BEMF/Advanced Consisting & Digitrax

Problem: Does your Digitrax Decoder stop working when in Advanced Consist Mode?

To learn more about all the different types of consisting and term confusion, go here: Consisting Information

Why?  
Digitrax decoder from the factory have BEMF control disabled when the decoder is part of an Advanced Consist.    Advanced Consisting is also known as "Decoder Assisted Consisting" using the decoder's CV19 to implement it with.  To be clear, is your using "Command Station based Consisting" also known as Basic/Standard consisting, this situation DOES NOT APPLY.
Digitrax command stations use Basic/Standard consisting by default, which Digitrax calls uniquely Universal Consisting, and is why this is not a problem for Digitrax users.

Why Does Digitrax Do that?  Given the goal of Advanced Consisting is no different then Basic/Standard Consisting from a operations point of view, then why is advanced consisting be penalized by default unnecessarily?  Other than Digitrax, who knows.  Does not make any sense. 

Symptoms:

1) Stand Alone Engine:  Engine runs fine at all speeds with good low speed performance.  Works fine in a Basic or Standard Consist setup too.  Engine speed is similar to other engines on the layout.

2) Part of Advanced Consist:  Engine seems dead in consist.  Will not move.  Turnout up the throttle will get the engine to move but the speed does not match the other engine in the consist.

Background:

CV57 is dual CV.  In other words, it is a complex CV that contains two independent number values that are put together to become a single combined number.   One number controls the intensity or strength of the BEMF when NOT part of a consist and the other control the intensity when you are in a consist.  Do not ask my why digitrax made this CV so complex.   Given there are two numbers involved that must be combined, it turns out that the only way to understand how to calculate the final number value requires understanding HEX numbers.  However, in addition to HEX explanation, I have a decimal discussion first.  

Read the next section for Solution.


1) DECIMAL DISCUSSION

CV 57 Range: 0 to 255

It is not easy to explain how to figure out the number value in decimal for CV57.   To keep it simple, we will ASSUME you want the BEMF intensity when operating in Advanced Consisting mode to be the same value when your not operating in an Advanced Consist.   This greatly reduces the complexity problem down to a set of 16 values to choose from. 

0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255

No BEMF: 0
Typical BEMF: 85  
Maximum BEMF: 255

SOLUTION:  I recommend you use the decimal value of 85 for CV57.   I do not recommend you go to higher value or you will start to see the engines fight each other.



2) HEX DISCUSSION

CV57 Range: 00 to FF

In hex, CV57 is an 8 bit CV that has been INTENTIONALLY broken up into 2 independent 4 bit values side by side.

Each 4 Bits can represent up to 16 unique values.  

Binary:     0000 - 1111  (0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111)
Decimal:        0 - 15      (     0,       1,      2,      3,      4,       5,       6,      7,      8,      9,      10,     11,    12,    13,     14,     15) 
Hex:              0 - F        (     0,       1,      2,      3,      4,       5,       6,      7,      8,      9,        A,      B,      C,      D,      E,       F)     


This makes CV57 have two INDEPENDENT hex values put together side by side in a single CV that requires no translation.

So the Hex range is: 00 to FF.

So CV57 is represented by two hex value represented by variable XY side by side.

The lower or first hex value "X" controls the intensity in effect when the decoder is operating normally.

The
upper or second hex value "Y" controls the intensity in effect when the decoder is part of an advanced consist .


SOLUTION: I recommend you use the HEX value of 55 for CV57.   I do not recommend you go to a higher value or you will start to see the engines fight each other.


3/3/16
8/19/17