Welcome to the forum   
Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Share
Options
View
Go to last post in this topic Go to first unread post in this topic
Offline fje  
#1 Posted : 30 June 2020 22:38:42(UTC)
fje

Spain   
Joined: 14/02/2011(UTC)
Posts: 103
Location: Madrid
Hi, still working with the new 60906 decoder from Märklin. I installed one of them in a Märklin 3016, keeping its original SFCM motor 3-poles. It seems to me that now it produces more noise in the start and in low speed (and the same in my 3005 that I put the same decoder).

Today I did another test and, keeping the decoder in the 3016, I used an analog Märklin 6647 transformer. The noise is much lower (almost none) and the start is much more smooth than when using digital.

I thought that it could be the current type or form that arrives to the motor, but, being always the decoder in place, it should be the same.. or it is not?

I changed the CV 2 value, it was at 50, I dropped it to 30, but then it is not almost able to start, and the noise is still high. Finally I left it at value 40, it start somehow smooth (even not as with analog) but the noise, is still there, much more than with analog transformer.

So, my question to someone with technical/electronic skill enough, why it produces much more noise when using digital than with analog current in the tracks, even being the same decoder connected to the motor? Could it be the output current of the decoder different when it is feeded with analog than with digital and that could justify that the rotor behavior is different and it is more noisy?

Most probably changing the current/original motor with a 5-poles rotor (as a friend already did) surely the result will be much better in terms of smooth start and no noise, but I would like to stay with the original motor.

Thanks and kind regards.

Javier
Offline JohnjeanB  
#2 Posted : 01 July 2020 01:00:04(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 993
Location: Paris, France
Hi Javier
I am not a specialist but here is the little I know:
- the noise you hear is related to the frequency used to modulate the power to the motor (alas, unlike normal msd3 decoders there seems to be no CV for that frequency

- CV2 is the minimum speed so IMO it should only allows you to get lower speed and nothing else. It should be lowered until a value allowing the loco to start repeatedly /reliably

- normally (just my opinion) there is no reason to change the motor's driving method (frequency, etc) depending on the signal source (analog or digital) although the key difference is that in analog mode, at low speed there is very little power (very little noise) whereas with digital, even at low speed you have the full voltage (20 V sliced rapidly)

- on other Märklin decoders (60975, 60976; 60977- mSD3) CV 54 is the adjustment parameter K (factory value = 20) and CV 55 is the adjustment parameter I (factory value = 15)

I don't know if these CVs are working on this decoder 60906 (dedicated for a 3 pole series motor after all). I would try to change the frequency of speed control using the CV 55 but preferably by reading first its value using a CS2 or CS3.
Sorry it is not much. Try to double check this information.
Cheers
Jean
My lay-out videos
latest vid
humping yard
Offline fje  
#3 Posted : 01 July 2020 08:34:27(UTC)
fje

Spain   
Joined: 14/02/2011(UTC)
Posts: 103
Location: Madrid
Jean, bonjour et merci.

This was my first assumption, I tried to work with CV 53, but this gave to me a read of 0 and no way to write, always error. I will try again with CVs 54/55.

Anyway, could this imply that when working with analog current the signal is passing directly from the input of the decoder to its output? and in the case of digital, the decoder is converting it to a kind of PWM? This could be the reason for the different behavior I feel.

I will try to do the new test today or tomorrow and will come with results.

Kind regards.

Javier
Offline ktsolias  
#4 Posted : 01 July 2020 08:53:32(UTC)
ktsolias

Greece   
Joined: 01/05/2016(UTC)
Posts: 489
Location: Athens
Hi

My experience with the 60906 decoder:

Very noisy in low revs
Smooth running
Suitable better for LFCM and LSCM motors
Wrong results with DCM motors


I recommend the use of the 60906 only in locos where the use of a 5pole DC motor is impossible

Costas
Offline H0  
#5 Posted : 01 July 2020 09:12:46(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 13,792
Location: DE-NW
Originally Posted by: JohnjeanB Go to Quoted Post
- on other Märklin decoders (60975, 60976; 60977- mSD3) CV 54 is the adjustment parameter K (factory value = 20) and CV 55 is the adjustment parameter I (factory value = 15)
Those parameters adjust the load regulation implemented with Back EMF. The 60906 does not have load regulation and therefore there are no parameters to adjust the load regulation.


Originally Posted by: fje Go to Quoted Post
Anyway, could this imply that when working with analog current the signal is passing directly from the input of the decoder to its output? and in the case of digital, the decoder is converting it to a kind of PWM?
With digital operation the decoder reduces the voltage passed to the motor using PWM.
With analogue operation the track voltage varies anyway and PWM is not needed or less radical than with digital operation.
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
UserPostedImage
thanks 1 user liked this useful post by H0
Offline JohnjeanB  
#6 Posted : 01 July 2020 10:56:16(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 993
Location: Paris, France
Hi Javier
Originally Posted by: fje Go to Quoted Post

Anyway, could this imply that when working with analog current the signal is passing directly from the input of the decoder to its output? and in the case of digital, the decoder is converting it to a kind of PWM? This could be the reason for the different behavior I feel.


I don't know but it seems the motor is driven by a chopped voltage from the rectified track voltage (constant in digital, speed-related in analog).

The frequency and duty ratio (Pulse Width Modulation-PWM) will determine the motor speed and are influenced by the type of track voltage (digital / analog) so in good logic, in analog mode because of low feed voltage (approx 6 VAC), for the same motor speed, the duty ratio will be much higher than in digital mode (almost 100% at low speed in analog when very little in digital thus causing (may be) the noise you hear.

Cheers
Jean


My lay-out videos
latest vid
humping yard
Offline fje  
#7 Posted : 01 July 2020 12:58:43(UTC)
fje

Spain   
Joined: 14/02/2011(UTC)
Posts: 103
Location: Madrid
Thanks for all your answers.

At the end, very clear: 60906 noisy decoder in digital, easy to install, specially where there is space problem to change the stator (as in 3005), but noisy in digital use.

Would it be any electronic add-on to change the PWM form? Or is it 100% related to the PWM frequency and, if this is the case, no way to solve it?

Regards
Online kiwiAlan  
#8 Posted : 01 July 2020 15:40:46(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 5,211
Location: ENGLAND, Didcot
Originally Posted by: fje Go to Quoted Post
Thanks for all your answers.

At the end, very clear: 60906 noisy decoder in digital, easy to install, specially where there is space problem to change the stator (as in 3005), but noisy in digital use.

Would it be any electronic add-on to change the PWM form? Or is it 100% related to the PWM frequency and, if this is the case, no way to solve it?

Regards


with a 3 pole motor you cannot use a high PWM frequency because of iron losses in the motor core and magnet core.. This will cause excessive heating. Unfortunately there is little that can be done about this apart from keeping the PWM frequency at a frequency that is likely to be audible.

I suspect a significant amount of the noise is coming from the field magnet, and when run in analogue mode the magnet is being driven differently than when in digital mode, which could account for the different noise level.

thanks 2 users liked this useful post by kiwiAlan
Offline fje  
#9 Posted : 01 July 2020 16:45:44(UTC)
fje

Spain   
Joined: 14/02/2011(UTC)
Posts: 103
Location: Madrid
Thanks to everyone, it seems that it is the "con" to pay in exchange of the "pro" of an easy digitalization (even some times the only way, as in my 3005) and not too expensive.

Thanks again.

Javier
Users browsing this topic
OceanSpiders 2.0
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

| Powered by YAF.NET | YAF.NET © 2003-2020, Yet Another Forum.NET
This page was generated in 0.520 seconds.