Garden Railway Controls
Dore Lakes Railway was conceived with a number of purposes
in mind. Two of which are:
1. As
a test bed to try out my ideas in mechanical, electronic and software
engineering.
2. As
somewhere I can relax and watch trains go by.
It was planned that all main line signals and points were to
be controlled either remotely or automatically.
This required a considerable amount of development. Implementation is now being rolled-out
across the garden.
Point mechanics
Radio control servos are inexpensive but I had no idea how
they would survive when permanently installed in the garden. My early testing with a simple control system
showed that the servos worked well outside.
The first mechanical linkages to Peco points were
the main problem.
Currently I’m using miniature servos (Hitec HS-81) to control Peco
points. I’m using simple push-pull wire
in tube linkages, over-centre springs being retained in most locations. The servos will either be hidden in trackside
huts, other building or in “cabinets”.
This winter a Marcway double slip was
installed. This required much more force
to operate than the Peco points so I used standard
servos (Hitec
HS-322HD) pulling on double ended levers connected to the pointwork, giving a 2.5 : 1 mechanical advantage. The PTFE tube containing the operating wire was
inserted in 1/8” copper pipe for rigidity.
Controls
Servos are controlled by sending a 3 to 5V pulse of between
1 and 2mSec about every 20mSec. This is fairly
easy to generate using inexpensive microcontroller chips.
Semaphore signals can be controlled by servos as for the
pointwork but as Dore Lakes
is intended to be more of a modern scenic railway – part of my miniature theme
park I’m tending to use LED colour light signals, microcontroller digital
outputs drive these directly.
A more complex system has being developed where up to 16
switch inputs control a “signal box”, these being for either signals or
points. Up to 29 outputs can be
controlled from each box, either pulse outputs for servos or tri-state digital
outputs for colour light signals or route indicators. Interlocks are implemented
to ensure signals cannot be set incorrectly and that points cannot be changed
ahead of a green signal.
Each “signal box” is unique and requires complex programming. A spreadsheet has been developed to generate
the bespoke code and wiring diagrams for each box.
To avoid large amounts of wiring each “signal box” consist
of two parts, a master controller that operates the servos and other devices
and a remote controller that has switch inputs to request changes and LEDs to
show the current state of each point or signal, the two being connected by a
serial link. The remote controller
requests an action and the master acknowledges that the action has (or has not)
been made. Licence free radio transceiver modem modules are used to implement
the serial link.
Each “signal box” has its own custom control panel with
switches and LEDs laid out in the form of a track
diagram. This is connected to a more
generic microcontroller board.
Computer Monitoring
and Control
The design of the system permits multiple remote
controllers. These may be either hard
wired dedicated controllers for each box or a single PC monitoring and/or
controlling the entire system. This is
still under development.
Further enhancements are envisaged, including:
1. RFID
(i.e. a contactless card system) to monitor either the position of trains on
the track or block occupancy
2. Automatic
route selection based upon track occupancy
3. Automatic
signal operations
4. Timetable
operations
These will take some time to develop.
Control
Panel
Switches - LEDS
|
Servos, signals or devices
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Control
Panel
Switches - LEDS
|
Control
Panel
Switches - LEDS
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