Automatic - Railway Grade Crossing Circuit
- Prototypical Signal And Gate Operation -
2008
In the 2008 Grade Crossing circuit, the flashers are activated for a short time before the gates start to close and the signals will remain flashing until the gates are up fully. Both of the time delays can be adjusted to suit actual conditions.
The Grade Crossing circuit has a two output signal driver with two outputs allowing it to directly drive almost any signal wiring configuration.
The Grade Crossing circuit is designed to directly control crossing gates that are operated by stall-motor type switch machines.
The protected section of track can be 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. One board can also be use to protect more than one track if needed.
Printed circuit boards and parts are available for this circuit.
Click On The Picture For A Much Larger View
The 2008 Grade Crossing circuit is an upgraded version of the 2004 - Automatic Railway Grade Crossing Circuit that is available through this site.
The 2008 circuit uses the same phototransistor control scheme as the 2004 Railway Grade Crossing Circuit and is fully compatible with the earlier circuit 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 circuitboard 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.
One Track Crossing - Circuitboard Connection Diagram
The following diagram shows how the 2008 Automatic Grade Crossing circuitboard is connected for a typical 1 track crossing.
Typical flasher, bell and gate drive motor connections are shown on other diagrams.
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 timing of the signals and gates a train passes through the protected section from left to right. (The delays work in both directions of travel.)
2008 Railway Grade Crossing Flasher Operation
- When a train traveling in either direction covers one of the "START" sensors, the crossing signals will start to flash.
- After a short delay the crossing gates start to lower. (The delay is adjustable.)
- When the train has cleared the crossing the gates will start to lift after about 2 seconds.
(The grade crossing will be protected until both of the "STOP" sensors are uncovered.)
- The signals will remain on for a short time after the gates are fully up. (The delay is adjustable.)
- 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.
Signal Driver 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.
Signal Light Connection Options
The 2008 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.
The 2008 Grade Crossing Flasher circuit can drive signals with 'common anode' connected LEDs such as TOMAR Industries crossing signals without the adapter circuitry needed by the 2004 Grade Crossing Circuit.
Crossing Gate Drive Motor Connection
'Stall' Type Motors
Operation of the stall-motor can be slowed by adding a resistors or potentiometer to the circuit. The 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 conneced 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.
Other Motor Types
The power from terminals 9 and 10 does not turn OFF. If motors other that the stall type are used to drive the 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 its power and speed requirments, a separate power supply will likely be needed for the gate drive motor.
Grade Crossing Circuit Operation Notes
- The 2008 circuit uses the same operating system as, and is fully compatible with the 2004 - Railway Grade Crossing Circuit. The basic control and operating information for the 2004 circuit applies to the 2008 circuit.
- 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 the "DISABLE" sensors are uncovered. If a departing train is still covering a "START" sensor after this time the flashers will be restarted.
- MANUAL controls can also start and stop the flashers if desired. The START push button could be replaced by a toggle switch in order 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 is used to connect circuitboards 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.
In the 2008 Grade Crossing circuit the 'MULTITRACK' terminal is an input only and cannot be used to control other circuits. Terminal number 11 can provide signals 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 changing the values of resistors R1, R2 and R3 or by using external resistors in series with the photocells.
- Small relays could also be controlled by terminals 9 and 10.
- Bell circuits and small relays can be controlled via terminal 11.
- The 2008 - Automatic Crossing Circuit requires a regulated 12 volt power supply.
Grade Crossing Flasher Connection Schematic (2008)
The following schematic is for the 2008 Grade Crossing Flasher circuit for a single track crossing. Connections for the signal lights, sound circuits and gate drive motors are shown on other diagrams.
WARNING - If the polarity of the power supply for this circuit is reversed or the circuit is connected AC or DCC source, the circuit will be damaged. The maximum supply voltage is 15 Volts DC.
Printed Circuit Board And Parts Information
Click On The Picture For A Much Larger View
The circuitboard measures 2 inches by 5.9 inches and has been commercially made but has not been tinned. The copper side of the board has a protective clear coat to prevent oxidation.
The circuitboard 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.
CircuitboardAnd Parts Prices
The price for 1 Printed Circuit Board is 15.00 dollars US plus postage.
Each additional circuitboard is 14.50 dollars US.
The price for 1 - Unassembled printed circuit board and all of the parts is 31.00 dollars US. - Plus postage.
The price for 1 - Assembled printed circuit board and all of the parts is 36.00 dollars US. - Plus postage.
NOTE: - The above prices include 6 visible/infrared sensitive, 3mm diameter phototransistors. The phototransisitor 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:
2008 Grade Crossing circuitboards sold: 28
Parts List
Qty / Circuit Part Number / Part Type / Digi-Key Number2 / - / IC 1, 2 / - / LM339 / - / LM339NFS-ND
2 / - / IC 3, 4 / - / LM556 / - / LM556CNFS-ND
6 / - / D1, 2, 3, 4, 5, 6 / - / 1N4148 / - / 1N4148DICT-ND
6 / - / Q1, 2, 3, 4, 5, 6 / - / PHOTOTRANSISTORS / - / 160-1030-ND
- / - / - / - / - / - / -
1 / - / Q7 / - / 2N3904 / - / 2N3904FS-ND
1 / - / Q8 / - / 2N3906 / - / 2N3906FS-ND
- / - / - / - / - / - / -
3 / - / C1, 5 / - / 10uF / - / P5178-ND
1 / - / C2 / - / 2.2uF / - / P5175-ND
1 / - / C3 / - / 4.7uF / - / P5177-ND
1 / - / C4 / - / 0.22uF / - / 495-1106-ND
2 / - / C6, 9 / - / 1.0uF / - / P5174-ND
1 / - / C7, 8 / - / 22uF / - / P5179-ND
- / - / - / - / - / - / -
6 / - / R1, 2, 3, 4, 5, 8 / - / 1M / - / 1.0MQBK-ND
3 / - / R6, 7, 9 / - / 33K / - / 33KQBK-ND
4 / - / R10, 15, 17, 24 / - / 100K / - / 100KQBK-ND
7 / - / R11, 12, 13, 19, 20, 22, 25 / - / 10K / - / 10KQBK-ND
2 / - / R14, 21 / - / 2.2K / - / 2.2KQBK-ND
3 / - / R16, 18, 23 / - / 1 MEG POT / - / 3318F-105-ND
- / - / - / - / - / - / -
4 / - / Terminal Block / - / 2 Position, 5mm. / - / ED1601-ND
2 / - / Terminal Block / - / 3 Position, 5mm. / - / ED1602-ND
2008 Grade Crossing Circuit PCB Parts Placement Diagram
Circuit Board Parts Placement Diagram
Print this diagram to aid in assembling the circuitboard.
Additional Information
For fully automatic protection of a 2 or more track crossing, the second and subsequent tracks should be protected by the 2004 - Automatic Railway Grade Crossing Circuit.
All additional tracks will have the same flasher and gate delay times as the first.
Additional Circuits
Many of the circuits and adaptations in the Additional Circuits section of the 2004 Automatic Grade Crossing circuit page can be used with the 2008 Grade Crossing circuit.
Circuit Board Assembly
When installing the components on the circuit board start with parts with the lowest height and work up to the tallest parts. For example starting with the jumper wires then diodes then resistors, IC's, transistors, capacitors and terminal blocks.
Recommended Tools
Soldering
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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.
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14 February, 2010