Re: Automatic Train Control

Jan Frelin <jan.frelin@...>

We're still considering a DCC solution, not in the least because of the
opprtunity of controling some accesories with the computer while you're at
it. Thus I have some followup question to this list:

1) What are the options for arranging feedback regarding stock position
with DCC? The basic scenario is still a tram going back and forth between
two locations.

2) We require a pair of working crossing gates, which need to do the
following: a) start ringing bells to warn traffic. b) start closing 10
seconds later c) grow silent when down d) open silently. An interesting
automation project. Any ideas?


At 11:18 2005-07-01 -0700, Mark Gurries wrote:


My club has a requirement for a tram that just goes back and forth
between it's terminal track and staging/storage. We want this to be
automatically controled. There are several kits for doing just this on
the market, but all I have found are DC based. As this track is
connected with the general layout, we would prefer a DCC solution, but
this seems to require a computer, a computer interface, and track

My question is: Is there a simpler solution with DCC? What's the
cheapest DCC-based solution (without building your own hardware or
Nothing is simpler or more cost effective than a DC solution.

DCC has layout automation software for DCC.


is an example of such software.

But you will need a computer, a computer interface to the DCC system,
sensors in the track (DC will need that too) and do some programming.

Definitely more expensive and requires a computer running to make it
happen. The DC solution would be hands off easy to setup and forget.

Some thoughts...

Generally mixing DC and DCC is not recommended by anyone. I can result
in destruction of a booster, DC throttle or both if both power sources
connect to each other. (DCC is a form of AC power) If you must run DC,
the recommendation is that one have a master switch that toggle the
whole layout between DC or DCC but NEVER both at the same time. Many
layouts have done this successfully. There was an article about how one
club did it in MR magazine.

If you MUST have DC and DCC present, there are some recommended rules.

1) Isolate at least a 12: section of track the goes between the DC power
section of the layout and the DCC powered portion of the layout. A no
mans land with not power. Using a momentary center off switch, you
would toggle the power of the dead section of track to DC or DCC
depending on which side of the dead section of track you need to get
power from. The key is momentary switch. A standard toggle will no be
safe for you will forget to turn it off.

2) Another option to isolate the approach track from the DCC portion of
the layout and power it through a Lenz LT100.


The LT100 is connected to your DC power pack output. It monitors for
signs of DCC and will instantly disconnect the DC power pack from the
track protecting both system.

I should say that running a locomotive from DC section of track to a DCC
section of track can lead to a runaway locomotive. Most decoder make a
decision on first power up to run in DCC or DC mode. As long as power
is maintained, that decision remains true. So if the decoder see DCC
power after while it has been running in DC mode, the decoder will not
recognize the DCC and assume the DCC is nothing more than full throttle
DC power and vrooom.....

The reverse DCC to DC is less predictable. The engine may simple stop
and not run OR switch to DC mode with a very erratic reaction in the

Part of the randomness to all this is the nature of an engine rolling on
track with the corresponding momentary loss of power. Dirt, oxidation,
clean wheel, number of wheel pickups and other such factor play into the

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
Model Railroad Club and NMRA DCC presentations are at:
Audio Enthusiast (Love SAE equipment)

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