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I've partitioned this page in blocks, like our layout,
Here an overview of the blocks.
This page is far from finished.
The power supply.
Train detection.
Train speed control.
Manual control tableaus.
Point control.
The crossing stations.
We'll have more to come.....
The power supply.
We use a separate power supply for for the trains in each switched part of the track.
That means that we have a power supply for all 15 blocks of the layout.
Then there is a separate power supply for the electronics and one for the motorway, for its
stoppers and point switches.
The transformer we use to power everything is a ring core transformer with 2 secondary
windings, each 9 Volt, 5 Ampere. These windings are connected serial to give 18 Volt AC.
After making it DC, this gives approximately 26 Volt DC. This gives enough capacity to
power the 12 trains we are planning to have on our track simultaneously.
The power supplies for the trains are set to 16 Volt, Those for the electronics to 12 Volt
and those for the motorway to 24 Volt. All power supplies are protected against short circuit.
For the train we have set a max current of 2 Ampere, sufficient to power 2 motorcars
or locomotives on 1 power supply. This because the majority of trains on the Bernina run double traction.
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Train detection.
Trains can be detected easiest by their power consumption, no current = no train.
With DC, like we use, I've put 2 diodes in the wire leading to the minus.
Here I can measure with a resistor and a transistor if there's a current going through the diodes.
A drawing will follow later. Detecting the end of the train is far more difficult.
You could put a signaler in the last car like a magnet and then put a reed relays in the rails
Or put conducting glue on each axel of every car. This has all kind of disadvantages and
you can't take any car from the shop and put it on your track or you can not put the last
car on a shunting yard. That's one of the things that we really want to do.
Other option would be an infra-red port where the train passes through.
This can give a pulse once the train is through but this will lead to camouflage issues
For the time being we don't detect the end of a train.
With some blocks, however, (the crossing stations) we do need to know that the train has
passed the point before switching it. We have chosen to do this by detecting if the front
of the train is at the end of that block. The length of the trains and the blocks enables
us to do that as the end will always be past the point at this time.
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Train speed control.
The electronic speed control has been based on pulse with modulation. This has
2 advantages. The transistors don't get hot during normal operation because
there is little voltage over them ( They only switch on and off ) And this enables you
to easily pull up and slow down gradually. many of these kind of speed controls operate at
a frequency of around 400 Hertz. This means 400 times per second on and off.
This is also the case with built-in digital train systems.
This has a few disadvantages and therefore we decided to use a frequency of 16000 Hertz
( 16 kHz ).
The disadvantages are; you can hear the train buzz at 400 Hertz during driving
and specially when pulling out of the station. Further, not all engines can withstand the
400 Hertz frequency, e.g. engines without a metal core, with glued windings can
vibrate and disintegrate at these frequencies. This doesn't happen at higher frequencies.
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Manual controlling tableaus.
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Point control.
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The crossing stations.
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