Automatic Control of Loop Switches

While the RC&G is designed to provide plenty of opportunities for operations I wanted it to be capable of running continuously for guests or times when I just want to kick back with an adult beverage and watch it run. To that end the layout functions as a loop to loop design and for it to be used in a continuous running mode some method of operating the loop switches at each end automatically.

Some folks just use spring operated switches by my experiments with them were less than satisfactory and I also wanted to be able to manually operate them when doing operations so I decided to go a different route. Since locomotives would be equipped with magnets to operate the signal system I decided to use them to control the loop switches as well.

The loop switches are operated by air cylinders and when not activated they hold the switch points in the position for normal flow. In what I call the automatic mode, when the locomotive completes the circuit of the loop and is approaching the switch, its magnet will activate a reed switch mounted under the rails. This in turn will activate a time delay relay which applies power to an air solenoid valve which supplies air to the air cylinder and throws the switch to the position needed. This uses the same time delay relay as used in the signal system which is described in another article. The relay holds the switch in the new position long enough for the train to pass then returns to the default position. The time is adjustable and is nominally set to 90 seconds which is more than adequate for the train lengths and speed I use.

That's all well and good for the automatic mode but I also needed other options for use during operations. The two I selected are a manual mode which is controlled by an electrical toggle switch located near the loop switch and a radio control mode. The Revolution system I use to radio control my locomotives also as accessory boards which can be controlled by the hand held transmitter. By using one of these boards to activate the air solenoid radio control can be achieved.

OK, I had a plan but I needed somewhere close to the loop switches to install this stuff that would be weather proof. I decided to put the circuitry in a weather proof plastic electrical junction box. The next photo shows the parts installed and wired up. The Revolution accessory board is at the top, the air solenoid valve bottom center, the time delay relay bottom right. The orange device mounted right center is a small DC relay. This is activated by the accessory board and in turn activates the solenoid valve. I wasn't certain that the accessory board could handle the current required by the solenoid valve so this was added as a safety feature. One other task this box would handle is that of a junction box for the 12V circuit that is routed around the layout for lighting and other devices like this. The terminal strip not only provides tie points for the internal parts but will terminate the 12V DC in and out lines.

To camouflage the box I decided to build a section house to enclose it, it also allowed me to keep it above ground. I wanted the roof to be removable but it needed to be heavy as well as we have a lot of high wind days in the area. The roof was made of solid wood. Pieces were glued together to get the desired height then the angles were cut on the table saw. The structure part was built from coroplast and sheathed with Precision Products siding. Windows and doors and their frames were made from styrene. The building was mounted on a block of Trex. 

A rabbit joint was routed around the bottom of the roof to allow it to fit inside the walls.

The center of the Trex block was cut out to give access to the liquid tight fittings on the bottom where the electric will enter and exit and where the air and lines to the reed switch and the manual operating switch will enter the box.

The section house with the roof sheathing installed and ready for paint.

And painted up and installed on the layout.

I did not include a schematic for this as the only thing I have are some pencil scratchings on a legal pad. No rocket science was used and everything is pretty straight forward. If you have any questions please feel free to email me.

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Updated  4/6/19