Well, if you wire a toggle in DCC the same way it's wired in DCC - you switch ALL of the layout, except the loop. In DC the extra reversing toggle comes before ALL block toggles, the equivalent would be havign the switch before ANY breakers dividing the layout into power districts.
CHanging the phase under a moving train has no effect - it's exactly what an autoreverser does.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinkerWHat I suppose confuses people is that it would work FINE wired like a DC reverse switch. You'd be flipping the phase under EVERY train except the one on the loop - but this is fine.
I guess that I question this. Let us suppose that one train is entering the loop and there is a following train. Are we saying that when the first train totally enters the loop and the toggle switch is thrown to change the phase under the following train there is no effect on the following train during the phase change?
And in another scenario let us assume that a single train enters the loop and the toggle is thrown to change the phase on the track entering the loop. Let us further assume that this section of track eventually encounters a boundary with another power district. Certainly the phase change will cause a problem at that boundary similar to what would occur if the track in question had been wired incorrectly to begin with. Is that not correct??
Bob nailed it - if you should want to use a DPDT toggle for the reverse loop, it gets wired like the AR, not like you would wire a reverse loop direction switch in DC, so it flips the loop, under a moving train.
WHat I suppose confuses people is that it would work FINE wired like a DC reverse switch. You'd be flipping the phase under EVERY train except the one on the loop - but this is fine.
The relay method automates it with no special circuitry. As the train runs around the loop, you have to change the turnout from allowing access to teh entrance of the loop to conencting the exit of the loop, otherwise you will have a derailment on your hands. So the relay gets controlled by the motion of the switch machine. Sure, you can ALSO do it with som sort of IR beam breaker detection, like IRDOT or something, so that as the train passes a certain point, it flips the relay, but this gets right back to being complicated.
What might be missing - a decent relay for this purpose has a low current coil - 30ma or less. In one position of the turnout, the relay will be on, solid. But they are deisnged for this, and also draw 30ma or less, so it's like a stall motor switch machine. No fancy arrangments of relays to emulate a latching relay, or a real latching relay, are needed.
richhotrain Randy, thanks for that follow up. It makes for an interesting discussion and for some difficult considerations in layout building If your layout calls for one or more reversing sections, I see three options. One, just use commercially available auto-reversers. Two, avoid shorts and build in DPDT toggle switches to reverse polarities manually before the short occurs. Three, design a relay system to automate the reverse polarity process before the short occurs. Rich
Randy, thanks for that follow up. It makes for an interesting discussion and for some difficult considerations in layout building
If your layout calls for one or more reversing sections, I see three options.
One, just use commercially available auto-reversers.
Two, avoid shorts and build in DPDT toggle switches to reverse polarities manually before the short occurs.
Three, design a relay system to automate the reverse polarity process before the short occurs.
Rich
I have been following this discussion. I would add that a couple of determining factors for deciding which approach to use might be a person's 'comfort level' with one method over another and maybe individual knowledge. I am perfectly comfortable using an auto reverse unit but don't ask me to build a relay system. Wouldn't have a clue.
I also appreciate what Randy has been saying. It's great to know someone who takes such pride in building an error free layout. I did see a comment he made about running a common power bus for turnouts, lights, etc. To some degree I have done that but since I am planning some modifications this winter, that one is now in the cooker.
There's never time to do it right, but always time to do it over.....
retsignalmtr With the use of DCC I would think that using automatic reversers like the AR1 or PSX-AR would be the only way to go. using a DPDT reverses the polarity on the main line while the AR units reverse just the reversing section.
With the use of DCC I would think that using automatic reversers like the AR1 or PSX-AR would be the only way to go. using a DPDT reverses the polarity on the main line while the AR units reverse just the reversing section.
You use the DPDT switch on the Reverse Loop when using DCC - It acts exactly like the AR1 (seeing as how it is using a Mechanical Relay).
Don't get the 2 technolgies mixed up (DC & DCC) the way they handle Reversing Loops is way different!
BOB H - Clarion, PA
I am not aware of any problems or damage that an auto-reverser can cause or any problem caused by the occurrence of a short due to reverse polarity.
I hope that no one on this thread is suggesting that the use of an auto-reverser is a bad thing.
Alton Junction
From an engineering standpoint, the idea is to design a system so there are no faults.
Fault recovery is second level, a backup as it were, for a fault creeping in regardless of attempts to prevent them.
Not that it's on the same scale, but, theoretically, if you short a wall outlet in your house, your house won;t burn down because there is a circuit breaker that trips and cuts off the power. It's there in case soemthign you plug in shorts out. Ideally, you never want to have the short in the first place.
It does follow through with the rest of my layout building - the booster has a circuit breaker, and I do have downstream circuit breakers. But I srive to make my trackwork as buleltproof as possible, so nothing ever deraisl adn NEEDS that circuit breaker to act. SO far that's worked out pretty well, when I can shove cars through the trackwork at warp speed and they all stay on the rails, I know it's going to be pretty good for runnign at proper speed, and that's proven out across the two layouts I've built since going DCC. I expect my next one to be no different, even though it is going to be by far the largest layout I've ever built, AND i will be using a track brand that I have personally never used before. But with slow, careful work and making sure all straights are straight and not all kinked, and all curves flow smoothly with easements, and the roadbed nice and even withou humps to put vertical kinks in the track, and grade transitions made very gently and smoothly, I expect nothing less than the same high reliability I've gotten from my previous layouts.
I guess I am just picky. I'm not very good at scenery, but dang it, my track and electrical work is as bulletproof as I can make it. There may be no pretty scenes for the trains to run through, but run they do. With my usual slow rate of construction, I may dabble in some of my own control circuits for this stuff, but it's hard to justify other than for satisfying a curiosity since the commercial products are relatively inexpensive and I can just buy something and hook it up and know it works, without trying to put my own code into my own hardware and test and test to validate it all.
rrinker Rememebr the DC days? There was never a short, you flipped the toggle BEFORE a short happened. Only more recently did anyone figure out that if you can build a circuit to ract fast enough, you can wait for the short and then fix it. It conflicts with my engineering background that says a short is a fault. Every time.
Rememebr the DC days? There was never a short, you flipped the toggle BEFORE a short happened. Only more recently did anyone figure out that if you can build a circuit to ract fast enough, you can wait for the short and then fix it. It conflicts with my engineering background that says a short is a fault. Every time.
OK, I hear ya. A short is a fault.
But, what's the harm if the auto-reverser immediately corrects the short?
Plus, I control my reverse loop with a $3 relay and I don't need a $14.95 AR1 or even more expensive PSX-AR. I'm also cheap. I haven't checked for mass quantities from eBay seller in China like for other electronic components, but I suspect I can probably get relays with sufficient current capacity for even less than that.
No doubt the 'black box' of an autoreverser is easier to understand, if treated as a black box, anyway. 4 wires to hook up, done. Relay needs the crossed wiring plus the 4 wires, plus connections to the coil via the switch machine contacts, and a power supply (no big deal since my layou will have an accessory power bus around it to tap off for lights, switch machines, UP5 panel power, etc.). Zero adjustments, and the train will always roll smoothly across the gaps, jut like moving from one piece of mainline track to another, no chance of even the slightest hesitation or stutter or break in sound.
OK, let's go over this once again.
On a DCC layout with a reversing section (loop), a short occurs but an auto-reverser like an AR1 or a PSX-AR reacts quickly to reverse the polarity and end the short before any harm is done.
It happens so quickly that the momentary short isn't even noticeable.
What's wrong with that?
What's with the obsession to prevent a short from occurring in the first place?
HaroldAI remember, and not too fondly, the days of an Altas Controller that only worked when I was very profane, or of the days of block wiring when it seemed as if I was forever throwing toggle switches.
HaroldAWhen someone starts talking about PSX's and MOSFETS, my eyes just glaze over because I don't have the understanding.
Well then, I'm afraid that they have baffled you with BS, or at least with more information than you needed. The PSX or AR devices are what I would call black box items. That is, you only need to have a minimum of knowledge to get them to do what you want. In the most basic case there are two wires going in from your power bus, and two wires coming out to the loop. If you managed to get the rest of your layout wired for DCC, I think you will have no trouble figuring out how to make the connections. You don't really need to know what happens inside the device.
There are no relays, contacts, or toggles to contend with. And if there is really some small power loss associated with the device, I don't think you will notice.
Just my opinion.
For a revers loop, of course you need a DPDT relay. It gets wired just like a DPDT toggle, with the X wiring. The coil is triggered by switch machine contacts. The reason for a relay is that most switch machine contacts aren't rated for the full load of a train. For a frog, it's fine, there can not possibly be more than one loco or lighted car on a frog at any given time so there never can be that much current flowing through said contacts. For the entire power to a complete reversing section - there could be multiple unit locos plus lighted cars, easily exceeding the rating of the switch machine. Plus most have 2 sets of SPDT, or in other words, one DPDT, which means if you use all the contacts for the loop you have none left for signals or frog power.
As for the eyes glossing over, I did say youc ould ignore the terms and just go on with what I explained they mean. No model railroad book will explain any of this. Even basic electricty, model railroad boosk tell you how but do not explain theory. The palce to go would be to find a book on basic electricity. A PSX is just a name of a device, like the AR1 is the Digitrax device, the PSX is Tony's product. A MOSFET - well, it will take a lot more tha a basic electricty course to understand what a MOSFET is and how it works. Suffice to say, they are commonly used as high current solid state switches. Which is what I thought I got across in my explanation. Unlike physical contacts, such as a relay or switch, a semiconductor device will have some measurable resistence between its electronic 'contacts' and resistence is what causes voltage drops. No need to dig further. To inderstand the DETAILS of how one works and what all the parameters are, would require a course in solid state electronics. There's no 'cheat sheet'. Explaining what MOSFET stands for - Metal Oxide Semiconductor Field Effect Transistor - I'm sure makes even LESS sense. Again, the 'cheat sheet' as best as can be is that it is a switch, but an electronic one, not a physical toggle switch. The detailed properties of the device explain why it is the preferred device for some types of circuits whereas others may use an ordinary silicon transistor. Knowing which to pick and when - that's a whole Electrical Engineering degree.
A couple of additional comments from the OP - First, I realized I needed another way to turn trains and the solution was a second reverse loop. I finished it up yesterday and it going to add so much to the ability to run trains and to keep my interest. In addition, it is going to finally allow me to create a little place called Elmer's Crossing in memory of my dad.
Second comment is this - I remember, and not too fondly, the days of an Altas Controller that only worked when I was very profane, or of the days of block wiring when it seemed as if I was forever throwing toggle switches. if I read the posts correctly, maybe components like the Digitrax AR1 have been the next step in the evolution of reverse loop controls and the new all electronic components are the next generation.
For me, it was once again a matter of cost and then simply not having the knowledge to do it any other way. When someone starts talking about PSX's and MOSFETS, my eyes just glaze over because I don't have the understanding. As I said in an earlier post, I wish there was a print resource for guys like me who aren't familiar with the intricacies of electronics - one that started with the basics and went from there. I have found places on the internet but even some of those assume too much.
Richhotrain,
Seeing You are determined to find fault with my replys...Bob H and Randy, gave You my answer.
I also have over 60 turnouts on my layout, original Shinohara and Atlas and they all perform quite well, Thank You, along with 3cab DC control.
Take Care!
Frank
Bob, thanks for that reply.
I wondered if Randy was referring to a DPDT. I have used that approach in the past to manually switch my reversing section(s) before moving to an auto-reverser mechanism.
I appreciate your making that distinction between a manual DPDT toggle switch and an automated DPDT relay.
richhotrain rrinker Since with DCC you can change the phase under the moving train at any time, you can use a relay to change it when you line the switch, BEFORE the train hits the gaps. What type of relay are you referring to, Randy? Rich
rrinker Since with DCC you can change the phase under the moving train at any time, you can use a relay to change it when you line the switch, BEFORE the train hits the gaps.
Since with DCC you can change the phase under the moving train at any time, you can use a relay to change it when you line the switch, BEFORE the train hits the gaps.
What type of relay are you referring to, Randy?
You can use a DPDT relay (your choice of coil voltage) and cross wire like a reversing DPDT toggle switch!
I used a DPDT toggle sw for a few years on my current layout to control the polarity of my huge Reverse loop staging until I rebuilt the layout to use a differeny type of staging tracks.
I had the toggle sw at the end of the Reverse Loop and would have the Toggle handle set that it would point into the Loop or out of the Loop when flipped to show direction of the Train and thus track polarity!
Each time a train went into the Reverse Loop staging I would just flip the toggle to set the polarity for the next train coming out of the Reverse Loop Staging!
I could have easily replaced the Toggle Sw with a Relay and using a Caboose Ground Throw w/Electrical Contacts - to auto throw the Track Polarity.
One doesn't have to have the ELECTRONIC Auto Throw Auto Reversers as good old Mechanical Relays lasted for years in the good old days!
rrinker No, avoid auto-reversers.
No, avoid auto-reversers.
No, avoid auto-reversers. Since with DCC you can change the phase under the moving train at any time, you can use a relay to change it when you line the switch, BEFORE the train hits the gaps. This applies to any loop that is at least as long as the train that will be running over it - line switch, train enters, any time after the last car clears the switch but before the loco hits the switch, you line it the other way, and this also flips the loop track phase. No short ever occurs. Works for a wye as well. ANd yes, even a turntable - that fancy NYRS PTC III turntable controller has an option to drive a relay to reverse the bridge polarity when it turns more than 180 degrees. So you get instant flip instead of the dead zone of split rail, so sound doesn't cut off, and there's no short to be corrected by an autoreverser.
Yes, it's slightly more complicated to set up (depending on things such as what sort of switch machines you use - the servo drivers I use already HAVE a connection to drive a relay, and there are others that even shut off frog power while the servo is moving and then applies correct polarity only after it reaches the end of throw, so you don't have to worry about "DCC friendly"), but there is never any chance of hesitation and no issues with high inrush reset.
zstripe rrinker As far as reversers (and frog power, for that matter), I will have PLENTY of "old fashioned" relays on my layout - to set frog polarity and also automatically flip reverse loops when the turnouts change position. Rather than wait for a short and then fix it, my plan is to avoid shorts altogether. Sure it's a bit more complex than hooking up 1 wire from a Frog Juicer to the frog, but a short is a fault. The idea is to avoid faults. --Randy Randy, My sentiments exactly. Like I have said before....''I avoid them, like the plague''. Frank
rrinker As far as reversers (and frog power, for that matter), I will have PLENTY of "old fashioned" relays on my layout - to set frog polarity and also automatically flip reverse loops when the turnouts change position. Rather than wait for a short and then fix it, my plan is to avoid shorts altogether. Sure it's a bit more complex than hooking up 1 wire from a Frog Juicer to the frog, but a short is a fault. The idea is to avoid faults. --Randy
Randy,
My sentiments exactly. Like I have said before....''I avoid them, like the plague''.
Reverse loops or reversers?
I suspect that you are referring to reverse loops. But, at least some of us have one or more reverse loops on our layouts including the OP who has two reverse loops. I have 5 reversing sections on my layout. Nothing wrong with reverse loops, certainly not the equivalent of the plague.
As far as reversers like the AR1 and the PSX-AR are concerned, they don't work on DC layouts anyhow, so they only matter to DCC users in the first place. The AR1 works just fine in the right environment, and Harold nicely solved his problem with a simple turn of the TTC adjustment screw. Once you start to add some solid state electronics like a PSX circuit breaker to your layout, however, only then does the AR1 show its age.
As far as powering the frog, you can get by quite nicely with an unpowered frog in most cases. I do. I have over 60 turnouts on my layout, and none of the frogs are powered. No problemo!
There is one huge advantage relay devices like the AR1 and PM42 have over the others (besdes that the PM42 can report state to Loconet) - thsoe relays have effectively NO voltage drop. Even the best MOSFETS like used on the PSX4 and PSX-AR (assuming they DO use the best) do not have a zero resitence when 'on' and those cause a little voltage drop. If you build your own computers at all, you may have seen motherboards advertised as using "Low RDS MOSFETS" - This is the resistence, drain to source (don;t worry, you don;t have to undertsand all that) - basically, this is the resistence you will measure between the terminals that the power flows through. It's never 0. It can;t be zero (unless someone invents the ideal semiconductor). Just like long runs of bus wire, or on a larger scale, the resistor in series with your LED headlighs, the more resistence, the larger the voltage drop (also proportional to current). Relays don't have this problem.
As far as reversers (and frog power, for that matter), I will have PLENTY of "old fashioned" relays on my layout - to set frog polarity and also automatically flip reverse loops when the turnouts change position. Rather than wait for a short and then fix it, my plan is to avoid shorts altogether. Sure it's a bit more complex than hooking up 1 wire from a Frog Juicer to the frog, but a short is a fault. The idea is to avoid faults.
Harold, glad to hear that the TTC adjustment worked. As long as it is working properly, there is no need to move to PSX-AR solid state technology at this time. I might suggest that the same applies to adding circuit breakers or a second booster at this time.
Chances are, if you create power districts and use solid state technology for the circuit breakers, you are going to have to replace the AR1s as well. That gets expensive, so hold off until you absolutely need to go in that direction.
But definitely get those bus wires and feeder wires in order.
First of all, thanks guys for your help. I did go down and adjust the trip current on one of the AR1's and it works perfectly. The one which controls the reverse loop I was referring to is also fine. i am almost ashamed to admit, but when I crawled under the layout to add more feeders I said 'what was I thinking when I wired this????' The feeders are way too long, there aren't nearly enough of them and the bus is way too short which probably accounts for the feeders being too long. SO, tomorrow there is a trip to Lowe's in my future along with a significant re-wiring project in this one area. Going forward I will also look into the PSX devices as the Digitrax devices are probably updated. Thanks for that tip.
Like I said, there's never time to do it right, but there's always time to do it over. (sigh)
I was an avid user of AR1s for years. But they are, admittedly, out of date technology with the mechanical relay.
I have no regrets with the switchover to the solid state technology of the PSX-AR along with the PSX circuit breakers.
It would have been nice if you mentioned the reverse loops in your original posting. The AR1 operates by detecting a short circuit condition when a loco enters the reverse loop and it flips the polarity of the loop to correct that condition. Either the AR1's sensitivity is too low or it is detecting a short in the reverse loop that it cannot correct. Make sure you have all the insulated joiners or gaps in their correct places and try readjusting the trip sensitivity. The PSX AR's are a better choice but they are a little more costly.
Adjusted properly, the AR-1 should click once when the rails are shorted and if the short persists after the relay clicks, the booster should shut down.
It's OK to run smaller wire to the AR-1 terminals, but it should be kept short, a few inches to give enough room to connect it to the full-size bus. Voltage drop in the wire is proportional to botht he size of the wire and length, so short lengths of smaller wire will not cause enough drop to be a problem, unless everything else is marginal to begin with. You should be able to fit at least #18 wire in the screw terminals of the AR-1.