Railway Crossing Control with Flash and Ding - PIC based - Code: RK-XCtlP
Needs separate detector board.


This unit generates a ding sound, and controls the flashing of LEDs to simulate crossing control signals. Most of the control is done by a Pic micro-controller. The unit accepts input from up to four pairs of detectors (4 tracks) which may be any of current, infrared, light or magnetic sensing.

The unit becomes active as soon as it senses a train on any detector. It will then record that track as occupied, and set the other detector for that track as the stop detector for that track. It will ignore any further input from the initial detector, and wait for input on the stop detector. After it records input from the stop detector, it will wait for there to be no further input from that stop detector for about 2.5 seconds before treating that track as clear. (This is to avoid the likelihood that when light detectors are being used, the unit detects the first wagon behind the loco as another train entering the crossing section from the opposite direction.) It continuously monitors all detector inputs in turn, and so long as any track is seen to be occupied, the crossing will be active.

When the last train has left the crossing, after the 2.5 second delay noted above, the unit may be kept active for a further period of approximately 5, 10, or 15 seconds. This may be useful with current detectors (which detect the locomotive rather than the end of the train) or if a detector needs to be placed very close to the crossing (e.g. because existing scenery doesn’t allow easy installation of the sensing section further away) and extra time is needed to allow the train to completely clear the crossing. It can also be useful if additional equipment such as a crossing barrier needs time to complete operating after the train has left the crossing. (See relay details below.) The additional delay is controlled by means of jumpers.

The unit requires two detectors per track, up to 8 detectors (4 tracks) Detector kits D2C, D2IR, D2L or D2M are designed to work in conjunction with this unit. The light detectors are easier to use and install, but may be subject to false triggering depending upon how the light may be interrupted at the detector site, and of course, will not work in the dark. Infrared detectors are of similar ease to install, and will work in the dark, but need reflective material to be fixed to rolling stock. Current detectors need track to be isolated, and may not work at very low speeds with DC control, depending upon the current drawn by the motor. Magnetic detectors require magnets to be fixed to the rolling stock to be sensed.

The unit is designed to drive a crossing stand with LEDs. Three millimetre LEDs (supplied) will replace incandescent globes in many commercially available crossing control stands, (or make your own, using brass washers and brass tube.) The LEDs may be connected in common cathode, common anode, or bipolar configuration. (Shown below is common cathode connection.)

There is a relay on the PCB with a 2 pole changeover contact set. (DPDT.) The relay can be used to control anything within the switching capability of the relay (2 amps at 200 volts) However, the PCB is not designed for voltages as high as 200. 50 volts should be considered a maximum. The relay becomes energised when the crossing first becomes active. At the end of the activity cycle, it ceases to be energised after the last train has left the controlled area, plus the 2.5 seconds noted above – it does not remain energised during the 5,10 or 15 second additional delay. The relay could thus be used to control a crossing barrier.

The controller may be manually started or stopped at any time by means of push buttons, which may be mounted remotely on a convenient control panel, or wherever is required.

Power requirement is 12volt, at an average of less than 100mA.

The diagram below shows how the unit is installed, using either current or light sensing detection. In each case the XCtlP printed circuit board (PCB) is mounted in some suitable place convenient to the desired crossing, and supplied with 12 volts. Connections are made between this and the detector board for +12volts, +5 volts, and ground. The required number of detector connections are made between the boards, and any unused detector inputs on the XCtlP PCB are tied to ground.

For details on detector boards, see the detector section of this website.

Click here for larger image of above.

Please note an error on the silk screening of the PCB
version 2.0. The "+12V" and "Ground" terminal labels
have been   interchanged.   The silk   screening   label
should be ignored - the labelling shown on the overlay
diagram in the documentation   supplied with the kit
is correct.
Apologies for any inconvenience.



Click here for larger image of above.




                To hear how this unit sounds, click the "film" above.


The "Ding" generator from this module is available separately
as the kit RK-XDing. It produces the "ding ding ding ... "
sound when a control input is set high.

A large scale crossing flasher suitable for use in an approximately
1/8 scale crossing stand, with 12 LEDs per lantern, is available
as RK-LRXF

A simple crossing flasher suitable for use with common anode
crossing stands is also available as RK-SXF
A version of this for use with bipolar crossing stands is available.
as RK-SXFB

Kit prices for
Code: RK-XCtlP Crossing Controller (up to 4 tracks)         Kit price: $47-50
Code: RK-XDing Crossing Ding Generator         Kit price: $19-50
Code: RK-LRXF Large Scale Crossing Flasher         Kit price: $34-50
Code: RK-SXF[B] Simple Crossing Flasher         Kit price: $19-50
Codes: RK-D2C, RK-D2IR, RK-D2L & RK-D2M         Kit price: $22-50



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All kits available from :                                                
Aztronics Pty Ltd       Phone 8212 6212                                                
170 Sturt St,                     Fax 8212 4212                                                
Adelaide, SA, 5000.                                                                                
email:               sales@aztronics.com.au                                                


Information:         David Crosby         david@railwaykits.net

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Last updated 25th March, 2018.
(C) D. Crosby, August, 2010.