Hello from Savannah

AlexW Mar 20, 2017

  1. AlexW

    AlexW New Member

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    I'm a relatively new modeler and my focus is on 3-rail Marklin digital. I have modified a number of locos to digital and I run my layout with an Arduino computer board, CAN Bus shield (a peripheral board that connects to the Arduino), Marklin track box which converts CAN Bus messages to Track commands, and various software packages. It has been a journey of discovery by trial and error, mostly because Marklin documentation is limited and at times confusing. My next step is to try and implement a DCC protocol on Marklin, which in theory should work with the Arduino, a motor shield, and various open source software packages such as DCC++, JMRI, and Desktop Station. If there is interest, I'll post my findings and experiences as they unfold.

    Thanks to TrainBoard for this site and online community!
     
  2. Doorgunnerjgs

    Doorgunnerjgs TrainBoard Member

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    Welcome, sounds like you will fit in really well here. The DCC++ folks should be a great help and will be interested in your experiences.
     
  3. BoxcabE50

    BoxcabE50 Staff Member TrainBoard Supporter

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    Welcome to TrainBoard!
     
  4. Eagle2

    Eagle2 Staff Member TrainBoard Supporter

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    Welcome aboard! I'd say I can't see any downside to sharing your experiences, should be a good place to start some discussions.
     
  5. fitz

    fitz Staff Member TrainBoard Supporter

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    Welcome aboard, AlexW. Sounds like you have a good start.
     
  6. Hytec

    Hytec TrainBoard Supporter

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    Hi Alex, welcome. what you describe sounds interesting, though far beyond the capabilities of this DC Dinosaur. o_O
     
  7. bremner

    bremner Staff Member

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    Isn't Marklin 3 rail AC?
     
  8. Ironhorseman

    Ironhorseman Staff Member

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    Welcome aboard, Alex. :)
     
  9. PeaceRiverRailway3210

    PeaceRiverRailway3210 TrainBoard Member

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  10. WFOJeff

    WFOJeff TrainBoard Supporter

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    Welcome aboard Alex, wish I had your knowledge.
     
  11. AlexW

    AlexW New Member

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    Very good question and I will try to provide the long answer. Others may find some flaws in my response and all comments and corrections are welcomed!

    To answer the question, we need to discuss three Marklin related topics, as follows;

    1. 3-Rail vs. 2-Rail

    As most of you know, Marklin uses what we refer to as a 3-rail system, where the standard 2 rails are augmented with a series of small studs concealed in the roadbed. However, the 2 rails are electrically connected together and can be considered the “common,” negative, or ground connection. The center studs carry the positive or power connection. Note that depending on the protocol being discussed, electrical connections will take on different meanings. Also note that not all Marlin systems are 3-rail but we will limit this discussion to 3-rail.

    There are various advantages to 2 and 3 rail systems and the one that seems the most compelling for 3-rail is the simplicity of reversing loops and turnouts. The polarity of the rails never changes. Marklin has remained committed to 3-rail.


    2. AC vs. DC

    Most everyone knows the difference between AC and DC. Although Marklin had wind-up and battery power locos in their early years, their first powered locos were AC analog. This simply means the motors were AC powered and speed was a function of track voltage. So how do Marklin AC motors work? First, the field magnet is an AC magnet – wires wound around an iron core magnetized by passing an AC current through it. The armature has brushes and a commutator which direct AC current through the armature windings, also producing a magnetic field that interacts with the field magnet causing rotation when properly designed. Pretty straight-forward and can be done with 2 or 3 rails.

    Again, there are various advantages and disadvantages to AC motors. For this discussion we will focus on two disadvantages. The first is the ability to reverse the motor. To do so, you have to reverse the voltage going to the AC field magnet. There are two windings in the field magnet to help accomplish this task and there is a separate reversing relay in the loco that responds to a high voltage pulse for switching the polarity of the field magnet voltage. Pretty complex. Second, AC is not compatible with DCC digital standards.

    On the other hand, DC motors use a permanent magnet as the field magnet versus the AC magnet in AC motors. The armature is the same as AC motors with the exception that the brushes and commutator direct DC instead of AC voltage through the armature windings. Reversing the motor simply requires reversing the voltage polarity of the DC voltage to the armature. Pretty easy. Furthermore, DC is compatible with DCC standards.

    Marklin no longer makes AC locos and virtually all older AC motors can be converted to DC by simply replacing the AC field magnet with a permanent magnet and removing the reversing relay. This is a simple and low cost modification and can be done in a few minutes.


    3. Analog vs. Digital

    As stated previously, analog control of locos is done by controlling the track voltage. The higher the voltage, the faster the loco goes. Also, this applies to AC or DC motors. Unfortunately, all locos on the same power circuit respond to the analog voltage simultaneously. Analog layouts require isolation of track sections so that the track rather than the locos can be individually controlled. Furthermore, low speed operation is more difficult because motors have less torque and more starting resistance at low voltages. In addition, anything being powered from the track, such as lights, responds to the raising and lowering of track voltage. You can’t have a loco light turned on using track power when the loco is stopped.

    Digital is common today and uses constant track power to both provide power and messages to anything listening to the track. This can include accessories as well as locos. If you scope the track voltage, it looks like an unsymmetrical square wave because it is being switched or modulated to communicate with decoders connected to the track. For this reason, it is often argued that the track voltage is AC although the power to the motor is DC. The problem comes about because the track voltage swings between plus and minus a fixed voltage, somewhere between 12 and 18 volts depending on scale and system. Is this AC? Some will argue yes and some will call it a third protocol called bipolar. But what goes to the DC motor is not track voltage but a pulse width modulated unipolar signal, so in digital we have to be careful not to confuse bipolar track voltage with unipolar (DC) motor voltage.

    Marklin has AC and DC digital, but AC digital is considered obsolete and no longer produced. AC digital meant that the motor had an AC field magnet. All new Marklin decoders fall under the DC mantra and support a wide range of standards include Marklin proprietary and DCC.

    So the question was, “Isn’t Marklin 3-rail AC?” Yes, it is mostly 3-rail, older equipment is AC but is no longer produced, new equipment uses bipolar track voltage but this is not normally considered AC, and as far as I know, all modern motors are pulse width modulated DC motors.

    AlexW
     
  12. subwayaz

    subwayaz TrainBoard Supporter

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    Welcome aboard AlexW


    Sent from my iPad using Tapatalk
     
  13. Hytec

    Hytec TrainBoard Supporter

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    Alex, excellent description of the three basic power processes. I admire that Marklin has developed their own protocols, regardless of international convention. That has made their devotees very dedicated, but unable to leave Marklin without having to start from scratch. Marklin craftsmanship is without peer. However by taking their parochial design approach, they have become much like IBM in the early PC marketplace. IBM was determined that they knew best and had the correct design approach, yet they watched the innovative open market entrepreneurs race off and leave them in the dust. Eventually IBM left the PC marketplace with their tail between their legs. I admire that Marklin has their dedicated loyalist, but eventually those loyalists will diminish to zero due to aging, and the younger modelers will have followed the Kato, Model Power, Athearn, Bachmann innovators into the model railroading future.
     
  14. AlexW

    AlexW New Member

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    To your point, Marklin filed for insolvency in 2009 and was later acquired by Sieber & Sohn in 2013. However, they appear to be operating profitably at this time. Regardless, I'm not trying to promote or defend any system, rather I'm interested in the technical side of the hobby and sharing what I learn as I work through the discovery process.

    Alex
     

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