individual switches.

One year I wanted to use the lighted controllers that came with the switches instead of going thru the AIU.  I had to tie all of the "main" grounds from each controller together and then connect that bundle to the trannie ground.  I use the term 'main' because one wire makes the switch go curved and the other wire makes the switch go straight.  The controller completes the proper circuit with the 'main' ground to throw he switch.  I still used the fixed 14V + for powering the switches.

I don't know the output of the brick that you're using but I'm guessing it's at least 18V.  That might be a bit too much.  I know because one year I didn't feel like running a power wire to 2 switches and used track power, which in the DCS world I use 18V.  At times when I threw one of those 2 switches it would 'bounce back' and leave a gap, which is a true derailing situation.

I hope some of that helps you

walt

I'm with Walt on this one, I'd power the switches with 12-14 volts, that would be the optimum supply voltage.

Thanks. Your comments help, plus I went back and re-read the switch directions which also helped. They re-enforced that the 2 switch posts not going for the controller are both used only if powering the switches via track power. They get "jumped." Only the F terminal gets the fixed voltage from the transformer if powering independent of track.

The instructions say to "be certain the fixed voltage tap has the same ground reference as the running voltage for the train. If not, tie the two grounds together at the transformer or the track."

Based on your suggestions, I will use a old PW transformer set at 14V instead of a 180W/18V brick to power the switches. I don't plan to run it through the TIU since I've already used all 4 channels. Instead, I'll run a bus wire from the switch transformer's hot side to all the yard switches, then drop a wire from each "F" tap on the switch. Then, to complete the switches' circuits, it sounds like the common/ground goes through the track back to the switch transformer by tying its common/ground side to the common/ground side of the transformer powering the yard's track.

I'm powering the yard through a fixed channel on the TIU, so I could tie the switch transformer to the input or output side of the TIU or, I suppose, to the terminal block between the TIU and track. If accurate, any one of those three options better than the other two?

Make sense @walt rapp @gunrunnerjohn?

Sounds good to me.

I was anxious to get back to this topic today.  I want to clarify a comment that I made.  When I said one year I wanted to use controllers, I need to qualify that which will also explain why I had to bundle all of the "main" grounds together.

I was already using DCS and had and AIU for a few years.  That particular year since I was planning on having a lot of younger kids visit and run trains, I wanted for them to be able to control things without having to use my hand remote.  So what I did was kind of neat, even if I must say so myself

I hooked up all of the switches the 'normal' way that i always did running the wires thru the AIU.  To use the controllers and LIMIT WIRE RUNS, I connected the 2 "non-main" wires of each controller to an AIU port that already had wires running to the switch that it would control.  Thus I HAD to tie all of the grounds together since I was not planning on running controller wires to the switches.

In your case, I agree.  Run the controller wires to each switch as normal.  Since the power is a separate trannie that the track power, just tie the grounds of the 2 trannies together to complete the circuit.

Funny how last night I was beating myself up for not explaining the first time why I had to tie the 'main' grounds together!!!

- walt

@walt rapp posted:

Funny how last night I was beating myself up for not explaining the first time why I had to tie the 'main' grounds together!!!

Why would you not always tie the commons of all the transformers together?

Because not all of us are as electrically smart as you @gunrunnerjohn

- walt

Well, it's pretty normal for all the transformer common's to be connected on most layouts, that's why I ask.

Didn't know that.  Never read of heard that comment before either.  First time for everything I suppose