Braking digitally

Back to "My hobby"

The art

I never though braking should become so complicated. It's true the the digital system enables things like several locos to be run simultaneaously, and also makes it a lot easier to loose control! For example you started some trains, and begin to do some shunting. Suddenly you realize that one of the turnouts didn't throw for some reason, so one train is going to crash into another. Well, what was the number of that little one? lets try 35 , etc... No that wouldn't do. So there is the emergency stop which cuts the power to the track, and the trains are saved. But how should the layout be started again? Yes, it's possible, but more difficult than you thought, isn't it?

Another issue is when you get taste of these little marvels. First, the more advanced loco-decoders have the ability to start and stop smoothly; each loco is programmed with the acceration rate, and then when they get the signal to change speed, the speed change will not be abrupt. But this requires there is power available. The old way, to just cut the power in front of red showing signals, will cause many locos to stop so abruptly that the cars might derail, escpecially with some of the motors used nowadays.

And this will also take away other advantages with digital; the lights are no longer one, but worst of all (for the moment), the sound will disappear. Not many locos have sound, but the ones that have continous sound, will just appear ridiculous if the power is cut. On the contrary, if they are allowed to do the braking themselves, the sound will nicely follow, it you will get success instead of disaster!

My findings

I use block sections with braking sections of Lenz type; so I prefer Märklins, Lenz or ESU decoders that understand this (DC) brake signal. On the main line there are five block sections; and this is the visible part, so it's here they are. On the hidden part I just cut the power. The idea with a hidden yard is to forget about it, so you don't want a loco to stand there and say "here I am", do you. I admit that the other stop sections could have brake sections, but it also takes some space, so I skipped it.

How is this done then? Well, I didn't buy the Märklin 72441, as it appears to be far to expensive than could be justified by the task. But there were hints on the net how to do it yourself, and I begun to experiment, got interested, and ended up in buying one 72441 for comparison. Or rather, a year ago that was how I thought it ended; and I deemed the competition even between different solutions, the winner depending on what demands was most important. But now, since some months, I've realized that I and we were on the wrong track all the time.

I think it's a interesting story how things evaluate these days. I think Lenz patented the idea of letting the locos brake by giving them a DC signal around 10 years ago. As Märklin initially cooperated with Lenz, the idea was adopted in their c90 decoders and 37xx locos, before there was any easy way of producing this brake signal! Then, a few years ago Märklin begun to produce the 72441. This gave thoughts to people how to do it cheaper themselves; the components needed really weren't expensive at all. Probably some people had thought of it, but again Märklin draw some interest to the idea. But all these solutions had one potential drawback: when a train passes from the digital track into the DC fed brake section, a short occurs through the slider. This short may be limited so that the power feed doesn't shutoff, but fact remains: some trains make a little jerk at this situation. And in my eyes, the whole idea with brake sections is to get perfect behaviour.

So it was when I stumbled upon the solution, which of course others probably had realized long before me. One shouldn't let the train pass from a section fed with digital, into a section with somehting else at all. One should switch a relay, changing the current to the whole section where the train resides momentary. And, of course, the switching is done by the train itself at a certain point, provided the following signal is red.

Deeper

I’ve produced two articles about how to do. The first is more general and was first published at www.marklin-users.net. It makes an overview over different methods to achieve the brake signal, and comparing them. It ends up in my conclusion, that a relay-based approach is the best in almost all aspects, contrary to most opinions, especially as all manufacturers (I know) have choosen another way.

The second is about this relay-based approach, how it can be done and used.

The third is about using the new Märklin 76xxx signals with graceful braking; a task that is not trivial.

On my layout

As I said, I have 5 brake sections. The layout was constructed before the last findings, and I've found it interesting to dig deeper in this area. So I have now decided to have a variety of brake sections on this. Currently I have four different types.

1. One state of the art, releay switched when the train is in place

2-3. Two with a car bulb (acting as a fast PTC resistor) protecting the power feed, one brake and one stop section.

4. One Märklin 72441, with an additional half track transition section.

5. One self built with two diodes, and a DC signal. Needs a transition section as 72441 does, but much cheaper.