Massoth Decoder Load Control

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idlemarvel

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I've used MASSOTH decoders for years and I'm still puzzled by what they call "load control".

I'm referencing the MASSOTH eMOTION configuration manual.

CV 49 (MASSOTH configuration) bit 1 sets "Digital load control" on, which is the default setting. With this set off, a loco will not move until speed step 4 or 5 is reached for example, the exact speed step depends on the loco. With it set on, the loco will move on speed step 1 afer a short pause. This is what I understand to be "back EMF" in action.

Then we have what MASSOTH call in English "PI-Load control". I don't know what PI stands for; in German is it just called Lastregulung which is the same word used to describe "Digital load control" mentioned above. According to my understanding, it is designed to maintain loco speed when climbing gradients. There are four CVs which adjust this feature (CVs 60-63). I can't test this as I have no gradients on my layout. It can be turned on or off with a function key defined in CV 64.

In the manual section on acceleration and deceleration (CV 3 and 4), the same CV 64 is used to turn the effect of CV 3 and 4 off, so that locos respond immediately to speed step changes, which could be useful when shunting. I suppose this is a side effect of turning on "PI-Load control".

My summary, which I would like some MASSOTH experts on here to confirm is:

1: "Digital load control" is back EMF, is on by default, and can be turned off in CV 49 bit 1

2: "PI-Load control" is (only?) useful if you have gradients (or is it used to fine-tune back EMF?)

3: You can turn off acceleration/deceleration settings using a function key defined in CV 64 (but this will turn on "PI-Load control").

Thanks, Dave
 
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So, I am not a Massoth expert, but you might read an article on BEMF parameters in the real world.

This one is not bad: Back EMF - DCCWiki

Then realizing the 3 BEMF parameters to set are usually called PID (and you can learn what P, I and D stand for), you can learn that several manufacturers do NOT give you all 3 parameters but lump some of them together.

I think Massoth lumps a couple together, i.e. P and I.... now the Massoth experts can come in and translate the real world of BEMF to what is available in Massoth decoders.

Greg
 
Thanks Greg that's very helpful. At least I know what PI means (Proportional Integral) and the article states that not all manufacturers implement the D part (Derivative). It's curious that PI is not used in the original German text only in the English translation but leaving that aside it is a bit clearer. If PI is a feedback loop mechanism then I can see how that would be inconsistent with normal acceleration and deceleration settings. The MASSOTH manual could be clearer, I'll send some feedback to them.
 
I've done some more research and I think a lot of my confusion is around nomenclature. Looking at an old version of a MASSOTH XLS manual it describes CV64 as "disengage acceleration/deceleration times" (CV3 and CV4) and CV 49 bit 1 to turn off PI-Load control. This is consistent with my observations. This is also consistent with the JRMI Decoder-Pro definitions which also describes the PI-Load control variables as Back EMF adjustment variables.

Now it all makes sense, to me anyway. Revising my three statements:

1: "Digital load control" is their name for Back EMF, is on by default, and can be turned off in CV 49 bit 1

2: "PI-Load control" is their feedback mechanism for Back EMF, and the PI-Load adjustment CVs 60-63 are used to adjust how Back EMF performs

3: You can turn off acceleration/deceleration settings CV3-4 using a function key defined in CV 64 but PI-Load control is turned off along with Back EMF in CV 49 bit 1 (this last statement is inconsistent with latest manuals).

IMO the older MASSOTH manual is a lot clearer and more accurate on this topic than the newer ones.
 
I get people asking what 'PI' (they immediately think 3.14159..) has to do with 'Load Control'..

They think of the Greek letter, rather than it being an abbreviation. :nerd:
 
PhilP said:
I get people asking what 'PI' (they immediately think 3.14159..) has to do with 'Load Control'..

They think of the Greek letter, rather than it being an abbreviation. :nerd:
Click to expand...
PI is controlled by not eating as many Steak & Kidney (Pies) (other types are available. ;)
 
PhilP said:
I get people asking what 'PI' (they immediately think 3.14159..) has to do with 'Load Control'..

They think of the Greek letter, rather than it being an abbreviation. :nerd:
Click to expand...
Indeed, to use PI as an acronym without an expansion of that acronym is at best confusing.
 
Also, it appears that 2 of the 3 separately adjustable BEMF parameters are lumped into one.

I prefer the ability to tune each of the 3 independently, but it can be difficult for users if they do not take the time to understand, and perhaps Massoth figures it was too confusing.

Sort of like the difference between my Mercedes and my Audi... The Mercedes has a simplified dash with not all information presented, just what they think I need. My Audi treats me with more respect and lets me make the decision how much to see and control.

(I like my Audi better, but unfortunately its not a convertible, so like decoders you have to make compromises)

Greg
 
Greg Elmassian said:
Also, it appears that 2 of the 3 separately adjustable BEMF parameters are lumped into one.

I prefer the ability to tune each of the 3 independently, but it can be difficult for users if they do not take the time to understand, and perhaps Massoth figures it was too confusing.

Sort of like the difference between my Mercedes and my Audi... The Mercedes has a simplified dash with not all information presented, just what they think I need. My Audi treats me with more respect and lets me make the decision how much to see and control.

(I like my Audi better, but unfortunately its not a convertible, so like decoders you have to make compromises)

Greg
Click to expand...
Merc convertible or Audi saloon, some compromise ;)
 
PID is a very common acronym in the world of control systems. Its been awhile since I've actually tried to understand but it's basically a method of control to smoothly and rapidly maintain a given setpoint under conditions of system upset. We used a PID controller to move the control rod that maintained power when in "automatic" at the nuclear research reactor I used to run. As I understand it the proportional, P, setting causes a given amount of input to the controlling variable based on how far a system's measured value deviates from the desired setting. The integral, I, setting is how often the P setting is repeated if needed to get back to the setpoint. The differential, D, setting adjusts the P and I input to the controlling variable based on how rapidly the measured value is responding. It will dial back the controlling variable input and is selected to minimize both overshoot and undershoot of the measured value's desired control setpoint.
 
I see you clearly have the gist of it.

I normally explain that BEMF can control variations in speed irrespective of changes in load, and you can change the "window" in time over which it can be controlled.

So some BEMF systems on trains have a very long window, and one manufacturer calls it "cruise control", set to make it so a locomotive keeps the same speed on the flat, up and down grades.

Another use is with a much smaller "window" in time, that that one is helpful in smooth running at slow speeds, where intermittent changes in friction will make make a motor not run smoothly.

I think that is a reasonable overview and explanation for most. What is surprising when a manufacturer does not give access to all 3 parameters REQUIRED for the equation to operate.

Greg
 
I'll see if I can get Massoth support to give me more information on this topic. I'm sure I'm not the only one confused. If I get anything useful I'll report back.
 
So it looks like CVs 60 and 61 are BEMF related, and perhapsCV63...

I found a long thread on setting these parameters, where a so-called expert could not get things set right, and also steadfastly refused to work with cv63.....

Not sure it is helpful on how to make things better, but it does give some experience with someone trying to set the parameters:

forums.mylargescale.com

Massoth XLS BEMF Slow Speed Issue

I've got an LGB Forney (China manufacturer, if that makes a difference with regard to the motor) fitted with a Massoth XLS decoder (Forney sound file). At issue, with the BEMF motor control turned on, the locomotive lurches to a slow-to-moderate crawl as soon as I bump the throttle to speed step...
forums.mylargescale.com forums.mylargescale.com

(warning, Massoth foamers might not like this thread)

Greg
 
John S said:
JMRI Massoth XLM version 1.4, dated 24 Jan 2011 only includes info up to Firmware version 2.6.

Massoth Service Tool 3.3, Massoth XLM from Firmware Revisions and version 2.90, dated 09/07/14 to Firmware Revisions and up to and including version 4.2, dated 20/09/18.

CV49, to activate Load Control, Bit 1 with a value of 2, Digital Load Control ON.
CV49, is a digital binary switch, and NOT a physical switch that requires an operator to push a Function Key.

CV49​
Bit 0​
Bit 1​
Bit 2​
Bit 3​
Bit 4​
OFF​
0​
0​
0​
0​
0​
ON​
1​
2​
4​
8​
16​
CV9, default value 0 for 16kHz, selectable values of 0,1,2 and 3.

The motor control frequency is defined by one of four options in CV9. The integrated load control works only when the 16 kHz option is selected.

CV64, default Function Key 7.
Load Control ON-OFF (Physical action to push Function Key), Function Keys 1 to 16 are valid selectable options, Function Key 0 is OFF.
Also any Acceleration-Deceleration settings in CV3 and CV4 may be disabled (during shunting) by the Function Key value stored in CV64.

CV59, default Function Key 8.
Switching Speed Half Speed command allocation, Function Keys 1 to 16 are valid selectable options, Function Key 0 is OFF.

CV60, default value 2, range of CV values 1 -15. The higher the value, stronger the readjustment.
Maximum readjustment factor, by decreasing the value in CV60, this then decreases the maximum allowed readjustment per adjustment interval. The decoder will adjust in smaller steps and restricts the tendency to over-control.

CV61, default value 60, range of CV values 1-255.The higher the value, slower the readjustment.
Readjustment retardation, increasing the value in CV61, increases the time between two adjustment intervals. The decoder will then carry out any adjustments at less frequent intervals.

CV62, default value 255, range of CV values 1-255. Value of 1 for fast limitation. Values up to 254 for slow limitation, and a value of 255 for no limitation.
Readjustment strength, the value sets the limit for the decoder to readjust either up to maximum power or to a limit as set by the Operator.
If CV62 was set to a value of 128, the readjustment strength will be limited to 50%. If and when the limit is reached the decoder will stop adjusting, and the locomotive will slow down when the load is increased.

CV63, default value 60**, range of values from 0 to 255.
Start up behaviour, defines the driving characteristics of slow driving. A slower adjustment value results in smoother slow speed operation.
CV63 defines the speed range for slow driving in increments of 16 speed steps from 16, 32, 48 up to speed step 254.

Ensure CV3 and CV4 are set to 0 prior to testing the various settings and CV's used for Load Control.
After amending the various settings and CV's for Load Control, reinstate the values for CV3 and CV4.

** Contact Massoth Support for further advice, prior to amending this value.

Correct as of 18/11/2019, subject to amendments and corrections, if and when deemed necessary.
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Thanks John, informative and helpful as always. I was waiting for you to chip in!
This writeup is a great improvement in the published manuals, and I see there is no mention of "PI-Load Control" unless you edited that out! :)
I don't need the "cruise control" features as I have in indoor railway with short trains and no gradients running at narrow gauge scale speeds, but the slow speed operations are important to me. I will do some more testing with the information above.
 
I have to admit after following this thread (as I do with most technical threads), I haven't a clue what it really means, and how I would manage the output, so really pleased I haven't gone down the DCC route, and threads like these that show how complex and difficult the subject can be to understand (even by experienced users) does not pursued me to move to DCC.
 
JimmyB said:
I have to admit after following this thread (as I do with most technical threads), I haven't a clue what it really means, and how I would manage the output, so really pleased I haven't gone down the DCC route, and threads like these that show how complex and difficult the subject can be to understand (even by experienced users) does not pursued me to move to DCC.
Click to expand...
Watch out, you may have PID control built into your radio gear!

Geoff
 
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