Friday, June 13, 2008

More thoughts on how to control trains

I'm still trying to figure out wht I really want. Use advanced features to control trains, or keep things simple and economical (so I don't need computer assistance).

While I don't really want to write software (no time to do this right), using computer control sounds very sweet. This would require I stick s88 control points at every switch and track that will hold more than one loco.

The first problem is how to identify locos. There are several commonly used methods:

  • Cut one rail of Maerklin K track and use the loco and car axles to bridge the cut. This is very common, and well supported with s88 modules. The drawback for control is this method can't differentiate between locos and cars, and I have a bunch of M-track on my layout.
  • Use a powersensing circuit to identify if a section of track is occupied by a train, and hook that up to the digital system. This works but isn't well suited for control because it's not very location aware. However, it's good for use in hidden staging to figure out which tracks are occupied by a train.
  • Use a s88 control point that is trigger by the power pickup shoe of the loco. There are contact tracks made by Maerklin, as well as several build-it-yourself approaches. This works well for control if you mainly run freight trains. The method can't differentiate between the pickup shoe of the loco, and a pickup shoe, that e.g. powers lights in the passenger cars, or the rear illumatination of a freight train.
  • Use reed contacts between the rails and a little magnet on each loco. This method clearly identified locos. However, each s88 contact needs to be made from reed contacts which are visible between the tracks and cost additional money, and each loco needs to be fitted with two small magnets.
  • Uhlenbrock offers LISSY which is a digital control system to solve the problem. It's clearly the most complete and powerful solution, but also the most expensive.

In what situations do I need digitally controlled stops?

Stop a train before a signal that shows red automatically.

  • Trains should stop in front of a red signal and preferably decelerate before coming to a stop.
  • Most digital locomotives don't roll very far when the loco looses power, so I don't really want to run them into section of track with no power (like in the old analog days).
  • On a green signal the train should accelerate automatically.
  • lights and functions should remain on while the loco is stopped.

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