Block Occupancy Detector Infra Red BOD2-IR

BLOCKsignalling BOD2 Block Occupancy Detector for Model Railways

Detect Trains Crossing an Infra-Red Sensor under the Track Bed


This Block Occupancy Detector detects trains by projecting infra-red light upwards and detecting when this is reflected back from rolling stock passing over the detector.  It can operate 2-aspect light signals and remote indications on a control panel.

 

Power Supply

The module requires a 12V DC supply.

Please double check all wiring before applying power, as incorrect wiring can damage the unit.

 

Programming

Programming for the particular application can be completed before or after testing the wiring, and also before or after completing the installation.

This is performed by holding down the Push Button when switching on the power.

Block Occupancy Detector Programming

 

For each program there are two values to be stored.

The red led on the PCB flashes at 1 second intervals. When the required number of flashes is seen (see later for the list of possible choices) the button is released to store the first value. At this point the led comes on for five seconds to confirm the value is stored.

The led then starts flashing again, and this time the button needs to be pressed to store the second value.

Once both values have been are entered, the led flashes 10 times rapidly, and the module starts operating.

Each value entered can be up to 255 flashes. If more are seen, or the programming is aborted by switching off, then the programming must be repeated.

 

Factory Reset

To reset the module back to factory default settings, switch off the power to the module and hold down the Push Button. Apply the power and continue holding the push button until 1 flash of the led is seen. At this point, release the button. You will see a long flash of five seconds.

The led will begin flashing again. When you have seen 1 flash press the button. You will see a long flash of five seconds and then 10 rapid flashes. The reset procedure is then complete and the module will restart with factory settings, and run the lamp test mode. If you make a mistake programming, simply repeat the process.


Testing the Infra-red Detection

An Infra-Red source and Infra-Red detector are moulded into a single 5mm x 6.5mm package that can be located below the track bed to reflect light off rolling stock.

RPR220 connections

 

Identify the leads from the diagram and connect to the terminals marked A, K, C and E on the PCB. The wires can be extended using small chocolate block and extra lengths of cable if required (not supplied).

 

Connecting the RPR220

 

Sensitivity Setting

The module is supplied with the sensitivity pre-set to suit most installations and should not need adjustment.

In locations such as tunnels, or when the module is not being used under the track bed, then it may be desirable to adjust the detection threshold.

The sensitivity is factory set to 5, and can be adjusted from 1 to 10 (with 1 being the most sensitive and 10 being the least sensitive).

 

Sensitivity Table

 

To change the sensitivity, switch off the power to the module and hold down the Push Button. Apply the power and continue holding the Push Button until 9 flashes of the led are seen. At this point, release the button. You will see a long flash of five seconds.

The led will begin flashing again. When you have reached the desired number of flashes to set the new sensitivity, press the button. You will see a long flash of five seconds and then 10 rapid flashes. The programming is then complete and the module will restart. If you make a mistake programming, simply repeat the process.

Performing a factory reset will reset the sensitivity setting back to 5.

 

Installation

The Infra-Red sensor is normally installed below the track-bed.

The detection range of the unit is up to approximately 25mm from the face of the package when normal sensitivity is set  (for dark surfaces with low levels of reflectivity).

Detector Below the Trackbed

 

The detector can be mounted in an 8mm hole drilled through the track baseboard. If required, the detector can be held in place using a small amount of blutack, expanded polystyrene or similar.

The led diameter is 2.2mm, so on smaller scales the leds can still have a clear view between the sleepers.

Plan View of the Detector between the Rails


Connecting the Outputs

Each channel output has a transistor, which conducts to ground to switch the output to on. This means that any devices such as leds connected to an output will be switched to ground to operate them.

It is recommended that leds are fed from the +5V DC output terminal provided for this purpose and have a 300 ohm current limiting resistor in series.

In cases where the leds are never on together, such as with the two-aspect signal, they can share the same resistor.

 

Program 1 – Lamp Test Mode

This is a test program to switch the output channels in a set sequence and may be set when the unit is supplied.

Block Occupancy Led Test Mode

 

In this sequence, first all outputs are on, then they all go off except ch1. Then ch1 is switched off and ch2 comes on, then all the outputs are switched off and the sequence is repeated. Each step takes 1 second. The led on the PCB switches on and off with each step.

When supplied, or following a factory reset, the module will operate in lamp test mode. It can be also be switched to this mode at any time as follows:

To select this program, switch off the power to the module and hold down the Push Button. Apply the power and continue holding the push button until 2 flashes are seen. At this point, release the button. You will see a long flash of two seconds and then the led will begin flashing again.

When 1 flash has been seen press and hold the button. You will see a long flash of five seconds and then 10 rapid flashes. The button can now be released and the programming is complete. The module will start running the program. If you make a mistake programming, simply repeat the process.

 

Program 2 - 2-Aspect Signal Operation with Train presence Indication

This program is designed to operate a 2-aspect light signal on a layout in response to the train passing over the sensor.

The signal normally operates at Green (Clear).

When a train crosses the sensor, the signal will change to Red (Danger).

If the train remains over the sensor, the signal will stay at Danger. Once the train clears the sensor, after a delay (default 5 seconds), the output will be switched back to Clear (Green) This is adjustable with the post-release delay setting.

So that the small gaps between carriages do not cause the module to falsely trigger, the above delay will not start until the current has stopped for 4 seconds (the release time).

The trigger time, release time, and post-release delay are adjustable.

 

Block Occupancy Detector for DCC

 

There are a second set of outputs which can be used to operate separate led indications on a control panel.

Block Occupancy Detector for DCC

 

If it is required to have an indication which only lights if the train is currently over the sensor, then this can be connected to CH6.

Block Occupancy Detector for DCC

 

When supplied, or following a factory reset, the module will operate in lamp test mode. It needs to be reprogrammed as follows.

To select this program, switch off the power to the module and hold down the Push Button. Apply the power and continue holding the push button until 2 flashes is seen. At this point, release the button. You will see a long flash of two seconds and then the led will begin flashing again.

When 2 flashes has been seen press and hold the button. You will see a long flash of five seconds and then 10 rapid flashes. The button can now be released and the programming is complete. The module will start running the program. If you make a mistake programming, simply repeat the process.

 

Adjusting the Release Time

When a train passes over the sensor, gaps between the carriages could be recognised as the train having passed, when in fact this is not the case.

The module is set to ignore gaps in detection for up to 4 seconds, before registering the train having cleared the detector. This value (the Release Time) can be adjusted to cover longer breaks, before registering the detector as clear.

This delay is adjustable from 1 to 255 seconds by setting parameter 6 to the number of seconds required. So, if it is required the current be absent for 7 seconds before it is confirmed the train has fully cleared the section, then set this parameter to 7.

The full procedure is as follows:

Switch off the power to the module and hold down the Push Button. Apply the power and continue holding the push button until 6 flashes of the led are seen. At this point, release the button. You will see a long flash of five seconds.

The led will begin flashing again. When you have seen 7 flashes (or other duration you wish to set) press the button. You will see a long flash of five seconds and then 10 rapid flashes. The programming is then complete and the will start running the program. If you make a mistake programming, simply repeat the process.

 

Adjusting the Red Time

Once the trtain has been detected as having cleared the sensor, the signals remain at danger for a period.  This time is set by the red time delay.

If you wish to set the post-release delay to 6 seconds, the full procedure is as follows:

Switch off the power to the module and hold down the Push Button. Apply the power and continue holding the push button until 3 flashes of the led are seen. At this point, release the button. You will see a long flash of five seconds.

The led will begin flashing again. When you have seen 6 flashes (or other duration you wish to set) press the button. You will see a long flash of five seconds and then 10 rapid flashes. The programming is then complete and the will start running the program. If you make a mistake programming, simply repeat the process.

 

Programming Flow Diagram

The following diagram shows the programming options available.

Block Occupancy Detector Programming