Lenz CV question

[CaptOblivious]

Could someone explain Lenz's CV50 to me? Esp what the 5 motor type settings do? The English docs are absolutely opaque on what the various settings for this CV mean. A quick Google search reveals that most people either ignore it, or use trial-and-error to find a good setting. Blah to that, says I.

Could someone explain, moreover, how CV50 interacts with CV9, CV113, and CV114?

[Martijn Meerts]

It's a bit of a weird feature, and them calling it "motor type" is a bit unlucky. It has nothing to do with physically different motors, but it's just a set of predefined values that adjust the motor control.

The first 4 "types" are presets, the other 2 (some people clain they're for "faulhaber" motors) are presets that can be further fine tuned with CV's 113 and 114.

The initial thought behind it (and probably why it's called motor type), is that they wanted to add presets for various physical motor types, but they quickly found out it's impossible to do. The same motor will have different characteristics in different locomotives.

What Lenz recommends, is to put a loco on the track, have it run at very slow speed (speed step 1), and start programming on main. Change the motor type while the train is running, and just leave it at the one with the best running characteristics.

No idea what CV114 does, but I believe 113 will change the width of the pulses.

There is no 1 good setting here, because a motor in a loco with 4 driven axles runs different then that same motor in a loco with only 2 driven axles, or a steam loco, or a loco with a different drivetrain etc. etc. etc.

[CaptOblivious]

Thanks, Martijn, that's very helpful. Do you know what the presets are?

Second, how does CV9 affect BEMF? It's called "BEMF Repetition Rate", but I don't know what's being repeated.

Finally, what settings should I choose to turn PWM operation off? I've found that spring-drive locos run (perhaps ironically) much worse under PWM power (and I just happen to be dealing with just that at the moment).

[Martijn Meerts]

No idea what the presets are. I got the info off the German Lenz site and the manual.

The repetition rate has something to do with the physical motor you're using. Older and lower quality (3 pole) motors will want a lower repetition rate, whereas good quality motors will want something higher. I don't know the exact details though.

I'm not sure it's possible to turn off PWM completely, but you could try setting it to motor type 4 or 5, and then play with CV's 113 and 114.

Unfortunately, the Lenz documentation expects people to know everything about PWM, BEMF, and any other term they decide to throw in there. It's the 1 thing I dislike about Lenz, and it's not just the decoders that have bad documentation. I'm reading the documentation in German, and even there it seems incomplete and sometimes just confusing.

A lot of people complain about the "motor type", saying how other brands make it much easier by explaining exactly how and what. The problem with that is, as already mentioned, that the very same motor will respond different to the presets based on which locomotive they're built into.

That reminds me though, I should have a look at my 0-scale V100 and do the motor type trial and error. The loco itself is from Lenz, and was designed with their own decoders in mind. The decoder comes pre-installed and pre-programmed. However, I do feel that it doesn't run as smooth as I would like on speed step 1. Maybe changing the motor type will fix that. Of course, the problem could also be the track, considering the bit of track I have is hand laid... Can hardly wait to get my hands on the Lenz 0-scale starter set =)

[CaptOblivious]

Bizarre, the English instructions on the German site are considerably better than the English instructions on the American site, or that came with the decoder.

http://www.digital-plus.de/pdf/SILVER_Manual_e.pdf

[update]

Also, it turns out that (surprise!) CV9 is an NMRA standard. So, from NMRA RP 9.2.2:

Configuration Variable 9                Total PWM Period

The value of CV#9 sets the nominal PWM period at the decoder output and therefore the frequency is proportional to the reciprocal of the value. The recommend formula for PWM period should be: PWM period (uS) =  (131 + MANTISSA x 4)x 2 EXP ,Where MANTISSA is in bits 0-4 bits of CV#9 (low order) and EXP is bits 5-7 for CV#9.  If the value programmed into CV-9 falls outside a decoder's capability, it is suggested (but not required) that the decoder "adjust" the value to the appropriate highest or lowest setting supported by the decoder.

[Martijn Meerts]

The american Lenz site is downright terrible. They tend to be a year behind on new product announcements and such ;)

I can't say I completely understand the PWM formula, but then again, I haven't played around with the Lenz decoders that much ;)

[CaptOblivious]

The american Lenz site is downright terrible. They tend to be a year behind on new product announcements and such ;)

I can't say I completely understand the PWM formula, but then again, I haven't played around with the Lenz decoders that much ;)

I understand the formula…I just don't get the rationale for it. Ah well. Setting CV9 to 0 doesn't turn off PWM is all I really needed to know :D

[inobu]

The PWM (Pulse Width Modulation) determines the rate in which the DC motor is energized. The best example is spinning a
bike wheel.

Remember spinning the tire on your bike. You would hit or slap the tire and it would rotate. Slow steady taps would keep it rotating. Increase the tapping rate and duration and you controlled the speed.

So, your hand act as the decoder, the rate of your tapping is the frequency and the duration of your hands contact with the tire is the width of the Pulse.     

Here is good data for PWM and CV9 and CV94.  http://www.ncedcc.com/pdf/pwm-desc.pdf

These values allow you to tune your motor control.

Inobu