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Controlling Hidden Staging with the PSX Series

Text Larry Maier, Illustrations Don Fiehmann


Larry Maier and Don Fiehmann tell how to exploit some of the special features of the DCC Specialties PSXs to automate and protect hidden staging.

The PSX series of circuit breakers and reversers were designed to help you manage hidden staging tracks. The issue with hidden staging tracks is that you can’t see them, by definition, so how to you stop a train in the correct location and how do you tell if there is a train in a particular staging area? Another problem with hidden storage is with consists. If you have a stopping section without power, the lead engine will go into the dead section and stop, but the trailing locomotives still have power and will continue to run. The PSX series has features to address these problems.

J4-1 and J4-2 are designed as an input for a photocell. These photocells are available through your dealer. When connected, the photocell can perform two operations: it can trigger the PSX to turn off power to the track, and it can provide an indication of block occupancy.

Photo Cell and Block Power Chart

By default, the PSX series will use block current to trigger the block occupied output. However, if CV50 is set to 1, then the block occupied output will be on when the photocell is covered and off when it is uncovered. The block occupied output is from an optical coupler, so it can be connected to anything without danger of shorting things together. The actual output is an open collector transistor. You can connect it to a bus interface such as the LocoNet, or you can just connect it to an LED. For the LED function, connect the positive lead of a 12 volt power source through a 2K resistor to the positive terminal of an LED. Connect the LED negative terminal to J4-3. Connect J4-4 back to the negative terminal of your power source. Install the photocell from J4-1 to J4-2, either polarity is ok. Now any time you cover the photocell, the LED will come on indicating block occupancy.

Now, arm the photocell by sending an accessory on command to address 2043 (this is the default, see the PSX series instructions on how to change the address). The next time the photocell is covered, the PSX will turn the track power off and the block occupied LED will come on. The LED will be on as long as it is covered. Locate the photocell where you want the front of the train to stop in your hidden staging yard. You can locate it between the ties so that the top of the cell is even with the top of the ties. When a train is entering the staging, send an accessory “on” command to the photocell arming address. When the train just covers the photocell, the occupied LED will turn on and power will be removed from the staging track thus stopping the train and turning off all sound and lights. Once the photocell has triggered, it is automatically disabled until you arm it again. This means that when you are ready to move the train out of the staging, you simply send an accessory “on” command to the PSX breaker control address (2042 by default), note that this is a different address from the photocell arm address and the staging track will be powered. Since the photocell is disarmed, it will not immediately turn power off, although the occupied LED will remain on until the train leaves the staging area.

If you really want to get fancy, then include the photocell arming address in a macro or route that aligns the switches into the hidden staging area. Simply aligning the switches for the destination staging track will then arm the photocell for the incoming train. Include the PSX on/off control address in the macro or route for the exit switch configuration from the staging area, and the PSX will automatically turn on power to the staging track when you execute the command to align the switches to allow the train to exit the staging area.

One other feature of the PSX is that the photocell is calibrated to the ambient light level every time that you arm it. If light levels are changing, the PSX will adapt! If your staging area is both hidden and dark, you may need to add a small grain-of-wheat bulb or similar light source above the photocell to allow it to operate correctly. Don’t worry too much about this light since the PSX will calibrate the circuit to the light level for you.

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