Turnout and Signal
control with a separate Accessory
bus
General
Operation:
This scheme provides for turnout and signal control using
a Team Digital SRC16(s), SIC24AD(s) and DBD22(s) in a DCC system. It also
demonstrates the concept of an accessory bus.
An accessory bus is defined as an independent serial bus
separate from the throttle bus. It provides a way for
accessory devices to communicate with each other. This
can provide several advantages for a DCC system. In a
Digitrax system an accessory bus can be used to keep
accessory communication traffic off the main throttle
bus. This can provide fewer throttle control issues when
multiple throttle are in use. In other DCC systems, such
as NCE, an accessory bus can expand the selection of
devices available for applications. Also trouble shooting
is made easier.
The SRC16 is an accessory decoder and can be powered from
DCC track power. Since it can be controlled via DCC
commands it's gateway feature provides a very convenient
way to pass turnout (switch) commands to the accessory
bus. This allows DCC turnout commands to control devices
connected to the accessory bus. Thus, turnouts can be
controlled either from the throttle or from fascia
buttons.
Turnouts:
SRC16(s) are used to control turnouts and indicate
turnout status. They can drive stall motor type switch
machine with 5 volts or with a higher voltage using
MotoDs.
Block Status:
DBD22(s) are connected to the SIC24AD(s) to provide block
status.
The SIC24AD(s) use the block status information in the
signal logic.
Signaling:
SIC24AD(s) are used to drive the signal aspects. The
specific aspect to light is determined by the SIC24AD
logic. The logic uses block status information and
turnout state to determine the signal state. When
multiple SIC24s are used internal logic information of
the SIC24ADs are passed over the serial bus to each
other.
The serial bus greatly simplifies wiring because the
SIC24s can be located around the layout near the signal
aspects they are driving. This means the DBD22s will be
near the blocks they are detecting.
Power:
The SRC16(s) may be powered from a dedicated power supply
or the track. Using the rail sync lines in a separate
accessory bus provides easy power connections. When a
large number of devices are used a separate power bus is
recommended. DBD22(s) are powered from the SIC24AD(s).
Note: SIC24 is
sometimes used to refer to both the original SIC24 and
the new SIC24AD. The original SIC24 can NOT be powered from the track.
DCC system with a separate Accessory bus
