CV9, Motor Frequency...?

[Zerogee]

Quick question to the DCC experts out there:
What does the "motor frequency", adjusted by CV9 on Massoth decoder, actually DO? From the manual, the default setting is 16 kHz (CV9 set to 0), but the other CV9 alternative settings listed in the manual are 1 = 2 kHz, 2 = 250 Hz, 3 = 60 Hz.

What is this? Is it the rate that power pulses are sent to the motor? Should it always be on the highest frequency setting (16 kHz) or does it vary for different types of motor?

Thanks!

Jon.

 

[Neil Robinson]

What is this? Is it the rate that power pulses are sent to the motor? Should it always be on the highest frequency setting (16 kHz) or does it vary for different types of motor?

I can't speak from experience of DCC but once upon a time I knew a bit about motors.
I think it fair to say that the optimum frequency setting will vary with different types and manufactures of motor. If it were a "one size fits all" situation there would be no need for the decoder makers to provide such a CV.
I strongly suspect a less than ideal setting will cause the motor to heat up internally more than usual and, in a worst case scenario, even possibly burn out.
I fear that experimental experience may be the key to determining the best setting. I would hope the decoder makers have performed tests and that their advice should be obtained and followed.

 

[ntpntpntp]

Higher frequency seems to be favoured these days, if nothing else you get less "buzz" or "growl" from the motor. Sometimes with the high frequency I'm sure I can hear a "singing" noise.

I'm sure Neil's right that poor choice of setting could cause unwanted heat build-up. In the small scales a lot of folk maintain that the low PWM frequency of old controllers has a bad effect on some modern motors.

 

[Zerogee]

Thanks Neil - hmmm, so one would HOPE that the default setting used by Massoth is the optimum for LGB motors....
Can you (or anyone else) explain what the term "motor frequency" actually MEANS in this context?

Jon.

Edit: Nick, thanks, you posted while I was composing my earlier post; so it IS the frequency of the PWM power pulses fed to the motor by the decoder?

 

[Zerogee]

Just to give some further info, this is actually in relation to the Trainline45 V3 that I posted about yesterday (my thread about DCC chipping it with an LS and a powercap micro); while all the installation and the electronics are working fine, I'm less than impressed with TL45's actual gearbox unit - at anything above speed steps 3 or 4 under Massoth control, it seems fine - but at very low speeds (steps 1 or 2) it "growls" a lot and seems rather jerky. It was a bit that way when originally tested under analogue, but I had hoped that installing the chip might smooth it out - if anything it's made the problem more noticeable.
Looking at all the things I could think of that might be contributing to it, I wondered if CV9 could have anything to do with it? TL45 make a big thing about it being a Buhler motor (like LGB), so I'd expected a nice smooth drivetrain at all speeds....

Jon.

 

[ntpntpntp]

Hi Jon,
yes "motor frequency" in this context refers to the PWM frequency used to drive the motor.

One thing that's often said about DCC is always make sure the mechanism runs smoothly on analogue DC before contemplating chipping a loco. For a new loco, allow it to run in on DC. Don't assume the decoder will always improve things, although it is true that PWM can help sometimes with a "sticky" mechanism or a "coggy" motor it's really just masking the underlying problem. The addition of BEMF can have the effect of amplifying any jerkiness as the decoder over-compensates, so you could try turning BEMF off and see if that smooths things out?

Having a lovely Buehler motor is no guarantee of good running if the rest of the drivetrain is sticky (or too slack for that matter).

 

[Zerogee]

Further to the above, just tried a little test with altering CV9 (using POM, which makes it very quick and easy to change a value then immediately test it) - set it to 1 (2 kHz) and the motor developed a really annoying whine, so immediately switched it back to 0 (16 kHz). I have a feeling that the problem may well lie in TL45's gearbox design, which appears considerably more basic than the classic LGB design (and seems to use much thinner plastic for the casing). Though I do like the V3 despite its foibles, I REALLY hope they do a better job on the forthcoming Harz steam locos - almost makes you wonder if this isn't one of the reasons behind their much-delayed release....? I guess we'd all rather have them RIGHT, rather than NOW, though?

Has anybody seen a review of the V3 in English, by any chance, perhaps on another forum? There is a lengthy one in German in a copy of GB Profi, but short of scanning in the text (which I'm not enough of a computer geek to know how to do) there is way too much there to translate....

Jon.

Edit, once again I was typing this post as Nick replied, so we're out of step again! Thanks for the advice, Nick - and I certainly agree about there being not much point in a quality motor if the rest of the gearbox lets it down....

 

[Zerogee]

Thanks again, Nick - I think I'll drop the motor block out (fortunately quite easy to do), bridge the power/motor terminals and stick a bit of weight on top, then let it run-in under DC on the rollers, as you suggest. We'll see if it's any better after that.....

Jon.

 

[supagav]

Hi,

Sorry to muscle in on this thread but I'd like to echo Nick's comments about DCC. It's often really important to try to make sure the loco works well under analogue operation as it is often far harder to alleviate the symptoms of a bad drive-train or motor block using the chip CV's than to sort out the problem itself.

Funnily enough I had almost exactly the same problem with the Aristocraft U25B that I'm currently working on following the fitting of a chip and separate sound decoder. It had one of the first generation Aristocraft motor blocks, and coupled with the fact that the loco is now very old itself, it was hopelessly poor and juddery when starting and at slow speeds. I spent almost two or three hours one evening messing with the motor torque settings on the NCE chip only to slowly realise that the problem was really with the motor block. In the end I swapped it out for a newer Aristo version, but I guess what I'm trying to say is that it will pay off to try and get it running well under regular analogue, saving you much time and frustration further down the line. Hope you manage to get it sorted!

 

[Zerogee]

Thanks chaps, especially to Paul for the reminder re Piko motors.....

A supplementary question.... just because something has a Buhler motor, does that automatically mean that it is a top-quality seven-pole type as used by LGB - or do Buhler also make "budget" ranges.....?

Jon.

 

[ntpntpntp]

Well... they obviously do a wide range of motors. Just looking through the data sheets of the first few items in this section show they do 3-pole motors in the smaller sizes:
http://www.buehlermotor.com/EN/Products

Not sure if they do a "budget" range - probably will make whatever spec motor you want if the price is right!

 

[dunnyrail]

Have been working on my Trainline 45 Battery DCC Black Mallett having finally gone to the effort of replacing the chip with a different one a Massoth XL. I am getting slightly lumpy running and wondered if CV9 was anything to do with it. Currently set to 0 I.E 16 kHz. Now I know that the very early TL locs were not that good but this was a great runner on its original chip a eMotion XLII PluG and an eMotion S PluG module. I guess that I could (with a little difficulty) look to see what that was set to.

But would any damage occur if I were to test out the other settings on CV9?

 

[The Shed]

But would any damage occur if I were to test out the other settings on CV9?

Mainly to your ears! and probably the howling, whistling and general kangaroo effect on the motor and gears won't do it a lot of good either!

The old adage, if it ain't broke, don't fix it!

More useful to look at CV2, CV5 and CV6, check CV29 if you are using these as the internal speed table, these are based on full track voltage of around 22V, would need slight tinkering and adjusting in relation to available battery voltage, or if able create a user speed table....

Also have a look at CV49, CV60, CV61 and CV62........

eMotion XLII PluG
CV2 = 2
CV3 = 3
CV4 = 3
CV5 =200
CV6 = 50
CV9 N/A
CV29 = 4
CV49 =2
CV60 = 4
CV61 =2
CV62 =100