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tortoise control using AR

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  • From: somerset, nj
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tortoise control using AR
Posted by gregc on Thursday, October 17, 2019 1:54 PM

i thought Larry Pucket's description of using an auto-reverser to control a Tortoise switch machine in the Nov DCC Corner was interesting.   Was news to me.

greg - Philadelphia & Reading / Reading

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Posted by rrinker on Thursday, October 17, 2019 2:31 PM

 I tend to read up on anything and everything, so I knew the PSX-AR had that capability. Of course, you have to carefully locate the gaps so that there's sufficient time for the Tortoise to move the points, so on a basic baloon loop, the old way of simply insulating the joints right at the turnout won't work.

For wyes and simple loops - I'm still a fan of switching the polaity with a switch machine controlled relay. Rather than cause a fault and correct it, which is really what an AR is doing, why not avoid the fault in the first place? And relays make/break contact plenty fast enough. Just using the contacts on eg a Tortoise isn't a good idea, they aren't meant to switch high current loads, and you need to use both sets to make a DPDT reversing switch, leaving none for frog power. 

                                         --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by MisterBeasley on Thursday, October 17, 2019 3:32 PM

I'm not sure what you're saying, Randy.  I was thinking about this just today, with an idea of continuous looping with a single track and a balloon reversing loop an each end.  I had the same realization that the PSX-AR solution needs to account for the throw time for slow-motion machines.

If the Tortoise controls the polarity, what controls the Tortoise?  I really don't want to have to manually flip the turnouts each time in continuous running more.

It takes an iron man to play with a toy iron horse. 

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Posted by gregc on Thursday, October 17, 2019 4:06 PM

MisterBeasley
If the Tortoise controls the polarity, what controls the Tortoise? 

the early part of the article discussed using the Tortoise contacts to control the reverse section track polarity.   So regardless of the turnout position, the rails at the diverging or non-diverging ends have the correct polarity because of the switch contacts. (see post below)

gaps on the diverging and non-diverging rails will short when the train comes around the loop back towards the turnout causing the AR to reverse the turnout by reversing it's polarity.   (the article mentions that the gaps need to be far enough away from the turnout to give it time to switch).

presumably, there are no gaps on the points side of the turnout, nor need to be.   The article describes adding 2 pushbuttons to short the rails at one of the gaps to force the turnout to one or the other position.    This would be needed to force the train around the loop in one direction or the other when entering the loop.

greg - Philadelphia & Reading / Reading

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Posted by rrinker on Thursday, October 17, 2019 5:44 PM

 Well, as my planned layout is double tracked, dogbone style, the end looops ARE reversing loops, but I can also continuously run trains for display purposes without using the reversing at all - go into the staging loop eastbound on the eat main, come back out westbound on the west main, no reverse loop. Just can;t do any crossovers during display running - if I use the contact method of changing the loop polarity.

 With the PSX-AR, then the AR can control the Tortoise, when it detects the short and reverses the polarity - this is where the gaps need to far enough back to allow the Tortoise time to work. If you stop there, the first train will go through the loop clockwise, then the next one will go counter-clockwise - alternating each time, because the turnout is left lined for the last used exit path, which becomes the entrance path next time.

 The article shows adding a couple of pushbuttons to create a short so that the PSX-AR activates and flips the polarity and also changes the Tortoise.

                                   --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
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  • From: somerset, nj
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Posted by gregc on Thursday, October 17, 2019 6:07 PM

in thinking about this more, i believe I am wrong in saying that the tortoise controls the rail polarity of the reverse section.

If, as I said above, the AR changes the polarity of the switch machine to start it to switch,  the short will persist as the train crosses the gap until the switch contacts change the rail polarity.

the photo in the article show the PSX-AR connected to the mainline rails (DCC), the reverse section rails and the tortoise.   The photo also shows a tortoise switch machine connected  to J5 on the PSX-AR which is intended specifically for this purpose.

it appears that the PSX-AR has ~12 VDC on the board and the ability to invert its polarity on the J5 terminals.

 

greg - Philadelphia & Reading / Reading

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  • From: Reading, PA
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Posted by rrinker on Thursday, October 17, 2019 6:43 PM

 That is correct - the PSX-AR triggers the Tortoise when it reverses the track polarity. 

                              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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