Track Circuit Occupancy Detection

This forum is dedicated to Riding Scale Railroading with propulsion using other than steam (Hydraulics, diesel engines, gas engines, electric motors, hybrid etc.)

Moderators: Harold_V, WJH

User avatar
Atkinson_Railroad
Posts: 168
Joined: Mon Jun 08, 2015 6:27 pm
Location: Michigan
Contact:

Track Circuit Occupancy Detection

Post by Atkinson_Railroad » Sun Oct 29, 2017 6:07 am

Track Circuit Occupancy Detection

A URL to the information attached was posted a while back and later deleted from the offsite source it resided.
I’m re-submitting it here for discussion and for myself included to learn more about the subject of outdoor miniature railroad Track Circuit Occupancy Detection.

Terms like “multi-plexing”, high frequency joint less track circuits, motion detection, axle counting
and so on are complex topics to fully understand. For the miniature railroader seeking a more primitive
signaling arrangement, the diagrams and jpeg illustrations attached may be helpful.

In the 1990s, studying the numerous obstacles related to track circuits on out-of-doors miniature railroads and testing different arrangements,
it was learned an inexpensive transistor detecting very small current on an outdoor track subjected to varying temperature and weather conditions could drive off-the-shelf relays for controlling wayside signaling equipment.
The operating tests and confirmation of the functioning outcome of the track circuits described here was conducted on my track when it was set-up along US-31 near Interlochen, Michigan.

Today, the attached information is dated. The drawings shown don’t explain what some of the symbols mean because they related to the coils in my 3-coil searchlight models. My searchlights were later re-designed with a single polarity controlled coil unit and newer drawings were never rendered. The coils shown on the schematics could be viewed, substituted or interpreted as a lamp or a LED light source.
The Radio Shack relays mentioned in the material are no longer available, but numerous multi-pole equivalents
can be substituted. (Relays are not extinct by any means as you’ll discover in browsing the popular electronic suppliers on the Internet.)

The schematic drawings have omissions such as fuses to protect the battery circuits. Back EMF protection diodes across the relay coils are not shown, and so on. In spite of these missing circuit elements, the basic premise or concept of the information submitted here for discussion can provide a means or place for the Do-It-Yourself person to get started or work from.

Power supply options have greatly improved since what was available early on. There are new battery designs and solar power arrangements which did not economically exist when the following writing and attached material was researched and type-written on a type writer. One of the greatest visible innovations related to what one “sees” today along the right-of-way has been the Light Emitting Diode.
Light sources that draw a mere 8 milliamps can be powered by flashlight or penlight batteries for a considerable length of time.

Seeking out better methods of bonding rail track joints was also being explored at the time of writing. Including the concept of stud welding rail jointed bond wires to insure a better than good connection to aluminum rail. It was never included in the attached.

Clicking the [submit] button,

John
Attachments
1PAGE 9-6,9-7.JPG
2PAGE 9-8,9-9.JPG
3PAGE 9-10,9-11.JPG
4PAGE 9-12,9-13.JPG

User avatar
Atkinson_Railroad
Posts: 168
Joined: Mon Jun 08, 2015 6:27 pm
Location: Michigan
Contact:

Re: Track Circuit Occupancy Detection

Post by Atkinson_Railroad » Sun Oct 29, 2017 6:09 am

Note: The Direction Control Segments shown in this attached drawing were not “closed track” circuits.
Today, I would label it a discrepancy in the circuit design.

John
Attachments
5PAGE 9-14,9-15.JPG

User avatar
ChuckHackett-844
Posts: 80
Joined: Wed May 03, 2017 3:54 pm
Location: Tampa, Florida

Re: Track Circuit Occupancy Detection

Post by ChuckHackett-844 » Sun Oct 29, 2017 12:56 pm

John, et. al.,

As I mentioned in an earlier post, I have designed, but not built, a module that would incorporate my adaptive train detection algorithm and provide either open-collector or dry-contact output to indicate occupancy. I'm thinking of a module containing four independent channels.

Question for you and others: To be most useful in terms of substituting this module into existing systems just to address reliable detection under any track conditions: is open-collector enough (i.e.: ground upon activation) or is it more desirable to have full access to all six terminals of a DPDT relay. This is mostly a cost/space consideration, either is easy to do.

This module would contain no "block logic", etc. strictly a train detector.
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
"By the work, One knows the workman"

User avatar
BigDumbDinosaur
Posts: 615
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Track Circuit Occupancy Detection

Post by BigDumbDinosaur » Sun Oct 29, 2017 4:16 pm

Atkinson_Railroad wrote:Note: The Direction Control Segments shown in this attached drawing were not “closed track” circuits. Today, I would label it a discrepancy in the circuit design.
Such a design is fundamentally unsafe. Also, a circuit that connects any part of an active electronic device to the track is a recipe for trouble, as it exposes what is an inherently fragile device (the transistor, in this case) to whatever appears in the track circuit due to external causes, such as a transient caused by a nearby lightning strike.
bod_assy_small.jpg
Block Occupancy Detector (BOD)
dbod_assy_reduced.gif
Directional Block Occupancy Detector (DBOD)
Above are the two block occupancy detectors produced by BCS Technology Limited for riding scale railroads—these items have been available since 2006. Primary detection is through a low voltage relay—no solid state devices are connected to the track. This is the classic Robinson failsafe track circuit that is in use in most signaled territory in Canada and the USA. It is also the least difficult detection method to implement in most applications.

The modules include an adjustable damping circuit and other features to deal with the vagaries of electrical contact experienced in riding scale applications. No software is involved—the module is connected to the rest of the ABS and it's ready to function. Outputs are all dry relay contacts, which means the module will adapt to almost anything that is to be controlled.

The DBOD is used to determine direction of travel, as well as block occupancy, which facilitates the implementation of absolute permissive block (APB) signaling. There is also a three-way module for block occupancy detection around a grade crossing, making it possible to operate the grade crossing signal(s) in a realistic, bi-directional fashion.

For hobby signaling as we are doing, the simplest practical method to achieve the desired results is usually the best method. Also, the devices that are used to achieve the desired results should be field-repairable to the maximum extent possible. Quick changeout of a malfunctioning device without having to program anything is highly desirable, especially during a big meet. System repairs should be made possible by personnel who are not highly trained in electronics, but understand basic electrical principles, know how to use a voltmeter and have some experience in basic electrical troubleshooting.

My experience with this stuff (which stretches back into the early 1970s on full-sized railroads) is that once a territory has been signaled, changes to the workings of the ABS are rare. In most cases, changes only are necessary when changes to the trackage itself are made, such as adding a new crossover or passing track. This tends to make the case for programmability in an ABS component a weak one, in my opinion.
Science makes it known. Engineering makes it work.

User avatar
ChuckHackett-844
Posts: 80
Joined: Wed May 03, 2017 3:54 pm
Location: Tampa, Florida

Re: Track Circuit Occupancy Detection

Post by ChuckHackett-844 » Sun Oct 29, 2017 4:56 pm

BigDumbDinosaur wrote:Above are the two block occupancy detectors produced by BCS Technology Limited for riding scale railroads—these items have been available since 2006.
What do each of these modules cost?

What are their power requirements?
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
"By the work, One knows the workman"

User avatar
Atkinson_Railroad
Posts: 168
Joined: Mon Jun 08, 2015 6:27 pm
Location: Michigan
Contact:

Re: Track Circuit Occupancy Detection

Post by Atkinson_Railroad » Sun Oct 29, 2017 5:27 pm

All good comments and valid opinions.

Hmmm… Good question related to your module question Chuck.

Drawing upon the analogy of having additional spaces to install more circuit breakers in your home
service entrance panel, I would lean toward having full access to all six terminals of a DPDT relay
because the end-user always has an additional "want" that's often difficult to predict or know about.

(Granted, those empty spaces in a service entrance panel may never ever be used.)

All products have a line drawn somewhere as to what they perform.
Enabling a variety of installation and wiring possibilities for the end-user is sometimes not
worth the additional cost factors.

Less is best, and more is better.

John ; )

User avatar
Atkinson_Railroad
Posts: 168
Joined: Mon Jun 08, 2015 6:27 pm
Location: Michigan
Contact:

Re: Track Circuit Occupancy Detection

Post by Atkinson_Railroad » Sun Oct 29, 2017 7:33 pm

Dino;

Googling "BCS Technology Limited", there are several URLs to pick from.
I did not happen to see or find any direct link to a product devoted to Miniature Railroading.
I missed it, if it's out there somewhere.
Is there a more specific URL you are aware of... to gain info, specs, etc. about the product
that provides detection for a miniature railroad track signal block?

I'm curious about the cost as well.

Thanks!

John

jabsteam
Posts: 48
Joined: Sun Feb 19, 2012 10:31 pm
Location: Colorado Springs

Re: Track Circuit Occupancy Detection

Post by jabsteam » Mon Dec 11, 2017 8:01 pm

I searched for 3 hours for BCS and only found a Facebook reference for their MABS system- Modular Auto Block Signals that I did not have permission to view, and when I went back to that exact worded Google search, the Facebook link was gone. Nothing on Facebook either for BCS Technologies Limited.

BigDumbDinosaur - Could you please post the URL for those Block Detection cards manufacturer?
Eaton Huskie electric
Invicta coal burner
Electric Goose (being built)

User avatar
BigDumbDinosaur
Posts: 615
Joined: Tue Jun 28, 2011 9:19 pm
Location: Midwestern United States

Re: Track Circuit Occupancy Detection

Post by BigDumbDinosaur » Mon Dec 11, 2017 9:37 pm

jabsteam wrote:BigDumbDinosaur - Could you please post the URL for those Block Detection cards manufacturer?
This is the company website. You'd have to call about the ABS stuff. It's not advertised on the website.
Science makes it known. Engineering makes it work.

jabsteam
Posts: 48
Joined: Sun Feb 19, 2012 10:31 pm
Location: Colorado Springs

Re: Track Circuit Occupancy Detection

Post by jabsteam » Tue Dec 12, 2017 1:45 pm

Thank you sir!
Eaton Huskie electric
Invicta coal burner
Electric Goose (being built)

stickfigure
Posts: 7
Joined: Wed Jun 21, 2017 3:31 pm
Location: California

Re: Track Circuit Occupancy Detection

Post by stickfigure » Fri Dec 22, 2017 1:30 am

What do folks use to electrically isolate blocks on hobby-sized railroads? I mean literally, what are the isolators and joiners made out of?

User avatar
ChuckHackett-844
Posts: 80
Joined: Wed May 03, 2017 3:54 pm
Location: Tampa, Florida

Re: Track Circuit Occupancy Detection

Post by ChuckHackett-844 » Fri Dec 22, 2017 7:39 am

I sell "Profile Insulators" that are CNC cut in West Coast rail profile ($9 per dozen). These are placed between the ends of the rail and held in place by the plastic joint bars. These prevent the rails from coming into contact due to heat/vibration, etc.

I plan on offering injection-molded "Joint Bars" but have not yet finished the mold. For now we use 1/8" plastic punched on the same punch we use for the normal aluminum joint bars and fasten them with the same bolts/nuts used for the aluminum joint bars. I would like to use 3/16" x 1/2" fiberglass strip but I have not been able to find any. If you use a metal joint bar you will have to use a more complex assembly method to prevent the metal joint bar from contacting the rails.
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
"By the work, One knows the workman"

Post Reply