John Houghton, fellow member of our Nottawasaga Model Railway club and a regular attendee at weekly operating nights on my HO Utopia Northern introduced me to servo control of turnouts with the addition of Tam Valley electronics to activate LEDs to indicate position on a panel. See my "servo control" page for more information. John worked up a circuit for signal boards that could be connected to the relays on the Tam Valley boards and added signal heads to a signal bridge that I had built.
I am posting John's circuits here for those who might be interested in trying this for themselves. Here is the first of the signal boards. After making sure it functioned correctly we mounted it behind the fascia. Here you can see the well marked leads that connect to the relays and to the signals.
John glued two dwarf signal heads on top of each other offsetting them to each side. The LEDs mimic the panel indications so that an operator at Utopia can look down the mainline to East Utopia and see which way the three-way turnout points are set without having to check the panel. John cleverly set up the signal heads on the bridge so that green over green indicated the points are set straight through for the mainline track. The offset LED that turns red on the left hand side indicates the points are set for the CP yard tracks that are to the left while the LED offset to the right indicates that the points are set for the CN tracks that are physically located to the right.
The wiring for the signal heads is located inside a signal box that John located at the foot of the stairs. We cut a channel for the wires to run down underneath the module. The East Utopia module has to be moveable to provide access to a storage cupboard. We left enough slack in the connecting wires so that the bridge can be swung around onto the module. John wired the plugs and added printed tags so that they cannot be mismatched.
The Tam Valley electronics are powered from the DCC bus beneath the East Utopia module. John designed a circuit using 556 dual timers to drive the LEDs. One side is used for the CN indications and the other is for the CP indications. The relay provides +5v (white wire) and grund (black). The center pins will give a red indication for each dwarf depending on whether they receive +5v or are grounded. The voltage from the DCC bus is dropped to a level that the LEDs can handle. John built the circuit on a piece of experimenter's PC board. The parts are cheap and easy to source.
Below are pdfs of the circuits and signal boards.
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