Switch yard spur selection

Very possible with some whipping together some diodes and transistors to decode the bi-polar position signal and drive relays. The relays will then switch the AC track power to the spurs.

I think it will depend on how complicated the ladder is to the yard how difficult this is.

For instance, here's my entrance to my 10-track freight yard.  Some paths have up to four switches that will affect which yard track is switched to the mainline.

I didn't attempt to automatically switch yard track power, I just added a 10 position illuminated switch panel to power tracks on demand.

FasTrack switches RSC Lights out (terminal under the switch) outputs either + or - 5VDC (relative to the Ground terminal) depending on the switch's position.  The available current from the board is minimal, not sure exactly how much.

Don't count on more than a few milliamps.

It seems the RSC output current would need to be boosted to be able to drive a relay coil.

@bmoran4 posted:

Very possible with some whipping together some diodes and transistors to decode the bi-polar position signal and drive relays. The relays will then switch the AC track power to the spurs.

@bmoran4 it seems like you may have some additional thoughts about how to accomplish the OP's request using Solid-state components to drive the relay.  What components/ arrangement do you have in mind?

I haven't spec'd any specific components out, but if you tap into the bi-polar position indicator signal that goes to the remote controller, run it through some diodes to detect your desired "on" state, feed that to a transistor to get enough power to drive a relay coil, and drive the relay. You may be able to even use a multi-channel opto-isolated board similar to something like this without a transistor:

https://www.amazon.com/SainSma...Caps%2C72&sr=8-5

I'd guess the optos may draw more than the LED lead from the Fastrack switch can provide.

The optos on the inputs of the multi-channel relay modules will trigger with, say, 1 mA of drive current.  If you do go this route, there is a "quirky" behavior on some of these relay modules where a -5V signal will "look like" at +5V trigger so both FasTrack feedback signals will trigger the relay; it has to do with how some relay modules use AC-input optos.  Can explore this if you indeed choose this path.

In the category of measure-twice, cut-once, and pardon my ignorance on how one operates a yard...but don't you think in your mind "I want to turn on Spur #X" rather than think "Which switches do I need to set/reset to turn on Spur #X."  In other words, wouldn't you want to simply turn on power to Spur #X and then let the fancy electronics (diodes, resistors, transistors, whatever) set/reset the switches to the correct positions to steer to Spur #X?

I understand you are using command controlled FasTrack switches.  So if remote control is a requirement, the power to the spurs could be TMCC controlled by an Accessory controller box.

Stan, the beauty of the Fastrack Command switches is they also respond to a conventional switch contact switch, so you don't have to go to all that trouble.

@Hobbit posted:

...

I am using TMCC and Fastrack switches.

@gunrunnerjohn posted:

Stan, the beauty of the Fastrack Command switches is they also respond to a conventional switch contact switch, so you don't have to go to all that trouble.

I guess I'm not clear on whether by "using TMCC" he means the FasTrack switches are under command-control and that's a requirement.

If conventional "manual" toggle/pushbutton switches are acceptable, then I'm pondering whether each spur should have a manual toggle on/off power switch...and then some electronics is added to automatically set all the switches to the appropriate positions.  Tail wag dog or dog wag tail?

I was under the impression that @Hobbit was asking that for a given switch, if set diverging (for discussion sake, logic can be altered for through) regardless of if initiated by Command Control or Remote Control throw switch, that the cosponsoring track block become energized. This can be repeated as necessary for building up a yard. This especially makes sense if thinking about a ladder track formation. Of course, one could extrapolate on this and get as complex as one wants - maybe overly complex as @stan2004 suggests, but it boils down to taking the relay logic and building it out as required/desired. One could use TMCC/Legacy Routes functionality in conjunction with this to throw a complex series of switches to make the path and power the spurs instead of trying to build that additional logic externally.