Speed change on the reverse loop

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I have a DCS100 as a command station and a DB150 running the reverse loop. When my train is running on the main line (controled by the DCS100), and when I set the switch to enter the reverse loop, the train enters the track. After crossing the gapped area, the speed slowed down some. Is that a natural or is it something I need to do to ocnfigure the system.

-- Lawrence Hannahan (lhannahan@aol.com), October 18, 1999


Be sure that the transformer supply feeding the DB150 is of the same voltage and current capability as that used for the DCS100. If they are different, you will have a different voltage on the engine motor with the same DCC throttle 'speed' setting.

DCC decoders with CEMF speed compensation (Lenz '30 & '130) solve that problem at additional expense.

Another possibility is that there may be loose connections or too thin wires feeding the reversing track section. These also will cause voltage drops.


-- Don Vollrath (dvollrath@magnetek.com), October 20, 1999.


This can be from multiple causes. Such as; The wiring/connections to and in the loop have a higher resistance then that of the main. Another is the actual output voltage of the DCS100 and DB150 may or may not be the same. Both besides the external scale track voltage selector have an internal trim pot to adjust output voltage.

And another, but more common cause, it not wiring the ground connector between boosters, as per Digitrax manual. This is more important as the distance between boosters increases, but should be done no matter what the distance is when one booster is in auto- reverse mode. In other words make sure you have a good heavy conductor running from booster to booster on the ground or green wire terminals, say a #12 gauge. You might also want to connect this common bus to an earth saftey ground while you are at it.

BTW to check the booster output voltage, use a standard DC voltmeter. Measure from the ground connection of the booster to either rail output, then multiply by 2, this will give you the Digital voltage on the rails. Check this on both boosters, make sure that address '00' is at speed '00', ie no stretched pulses, and there is no load on the booster outputs. Once you know the voltage output of both boosters, if they are much different from the other with the scale switch set the same, you can open up say the DCS100 and use the trim pot to adjust it to match the DB150.

Next once you are happy that both boosters are close enough in output voltage, you can take the same measurements with a typical load, loco/train, etc out on the main and in the reverse section. This will show any resistance that might might be in the wiring/connectors of either, this shows a a voltage drop, the more the drop in voltage, the higher the resistance here.

I would suggest, that if you do not have the common ground connection between boosters, do that first, I think that may be all you need. If it is already there or does not do it for you, then check the boosters output voltage, and if need be adjust to get them closer together. Then if still a problem, check the actual track voltage with load to see if you might need a larger bus and/or more drop feeders, or possibly correct a high resistance connection.

If you have any other questions, or need more help here feel free to ask away.

I might note this is a common question on the Digitrax Chat List. If you would like to join over 950 other Digitrax users in one place. You can join the list by going to http://www.onelist.com/subscribe.cgi/digitrax

Remember Always Have Fun and Enjoy!, Don Crano Akron, Oh NMRA #096211 mailto:donc@sssnet.com Visit Model Railroading with DCC at: http://pages.sssnet.com/donc/

-- Don Crano (donc@sssnet.com), October 21, 1999.

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