I've been using TCS BEMF-capable drop-ins for the engines where they are supported, but I also need to buy some wired decoders for a number of engines where no drop-ins are available. In doing a search on-line I ran across some admittedly old but interesting information about the low speed capabilities of some BEMF decoders. Apparently the way it's implemented can have a difference. http://tonystrains.com/technews/stef_load_comp.htm http://www.rmweb.co.uk/forum/viewtopic.php?f=10&t=32457&start=0 (especially Nigelcliffe's comments about halfway down) I happened to be looking at the Silver Mini, DZ125, and the TCS Z2. Can anyone comment on their experience with this particular issue and any of these decoders? Is there a brand (besides Zimo which is like unobtanium here) which has superior low speed performance with the typical motors used in many N scale locos?
I exclusively use the Lenz silver mini decoder for many of my hard wired installations that aren't sound related. It's a fine decoder and I highly recommend it. All of my hard wired loco's that have the Lenz silver mini decoder can run at the speed of one "tie at a time". The Lenz gold mini decoder is a higher priced version of the same decoder.
I trust your judgement Bob, but I am then also at a loss to reconcile that Nigel guy's comparison. It seems like even with iron core motors it didn't do as well as the mysterious European decoders, and I sense that he was admitting that the DZ125 was a close comparison to his favorite. Do you have any experience yet with the 125? I'm wondering if the TCS decoders with "non user-adjustable" BEMF may be a bit of a limiting factor.
Tony, if you are using the TCS drop-ins, why not use the TCS M-series hard-wired versions? Same BEMF features as the drop-ins. It really depends on what you call 'user-adjustable' BEMF. I'm under the impression you can set the BEMF cut out point where the dither feature comes into play on TCS decoders.
I thought the M series was a bit bigger than the Silver Mini or DZ125. Wasn't sure if it would fit in a couple of the N scale engines I'm looking to convert. I read the instructions, and the PDF on the TCS website, and I have to admit I was a bit confused. Their BEMF feature cartainly seems to be "self-adjusting", and it seemed like it was either BEMF or dither - with no way to do any sort of hand off. But it's quite possible I misunderstood. Edit: so I misunderstood. I reread the BEMF stuff on the TCS website and see that it can be made to handoff.
I prefer not to use Digitrax decoders if I can avoid them. Lenz has an excellent waranty policy. I've used the Lenz mini silver decoder for several years now. There is one Zimo dealer in North America for your information
I agree with Bob. I've used Lenz silver mini wired decoders in a number of steam and diesel units. All of these will creep along at 1 smph with the Lenz. Maybe there are better decoders out there, but the Lenz is widely available, has excellent factory support (great warranty policy) and fits just about anywhere. John C.
Thanks John. I haven't gotten to those engines yet so I am still looking over the features and sizes of the various small decoders. Have you experimented with the Lenz BEMF and/or dither functions to see how much "tweakability" there is in extreme slow speed performance? So far with my four axle Atlases and the TCS drop in decoders I've seen speeds as low as ~.3 smph (yes, POINT 3). Having said that, I wish their BEMF capability had some user control beyond being able to cut it off.
The Lenz has a number of CV's that let you play with the BEMF function. First, there is CV9, which lets you vary the repetition rate. CV50 lets you select from 5 different "motor types" and also lets you vary the frequency of the motor control between 19 and 23khz; motor types 4 and 5 can then be further customized in CV's 113 and 114 for PWM value and duty cycle. Unfortunately, the Lenz "manual" that comes with the silver mini doesn't document these features well (e.g., it doesn't tell you what, exactly, these things do). I've played around with them some and found some improvement in switching "motor types" in CV50 for my LifeLike switchers, but otherwise I don't notice much difference; it could be just the way I operate. But I can tell you that with just standard settings, I can get an Atlas (China) GP9 torpedo tube unit to take 3 seconds to go one tie. I don't know what that is in terms of smph, but it's got to be slow . . . John C.
Let's not confuse BEMF with varying forms of motor control such as dither or PWM. My understanding of the purpose of BEMF in decoders is to monitor the rotational speed of the motor through measurement of the AC voltage generated as the poles (armatures) pass the magnets. As the motor reacts to differing load conditions, slows or races, the decoder increases or decreases the DC voltage to the motor to maintain the initial set speed. It's the adjustment of PWM or dither that controls the motor action, particularly at very low speeds, much like a pulse DC power pack does. It is set to your preferences and needs.
Correction. There are 15 ZIMO dealers in the US and Canada. They are all listed on the ZIMO web site. Regards, Art ZIMO Agency of North America http://www.mrsonline.net
