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I have just installed a large "dogbone" loop ,using LGB #16050 turnouts with an electric #12010 style switch mach. I would like to let the train run into the loop and then "runthrough" the LGB switch coming out of the loop. I just want the train to run into and out of each loop without having to throw a switch machine or manually throwing a DPDT switch to reverse the polarity. The problem is reversing the polarity when the train is in the loop. I have tried using an Atlas "Snap Relay", but so far I have only fried it! I tried using a momentary micro switch, but the relay will not throw unless it is powered and then touching the mico switch. The train will activate the micro switch, but my problem is powering the snap relay without burning it out. Thanks in advance for any help.
Mike McILwaine
 

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Your easiest solution would be the LGB reverse loop track set. It comes with two sections of track. Each section has its purpose. Both sections are placed inside of the loop. In your case you will need two sets. They can be had on Ebay from time to time. If you have LGB's book "The World Of LGB", it explains reverse loop[s in great detail. Even I can understand the three different ways they give to build a reverse loop for analogue layouts. If you don't have a good relationship with electronics, like me, this book will be your bible.
 

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I would suggest you try this set up - the original comes from Maarten in the Netherlands.
You need reeds between the rails and a magnet attached underneath the loco to automate everything.

Big picture but at least you can see the electrical connections clearly

Knut
 

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Posted By Madman on 22 Aug 2009 04:43 PM
Your easiest solution would be the LGB reverse loop track set. It comes with two sections of track. Each section has its purpose. Both sections are placed inside of the loop. In your case you will need two sets. They can be had on Ebay from time to time. If you have LGB's book "The World Of LGB", it explains reverse loop[s in great detail. Even I can understand the three different ways they give to build a reverse loop for analogue layouts. If you don't have a good relationship with electronics, like me, this book will be your bible.


That LGB track set requires that one manually reverses the direction switch on the throttle while the train is in the reverse loop.
It's very simple and effective but doesn't provide the fully automated operation requested.
 

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Posted By lownote on 22 Aug 2009 04:55 PM
It's things like this that make me think about going to DCC. A DCC system will do reverse loops automatically with no additional wire whatsoever.

Sorry - that is not quite true.

With a DCC reverse loop module you still need at least four wires, granted a lot fewer than wiring the switch machines, but no "no additional wires whatsoever"
But one really only does the wiring once - so I don't ree it as such a big deal.

DCC reverse loop modules have their own problems.
Most of them depend on the wheels of the loco creating a short-circuit which then triggers the DCC reverse loop module. Depending on the way the short is detected (voltage drop or current increase) and the switching time of the module, this can cause problems over time.
A number of new DCC reverse loop modules like the Massoth one for instance, now also provide the option to use reed switches and magnets to control the reverse loop module. That eliminates the short-circuit detection problem.


What I haven't seen in Large Scale yet (although it's popular in some smaller scales) is to use a double insulated gap in the rail as the trigger mechanism. That would eliminate the need for magnets and reed switches.

Knut
 

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This is something I came up with in dispute of the falicy that the train always has to go through the reverse loop in the same direction. This can be used with manual or electric turnouts and the trains alternate directions each time they go through the loop. The relays and power supply can be any voltage, just so they are matched. A magnet is placed under the engine. Note that while the schematic shows five 4pdt relays, only two are 4pdt and the others can be spdt.

 

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Posted By toddalin on 22 Aug 2009 05:35 PM

This is essentually equivelent to the LGB schematic posted by KRS except that the LGB system uses the 12050/12030 as latching relays. In my schematic the 4pdt relays will "self latch" and the other relays serve to "unlatch" them. Also, using no LGB parts, this can be constructed more economically.

 

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Todd,

2 questions: Does it really take that many relays for a common reversing loop? I'm tired, not grasping exacty what I'm seeing. And it's automatic? (For DC track).

2nd question:

Why is this screen so huge I've got to horizontal scroll like, 3 feet to see all of it? That's kinda hard, y'know?



Les
 

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Les,
I have a hunch that knut's diagram wasn't resized by the uploader and that widened the screen.
 

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Posted By Les on 22 Aug 2009 06:09 PM
Todd,

2 questions: Does it really take that many relays for a common reversing loop? I'm tired, not grasping exacty what I'm seeing. And it's automatic? (For DC track).

2nd question:

Why is this screen so huge I've got to horizontal scroll like, 3 feet to see all of it? That's kinda hard, y'know?



Les


OK - I reduced the size of my diagram so you don't have to scroll.

That answers your second question.

To answer your first question - there is also a DC reversing loop schematic (works for DCC as well) that uses a single latching relay. I'll dig it out and post it here.
That single latching relay still uses a magnet under the loco and reed switches between the track, but with a bit of work, that could be changed to use double gaps in the rail and no magnet or reed switches.

Knut
 

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Posted By Les on 22 Aug 2009 06:09 PM
Todd,

2 questions: Does it really take that many relays for a common reversing loop? I'm tired, not grasping exacty what I'm seeing. And it's automatic? (For DC track).

2nd question:

Why is this screen so huge I've got to horizontal scroll like, 3 feet to see all of it? That's kinda hard, y'know?



Les


Lizard Bash Loop Control

The included diagram uses five relays to automatically control the polarity of both the loop and main line. While all relays are shown as 4pole double throw (4pdt), not all of the poles are used on every relay. Furthermore, Relay 4 is redundant to Relay 3, but is necessary for a fifth pole on that relay. If a 5pdt (or more) relay is obtained, Relay 3 may be replaced and the pole contacts on Relay 4 may be shifted to Relay 3 alleviating the need for Relay 4.

As illustrated, the relays use 6 volts. But any voltage relays may be used, so long as the proper voltage is used to trigger them. The voltage connections that power the relay coils are shown in red while the current that goes to the tracks is in black. The Power Pack represents the power supply that actually runs the trains. The two Reed Switches are Normally Open (N/O). The Turn Out Toggle (TOT) represents the toggle switch that would be on the control panel used to activate an LGB turnout motor (or equivalent). We’ll use a double pole double throw (dpdt) switch that is off in the center position and spring loaded to return to the center. We’ll use one half of the switch (left blank in the diagram) to activate the turnout (assuming a common ground). The other half of the dpdt switch will activate the Lizard Bash Loop Control (LBLC).

Follow along the diagram as you take a ride through the loop and see what happens.

On our first trip, we’ll proceed from left to right (clockwise) going through the “straight section” of the turnout.

Current flows from the power pack through Relay 1, Pole 3 and 4 (counting up from the bottom of the diagram) (R1P3 and R1P4) to the main line so the train has power. It then flows from the track (would actually be from R1P3 and R1P4 but this is more intuitive and serves for illustration purposes), through R3P3 and R3P4 to the loop so the train has power when it enters the loop.

The operator toggles the turnout pushing the switch down. Voltage is applied to Relay 5 pulling down the armature. R5P1 is pulled down. Because no voltage is flowing to pole 1, nothing happens. (That’s OK at this point.) The train proceeds and first encounters Reed Switch 1 (RS1). The magnet closes the reed and voltage flows to R3P2. Because the circuit is open at this point, nothing happens and the reed switch is ignored.

The train continues on and encounters RS2. The magnet closes the reed and voltage flows to R3P2. From there it continues on to R1P2, firing Relay 1. When Relay 1 fires, it reverses the current to the main line. But that then reverses the current to the loop and if left like this, the train would go backward before it reaches the main line again. (More on this in a moment.) When Relay 1 fires it also completes the circuit so that voltage flows through R1P1. This voltage continues on through R2P1, and back to the Relay 1 coil. This then makes Relay 1 stay “fired” (keeping the current to the main line reversed) even after the train clears the Reed Switch.

As noted, when the current to the main line is reversed, it also reverses the current to the loop and the train would go backward when triggering RS2. As such, when the train passes over RS2 firing Relay 1, it also fires Relays 3 and 4 through R4P1. Relay 3 then reverses the current to the loop at the same time Relay 1 reverses the current to the main line. So the current to the loop is reversed and reversed again and stays as it was before the train passed over the reed switch. When Relay 3 fires it pulls R3P1 completing that circuit. Voltage flows thought R3P1, then though R5P1 keeping Relays 3 and 4 fired after the train clears the reed switch.

At this point, the control of the turnout points can be accommodated though this circuitry (with some modification), can be controlled using the typical LGB circuitry (adding the appropriate reed switch to activate the turnout) but without the bother of polarity control), or the train can simply “push the points” into position as the train transitions out of the loop onto the main line and pulls away.

So the train pulls away and takes care of business later to return to the loop. The turnout points are still where they were when the train left, either because they were fired by circuitry or because the wheels simply pushed them over. If left unattended, the train proceeds through the loop, this time in a counter clockwise direction through the curved leg of the turnout and first encounters RS2. Voltage flows though the reed switch to R3P2. But the relay is still in its active state and the voltage comes to an unconnected relay contact, and the Reed Switch is ignored. The train proceeds on and encounters RS1. Voltage flows again to R3P2 and this time passes through the relay on to R1P2. Relay 1 is also still energized, and the voltage passes through R1P2 and fires Relay 2. When Relay 2 fires, R2P1 opens interrupting the voltage that has been holding Relay 1 open and Relay 1 closes. This then reverses the current to the mainline.

Again, the mainline feeds the loop and to keep the train from going backward before reaching the main line, the voltage from RS2 passes through R3P2 to R4P1 (that is still in a fired position along with Relay 3) to the coil on Relay 5. This fires Relay 5 that removes the voltage that holds Relays 3 and 4 open. Relays 3 and 4 then reverse simultaneous with the main line and the current from the main line and loop are again in sync.

This will go on repeatedly with trains alternating clockwise/counterclockwise as infinitum without intervention. If the user decides to alter this natural rhythm, he can do so by toggling the turnout. This resets the relays to whatever “state” is selected through the Turn Out Toggle (TOT) also used to activate the turnout. When the TOT is pushed down it sends voltage to the Relay 5 coil pulling the armature that breaks the circuit through R5P1 holding Relays 3 and 4 open and they revert to the original clockwise direction relative to the main line. When the TOT is pushed up, it fires Relays 3 and 4 to the counterclockwise direction relative to the main line and they will latch in that position by sending voltage through R3P1 followed by R5P1.

That’s it in a nutshell. Enjoy.

 

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The LGB diagrams shown in the book I mentioned provide for three modes of wiring reverse loops. Yes, one is manual operation, however the other two are fully automatic, no hands mom, operations. One of those allows the train to enter the loop from either direction, while in the other one, the train must traverse the loop in the same direction all of the time. I have this type on my layout, which is fully automated, in four places (four reverse loops) and they have been operating flawlwssly for years. The other opinions mentioned are from members alot more talented than I when it comes to fancy electronics. However, for me, I prefer the KISS method, as running an outdoor railway requires enough maintainance as it is.
 

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I was replying specifically to your post where you suggest the use of LGB Reverse Loop Set -

The easiest solution would be the LGB reverse loop track set. It comes with two sections of track. Each section has its purpose. Both sections are placed inside of the loop. In your case you will need two sets.

That LGB Reverse Loop Set will only give you manual operation.
If you want automatic operation, one will have to add at least one additional component to reverse track polarity.
Yes - two options of that are covered in the LGB book, there are also a number of other ways to do that - with and without LGB components.

I just didn't want to leave anyone with the impression that using the LGB reverse loop set will provide automatic operation.

Knut
 

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Posted By lownote on 22 Aug 2009 04:55 PM
It's things like this that make me think about going to DCC. A DCC system will do reverse loops automatically with no additional wire whatsoever.

Dave Bodnar has some info on reverse loops on his site:

http://www.davebodnar.com/

Also George Schreyer's fantastic site:

http://www.girr.org/girr/tips/tips.html


Specifically I would suggest checking this article on the TrainElectronics.com web page

Reverse Loops Article


dave
 

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Posted By dbodnar on 23 Aug 2009 11:26 AM

Specifically I would suggest checking this article on the TrainElectronics.com web page

Reverse Loops Article


dave


I haven't had a chance to read that article, just glance through it quickly, but it looks like excellent information.

One wiring diagram using a single latching relay is shown below.
It needs a bit of work because this was a design for an N-scale layout where switches use three-wire control instead of two-wire control as with LGB.

Also - some symbols might be a bit strange since this schematic is from Europe, but it's a great starting point for a simple and effective reverse loop controller.

With that particular one, one can travel around the reverse loop in either direction and everything is fully automatic.


 

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DCC is far and away the easiest way to deal with this for track power. Battery RC is also easy, just ignore the whole problem...

The DCC autoreverse modules do need a short to detect when they need to operate, but they operate so quickly that there seems to be no downside. DCC, however well it works, tends to have a high entry cost. However, once that barrier is past, it's great.
 

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Posted By krs on 22 Aug 2009 07:15 PM
Sorry -

That diagram isn't nearly as wide when I look at it on my mls web space.

But here is a smaller one (I hope):


I have been running this system for the past year in my basement. While it is wire intensive, it works great. Currently I have it torn apart to upsize the wires to cut the voltage drop (LGB wire and old phone wire to 16ga). The reverse loop using two LGB 10151 had a much more noticable drop due to the diodes.

If you plan on backing your trains inside the loops install magnets on your cabooses and it doesn't know the difference.

Paul
 
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