Kato N scale FEF TCS DCC problem

[Mark W]

Did either one of them test the installs before releasing them?  Did either one of them suspect a problem with the coreless motor?

So far, it seems not.  However, I don't know how much "Hands on" TCS would even get with the model before release.  I assume Kato just sends them the DC board schematics and 3rd parties build their decoders from that.  It's likely that by the time TCS tested the real mode, boards were already shipping out to dealers.  Although the coreless motor was a known feature way before release, and based on Marc's comment, it should have been known by manufacturers that they behave differently on DCC.   

[bobdobbs]

The installation is first rate and the decoder and engine work very well.  I assume when these decoders are being installed and tested the headlight goes on and the locomotive moves forward and backward, about all you would be looking for as a tester.   In the big scheme of things am I going to do allot of switching with my FEF? no.  Are most people gong to hook up the excursion train and set the throttle to 9 or 10 and let her run around the layout, probably.   There are quite a few of us that really enjoy the potential of this new engine and I do enjoy seeing locomotives start at a creep and accelerate slowly and smoothly.   I have a bad feeling the train set mentality and a rush to get these out to the public may leave the Kato Tcs combination lacking.   I am surprised the issues with the coreless motor were not taken into account.

[EspeeGoldenState]

Are the versions that are being affected the pre-installed K6D4? I installed mine and have had no issues with it creeping at throttle 1. I also make sure my CV2 is set to 0, but I also set my momentum on CV3 and CV4. I hate the sudden stops and starts or having to slowly speed a loco up manually.

Chris

[nstars]

Marc,
I doubt that any DCC decoder provides smooth DC to the motor.  That would mean that the motor driver was an analog circuit. Those circuits waste all the unused power as heat.  N scale decoders cannot afford big  heat sinks.

I suspect that the coreless motor friendly decoders still use PWM (and switching transistors) for driving the motor outputs. But the decoder firmware is specifically written to deal with the specific power requirement of those coreless motors. I don't know what specifically: Maybe lower or higher pulse frequency and maybe shorter duration pulses).  The BEMF feedback loop routine is most likely also written to deal with the specific BEMF output of a coreless motor.

I know it isn't straight DC, but what I ment is a current as smooth as possible. One way to smooth the output of PWM is to increase the frequency. Both Zimo and CT Elektronik feature high frequencies of 16 kHz of even 32 kHz. Especially at slow speeds you will see the differences with regular PWM. With regular PWM I have seen steam locomotive drivers vibrating back and forward at slow speeds. Don't forget that coreless motors don't have the iron core to prevent vibrating. With a high frequency decoder this behavior is gone. I do know Digitrax has a 'silent' drive, but it doesn't state the frequency. I don't know exactly the situation wIth TCS. BEMF is part of the whole software programming and it is important, but not the only important aspect. In some cases we even did get better performance with coreless motors with BEMF switched off!

Marc

[nstars]

Marc,

Thanks for the info.  I ordered a CT Electronik DCX33D and a Zimo MX621.  The CT Electronik decoders are harder to find in the US than the Zimo or ESU's, but Streamlined Backshop had one (they are now out of stock; I think I got the last one).  Going to try each of them in the FEF and see how they compare to my tweaked ESU LokPilot.  Will report on my findings (probably next week).  It may be that we're just going to have to be creative to get the best performance out of this new offering from Kato, but since I expect this motor to find its way into other Kato offerings in the future, it seems worthwhile to figure this out.

John C.

Good to hear you're going to try the CT Elektronik and Zimo. The Zimo is really good but relative expensive. The CT Elektronik are also very good. The designer used to work at Zimo and his decoders are very small. Unfortunately the DCX 33 is only a function decoder and not a motor decoder. The N Scale decoders are in the DCX 70 range. I just received another batch with a couple of DCX75, a DCX76z and the latest decoder, the DCX77z. It's really unbelievable how small that decoder is. That decoder is 7.6x5x1.8 mm.

However, as all decoders, the CT Elektronik are not perfect. Installing these decoders may result in a slower top speed.

Marc

[peteski]

I do know Digitrax has a 'silent' drive, but it doesn't state the frequency. I don't know exactly the situation wIth TCS.
Marc

One of these days I should hook up a TCS and a Digitrax motor outputs to my oscilloscope and take some measurements.

[jdcolombo]

Good to hear you're going to try the CT Elektronik and Zimo. The Zimo is really good but relative expensive. The CT Elektronik are also very good. The designer used to work at Zimo and his decoders are very small. Unfortunately the DCX 33 is only a function decoder and not a motor decoder. The N Scale decoders are in the DCX 70 range. I just received another batch with a couple of DCX75, a DCX76z and the latest decoder, the DCX77z. It's really unbelievable how small that decoder is. That decoder is 7.6x5x1.8 mm.

However, as all decoders, the CT Elektronik are not perfect. Installing these decoders may result in a slower top speed.

Marc

OOPS - yep, you're right.  Switched my order to the CT DCX74D.   I wish CT Electronik had wider distribution in the US - and I wish that they had US-prototype sound files for their sound decoders, which are even smaller than the ESU LokSound micro, and would more easily fit in our hood diesels like the GP7/9, RS3, etc.

Although . . . I suspect that ESU will have a smaller-profile decoder as a result of their work with Atlas on the S-2, Rapido on the GMD-1, and Intermountain.

No argument that the Europeans seem to do better with motor control.  For years, I used the Lenz Silver mini as my non-sound decoder; then they got hard to get, and noticeably more expensive than the ESU LokPilot, so I switched to ESU.   Anxious to try both the Zimo and CT to see how they work with the Kato.

John C.

[wcfn100]

Next time maybe some homework on DCC and coreless motors before jumping head first into it. 

Coreless motors have been used in model trains going back 15 years.  And they've had issues with BEMF since the beginning of it's use on decoders. 

I hadn't kept up with it, so the ESU decoder designed for the BEMF to work with coreless motors is great news.  The very early decoders can fry coreless motors so make sure it's something newer or that says 'super sonic' or 'silent drive' or something that indicates it sends the pulses at a very high frequency.

If you don't have the ESU, just turn BEMF off like everyone else has done the last decade. 

Jason

[peteski]

If you don't have the ESU, just turn BEMF off like everyone else has done the last decade. 

Jason

If you read earlier posts (here or in the recent related threads), tuning off BEMF is still not good enough to produce acceptable low speed even at step 1.

[wcfn100]

If you read earlier posts (here or in the recent related threads), tuning off BEMF is still not good enough to produce acceptable low speed even at step 1.

I get that.  My point was it never should have been expected that BEMF was going to help because historically is hasn't.

I can't imagine that this is the first time in a decade that low end speed control has been an issue with coreless motors and DCC.  Maybe a google search on that will yield positive results.  A good Nn3 forums could be a wealth of knowledge as well as some of those guys go back 15 years with coreless motors and DCC


Jason

[bobdobbs]

Actually running the Kato FEF with the TCS decoder in the BEMF on mode (CV61 to an odd Number) results in the slowest, but still not acceptable IMHO, speeds.  Your post is not adding anything to the solution.  We are focusing in on the Kato FEF and getting buttery slow speed operation, which can be achieved, just not from the TCS decoder.  I think results from the ESU, Lenz and CT elektronik equipped units will result in a more informative thread.  and I assume it will take a few days to get informative and useful results.  also I believe we all have done our homework on this particular situation, but need to collect more data.

[nstars]

if you read carefully the thread about hardwiring a Lokpilot decoder in the FEF3 you can see that to improve the slow speed running BEMF was reduced to 50% instead of the normal. I would be interested to know what would happen if the BEMF was turned down even further. However as I mentioned before, the key for good slow performance with a coreless motor is high frequency PWM. As Peteski mentioned, straight DC is very difficult for a decoder, so high frequency PWM is the next closest thing.

I can still remember the first time we tried to install a DCC decoder (old Digitrax without silent drive) into a locomotive with a Faulhaber 1524 coreless motor. The result was a real eye opener. It had two speed settings: 0 was stop and 1-128 was full speed . Installing a Lenz decoder with high frequency solved the problem.

Marc

[N-Jineer]

New guy late to the party....

I've just receive my FEF-3, Water Tenders and Excursion Train; although I pre-ordered the DCC version,  I actually have the DC version as that's all my retailer was able to get from his suppliers in both the US and Japan.
I'm not complaining, honest - it wasn't until 18th December he knew for certain that he was getting anything at all.

DCC and Sound will happen, and I think I'm going to follow in John C's footsteps (been watching your Videos on Trainboard and YouTube - very nice work sir) and go the 2 decoder route...

 

[jdcolombo]

New guy late to the party....

I've just receive my FEF-3, Water Tenders and Excursion Train; although I pre-ordered the DCC version,  I actually have the DC version as that's all my retailer was able to get from his suppliers in both the US and Japan.
I'm not complaining, honest - it wasn't until 18th December he knew for certain that he was getting anything at all.

DCC and Sound will happen, and I think I'm going to follow in John C's footsteps (been watching your Videos on Trainboard and YouTube - very nice work sir) and go the 2 decoder route...

 

I'm pretty satisfied with the Zimo MX621 for motor control and the Tsunami TSU-750 heavy steam in the tender for sound.   Once I figured out how to use the Zimo's speed table correctly (it's one of those decoders where the 28-step speed table interacts with CV's 2 and 5; so for something like this, you have to zero out CV's 2 and 5, and then use the speed table values exclusively), matching the chuffs to the driver rotation wasn't all that bad (took an hour, using ops-mode programming). 

But you might want to wait a while.   ESU LokSound is working on an FEF-specific sound file.  I have no idea when it will be released, but with the right tweaks to its BEMF parameters, the ESU performs almost as well at slow speed as the Zimo, and using it in a single-decoder solution would make chuff-matching a five-minute job (the ESU uses its BEMF circuitry to match chuffs; it has two CV's that you adjust, one at slow speed and one at medium speed to get the initial match, then it takes care of everything else). 

There is no "perfect" sound decoder solution yet for N scale.   But I'll keep looking!

John C.

[N-Jineer]

Thanks for the advice John.

I'm in no hurry, so I can wait and see what develops regarding the ESU LokSound.

I don't yet have a permanent layout, I just throw down some Unitrack and run trains  it's no hardship swapping out my NCE PowerCab for the KATO Powerpack in ordef to give thew FEF-3 a good run...