# how to automate a track switch



## sugermc (Apr 8, 2015)

Hi, new here, but have learned a lot.
MY question is, attempting to layout my train for a loop, but after it goes thru the switch to the left, it loops back to the straight and comes back on the original track thru a switch, it then should go straight pass the first switch to continue on. How do you reset the switches? Automatically, like if the last car of the train can activate the switch to allow the train to go straight instead of going left


----------



## Sjoc78 (Jan 25, 2014)

I can't find it off hand but I thought LGB used to make a track sensor for such things. It would just be some sort of electro-magnet that would trigger on a magnet attached to the engine. You could get into some electronics and build something with a flip-flop and a timer circuit so that it toggles it back after a period you gauge it takes for the train to completely clear the switch


----------



## chuck n (Jan 2, 2008)

It sounds as if you are building a return loop. LGB's manual throw has a spring that always return the points to the same position, but permits a train to pass through the "closed" point. I use this on some of my passing sidings. That way I only have to throw one switch, not two. Another option is the LGB electric switch. It's mechanism permits the engine to throw the switch as it goes through against the closed switch. In this case it stays in the new position. Upon returning to the loop on the next trip the train will go through the straight track and then throw it to the curved position when leaving.

In the first example with the manual throw it always takes the same path, while it alternates paths with the second. No wiring is needed, but you may need to add some weight if you have derailments. 

Are you using track power, battery, or DCC? A return loop with DC track power needs special wiring as it creates a dead short. 

Chuck

Manual spring switches can be made inexpensively with spring wire. John, aka Totalwrecker, has a design that works very well. If you are interested in this type of spring switch I can show you a slightly different spring wire design when I get access to my laptop.


----------



## Skeeterweazel (Feb 11, 2014)

Low tech:


----------



## Dan Pierce (Jan 2, 2008)

Check out this diagram for all LGB parts to make a reverse loop work.

http://www.altek.nl/graphtips/enkelekeerlus.gif


----------



## DennisB (Jan 2, 2008)

I am familiar with this diagram. It doesn't mention that your engine shudders as it passes over reversing module. Even LGB recommends that you cover this area so people can't see it happen.


----------



## toddalin (Jan 4, 2008)

DennisB said:


> I am familiar with this diagram. It doesn't mention that your engine shudders as it passes over reversing module. Even LGB recommends that you cover this area so people can't see it happen.



OK, I'm at a loss there. Please elaborate. Are you specifically referring to the MTS system and not analog power?

All the "module" is doing is changing the polarity of the mainline track while the train is in the loop. Why whould this cause the engine to "shudder" while within the loop?


----------



## pfdx (Jan 2, 2008)

I used the double return loop wiring diagram for a while and noticed the the train twitched when on the the switches threw in one direction. Turns out the 12030 and 12070 switches can, depending on several factors have a momentary short circuit when used to reverse polarity. It's a long enough short to make the engine slow but short enough not to be detected by the 51070 throttle.

I rewired to used the EPL switches to control a DPDT and a 4PDT relay and removed the second switch drive and eliminated the problem. I now wish I had used 3 DPDT relays with one controlling each district but oh well.

Here is the wiring diagram.

http://www.altek.nl/graphtips/keerlussen.gif

It's a good mind bender for people to figure out how it works.


----------



## sugermc (Apr 8, 2015)

Thanks for all the replies, I have learned a few things, but I must have not described well enough what I would like to do. I will try again.
It is not a reverse loop, but a complete circle. So if I am traveling left to right, I leave the main track turning left, make a complete 360 degrees, and come back onto the main track before the first switch and continue my travel going right. I guess it would be a left switch and a right switch back to back. Good lord I really must learn the proper terms! And I must find some teenager to show me how to either draw a diagram or scan a picture to attach to this thread. I really only have a "learners permit" for this information highway stuff. LOL


----------



## riderdan (Jan 2, 2014)

Like a circle within an oval?

Like so:









So on the first pass, you want it to take the left-hand switch (A) into the inner loop, come back around back to the main track on the right-hand switch (B), and then pass through the left-hand switch (A) again, this time staying on the outer loop?

You'll need some sort of switch automation to handle that. If you really want it to change the switch every time (so that it goes left, straight, left, straight, etc) you could probably automate it with a simple circuit, and a reed switch somewhere between switch A and B and a magnet on the locomotive... so that every time the loco magnet triggers the switch, it flips the direction of the switch.


----------



## sugermc (Apr 8, 2015)

YES, that's what I want to do. But when we attended a G-scale train convention in Ohio, all the owners of the displays were not "always" changing switches as they showed their layouts. And they were not doing it by some type of radio or sitting and some type main control area. What ever they had, it enabled them to visit and talk and not worry about if the switch was correct. It was cool
I have looked at a reed switch but do not understand how they work or how to wire


----------



## sugermc (Apr 8, 2015)

Would I be placing the "reed" switch in between the power supply and the switch? And would I not have to put the other half of the magnet somewhere on the switch? Or does a "reed" switch have the magnet in it?
 What a newbie I am, know just enough to get it wrong! LOL


----------



## riderdan (Jan 2, 2014)

sugermc said:


> Would I be placing the "reed" switch in between the power supply and the switch? And would I not have to put the other half of the magnet somewhere on the switch? Or does a "reed" switch have the magnet in it?
> What a newbie I am, know just enough to get it wrong! LOL


The reed switch is a switch that's triggered by a magnet. It wouldn't be connected to the track, but to whatever circuit you have for moving the switch--it acts like a push button getting pushed each time the train (with magnet attached) goes over it. You'd obviously need a motorized switch.


----------



## toddalin (Jan 4, 2008)

pfdx said:


> I used the double return loop wiring diagram for a while and noticed the the train twitched when on the the switches threw in one direction. Turns out the 12030 and 12070 switches can, depending on several factors have a momentary short circuit when used to reverse polarity. It's a long enough short to make the engine slow but short enough not to be detected by the 51070 throttle.


There is a simple fix for this. Open the LGB EPL and CA a shim onto the "bat" to change the throw spacing a bit. Very simple. I do this on several to get them to function properly.


----------



## sugermc (Apr 8, 2015)

riderdan, you would then need two reed switches, and if the first switch you come to, would be opened to enable you to go left off the main track, if the magnet was in the caboose, after it goes thru and over the "reed" switch, it would switch to make it enable the train go straight on the main track when it comes around.
Then at the 2nd switch the magnet would be on the maintrack. Because when the train was making its first pass, the caboose passes over it, making the switch open to allow the train to come back onto the main track. The when the train goes around thru this switch onto the main track, when it passes over the magnet a second time, it would return the switch to allow the train to go straight thru after it completes its large oval.
Yeah, how confusing is that


----------



## riderdan (Jan 2, 2014)

sugermc said:


> riderdan, you would then need two reed switches, and if the first switch you come to, would be opened to enable you to go left off the main track, if the magnet was in the caboose, after it goes thru and over the "reed" switch, it would switch to make it enable the train go straight on the main track when it comes around.
> Then at the 2nd switch the magnet would be on the maintrack. Because when the train was making its first pass, the caboose passes over it, making the switch open to allow the train to come back onto the main track. The when the train goes around thru this switch onto the main track, when it passes over the magnet a second time, it would return the switch to allow the train to go straight thru after it completes its large oval.
> Yeah, how confusing is that











Put the magnet in the loco and the reed switch between switches A and B, set to flip-flop the A switch. The first time around, the A switch is set for the inner loop. The train goes through switch A into the inner loop and exits switch B (cutting the switch). As it passes over the reed switch again, switch A is flipped for the outer loop. The train circles the outer loop, passes through switch B and goes over the reed switch again, flipping switch A back to the inner loop position.

Does that make sense? I don't think it's necessary to do anything to switch B. 

I can't remember for sure, but I thought that the LGB switch motors operate off a momentary pulse. So you just need the reed switch's momentary triggering by the loco's magnet to get it to flip the switch's direction. Someone else should be along shortly to explain why that's a bad idea


----------



## toddalin (Jan 4, 2008)

First you need to decide if you always want the trains to go one way, or should they go both ways.

The easy way, and allows you to go either direction, is to put a reed switch somewhere along the inner loop and somewhere along the outter loop, so that you longest train is clear of the turnouts when the magnet mounted under the engine trips the reed.

The reed switch on the inner loop "tells" the turnouts to throw to the straight position and the reed on the outter loop makes the turnouts throw toward their curved position.

So when the train goes along the straight, in either direction, it comes to the reed and throws the to turnouts to the curved position. The train comes to the first turnout and its wheels push the points into the straight position.

It comes to the next turnout and takes the curve into the inner loop. While in the inner loop it trips the reed to throw the turnouts to the straight postion.

It comes to the first turnout and the wheels push the points to the curved position. It continues on and this time the second turnout is in the straight position and the train takes the outter loop.

This can be done with the LGB system, but the reeds can only handle the current of one turnout at a time. Two is do-able for a while, but it takes its toll on the reed switches. I run multiple turnouts automated, but they are triggered by relays that can take more current.

So, how to get around the LGB limitation? Set the system up to just go one direction, then you only need to toggle one turnout with each reed at a time. If you want the trains to run the other direction, use a toggle switch to "tie" the reeds to the other two turnouts.


----------

