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Offline PMPeter  
#1 Posted : 09 November 2013 22:38:45(UTC)

Joined: 04/04/2013(UTC)
Posts: 1,105
Location: Port Moody, BC
The track plan is done, the benchwork is complete, and the roadbed is starting to go down for a mixture of K and C track. This is my first attempt at building a completely digital layout and I must say I am having difficulty getting the old block system out of my mind. So here comes what most will probably consider a dumb question, but I am wrestling with it as I start laying the track.

I read in another topic that you should try and keep the isolation points to a minimum and should generally limit them to areas where a booster is applied or where you may end up connecting to an analog section or loop. However, in the digital world where you want to have various trains and routes running simultaneously and use one of the mentioned tracks or reed switches, do you not need to isolate the sections into blocks again for the appropriate sections to receive power or not? Perhaps I am missing something very fundamental here, but I don't want to end up ripping up track to install isolators once I have it in place (especially since I bought 1996 vintage C track not knowing about the breakage problem).

Also fundamentally do all three items such as contact track, switching track and reed switches not end up providing the same information to something? I guess the contact track lets something else decide what control needs to be activated once contact has been made, whereas the other two can control something directly.

Once I actually start wiring things up perhaps this will become self-explanatory, but at the moment I feel fortunate when I get 2 pieces of C track to go together without little bits of grey flying off like little bullets, and don't want to chance taking them apart again.

Any advice would be appreciated.

thanks 1 user liked this useful post by PMPeter
Offline cookee_nz  
#2 Posted : 10 November 2013 08:28:12(UTC)

New Zealand   
Joined: 31/12/2010(UTC)
Posts: 3,626
Location: Paremata, Wellington
Hi Peter,

It can be a confusing area first time around so don't worry at all that you are missing something basic.

It has been my understanding from the earlier days of Digital that sections needed to be isolated if one of the sections is either powered by a Booster, or is still under Analogue control but Isolation for this reason is not to be confused with 'block' isolation as it applies to control by signals.

Some people still prefer the absolute fail-safe that if a signal is Red, then a loco cannot go past the signal, and this is probably a good thing if your layout is not going to be manned with some sort of human control over each train.

Others hold to the view that the model should reflect the prototype and that a pair of eyes should be on every signal and loco interaction. But even in the real world there are more and more calls for fail-safe controls to automatically stop or slow trains that run red signals, exceed speed limits etc.

If the layout is automatic or even semi-automatic, then you need some way to stop a train at a red signal, generally this would be either a person or a Computer running it but regardless of how the control is done, what if something fails?, having the sections wired to the signal to cut or apply track power is a good safeguard.

If I were in your shoes, my personal preference would be to isolate wherever your experience and instinct tells you, but at each isolation point be sure to have a dropper wire either side that you can easily connect should the isolation not be required. That way you have the best of both worlds where you have taken the precaution in advance of allowing for isolation, but can easily bypass it if you wish or your layout design changes.

You can either leave the droppers under the tracks and connect them there, or you could feed them back to a switch board.

Another side advantage of switchable isolation is in trouble-shooting. Cutting a section out in the case of a short-circuit will quickly confirm whether that section is causing you a problem or not.

As for the different types of feedback, well it really depends on how you wish to read that feedback and each has their advantages and disadvantages.

Circuit tracks (with the flipper) have the advantage of being directional, so you can control something according to the direction of the train. They are only activated by the pickup shoe, not by any wheels. The contact is brief, only active so long as the pickup is actually pressing on it.

They are known for sticking and can be a bear to adjust and get working reliably once they start playing up. But many people use them and many have not experienced any problems.

Contact tracks rely on the wheels to bridge the two outside rails, and generally these are used for longer duration control such as station lights, level crossings, and track occupancy detection. The only disadvantage with them is that for the duration of the contact section, you only have one outer rail giving you a feed to your loco and if you have rubber tyres, some Loco's will not run reliably, particularly at slower speeds.

Circuit and Contact tracks be indeed be used to directly control electromagnet accessories, up to a limit of course.

Reed switches have the advantage of being completely separate to the track, and can be customised to some degree by where the reed is placed in the track-bed (left or right), but also that you can choose which Loco's and items of rolling stock will have a magnet attached.

Personally I would be more cautious about directly controlling accessories from reed switches because the contact surface is much less and any device which draws a lot of current may burn the contacts prematurely. On the other hand, Reed switches can often be readily replaced without having to lift any track.

All of the feedback options above can be used to feed into a feedback decoder for Route or PC control.

At the end of the day, the better you design your layout for any 'what if' options, the more flexible it will be. If you even suspect isolation might be needed, put it in with an easy way to bridge it underneath. I would say better to have it and not need it, than need it and not have it.

The only other thing I can think of to take into consideration is whether you plan to also fit the small pickup shoe rocker/lifter at the same isolation points. That certainly is something that would require lifting the track to change and I understand that for reliable running you are better off without them to avoid loco's stalling should they cross one at slow speed but you may be able to overcome this in your design.

I also have not been able to find these items in the latest catalogue and seem to recall that the newer Digital controls are much more tolerant of two sections being bridged - someone else will be able to add to this I'm sure.

Hope this helps and happy to stand corrected if I've made a boo-boo with any of the above.

Be interested to hear what you finally do and how it works out.


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