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NCE AutoSwitch

WHAT DOES IT DO?

The NCE AutoSwitch is a programming protection device that prevents all the locomotives on the layout from accidentally being programmed when the system is using the programming track.  It also allows you to safely test decoders.  You can think of this device as an insurance policy to keep Murphy's law at bay.


WHO NEEDS IT?

Normally DCC systems provide a two sets of terminals.  One for the main line and one to connect to the programming track.  However, some low cost DCC system combine (Share) the main line power with the programming track function using just one set of terminals!!   The autoswitch re-creates the the two terminal setup by splitting up the main line power from the programming track power.

The AutoSwitch will work with any DCC system that combines both programming track power and main line layout power on the same set of wire terminals.


WHAT IS THE PROBLEM WITH ONE SET OF TERMINALS DOING EVERYTHING?

Terminal sharing actually creates two problems which shows the true value of the AutoSwitch.   One is electrical and the other one is procedural.

ELECTRICAL:  The NMRA has defined a true programming track as an ELECTRICALLY SAFE PLACE TO PROGRAM.  To meet that requirement, the programming track's power (Current) is intentionally limited to only allow safe programming of the decoder and nothing else.  Why?  So you do not burn up a decoder that has a  short circuit in it's wiring as soon as main line power reaches the decoder.  Stated another way, a true programming track will allow you to do some basic electrical testing for shorts without the fear of damaging anything.  If no short is detected on the programming track, programming can proceed.

PROCEDURAL: Normally one is supposed to REMOVE all of the engines that are NOT to be programmed from the layout FIRST.  But Murphy's law says: IF something can go wrong, IT WILL.  All it will take is one accidental "global programming" of all the engines on the layout to tell you the value of the Autoswitch.


LIST OF PRODUCTS THAT CAN BENEFIT FROM THE AUTOSWITCH (Partial List).

NCE: PowerCab.  (The AutoSwitch was developed initially for the NCE PowerCab)

MRC: Prodigy.


LIST OF PRODUCTS NOT COMPATIBLE WITH THE AUTOSWITCH?

The Autoswitch will not work with any DCC systems or Command Stations that DOES NOT SUPPORT a programming track output capability.  The following products are NOT COMPATIBLE with the AutoSwitch.

NCE:  DCC TWIN, SB3*, SB3A*, SB5*

*These devices are normally sold as an upgrade path for the PowerCab.  The PowerCab is expected to continue to perform the programming track function.

DIGITRAX:  DB150/Empire Builder.
 

HOW DOES IT WORK? (MAIN Output Terminals)

The NCE AutoSwitch is a device that constantly monitors the DCC signals/commands coming in on the AutoSwitch's DCC terminals to see if they are a programming track commands or not.  It then decides what to do with the MAIN terminals if the DCC command seen on the DCC input terminals are:

1) a programming track command, the Autoswitch will DISCONNECT the DCC terminals from the MAIN terminals and kill power going to the layout.

2) NOT a programming track command, the Autoswitch will CONNECT the DCC terminals to the MAIN terminals and restore power going to the layout.

You can think of the AutoSwitch as a DPST switch wired in series with the MAIN layout power terminals and is automatically controlled.


WHAT HAPPENS TO THE "PROG" TERMINALS?

NCE made two versions.  What happens depends on which version of the AutoSwitch you have.

Both version remove power to the rest of the layout eliminating the need to remove them when using the programming track function.  The difference is how the programming track power is implemented.

REV A: (Discontinued) The PROG terminal are alive at all times regardless of the operating mode of the PowerCab.   Stated another way, the A version does not meet the true definition of an Electrically Safe Programming Track.

REV B: The PROG terminals are disconnected, go dead, when you exit programming track mode.  Think of the AutoSwitch as a DPDT switch the toggles between MAIN and PROG terminals.

The manual have that came with the AutoSwitch should tell you in DESCRIPTION FORM what version you have.


WHAT ARE THE ADVANTAGES/DISADVANTAGES OF EACH TYPE?

REV B preserves the Program Track low current operation at all times.  This can be important if you installing a new decoder for the first time.  A programming track is a current limited mode of operation that makes is safe to test decoders.  The track is only alive when you in programming track mode.  The track cannot be used for anything else.

REV A always allows main line power to be available on the programming track at all time.  In other words, when the track is not being used for Programming, it can be used as a normal track.  However you no longer have a safe place to test decoder wiring since main line power is allowed to reach the programming track.  If there is some mis-wiring, you could end up burning up some wiring and/or your decoder.


IF ONE DOES NOT HAVE THE MANUAL, CAN ONE TELL WHICH ONE YOU GOT BY LOOKING AT THE AUTOSWITCH PCB BOARD?

Yes.   The REV A or REV B is printed on the back of the board.


CAN I CONVERT A "REV A"  BOARD TO A "REV B"?

Yes.  Connect the PROG wires to the 2 unused terminals of the relay.

CAN I CONVERT A "REV B" BOARD TO A "REV A"?

Yes.  There are two ways.

1) PCB modification.














2) Wiring:


























7/5/15