The 2004 Grade Crossing circuit board is no longer available. It has been be replaced by the 2011 - Railway Grade Crossing Circuit.
The information on this page will be maintained for the users of the existing 2004 Grade Crossing circuit boards.
The Grade Crossing circuit uses six - visible and infrared light sensitive phototransistors to control the operation of the flashers.
The protected section of track can be as long or as short as desired and does not have to be the same length on both sides of the crossing. The circuit works in both directions and can be connected to other grade crossing circuits to provide fully automatic protection for multiple track crossings.
The Grade Crossing circuit provides prototypical operation of the signals at level railway crossings and can supply up to 100 milliamps for LED flashers, small incandescent lights or other circuits such as crossing gates or sound units.
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.
An upgraded version of the 2004 circuit is at this link - 2011 - Automatic Railway Grade Crossing Circuit. This circuit is designed to prototypically control crossing gates and signals.
The following diagrams show how the circuit is connected for a crossing with 1 track. A diagram of the circuit board showing the terminal block positions is used.
The next two diagrams show how the phototransistor sensors are placed along the track and the actions that occur as each is covered by the train. The sensors that start the flashers can be placed any distance from crossing desired.
The signals will remain ON until approximately two seconds after the last car has passed completely through the crossing, uncovering both of the "STOP" sensors.
(The grade crossing will be protected until both of the "STOP" sensors are uncovered.)
As the train leaves the protected section of track, the "DISABLE" sensors prevent the flashers from being turned ON again by deactivating the "START" sensors.
The "START" sensors are reactivated approximately 5 seconds after the "DISABLE" sensors have been uncovered.
Sensors 1 or 6 must be covered before sensors 2 or 5, depending on the direction of travel, or the signals will not start. Sensors 2 and 5 disable sensors 1 and 6.
Variable resistor R15 sets the flashing rate of the crossing signals.
The next diagram show the changes in the output terminals of the crossing circuit as a train passes through the protected section of track.
The flashers will turn OFF if a train enters and then backs out of the crossing.
The circuit is ready for the next train in either direction approximately five seconds after the "DISABLE" sensors are uncovered. If the departing train is still covering a "START" sensor after this time the flashers will turn on again.
Manual controls can start or stop the flashers as desired. The START push button could be replaced by a toggle switch in order to keep the flashers activated during switching operations.
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 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.
The Crossing Circuit requires a regulated 12 volt power supply. The current draw is about 3 milliamps when the flashers are OFF and about 35 milliamps when they are ON.
Crossing gates and bells can be controlled buy using the MultiTrack terminal as an output to control these devices. The MultiTrack terminal is also used to connect the circuit boards together for crossings with two or more tracks.
The following diagram is of the 2004 Automatic Grade Crossing circuit showing connections for a single track crossing including manual controls and signals.
WARNING - If the polarity of the power supply for this circuit is reversed or the circuit is connected to an AC or DCC source, the circuit will be damaged. The maximum supply voltage is 15 Volts DC.
If you are interested in a circuit board and parts for this circuit please send a message to the following email address: rpaisley4@cogeco.ca
The following picture is the printed circuit board for the Automatic Grade Crossing circuit. The board is two inches by four inches and has been commercially made and pre-tinned. (An assembled example of the board is also shown.)
The circuit board measures 2 inches by 4 inches and has been 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.
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.
The following diagrams shows how two and three circuit boards are connected for multiple track crossing with full automatic protection for each track. Any number of tracks can be protected using circuit boards for each track at the crossing.
The circuits use only terminal number 8 of the circuit boards as the common to avoid forming "ground loops" with terminals 5 and/or 12.
The diagrams above show one circuit board for each protected track at a crossing. It is possible to use one circuit board to protect multiple tracks but fully automatic control is not possible when this is done.
Two tracks at a crossing can be protected by a single circuit by placing additional sensors in series with the sensors of the first track. This is a cost saving measure.
Because only one circuit board is used, fully automatic operation is not possible as with the two circuit board - two track crossing but if only one train uses the crossing at a time, the system will give prototypical operation.
The circuits on this page can be used with either the 2004 or 2008 versions of the Automatic Grade Crossing Circuits shown at this site.
These circuits include:
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.
08 December, 2011