ServoMaster for Crossing Gates by TDP

Review by Don Fiehmann

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Don Fiehmann uses and reviews the ServoMaster by TDP to animate his crossings:

Action on the Layout

Model railroading is a three dimensional art form. One thing that separates model railroading from most forms of art is motion. When you go to visit an open house, there are always trains running and lights flashing. Most people follow a train as it runs around the layout. Adding things that move adds even more interest. I recently added a pair of three position semaphores. Visitors are always surprised to see the arms move and the light change color as the train passes the signals. Another item that can add to layout motion is a pair of crossing gates that actually work correctly!

Crossing Gate Control

There are a couple of problems presented by controlling a set of crossing gates. Even the prototype has to use some special relay wiring to control crossing gates. One fan trip I was on had a photo run by at crossing on single track. The train went by while the crossing bell and lights were active. The train passed and the signals turned off. As the train backed up, the signal stayed off and the brakeman had to protect the crossing manually. Had the train gone far enough to clear the block, the control relays would have reset and it would have looked to the relays like a new train.

If the prototype has to use a complex relay setup, how is a modeler expected to figure out how to connect block detectors and relays to duplicate this function! There is good news. The same people that produced the TrainSpeed detector and readout have come up with a controller called ServoMaster that can solve all of the logic and control problems for a crossing gate or even a semaphore. The motion is done with servos that can also be used to operate turnouts.

ServoMaster

The ServoMaster comes with a printed circuit board, two servo motors, and program jumpers. Two cables are provided. One to connect the LEDs in the crossing signal and one for photo track detectors. The unit will run on 9 to 12 volts AC or DC. There is a manual with step-by-step instructions on using the ServoMaster for grade crossings, turnouts and semaphores.

The servos are small units made by Futaba, a name that will be familiar to those who work with model airplane radio control. The two servos are connected to the printed circuit board with an 11 inch cable. There are four modes of operation with the ServoMaster. The first is the crossing gate using the photo cells. The second is the crossing gates using other types of detectors. The third is use for turnout control and the fourth mode is for a semaphore. These modes are set with the adjustment control. It is factory set for crossing gate control with the photo cells.

There are four photo cells used for the crossing gate control, two for each direction. Each direction has a start photo cell that when triggered will activate the signal. The second photo cell is used to hold the gate down until the crossing is clear, then returns the gates to the up position. Since this is independent of the track block detectors, it is a lot simpler than trying to use track occupancy detectors when you also track signals. For dual track, one of the sets of photo cells is installed in the other track.

The photo cells are like those used in the TrainSpeed device to measure scale miles per hour.

The logic in the ServoMaster is programmed to simulate the action of the prototype crossing gates. When the operation starts the crossing gate LEDs start flashing before the gates are dropped. At the end, the LEDs continue to flash until the gates are up. If accidentally triggered, the gate will drop and then time out after a couple of minutes.

To complete the ServoMaster a 9 to 12 volt power supply and signals are needed. They suggest the N.J. International crossing gates.

Test Installation with Crossing Gates

There is a spot on my layout on a grade crossing where the signals would look good and add a bit of action as the train passes. This is a place where there are dual tracks. I bought a pair of the HO Highway Crossing Gates (No.1160) from N.J. International, Inc.

As the ServoMaster instructions say, do some planning before installing. There are a couple of items that should be checked out when planning. The spot you locate the crossing gates is clear under the layout and room for the servos. If you are using the photo cells, be sure that there is light to activate the cells in each location. Locating a cell in a tunnel would be a problem unless you add light above the cell.

The instructions start with a test procedure to set up the logic before installing the unit. Be sure to carefully read through the instructions. This is also a good bench test to be sure the unit is operating correctly. This setup procedure uses the push button and adjustment pot on the board to set the initial setting for the mode of operation and the servos. The two LEDs on the circuit board show the status of the setting as adjustments are made. Since final adjustments are needed when the crossing gates are installed, the instructions state to locate the circuit board so it is easy to get to for adjustments. Even the speed of the arm motion can be set with these adjustments. I went through the initial settings and all went per the instructions.

The instructions recommend putting a small hole in the cross gate arm that is further away from the pivot point of the crossing arm so the servo can have a longer throw for smoother action. I drill a hole in the arm and used a piece of 16 thousandths brass wire to control the arm movement. I mounted the crossing gates on a piece of styrene and installed a short section of 1/8 inch brass tube for the gate control linkage. A second hole was used for the wires. Two holes were drilled in the layout for the each of the crossing signals, one for the wires and one for the crossing gate control wire.

The two servos were mounted so they would line up with the wires from the crossing gates. This required a mount at a 90 degree angle from the bottom of the layout then installing the servos. I used a metal corner bracket and drill holes to fit the servo. The gate control brass wire was put into one of the many holes in the servo arm. Then the two were installed on the layout. Then the circuit board was mounted near the crossing gates and wired. I had a little trouble with the setup of the crossing gate arms. Then I started at the beginning of the setup and it setup per the instructions. Holes were drilled in the roadbed for the photo cells and they were installed by pushing them up from below.

If you do not have enough room light
the photo cell can be raised slightly
for more light to the photo cells.

When I turned the system on the gates came down and stayed down. The problem was there was not enough light on the photo cells. I moved the photo cell up higher so they got more light and turned on the rest of the layout lights. Then the crossing gates came down with power on, and in a while the gates came up. This is the normal power on sequence.

Now was time to run trains and watch all the LEDs blinking and the action of the crossing gate arms. The moving gate certainly add an interesting feature to the layout All that is missing is the sound of the crossing signal bell to finish the scene.

Conclusion

The ServoMaster is not a shake-the-box kit. It takes some time to install, but the final operation is worth the effort.

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