Advice Regarding an Automatic Reversing Component

[Chops]

I am fairly good at attaching a positive and a negative to a railhead, but beyond that my knowledge sags considerably.

What I have in mind is either building- no, I cannot reliably read a schematic- or purchasing a component that would automatically
reverse polarity as the train came to the distal ends of a single point-to-point. That would be simple, but I want said train to stop- and
then go- automatically at a station platform.

The layout I have in mind is for a subway train, as seen below, traversing a simple end-to-end with a platform midway. I recall someone explaining resistors in such a scheme, but I cannot recall much else. Any ideas?

[End2end]

Try looking under "shuttle model railway" or "station stop model railway". There's plenty of them around.
BLOCKsignalling do a few off the shelf ones amongst others. http://www.blocksignalling.co.uk/
Scroll down to the Train Shuttles menu on the left for the whole range.
Hope it helps.
Thanks
End2end

[Flashbang]

For DC (Analogue operation) I highly recommend Heathcoate Electronic modules. Their SA8-SB station stop with block control module seems to fit the bill exactly? http://www.heathcote-electronics.co.uk/ ... tml#SA8-SB

[Chops]

Remarkable how one can throw out a conundrum and be handed a really good answer within hours, from across the Atlantic, no less. Thanks Flashbang, that really would fit the bill. Plus, trial and error with electricity can bring hair raising results. I speak from experience. While it might be educational to try to assemble resisistors and the like, I cannot keep up with things as it is. I sent a letter of inquiry to Heathcote to make sure I get the right product for this simple affair.

[Bufferstop]

I have one of Heathcote's shuttle modules which reverses the track polarity after X number of minutes, Setting the time to be significantly longer than the time to traverse the line and cutting a break in one rail bridged by a diode, at each end brings the train to a stop at each end, where it waits until the polarity reverses. I have a video clip somewhere of it controlling a tramcar, demonstrating the way that a bow collector flips over so as to trail along the wire. You can combine Heathcote's units to build a totally automated system.

[RAF96]

I have a tram shuttling back and forth using a Gaugemaster SS1 unit. Works a treat.
Rob

[Flashbang]

Hi Chops.
I have re read you first post.
My earlier reply assumed all you wanted was a automatic station stop somewhere on a continuous loop of track.
However, re reading the question it seems actually you want an end to end auto reversing shuttle plus a middle of shuttle section auto station stop? If so, the Heathcote SA1.1 or their SA1.1-S with signal controls is needed.
The modules all need some form of loco positioning sensors and Heatcote produce IRDOT Infra-Red detectors for this, where no modification to any stock is needed or you could use a magnet bonded onto the underside of the loco and reed switches installed between rails.
Cost of module plus a number of IRDOTs is going to be quite expensive. Module plus suitable magnet and some reed switches would be cheaper!

[Chops]

Thank you for the clarification, Flashbang. That would be the case: traverse, stop, reverse, timed station stop, continue, reverse and repeat.

Sounds like the infared sensors might be the way to go- mechanical things, like a reed switch, seems prone to wearing out.

I checked out a US based manufacturer on the internet, but they don't have the all-in-one capacity of the Heathcote. To get it right, I'll gladly pay the difference.

For the space starved British modeller, this would be an idea. I am fortunate to have a bit of extra space, (at the expense of living in a god forsaken desert), but usually find a way to fill it up. This "layout" would be perhaps 4 inches in width, contained in a carpet tube, and hung upon the wall. Five, or six feet, ought to do it. The stage, as it were, will be a cut out of the subterranean platform, as previously described. So the visible activity will be limited to the train coming and going.

[Bufferstop]

I like the idea of the carpet tube. I know mechanical bits can go wrong, but microswitches are used and trusted in quite complex equipment. You will in any case want some kind of last resort mechanical stop just in case. I wanted to be able to stop a train in my hidden sidings so that the train ran in as far as possible. My answer was a small lever microswitch with a foam pad on the actuator standing up like a buffer stop. the supply came via the micro switch, when the train pressed on the switch it swapped to the normally open contact, which was connected back to the normally closed via a diode which allowed the train to run back when the current reversed. I had one at the end of each road didn't matter if the loco or pick up bogie was at either end or in the middle and much cheaper than infra red. The IRDOTs are good and almost invisible, but when you are controlling at a dead end that's out of sight a microswitch is all that's needed.

[Gordon H]

Have a look at the MERG ATC System:
https://www.merg.org.uk/merg_resources/atc.php
It can do exactly what you require as a built-in feature.
No under-track sensors or microswitches either, just wires to the track sections.

[Chops]

Very interesting information, going to pick up my paycheck today (before it bounces) and will be going with the Heathcote. Whilst the MERG schematic was most interesting, I just don't want to take on a project that would require me to learn this from the ground up. That beings said, are there any pros or cons about reed switches versus infrared sensors?

[RAF96]

Reed switches need magnets on the applicable passing vehicle. Latching reed switches are becoming harder to find and getting expensive.
IR may suffer unreliability in certain lighting conditions.
Rob

[Bufferstop]

It's amazing how one development leads to a huge supply of components for years to come. The almost glut of reed switches came about largely to BTs programme of introducing System X exchanges, compared to other users their requirement was huge. a similar thing happened post WW2 with radio valves particularly the various double triodes with two 6.3volt heaters in series. You could buy them from Mullard at exorbitant prices but even around 1960 you could buy unbranded ones in the surplus stores. In fact the wartime programmes (radar I think) used so many that when they built the replica of the Manchester MK1 computer (Baby) the ones they found in some warehouse were from the same batch that had been recorded in their notes in the 1940s.