Occupancy Detectors

[JamieC]

Hi everyone, 
I am building a DCC model railway and I am using an NCE Powercab. I like the idea of occupancy detectors especially ones that can talk to JRMI. The common one I found was a digitrax BD4.
I do however have a few questions:
1) What is Loconet?
2) Will BD4's/ loconet work with my NCE controller?

3)How do you connect it all up? i.e what other parts are required? 


Thanks,
Jamie

[JamieC]

Ok, thanks for the swift reply.

 

So basically my best chance is if I can find a NCE equivalent of the digitrax occupancy sensors ? 

[JamieC]

Manual is sitting right next to me.... to the book! :-P

[JamieC]

ok I can't see anything about loconet in the manual so I will take that as not included. I have however found some NCE manufactured occupancy detectors so that is me sorted. Thanks for your help 

[Nigelcliffe]

Jamie - check whether the NCE detectors work with the Powercab (some NCE features only work with the PowerPro systems). Then check those detectors will work with the software.

 

It is possible to build a "stand alone Loconet". This will work with NCE systems; many US layouts use the combination. There is some documentation on the Digitrax site for this, and lots more on the Yahoo groups for Digitrax and NCE users.

[JamieC]

I shall look into that, Thanks

[JamieC]

Yup, I would need the power house pro box and power supply. The problem would be with the usb interface. This is all for future reference anyway but it is good to know. 

Thanks  

[Phil S]

"3)How do you connect it all up? i.e what other parts are required?"

 

Occupancy detection can be done in 3 or more different ways ... and is only the first stage of a sequence of events in reporting back to the overall-controlling software - whether through the track (eg Railcom ®) or by a separate bus passing back through the Central Controller (eg Lenz, and some others including Roco with Rocomotion) or directly back to the computer (total freedom of choice - independant of the Controllers being used eg LDT. 

 

Detecting: 'Former analogue users' first thoughts might be 'current detection' if  they still think in terms of isolated sections of track - each passing its (dcc in this case) track current through a DETECTOR, such as a Torroidal Transformer.  Personally, I feel this is totally against the spirit of DCC ... which does not need track to be 'sectioned' except for reverse loops or buffer zones to analogue areas (unlikely. but possible). Only current-consuming devices are detected - eg obviously powered locos, but including illuminated coaches and brake vans. Resistors can be added to axles to make ANY chosen item 'appear' to occupy a section ... and with a large amount of stock on a layout, this adds up.

 

Sections need to be the length of a COMPLETE TRAIN if metal wheels are used for the loco and / or stock  [There ARE circumstances in which this is not the case - such as a train progessing through a series of Block Sections which can only be passed in a particular direction (ie Forwards).  I consider it to be a dangerous assumption that the only conducting wheels are at the front!

Push-pull trains ran in steam days as well as nowadays.  Engines assisting at the rear, etc...

 

MAGNETIC Detection: - with a reed switch - and a MAGNET mounted on the STOCK (usually a loco, but can be used to identify special wagons etc) - these provide a 'momentary pulse' when the magnet passes over the switch.   At 50-300 pence per switch (as a component) and modern Neomolydenum magnets, which are also cheaply available (BEWARE CHILDREN SWALLOWING)

this can give economical reliable 'SPOT' occupancly detection - eg entry, middle and end of platforms. Specifically Chosen items are detected (and in a specific part of the item - hence accuracy).

 

OPTICAL Detection: Optical Detection can report ANY OBSTRUCTION of the line - whether a single wagon or a  Big-Boy Locomotive ..... or a hand of god!

With devices ranging from a simple LDR light dependant Resisitor to Infra-Red Reflected/Broken beam detectors these too can provide reliable detection, and, as with the Magnetic detection, is completely electrically separate from the track signal.   problems can occur in 2 areas: changing light levels (eg sunshine and cloud cover, or Infra-Red transparency of materials used...   The 'better' detectors modulate the emitted signal and compare the results, giving good detection over a wide range of lighting conditions.  Beam-breaks can have very narrow beams across an entire junction - so 1 beam each side can trigger warning bells and lights for a level crossing.  You may be surprised at how 'translucent' some 'black' plastics may be at Infra Red!

I have found that a white self-adhesive label, placed on the underside of a tram gives reliable detection.

 

Obviously all 3 methods CAN be used in combination - particularly for the free-addition of 'local fx'  .... Rabbits popping out of Burrows, :Level Crossing Protection, resetting signals after passing, and station announcements.

 

BUT ALL REQUIRE a means of COLLATING and FORWARDING the information back to the ultimate control device (You or your computer)

Some 'other devices' include the collator with their other function(s) eg the Lenz LS100 Accessory Decoder includes Lenz's feedback bus, but their LS150 Point Decoder does NOT.

For most it will be a box of 8 input 'detectors' awaiting a 'pulse' from the chosen physical detector (as above)

 

The signal MAY pass back through the Central Controller (eg Lenz LS100 to base unit) or the RocoMotion receives the signals from a Bus of up to 20 of their '10787' Feedback Module and passes it immediately to the computer on the same interface as used to control the trains... this is how users pay for their 'free' 'Rocomotion' software IF they want Position Feedback as well as train and point control 8-), or it can be sent back via a common or proprietary independant bus eg HSI-88 bus .... but again requiring a set of 'modules' to capture the pulse(s) and forward them on request.

 

Railcom® or Railcom+  ... supported by some, more recent, and mainly european suppliers - Devices such as the Bachmann/ESU SwitchPilot or Veissmann Digital Point Motor can send back a code to say what point has moved to where .... by using a small gap in the dcc track signal (just like Teletext was added into the Vertical Interval of analogue TV ... but in the reverse direction)

 

Other Methods: TREADLES - mechanical detection - as also used by full-size railways eg London Underground Tripcocks, and in Marshalling yards

TRANSPONDERS - whether ultrasonic 'sonar'-like localisation, or RFid ....

RFid:   A unque code in a  tag read by a trackside Reader (provided the speed is in range) can be forwarded to a comtrolling processor - UNIQUE identity becomes KNOWN.

Optical Barcode reading - a subset of the international idea of product codes - in-track sensors can identify each coded item as it passes.

 

Hornby HAVE ANNOUNCED they will be releasing a system later this year ... no details as yet until the Patents are in place

 

To summarise: DETECTION can be electrical. magnetic or optical, or OTHER newer technologies .... the results of which need to be COLLATED and FORWARDED by a 'Feedback Module' using a METHOD OF YOUR CHOICE - which may be the Controller Manufacturer's or Parallel to it, or Independant of it .... back to the computer software which can then modify the behaviour of the trains.

EACH METHOD has its own advantages and disadvantages, problems and solutions, and costs.

Edited February 19, 2014 by Phil S

[tender]

Your easiest route is to use an NCE AIU interface. This has 14 logic inputs that you can connect almost any occupancy detector to. I've used the BD4, IRDot infra red detectors and MERG occupancy detectors all with good results.

You connect the AUI to the NCE bus along with the Powercab and a NCE USB interface to connect to the computer running JMRI or any other control software that is compatible with the NCE bus protocol.

 

If you go down the Loconet route (I've tried this as well) you'll need two busses connected to the computer. The NCE bus via the USB interface to control the trains and an Loconet bus connected to the PC with a loco-buffer interface for the detectors. Accessory decoders for the turnouts can be controlled with either bus depending on how they are wired to the system.

 

Having tried both systems I'd go down the NCE AIU route, it's much neater and less prone to conflicts.

 

Ray.

 

PS you need the version 7 USB interface for this to work with the AIU. If you have the version 6 USB I/F it can be upgraded by NCE.

Edited February 19, 2014 by tender

[JamieC]

Thank you all for the replies. It has given me some good ideas and increased my knowledge a lot!  

[Andy Keane]

On 19/02/2014 at 21:50, tender said:

Your easiest route is to use an NCE AIU interface. This has 14 logic inputs that you can connect almost any occupancy detector to. I've used the BD4, IRDot infra red detectors and MERG occupancy detectors all with good results.

You connect the AUI to the NCE bus along with the Powercab and a NCE USB interface to connect to the computer running JMRI or any other control software that is compatible with the NCE bus protocol.

 

If you go down the Loconet route (I've tried this as well) you'll need two busses connected to the computer. The NCE bus via the USB interface to control the trains and an Loconet bus connected to the PC with a loco-buffer interface for the detectors. Accessory decoders for the turnouts can be controlled with either bus depending on how they are wired to the system.

 

Having tried both systems I'd go down the NCE AIU route, it's much neater and less prone to conflicts.

 

Ray.

 

PS you need the version 7 USB interface for this to work with the AIU. If you have the version 6 USB I/F it can be upgraded by NCE.

Ray

Not sure if you are still picking up thiks thread but if you are I am about to use the MERG DTC8 detector with an NCE AIU to feed JMRI and was hoping to pick up any prior experince out there as I do this job.

I have JMRI working with my NCE gear switching points etc but have not yet tried to link the AIU in - do you have any experience on that?

any input much appreciated

regards

Andy