DCC reversing loop - how easy, how costly

[Harry2013]

Hi,

 

I'm trying to figure out both the technical and budgetary limitations that my simple DCC layout will have to be designed within.

 

I might want to use a reversing loop. I realise this cause problems with the track polarity.

 

I'm looking for a cost effective solution.

 

On http://www.digitrains.co.uk/ecommerce/dcc-accessories/auto-reversers/

 

There are various items from £10 - £60+

 

The AR1 Auto Reversing Module @ £22 appears to be suitable.

 

It says "operates with any DCC system except 1 Amp starters."

 

 

Not sure what they mean by a '1Amp starter' - an additional power supply ?

 

If so which is suitable ?

 

Is it really 'automatic', ie is continous running possible without me flicking/press a switch ?

 

Explanations, advice on better/cheaper solutions, or whether I should forget the reverse loop altogether, will be most helpful.

 

Thanks

 

Harry

Edited December 2, 2013 by Dicky W

[Porco Rosso]

'1 amp starter' refers to low-power DCC control systems, which only have a low power output.

 

There are specific modules available to suit these.

[Suzie]

Most layouts do not need an auto-reverse module to control the polarity of the reverse loop, it can be done simply with a switch (like a Peco PL15 for example) attached to the point that controls entry to the reverse loop.

 

Do you have a track plan of what you want to do yet?

[Phil Bullock]

Suzie is indeed correct

 

But for automatic operation solid state is always more reliable than electro-mechanical

 

As a very happy user of frog juicers if you decide to go solid state you wont go wrong with the Tam Valley product

 

http://www.digitrains.co.uk/ecommerce/dcc-accessories/auto-reversers/DFJ003U-dual-frog-juicer-universal.aspx

 

Hope you get sorted!

 

Phil

[Harry2013]

Thanks for the replies.

 

Most layouts do not need an auto-reverse module to control the polarity of the reverse loop, it can be done simply with a switch (like a Peco PL15 for example) attached to the point that controls entry to the reverse loop.

 

Do you have a track plan of what you want to do yet?

 

I dont have a track plan yet, Im trying to figure out the cost of doing things before hand. I dont want to plan on something and then find out it costs too much.

If I used a PL15 would that also mean I have to motorise that point?

 

Suzie is indeed correct

 

But for automatic operation solid state is always more reliable than electro-mechanical

 

As a very happy user of frog juicers if you decide to go solid state you wont go wrong with the Tam Valley product

 

http://www.digitrains.co.uk/ecommerce/dcc-accessories/auto-reversers/DFJ003U-dual-frog-juicer-universal.aspx

 

Hope you get sorted!

 

Phil

 

Yes I saw the frog juicer you mention Phil, but focused on the AR1 becuase its slightly cheaper.

 

Would the single frog juicer work - its a lot cheaper ?

Edited December 1, 2013 by Harry2013

[Phil Bullock]

Hi Harry

 

Yes PL15 switch is designed to fit on to PL10 point motor.

 

And no cant use mono frog juicer as you need to switch two channels (one for each rail)

 

If you are really looking for the cheapest option switch the loop section manually with a DPDT switch

 

Cheers

 

Phil

[Suzie]

All you need is a double pole switch that works in conjunction with the point. PL15 is designed to attach to a Peco PL10 motor and is not ideally suited otherwise. If you are being super-economy (less than £1) you can use the point's switch rails as one pole and just add a lever type microswitch that bears on the end of the tiebar for the other pole - but no one would recommend that method as it is less than reliable. Two microswitches will be OK!

 

Using a double pole slide switch as a point actuator is quite popular and that will give you all the switching you need for not a lot of money.

 

If your points are motorised it is easy to add a switch to motors that do not have a switch (many like Tortoise do have switches built in) and many decoders come with switches built in too (like ESU Switchpilot with extension) to make it all very easy.

 

It is very unlikely that you will need to go to the expense of a reverse loop module (a dual frog juicer is pretty much the same thing in this context) with all the pitfalls that using one can entail.

 

Design your layout with a reverse loop and there should be a simple low cost wiring solution for it as long as you can arrange for the switch on the point. If you cannot have a switch then you will need to budget for an auto reverse module, and bear in mind that you will probably be disappointed with some of the cheaper offerings.

[Suzie]

You could replace the microswitch in my super economy example above with a single frog juicer but you would still have the reliability issues.

[Harry2013]

Thank you both for your replies.

 

As you will have gathered I dont yet have a grasp of the basics.

 

From what youve said I would guess that the Blue Point switch machine which has a

"DPDT snap-action toggle switch inside the compact plastic housing changes electrical connections to the turnout frog to prevent stalling of locomotives"

would work if I'd rather have a manual controlled point.

 

Harry

[Phil Bullock]

That's a new one on me but yes am sure that will do what you want

 

http://www.ppw-aline.com/Blue_Point_Manual_Turnout_Control.htm

 

Cheers

 

Phil

[OFFTHE RAILS]

The OP asked :

 

I'm trying to figure out both the technical and budgetary limitations that my simple DCC layout will have to be designed within.

 

I might want to use a reversing loop. I realise this cause problems with the track polarity.

 

I'm looking for a cost effective solution.

 

Whilst there are many auto reverse modules available for DCC I believe there's only one which will fully automate the loop. That is, reverse polarity AND set the point at the exit of the loop. It's the PSX-ARSC (for single coil point motors) and PSX-AR (for tortoise etc. motors).

Ian

[Harry2013]

That's a new one on me but yes am sure that will do what you want

 

http://www.ppw-aline.com/Blue_Point_Manual_Turnout_Control.htm

 

Cheers

 

Phil

 

Thanks for confiming for me Phil, earlier Id been Googling turnout control options, your previous comment about DPDT sent me back to check what I read.

 

The OP asked :

 

I'm trying to figure out both the technical and budgetary limitations that my simple DCC layout will have to be designed within.

 

I might want to use a reversing loop. I realise this cause problems with the track polarity.

 

I'm looking for a cost effective solution.

 

Whilst there are many auto reverse modules available for DCC I believe there's only one which will fully automate the loop. That is, reverse polarity AND set the point at the exit of the loop. It's the PSX-ARSC (for single coil point motors) and PSX-AR (for tortoise etc. motors).

Ian

Thanks Offtherails, I was afraid that my the ideal solution would be expensive, unfortunately on my modest layout I'll have to make lots of compromises.

[Phil Bullock]

Just a couple of other points (pardon the pun) to consider

 

If polarity switching is linked to the entry/exit point of your reversing loop you cant change that point - and hence the polarity of your switched section - until the tail of your train has cleared the point. Only a problem if running long trains through a short loop  and not a problem with solid state switching if point is controlled independently.

 

And your switched section needs to be able to accommodate comfortably your longest traction unit - individual locos probably not an issue but a 4 car unit might be if 2 motors with pick uos at both ends which are connected through the unit - rare I suspect but applies to both solid state and manual switching

 

Cheers

 

Phil

[AndrewC]

I will throw out one limitation of the Digitrax AR1. If you are using power districts controlled by DCCSpecialties equipment like the PSX1, the AR1 won't work. Been there, done that, have a spare AR1 to dispose of. PSX-AR is the way to go.

 

If you only have a small reversing loop where you are only ever going to have one loco and a non-sound one at that, you can easily control the polarity of the loop with a switch attached to the entry/exit pointwork. However, if you are using sound locos or will have multiple locos in the loop at one time you are better off investing in a proper reversing module. The break to make of a simple switch is usually enough to trigger a sound decoder into restarting. Depending on the type of decoder it can take a few seconds for it to go through the power up sound sequences. The other limitation is with multiple locos in the loop the current is likely to exceed the rating of the switch. You need something that is double pole double throw with at least a 2a switching current rating.

[Crosland]

If polarity switching is linked to the entry/exit point of your reversing loop you cant change that point - and hence the polarity of your switched section - until the tail of your train has cleared the point. Only a problem if running long trains through a short loop  and not a problem with solid state switching if point is controlled independently.

That's not realy an issue. The train has to be shorter than the reversing loop, otherwise it will collide with itself.

 

Andrew

[Adrian Wintle]

One of the things I played with is a reversing loop without bothering to change a point. This can be done using Kato track in N, as the train will exit the reverse loop over the (very lightly sprung) trailing point blades with no problem. In this case the AR1 was the perfect solution.

 

Adrian

Edited December 3, 2013 by Adrian Wintle

[Erik84750]

Most layouts do not need an auto-reverse module to control the polarity of the reverse loop, it can be done simply with a switch (like a Peco PL15 for example) attached to the point that controls entry to the reverse loop.

 

Do you have a track plan of what you want to do yet?

If I understand this well: a DCC layout with a reversing loop which has a powered switch only needs a double pole double throw DPDT relay connected to the switch powerleads for the autoreversing to work?

 

In other words: (rails before the switch: A and B, rails after the switch and in the loop: X and Y, DCC booster connected to tracks A and B) the switch is set to "pass straight" and the DPDT relay connects rails before and after in correct phasing (A to X and B to Y). the loco continues in the loop, you set the switch to "pass curved", and the DPDT relay gets thrown to the other pole: rail A to rail Y and rail B to rail X.

 

Is it as simple as that?

 

Erik

Edited April 29, 2017 by Erik84750

[Erik84750]

Here's the basic diagram for a return loop:

 

keerlus-2.jpg

 

Can be used in clock- and anti-clock-wise directions, trains stop automagically (if loco-hauled, or power pickup only from the front car) and will only continue when you change the point and does all the necessary polarity switching required. Point motors with 4 sets of contacts are not quite common in the UK, but available from Herkat/Bemo (Germany) and Fulgurex (Switzerland, needs extra contacts but these screw on easily) or use extra relays instead.

Hi, so it is not as simple as I thought.

 

But looking at your diagram I see that the gaps are not identical (same place on both sides of the track) for both rails. For example the first part in the curve at the switch, at the bottom, is always connected to "black", yet when the poles of the relay are thrown, the upper part of the track in this curve also is connected to "black". So no traction there?

 

Also orange is either connected to "red" or to nothing, while grey is connected to nothing or to "black": what is the purpose?

 

I do not yet understand the benefit of using the 4-pole relay: if the contacts are thrown both tracks switch poles except for the orange and grey rails. Something I miss?

Edited April 29, 2017 by Erik84750

[Crosland]

With an auto-reverser the train does not stop. You have to change the points in a timely fashion to avoid a derailment.

 

By the same argument, you do not need stop sections when switching the polarity from the point setting.

 

You can also use microswitches mechanically linked to the point actuating mechanism.

[DAVE1562]

Had a psx-arsc on my reverse loop n gauge shown on exe valley post.... worked well and can be automated for point or manual selection... this was used on a powercab set up

 

 

red/black dcc bus supply...l/h is input......r/h will go to loop supply

white/blue/orange point motor(seep pm1)...

Edited April 29, 2017 by DAVE1562

[Derekl]

There is a simple way of doing this - DCC or analogue. On the assumption that the layout is as the diagram above, gap both rails on the loop side of the point and feed through a DPDT switch (centre off, if required to isolate the section). Centre terminals to the power supply, cross wire the outer terminals and supply the track from one of the outer sets of terminals. Mark one setting "in", the other "out". The "in" setting should have the loop polarities as the incoming line, the "out" will reverse as for outgoing.

 

Drive the train in. Stop before the exit. Switch point (manually or electrically) and switch DPDT to "out". Drive train out.

 

It isn't automatic and you need to be able to see the train to stop in the right place. It does not have the expense and complexities above, but it is simple and will work.....

[10000]

As Suzie said you can do it with Peco PL15 mounted on a Peco motor. I have been using this method on 2 different  reversing loops for a few years now. It operates fast enough that you should see no interuption in running or sound.

 

When I first set it up it took me all of 5 minutes to work out the wiring  using a multimeter. 

Edited April 29, 2017 by 10000

[melmerby]

That's not realy an issue. The train has to be shorter than the reversing loop, otherwise it will collide with itself.

 

Andrew

Andrew, that applies if you just have a simple balloon loop but a reverse loop can be formed in other track layouts where the distance is way over the train length.

 

I know - I have two on my layout! They are controlled by LDT reversing units. (no short ccts used to detect train in loop)

 

Cheers

 

Keith

[Suzie]

If I understand this well: a DCC layout with a reversing loop which has a powered switch only needs a double pole double throw DPDT relay connected to the switch powerleads for the autoreversing to work?

 

In other words: (rails before the switch: A and B, rails after the switch and in the loop: X and Y, DCC booster connected to tracks A and B) the switch is set to "pass straight" and the DPDT relay connects rails before and after in correct phasing (A to X and B to Y). the loco continues in the loop, you set the switch to "pass curved", and the DPDT relay gets thrown to the other pole: rail A to rail Y and rail B to rail X.

 

Is it as simple as that?

 

Erik

 

Yes!

 

Dutch Master has shown the ultimate way to wire things if you are likely to run an incorrectly set point, but there is no real need to do that unless you have dead sections on the frogs of all your other points too. If you study Dutch Master's diagram you will see that the brown wire and the blue wire are always the same polarity so the lower pole of the switch is unnecessary, and if you wire the inner rail of the loop all the way to the frog with no insulated joiners eliminating the dead sections the third pole down is not required either.

 

Suzie x

[Erik84750]

There is a simple way of doing this - DCC or analogue. On the assumption that the layout is as the diagram above, gap both rails on the loop side of the point and feed through a DPDT switch (centre off, if required to isolate the section). Centre terminals to the power supply, cross wire the outer terminals and supply the track from one of the outer sets of terminals. Mark one setting "in", the other "out". The "in" setting should have the loop polarities as the incoming line, the "out" will reverse as for outgoing.

 

Drive the train in. Stop before the exit. Switch point (manually or electrically) and switch DPDT to "out". Drive train out.

 

It isn't automatic and you need to be able to see the train to stop in the right place. It does not have the expense and complexities above, but it is simple and will work.....

In my opinion no need for center off DPDT: reasonable quality (even Chinese) regular DPDT switches do the job. The construction of a DPDT is such that no overlapping contacts occur.

 

And the loco does not need to be stopped: you can do it on-the-fly.