Revo DCC Handset / CV29 help

[DGE-Railroad]

Reporting back with some positive news!

So I pulled the decoder, hooked it up to the ESU programmer and delved into the motor control section.

I'd originally intended setting CV54 to enable auto-tune, popping the loco on the rolling road and hitting F1.

I found this page though, on the very informatinve Streamlined Backshop site that reports occasions when the auto-tune doesn't help.

There's a deal of helpful information around the various CVs and the way they're exposed in the programmer, so I decided to compare the authors recommendations with the decoder settings

CV49 - DC Motor PWM Frequency: RV (Recommended Value) = 40Khz, (Decoder Value) DV = 40Khz
CV10 - Back EMF Sampling: RV = 8, DV = 8
CV56 - Regulation Influence: RV = 255, DV = 255
CV51 - Slow I value: RV = 0, DV = 0
CV52 - Slow K value : RV = trial and error, DV = 15
CV124? - Adaptive Regulation Frequency: RV = OFF, DV = ticked
CV54 - K value : RV = probably less than half of what is set, DV = 50
CV55 - I value: RV = <10, DV = 100

I reasoned I could try bringing the relevant CVs (124, 52, 54, 55) into line with the recommendations and if things didn't improve, trust to an auto-tune.
I had also thought about switching off the BEMF completely as Alan suggested, as a test. I decided to keep that in my back pocket as a last resort

Well it has indeed made an improvement - nice and smooth from a standstill to maximum speed and back again. There is still a slight lag of the front truck when starting from a standstill but I'm putting that down to the extra drag put on it, or a difference in the motors. I may look to test the drag theory at some point by removing the Shay drivetrain and checking again, but if it's behaving okay on the track...meh.

Thanks for all of the fantastically useful and knowledgable input - it was indispensable!
Darren

 

[PhilP]

Thank you for coming back with your results, and a useful looking URL.

Glad you seem to be sorted.

 

[Hutch]

Reporting back with some positive news!

So I pulled the decoder, hooked it up to the ESU programmer and delved into the motor control section.

I'd originally intended setting CV54 to enable auto-tune, popping the loco on the rolling road and hitting F1.

I found this page though, on the very informatinve Streamlined Backshop site that reports occasions when the auto-tune doesn't help.

There's a deal of helpful information around the various CVs and the way they're exposed in the programmer, so I decided to compare the authors recommendations with the decoder settings

CV49 - DC Motor PWM Frequency: RV (Recommended Value) = 40Khz, (Decoder Value) DV = 40Khz
CV10 - Back EMF Sampling: RV = 8, DV = 8
CV56 - Regulation Influence: RV = 255, DV = 255
CV51 - Slow I value: RV = 0, DV = 0
CV52 - Slow K value : RV = trial and error, DV = 15
CV124? - Adaptive Regulation Frequency: RV = OFF, DV = ticked
CV54 - K value : RV = probably less than half of what is set, DV = 50
CV55 - I value: RV = <10, DV = 100

I reasoned I could try bringing the relevant CVs (124, 52, 54, 55) into line with the recommendations and if things didn't improve, trust to an auto-tune.
I had also thought about switching off the BEMF completely as Alan suggested, as a test. I decided to keep that in my back pocket as a last resort

Well it has indeed made an improvement - nice and smooth from a standstill to maximum speed and back again. There is still a slight lag of the front truck when starting from a standstill but I'm putting that down to the extra drag put on it, or a difference in the motors. I may look to test the drag theory at some point by removing the Shay drivetrain and checking again, but if it's behaving okay on the track...meh.

Thanks for all of the fantastically useful and knowledgable input - it was indispensable!
Darren

Good data for all of us.
Thanks ---Hutch

 

[Greg Elmassian]

Congratulations. Some time in the future, you might try the "autotune", I have found that in most cases it fixes the problem well enough.

Greg

 

[DGE-Railroad]

So, here's a follow-up.
I subsequently installed an ESU 5XL in an LGB loco and had the same low-speed stuttering with the ESU-provided sound file and default decoder settings.

A bit more digging showed the issue happened below speed step 10. This tallied with the ESU LokProgrammer low speed motor settings "Largest internal speed step that uses K slow" which was also set to 10, meaning the 'slow running settings are applied up to that speed step.

I performed an Auto-Tune (set CV54 to zero, place on a rolling road and Press F1)

This much improved the slow speed running, but the top speed was nearly half what it was before Because of this compression of the speed range, the sound synchronisation was also way off.

I noted the changes the auto-tune made
CV - Before -> After
cv51 - 10 -> 2
Cv52 - 10 -> 5
Cv53 - 130 -> 82
CV54 - 50 -> 6
Cv55 - 100 -> 21
Cv56 - 255 -> 255
Cv116 - 50 -> 50

The speed range compression came about because the auto-tune reduced CV53 which is the upper voltage limit, without the decimal point. Resetting this value back to 130 after the auto-tune retained the smooth low-speed changes whilst keeping the speed range window correct.