I recently installed an NCE Auto Switch to allow me to use a proper programming track with my Power Cab. However, after installing it, I discovered that there are two versions of the product, and many web discussions refer to what is actually a “Rev A” of the product, where the Auto Switch makes run DCC current available to the programming track. This is what I had intended to use it for, so that the programming track could alternate as a normal layout track. But the product has been changed, and the current “Rev B” never puts run DCC current onto the programming track. Thus I can’t run a loco wih address 3 from the layout onto the programming track, go into programming track mode, reset the address, and simply run the loco back onto the layout. Nor can I use the programming track as an ordinary spur, even though the product doc illustration implies I can.
A page at Tony’s Train Exchange shows how to convert it back to “Rev A” function, but cautions about having full run DCC current on the programming track.
Has anyone else run into this dilemma? What choices and pluses-minuses did you consider?
A simple toggle switch would have accomplished what you want to do – throw the switch in one direction for programming, and in the other direction to get DCC power on the track.
Sure, but the advantage of the Auto Switch theoretically is that it’s automatic. It also avoids the problem with the Power Cab that there’s no dedicated programming track output.
If you are talking about the PDF file on the NCE site under the Auto-SW product page called Auto-SW Live Program Track, the way that diagram is drawn, you would have power to th main and program track while running trains, and then if you switch to program on program track, it will turn off the power to the main track and still power the program track only. When you exit program mode and turn track power back on, the main will turn on as well so there will be no issues crossign the gaps.
The only potential danger, but it applies to using the auto-sw in the ‘normal’ manner as well, is that if you stop the loco with power pickups spanning the gaps, even thought he auto-sw will turn off main power, the program commands will bleed through to the main and program everything.
What’s diagrammed in that document shouldn;t matter how the Auto-SW unit itself behaves, the program track connection is before the Auto-SW, and the Auto-SW is only used to turn off the main track output, which it should do in both the A and B revisions.
The Power Cab apparently sends out signals in the DCC protocol that say it’s putting the output into program mode
It then reduces its output to reduced voltage for the program track
This applies to all output while in program track mode
The Auto Switch senses the program mode signals from the Power Cab and shuts down all power to the main while output is in program mode
Only output to the program track is available, whether with a stock Auto Switch installation, or bypassing the Auto Switch program output per the NCE pdf, when in program mode
When not in program mode, only run DCC output comes from the Auto Switch and the Power Cab. The Auto Switch does this whenever it does not sense a program track signal.
So modifying the wiring per the NCE pdf should have no potential hazard for any decoder in program mode
I’m not sure why NCE changed the Auto Switch from Rev A to Rev B.
Actually, it is reduced current, not voltage. This points to the one possible issue I see with the modification, and could be the reason for the change in the first place. The reason the program track outputs are a reduced current is so that if there is a short with a new decoder installation, the reduced current will hopefully protect the decoder from damage. With full power on the program track, if you place an engine with a new install on the track before it is switched to program mode you have a greater chance of damaging the engine if something is wrong.
It looks like this is a procedural issue no matter what. Even if you have a completely separate programming track, you would have to discipline yourself always to put a loco with a new decoder install on the separate programming track before you put it on the layout with normal DCC control.
The real problem the Auto Switch is meant to solve is the inability of the stock Power Cab to have any separate programming track. I discovered a couple times the downside of forgetting to toggle the main off when I went into program mode with my Power Cab. This solves that problem, for the approximate price of a decoder (and a couple hours wiring and web research). In my case, I’m not well positioned to put a separate programming track anywhere near my layout, so I simply have to follow the procedure.