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Offline Omo  
#1 Posted : 03 April 2021 22:02:34(UTC)
Omo


Joined: 15/12/2007(UTC)
Posts: 10
Location: ,
Digitally braking in front of signals or at stations can be made in a very simple and inexpensive way.

The Märklin 72441 braking module (or the similar from Viessmann) is a very expensive solution on a very simple problem. Not everybody doing model railways are electronic circuit specialists and Märklin really takes advantage of this. But making smooth braking sections is so simple that everybody can do it for little money. It is even simple to avoid the short transition section (explained by Märklin with the 72441), and which very often gives a jerk in the train when passed.

A train will brake when the digital supply to the rail (which is high frequency AC current) is rectified to DC current. Then all what you have to do is to switch a diode into the supply to the 3rd rail (thus rectifying the digital supply) and a capacity between that 3rd rail and the outer rail connection - when the train should brake. And it works not only with Märklin decoders but also on all other newer decoders able to run the Motorola system (as Märklin’s).

Avoiding the transition section can be done simply if the braking section is longer than the longest train and if the switching (by a relay) is done with a contact rail (isolated piece of rail) when the entire train (or at least all locomotives/motor coaches) is on the braking section - the principle explained on https://www.marklin-user...gital/breakmoduleLW.html - scroll down to solution no. 5 “Relay brake with Joerg Bruehe”.

A link to the circuit diagram is shown below and illustrates the situation, where a train should brake in front of a signal on stop. The components are a relay, a diode, and a capacitor - not very expensive! The relay is energised when the train is passing the short isolated track section (contact track) and hold itself via a contact. The relay switches the digital supply via the diode and the capacitor and the train brakes smoothly (with sound and light still on!). When the signal turns green, a signal relay contact makes the brake relay to release, at the train starts again (with the programmed acceleration of the locomotive decoder). The distance between the short insulated rail (contact track) and the stop section should be about 10 cm more than the braking distance, to which the decoders of the trains are adjusted (I use 110 cm, but on large model railways it should ideally be longer).

If the train does not brake sufficiently, it is stopped by the stop section at the signal.

The signal relay and circuit is also indicated on the drawing with its usual control of the stop section and the signal lamps. The signal relay should just have an extra contact for controlling the brake relay.

Se the circiut here: https://www.marklin-user.../album?u=1600&a=2039
[img=http://https://www.marklin-users.net/forum/album?u=1600&a=2039]Braking circuit[/img]

Relays can be any suitable simple type with shifting contacts. Here is 12 V proposed, but other voltages can also be used – depending of the voltage used for signal control. Voltage should be DC and not AC (like the usual Märklin 16 V light supply).

The funny thing is that Märklin actually showed the simple diagram in a Märklin Magazine in the 1990’ ties!

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