This circuit automatically controls railway grade crossing signals and gates in a prototypical manner.
The circuit has time delays that stagger the activation of the signal lights and lowering of the gates so that they operate as would be seen at a typical grade crossing when a train both arrives or departs. The delay times are adjustable for both arriving and departing trains.
The 2011 - Railway Grade Crossing Circuit replaces the 2004 and 2008 grade crossing circuit boards. The 2011 circuit board is fully compatible with the earlier circuits.
Configuration 1 - Controls + Crossing Signals And Gates.
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 time delays can be adjusted to suit actual conditions.
Configuration 2 - Controls + Crossing Signals. (For a crossing 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. (For two or more tracks at a crossing.)
In the Controls Only version of the circuit: The circuit is used to control a second and other tracks at a crossing via the multitrack terminal on the first 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.
The 2011 Signals and Gates circuit is designed to directly control crossing gates that are powered by stall-motor type switch machine drivers.
Components omitted from the Gates Only and Controls Only circuit boards can be installed later to restore the functionality of the circuits.
The Grade Crossing circuit uses six visible and infrared light sensitive phototransistors to detect a train and control the circuit.
The Grade Crossing circuit has a dual output signal driver allowing it to directly drive most signal wiring configurations without added circuitry.
One Grade Crossing circuit board can also be used to protect multiple tracks by using additional phototransistors.
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 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. Widely available and inexpensive components are used in its construction. None of the parts are static sensitive.
The PCB connection diagrams on this page show the board 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.
The following diagram shows how the 2011- Grade Crossing circuit board is connected for a typical 1 track crossing.
Typical flasher, bell and gate drive motor connections are shown on other diagrams on this page and others.
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.
After a delay the crossing gates start to lower. (Adjustable delay)
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.)
The signals will remain on for a short time after the gates are fully up. (Adjustable delay)
As the train leaves the protected section of track, the "DISABLE" sensors prevent the flashers from starting again by deactivating the "START" sensors.
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.
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.
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 DC fixed voltage output that can power signals, small relays and other low current loads.
A LM556 Dual Timer (IC 4) provides a complimentary, bipolar output that can directly drive most signal wiring configurations.
Higher current loads could be driven by adding larger transistors to the outputs of the circuit.
The 2011 circuit uses the same operating system as, and is fully compatible with, the 2004 and 2008 Grade Crossing Circuits. The basic control and operating information is the same for all three circuits.
The signal flashers will turn OFF if a train enters and then backs out of the crossing.
The crossing circuit is ready for the next train in either direction approximately five seconds after both "DISABLE" sensors are uncovered. If a departing train is still covering a "START" sensor after this time the flashers will be reactivated.
MANUAL controls can also be used to start and stop the flashers if desired. The START push button could be replaced by or paralleled by a SPST toggle switch to keep the flashers activated during switching operations.
When the MANUAL controls are used, the same gate and flasher delays are present as with the phototransistor sensors.
The 'MULTITRACK' terminal (8) is used to connect circuit boards together for multiple track crossings. When the MULTITRACK terminal is used to control the crossing circuit, the same gate and flasher delays are used as when the phototransistor sensors control the circuit.
The 'MULTITRACK' terminal is an input only and cannot be used to control other circuits. Terminal 11 can provide a positive output signal to control other circuits if needed.
Normal room lighting is used to detect the trains. If night operation is needed the circuit can be controlled by other circuits or by providing infrared light for the phototransistor sensors.
The circuit is designed to use phototransistors but can also be controlled by CdS photocells by using external resistors in parallel with the R1, R2 and R3.
Low coil current relays can also be controlled by terminals 9 and 10.
Bell circuits and small relays can be controlled via terminal 11.
The 2011 - Crossing Circuit requires a regulated 12 volt power supply.
WARNING - If the polarity of the power supply for this circuit is reversed or the circuit is connected to an to an AC or DCC source, the circuit will be damaged. The maximum supply voltage is 15 Volts DC.
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.
Oregon Rail crossbucks specify common anode wiring.
Unconfirmed - Walters #933-2914 crossing signals are wired in a common anode circuit but the Black wire is the positive and the Red wires are the negative.
The 2011 Grade Crossing Flasher circuit can drive common anode connected LEDs such as TOMAR Industries crossing signals without need for adapter circuitry.
This circuit when used with a 555 or 556 timer's output will cause light emitting diodes to turn on and off more slowly. This will make the LEDs appear similar to incandescent lamps.
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.
The voltage from terminals 9 and 10 does not turn OFF. If motors other that the stall type are used to drive gates, a method of stopping them at the ends of their travel will have to be built into the motor's power circuit. An example circuit is shown below.
Depending on the motor's power requirements, a separate power supply will likely be needed for the gate drive motor.
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.
Option 1: 1 - Printed Circuit Board is 8.50 dollars US plus postage.
Additional circuit boards are 8.00 dollars US each.
Option 2: 1 - Assembled - Signals And Gates circuit board is 30.00 dollars US. - Plus postage.
Option 3: 1 - Kit - Signals And Gates circuit board 29.00 dollars US. - Plus postage.
Option 4: 1 - Assembled - Signals Only circuit board and all of the parts is 26.00 dollars US. - Plus postage.
Option 5: 1 - Kit - Signals Only circuit board and all of the parts is 25.00 dollars US. - Plus postage.
Option 6: 1 - Assembled - Controls Only circuit board 23.50 dollars US. - Plus postage.
Option 7: 1 - Kit - Controls Only circuit board and all of the parts is 22.50 dollars US. - Plus postage.
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.
- Accepted Methods Of Payment -
Paypal. International money orders and personal cheques are OK but will have to clear before shipment.
If you are interested in a circuit board and parts for this circuit please send a message to the following email address: firstname.lastname@example.org
For full protection of a 2 or more track crossing, a Grade Crossing circuit boards for each track is needed. The board for the second and other tracks do not need the components for the gate motor control or the flashers.
This circuit can be used for two tracks by eliminating the third circuit board from the diagram.
All tracks at the crossing will have the same flasher and gate delay times as the first.
One circuit board and a second set of six phototransistors can be used at a multiple track crossing if only one train at a time occupies the protected sections of track.
If the first track's protected section is occupied and another train enters the protected section of the second track, the flashers might not start or could turn off before the first train leaves its section.
The second track at the crossing will have the same flasher and gate delay times as the first.
A crossover(s) could also be included in this system.
More phototransistors can be added to protect more tracks but there may be a practical limit to the number of tracks that can be protected.
The circuits on this page can be used with the 2004, 2008 and 2011 versions of the Grade Crossing Circuits shown at this site.
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.
This circuit is a driver for a mechanical - Grade Crossing Bell Ringer - that was originally built for the London Model Railroad Group.
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.
07 January, 2013