ASSIGNING 2 OR MORE FUNCTIONS TO SAME CIRCUIT TRACKS
             FOR DIFFERENT AUTOMATIC OPERATION SCHEMES
                       (c) 1997 Billy Bremer

THE BASIC CONCEPT is to use the same circuit tracks in the layout to
control different solenoid accessories according to different ways to
run the trains on the same layout. Different operating schemes at the
flip of a switch.

SUGGESTED KNOWLEDGE: Basic electric circuit concepts and understanding
of common ground returns.

REQUIREMENTS ARE MINIMAL:
      - A little additional wire and wiring effort;
      - A selector switch (SPDT toggle for 2 schemes or a rotary
        switch for more);
      - 2 or more transformers for 2 or more schemes; and
      - To strategically plan the circuit track placement to work
        well with the different operating schemes.

IMPORTANT: In this article we will only be dealing with the 10v
alternating current transformer terminals for accessories; power to the
engines is completely apart. Thus we will be talking about
yellow/gray/blue wires but NOT about the red/brown wires. So the 'O'
terminals used below will ALWAYS refer to the GRAY ones, never to the
brown ones.

The whole idea is to keep one of the transformers ground return 'O'
(gray terminal) separate from the others in order to have some, or all
of your circuit tracks control different solenoids. Every additional
solenoid you want to control with the same track (wired together) would
require to leave one more transformer ground independent.

The independent grounds, say, transformer terminals 'O1', 'O2' and 'O3',
for three different operating schemes must be connected to the primary
(center) terminal of a single pole rotary switch (or SPDT for 2
schemes); and the common terminal of the switch must go to the common
terminal of the circuit track.

Having done that, you can now connect up to THREE DIFFERENT solenoids
TOGETHER (blue wires) to one of the secondary terminals of the circuit
track. The 'L' (yellow) wire of each solenoid MUST go to terminals 'L1',
'L2' and 'L3' of the different transformers (which are ground
independent from each other). The ONLY SOLENOID that will RESPOND to the
signal triggered by the passing engine, will be the one that is
connected to 'Li' correspoding with 'Oi', as selected by the rotary
SWITCH or SPDT; thus, only 'L2' supplied solenoids will operate if 'O2'
is selected.

The system works because electric current is 'smart', and it always
seeks to return to the same 'own' transformer where it originated.
Current will never go to a different independent transformer, even if it
is connected to it.

			

			
A SIMPLE EXAMPLE: Assume you have two separate track loops in your
layout, and most of the times you want to run 2 trains on each loop,
running one behind the other using signals or semaphores (Scheme 'S1');
but some other times you feel like running only one train thru the whole
layout, alternatively going thru different routes (Scheme 'S2').

In the first case you could have your circuit tracks controlling your
signal relays to prevent back end collisions; and in the second case,
just by flipping an SPDT toggle, the SELECTOR, the SAME circuit tracks
would control your turnouts to route your train thru different tracks.

For the example you would only need 2 transformers and just 1 simple
SPDT switch. A schematic for a typical circuit track wiring, controlling
either a signal relay coil or a turnout coil, but not both,  follows:



With the previous schematic, an engine passing thru the SAME circuit
track upbound would EITHER set the relay to Halt OR the turnout to its
Normal position depending on the switch setting. In this case, the
Normal position depending on the switch setting. In this case, the
turnout will be thrown to its Normal straight position.

BOTH, signal relay and turnout blue wires of one of their solenoids are
CONNECTED TOGETHER (=====) to the SAME circuit track terminal, but ONLY
the TURNOUT will operate, because the signal relay has an open circuit
on its ground return path to its 'own' transformer T1 at the SPDT, which
in this case is shown selecting Scheme 'S2'. All other required circuit
tracks in the layout would connect to the same SPDT center terminal.

OPTIONAL ENHANCEMENTS:

1) The scheme selector switch may be substituted by one or more relays
that can be operated automatically from other circuit tracks, instead of
selecting operating schemes manually.

2) You can mix accessories of different voltage with their appropriate
power supplies or transformers, and still use the connections as
described above. You can always intermix voltages and different power
supplies as long as they are independent and so, their secondary
windings (low voltage side of a transformer) are also independent.

                              (c) 1997 Billy Bremer