Model Railroad Grade Crossing Circuit

Prototypical Signal And Gate Operation

Grade Crossing Circuit Demonstration Video

(Less Than Prototypical Demonstration Of The 2008 Grade Crossing Circuit Board)

  This crossing circuit automatically controls railway grade crossing signals and gates in a prototypical manner. The circuit can protect multiple tracks and unusual crossing approaches. Four-Quadrant type gates can also be controlled.

  Each crossing circuit uses six phototransitors to detect the positon of a train and control the signals.

  The crossing circuit has time delays to stagger the activation of the signals and lowering of the gates so that they operate as would be seen at a typical grade crossing when a train arrives or departs. The delay times are adjustable for both arriving and departing trains.

  The crossing circuit can drive all of the typical crossing signal flasher configurations.

  The crossing circuit is very flexible and can be adapted to large variety of crossing configurations including: Multiple tracks, Crossovers, Short Approaches, and Sidings.

Additional Grade Crossing Circuits Page


Assembled boards and kits are available for this circuit.

email

  If you are interested in circuit boards please send an email to the following address: rpaisley4@cogeco.ca Subject: 2011 Grade Crossing Circuit


One Track Crossing Circuit Board Connection Diagram

Full Crossing Protection

  The following diagram shows how the 2011- Grade Crossing circuit board is connected for a typical 1 track crossing. There are diagrams for mulptile track crossings, crossovers and other track arrangments at this site as well.

  More detailed information for connecting flashers, bell, and gate drivers is shown on various diagrams on this page and the Additional Grade Crossing circuits page.



The 2011 - Railway Grade Crossing Circuit board can be built in three configurations:

Configuration 1 - Signals And Gates (Fully protected crossings)

  In the Signals and Gates version of the circuit: When a train enters the protected section of track the flashers operate for a set time before the crossing gates start to lower. After the train clears the grade crossing, the signals will stay flashing until after the gates are up fully. Both gate time delays can be adjusted to suit actual conditions.

  See the Output Timing Diagram section of this page for delay times and signal flashing rates.

Configuration 2 - Signals Only (Crossings without gates.)

  In the Signals only version of the circuit: The flashers are activated when a train enters the protected section of track and will shut off approximately two seconds after the train clears the crossing. The components that control the delays for the flashers and gates are left off of the circuit board.

Configuration 3 - Controls Only (Second and other tracks at a crossing)

  In the Controls Only version of the circuit: This circuit is used to control the second and other tracks at a crossing via the multitrack terminal on the main track's circuit boards. The components that control the delays for the flashers and gates and the components that operate the flashers are left off of the circuit board.


2011 - Grade Crossing Circuit Schematics And Parts Lists


General Information

  The 2011 Signals and Gates circuit is designed to control crossing gates that are powered by stall-motor type switch machines.

  The Grade Crossing circuit uses six visible and infrared light sensitive phototransistors to detect a train and control the circuit.

  The 2011 circuit uses the same phototransistor control scheme as the 2004 and 2008 grade crossing circuits and is fully compatible with the earlier circuits for combined use at multiple track crossings.

  The Grade Crossing circuit uses a LM556 timer to drive the signals allowing it to directly drive most signal wiring configurations without added circuitry.

  One Grade Crossing circuit board can be used to protect multiple tracks by using additional phototransistors.

  The Grade Crossing circuit can supply up to 100 milliamps for LEDs, small incandescent lights or other circuits such as sound units or can drive larger loads through transistors or relays.

  The 2011 Grade Crossing circuit board has been designed to be easy to build and install. Inexpensive and widely available components are used in its construction. None of the parts are static sensitive.



2 Track Crossing Using 2 Circuit Boards

Full Crossing Protection

  For full protection of a 2, or more, track crossing a Grade Crossing circuit boards for each track is required. The board for the second, and subsequent, tracks do not need the components for the gate motor control or the flashers.

2 Track Crossing With Crossovers Using 2 Circuit Boards


2 Track Crossing Using 1 Circuit Board

Less Than Full Protection

  Two tracks can be protected by one circuit board as shown in the following diagram. Protection is not complete because the first train in the protected section could prevent a second train from activating the signals.

  Because only one circuit board is used, fully automatic operation is not possible as with the 2 circuit board - 2 track crossing but if only one train uses the crossing at a time, the system will give prototypical operation.

  If trains pass each other while the crossing is blocked this will not be a problem.

Many other crossing configurations are shown on the Additional Grade Crossing Circuits page.



- About The Diagrams On This Page -

  The PCB connection diagrams on this page show a circuit board that is configured to control crossing gates. If the board is assembled without the gate control or signal flasher components, these connections can be ignored. All other inputs and outputs remain the same.

  Schematics for the Grade Crossing Circuit are shown on a separate page.



Phototransistor Sensor Placement Diagram

  The next diagram shows the relative positions of the six phototransistors along a protected section of track.

  The lower portion of the diagram shows the order of operation for the signals and gates a train passes through the protected section from left to right. The delays are the same for both directions of travel.


  The protected section of track can be of any length on either side of the crossing. The Grade Crossing circuit works in both directions and can be connected to other grade crossing circuits to provide fully automatic protection for multiple track crossings.


Typical Phototransistor Installation

Additional Phototransistor Circuits And Information



Grade Crossing Flashers And Gates Operation

  1.   When a train traveling in either direction covers one of the "START" sensors, the crossing signals will start to flash.

  2.   After a delay the crossing gates start to lower. (Adjustable delay)

  3.   When the train has cleared the crossing the gates will start to lift after about 2 seconds.

      (The grade crossing is occupied until both of the "STOP" sensors are uncovered.)

  4.   The signals will remain on for a short time after the gates are fully up. (Adjustable delay)

  5.   As the train leaves the protected section of track, the "DISABLE" sensors prevent the flashers from starting again by deactivating the "START" sensors.

  6.   The "START" sensors are reactivated approximately 5 seconds after the "DISABLE" sensors have been uncovered.

  Sensors Q1 or Q2 must be covered before sensors Q3 or Q4 (depending on the direction of travel) or the signals will not start. Sensors Q3 and Q4 disable sensors Q1 and Q2.


2011 - Grade Crossing Circuit Schematics And Parts Lists



Gate Driver And Signals Output Timing Diagram

  The next diagram shows the changes in the output terminals of the grade crossing circuit as a train travels through the protected section of track.

  When the manual START, STOP or MULTI-TRACK inputs are activated the time delays above will also be applied.

  A LM556 Dual Timer (IC 3) provides a complimentary, bipolar output that can directly drive slow-motion switch machines.

  A 2N3906 PNP transistor (Q8) provides a 12 volt output that can be used to drive signals, small relays and other low current loads.

  Higher current flashers and gates can be driven by adding external transistors or relays to the outputs of the circuit.

  A LM556 Dual Timer (IC 4) provides a complimentary, bipolar output that can drive most signal LED configurations without additional components.



Grade Crossing Circuit Operation Notes


2011 - Grade Crossing Circuit Schematics And Parts Lists



Crossing Signal Flasher Connection Options

  The 2011 Grade Crossing Flasher circuit uses LM556 dual timer IC to provide two outputs of opposite phase that can drive LEDs in common cathode, common anode or back-to-back configurations.

  Only one set of signal LEDs is shown in three of the diagrams, more sets of signals can be connected as needed.

  The circuit's output can also drive small incandescent lamps connected in the same general arrangements as shown for the LEDs. Small relays and sound circuits can also be controlled by the output of the circuit.

  NJ International, Inc. Crossbuck Signal Model 1095 are wired in a common anode configuration.

  From NJ International products documentation; "All NJ LED crossing signals, block signals, and signal heads contain 3v common anode LED's. Dropping resistors are factory installed to protect the LED's and it is recommended to use 9-14v DC power. The wires with the resistor connect to (-) and the wire without the resistor is the common (+)."

  Oregon Rail crossbucks specify common anode wiring.

  Unconfirmed - Walthers #933-2914 crossing signals are wired in a common anode circuit but with Black wire being the positive and the Red wires the negative.

  TOMAR Industries crossing signals can be connected as shown in this diagram.


Incandescent Lamp Simulator Circuit

  This circuit can be added to the flasher's output will to allow LED's to turn on and off more slowly. This will make the LEDs appear similar to incandescent lamps.



Crossing Gate Drive Motor Connection

'Stall' Type Motors

  The speed of the stall-motor can be adjusted by adding resistors or a potentiometer to the motor's circuit. A potentiometer will allow better control of the speed of the gates.

  NOTE: In some installations, while the gate drive motor is running, the crossing signals may flash very quickly. A particular cause has not been found for this but with the potentiometer connected as shown in the circuit above, the problem can be eliminated.

  Several motors can be operated at the same time if needed but each should have its own speed reducing resistor.

Controlling Four-Quadrant Type Crossing Gates


Additional Grade Crossing Sensor Arrangements

For Multiple Track Crossings and Output Options

  Sensor placements and connections for many other grade crossing arrangements can be found on the Additional Grade Crossing Circuits page. Most of the diagrams show the 2004 circuit board but the sensor input terminals are identical with the 2004, 2008 and 2011 versions of the Grade Crossing Circuit.

  The phototransistor input circuits will work with all versions of the Grade Crossing Circuits.

  Also, there are various output circuits on the Additional Grade Crossing Circuits page that can with the 2004, 2008 and 2011 versions of the Grade Crossing Circuit.

  Some of the output circuits will not work with all versions of the Grade Crossing Circuits depending on whether the output flasher is and LM555 or LM556 oscillator.

  Circuits on the Additional Grade Crossing Circuits page include:





Printed Circuit Board And Parts Information

Click On The Image For A Larger View

  The circuit board measures 2 inches by 6 inches, is commercially made and has been tinned.

  The circuit board has been designed to be easy to build and install. Widely available and inexpensive components are used in its construction. None of the parts are static sensitive.

2011 - Grade Crossing Circuit Schematics And Parts Lists



2011 Circuit board And Parts Prices

  Grade Crossing circuit boards sold = 610.

Option 1:  1 - Printed Circuit Board is 8.50 dollars US plus postage.

Additional circuit boards are 8.00 dollars US each.

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Option 2:  1 - Assembled - Signals And Gates circuit board is 30.00 dollars US. - Plus postage.

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Option 3:  1 - Kit - Signals And Gates circuit board 29.00 dollars US. - Plus postage.

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Option 4:  1 - Assembled - Signals Only circuit board and all of the parts is 26.00 dollars US. - Plus postage.

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Option 5:  1 - Kit - Signals Only circuit board and all of the parts is 25.00 dollars US. - Plus postage.

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Option 6:  1 - Assembled - Controls Only circuit board 23.50 dollars US. - Plus postage.

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Option 7:  1 - Kit - Controls Only circuit board and all of the parts is 22.50 dollars US. - Plus postage.

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  NOTE: - The above prices include 6 visible/infrared sensitive, 3mm diameter phototransistors. The phototransistor have 5 inch - Red and Black leads soldered to them and are tested before shipment.

  Extra phototransistors are available if needed.

email

  If you are interested in printed circuit boards please send an email to the following address: rpaisley4@cogeco.ca Subject: 2011 Grade Crossing Circuit


2011 - Grade Crossing Circuit Schematics And Parts Lists


Grade Crossing Circuit Testing

Phototransistor Inputs Testing

  NOTE: The Grade Crossing circuit will not function correctly unless each input has a phototransistor or testing jumper connected.

  NOTE: When power is applied to the Grade Crossing circuit the flahsers will activate for about 2 seconds and then shut off. Also, the crossing gates may start to close and then will open again.

  The diagrams shows the expected input terminal voltages when the phototransistor input sensors are lit or dark.


Circuit Board Testing

  Before installing the Grade Crossing circuit on a layout, this circuit can be used to test the circuit board and demonstrate its operation.

  SPST switches are used in place of the phototransistors to simulate their function. An open or closed switch is the same as a covered or dark phototransistor.

  This circuit can be also used for the 2004 and 2008 circuit boards as the input terminals are the same for both.

  If switches are not available, disconnecting of connecting the wires where the switches are will also work.


Testing Phototransistor Installations


Additional Grade Crossing Circuits

  Also, there are circuits on the Additional Grade Crossing Circuits page can also be used with the 2004, 2008 and 2011 versions of the Grade Crossing Circuits.

  The phototransistor input circuits will work with all versions of the Grade Crossing Circuits.

  Some of the output circuits will not work with all versions of the Grade Crossing Circuits depending on whether the output flasher is and LM555 or LM556 oscillator.

  These circuits include:

  Most of the circuits on this page show connections for the 2004 version of the Grade Crossing circuit but the input circuits will also work for the 2011 version of the circuit board as the five input terminals are the same for both.

Additional Grade Crossing Circuits Page



Grade Crossing Bell Ringer Circuit (PCB)

  This circuit is a driver for a mechanical - Grade Crossing Bell Ringer - that was originally built for the London Model Railroad Group.



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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

email

  If you are interested in printed circuit boards please send an email to the following address: rpaisley4@cogeco.ca Subject: 2011 Grade Crossing Circuit

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12 May, 2017

(Non-prototypical) Demonstration of the 2008 Grade Crossing circuit board.