About 20 some years ago I had to pack up any model RR equipment I had due to a relocation. At that time there was talk of the new, great way of controlling several trains on a layout with one controller. I have finally gotten a living quarter with enough room to try to set up a system again.
Naturally, all the talk is about how great DCC is. I am not mechanically or electrically challenged, and I did plenty of research on whether I wanted to undertake the additional expense of DCC. Naturally, being so excited about getting back into the hobby and reading all the hype about DCC from manufacturers I chose to buy into the dream. It was going to be an easy thing for someone who had developed his own signaling system using relays 35 years ago.
Reality stomps its foot on my chest. Everything you try to do requires additional expenditures and significant work in order to get it to work. After these 20 to 25 years there has been no advancement by manufacturers to create products that will work with each other. What is all the #$!#$ about building to NMRA standards? Okay, wires are standard colors, sometimes; functions in the decoders are kind of standardized. But what about headlights? What about connectors? What about troubleshooting help?
Manufacturers can’t even clearly explain how DCC conversion should be done, neither the DCC manufacturers nor the actual equipment manufacturers. Engines are made with incompatible lighting and electrical isolation. Switches are still being manufactured that practically need to be rebuilt in order to use DCC. Is there no one in the industry with a clue??? I know no one else in this hobby and I work strange hours so I cannot look up a club or such group that have worked out some of the problems. I cannot really afford to have someone else install decoders in the half of the engines I have worked on that do not run after decoder installation. I can’t even find out if the problem might be the decoder (that are shipped out with incorrect CV’s) or if I have blown the decoder due to electrical isolation faults that I have not detected. Even that fine public service institution, Microsoft, has troubleshooting avenues available. There is no help available in this industry, but the manufacturers relish in the flow of dollars from those of us who just happen to love railroading this much.
Norm Koplin
Seattle, WA
I took the plunge into DCC less than a year ago, so I’m a relative newbie. Unlike some others, in my first year I’ve installed some 40 decoders from nearly 10 makers. I’ve picked up a few hints and tips along the way. If you don’t mind, I’d like to share a few. Please feel free to write with more questions. I’m neither the DCC industry’s appointed apologist nor some sort of expert, but I do like things that work, and I get cranky when they don’t.
First, when you install a decoder, before you put the loco on the mainline, put it on the programming track and try to change the address from 03 to the road number. If you get errors from the system, then either the decoder is bad or else you’ve got a wiring problem. Out of forty decoders, I’ve only burned up one because I didn’t follow this advice, and I had another come in DOA. The other 38 have all worked just fine. I have, however, found bad wiring by me or frame grounds, etc. Remember, if you can’t program the address, don’t put it on the mainline — fix it first.
Second, I don’t know how many locos you own, but start easy. Install DCC on your layout and then buy one loco with a built-in decoder and get that to work. Next find a locomotive on your roster with an 8-pin NMRA plug (Not the upside down one from Life-Like!) Convert one of those. Too many guys are tackling a ten year old Rivarossi or some other project which is not for the faint-hearted. Don’t do that to yourself!
Third, understand that while you will convert some of your locos, you probably won’t convert all of them. The ones that are hard to install I’ve set aside or put on display. If and when I decided to mess with them, I will, but I sure don’t worry about it.
Fourth, you are exactly right about the industry, but then every industry has the same problems and always has. In the heyday of passenger trains, my parents complained because you couldn’t just get on a train in LA and ride it all the way to New York. You had to change trains at least once and usually in Chicago, requiring a taxi ride between stations. There are no standards to the bolt patterns, sizes, and widths of automobile wheels now or ever in the past. Just about the time the video industry got standardized on VHS, along came DVD. Now we’ve got High Definition TV which will make my two year old RCA extinct. People built all of these industries, and people buy their pencils with erasers, knowing they will make mistakes.
Fifth, I don’t know what brand system you have, what scale you are in, what brand and vintage of locos you’re trying to convert, or what type of decoders you’re attempting to install, but I sense you’re plenty frustrated. Try going to the Atlas Web site — http://forum.atlasrr.com/ — and check into the DCC forum. Get in the habit of checking back and reading what goes on. Then, when you’ve got some scale and equipment specific questions, sign on and ask. Lots of guys will come out of the woodwork to offer advice and assistance. They aren’t bothered by the limits of your knowledge. — John
Decoders operate an the duty cycle modulation principle whereby the motor power source is full on, then off, then on again, etc. Quarter speed would be full on for 25 percent and off for 75 percent, half speed would be 50-50 and so on. It is in fact an electronic switch operating about 50 to 100 times per second as used in many DCC systems and analog command control systems. At low duty cycles, up to 15 percent or so, the PM motors used in most model railroad applications draw almost their stalled current. As the duty cycle percentage increases the current decreases due to back EMF. Therefore the decoder must be able to supply the motor’s stall current for short durations. This can be observed with an oscilloscope by viewing the current waveform across a low value resistor (0.1 ohm) in series with the motor. “Silent Running” decoders on the other hand switch at much higher frequencies (around 15 KHz) so that motor inductance limits the peak switching currents to less than the motor’s DC stall current. In summary: For low frequency PWM drive, worry about the stall current. For Silent Running PWM drive, don’t worry about it. However points raised in previous “Letters” are still valid.
In Model Railroad News the phrases AC current and DC current often appear. AC means Alternating Current and DC means Direct Current so AC current really says “alternating current current” and DC current says “direct current current.” It has become popular but it is incorrect.
I look forward to receiving my copy of Model Railroad News each month. Keep up the good work.
Sincerely,
Abbott Lahti
New London, NH
I really appreciate your explanation of the various type of pulse modulations and their impact on current draw. Into this we should add the two types of amperage ratings found on many decoders: continuous and peak, where a decoder has, say, a 1.3 amp continuous and 2.0 amp peak. This implies that the decoder can handle much more than 1.3 amps for very brief intervals. In theory, the draw from pulse modulation should be picked up by the peak current rating, but getting hit with 1.6 amps for a quarter of a duty cycle a hundred times each second for several minutes can lead to overheating, the real bad guy. Loco makers haven’t published numbers on the stall currents of the motors they use since no one cared about it before, but they will need to at some time in the future. It would be nice if we didn’t have to test every single loco we buy, but until we have that information available without testing, it is in the modeler’s interest to perform current draw testing before selecting a decoder to install. Our By-The-Numbers testing usually offers this information with the understanding that this is just a single sample. — John
I just wanted to let you know how much I enjoy MRN. I got one of your trial issues and was immediately “hooked” and subscribed right away! I really enjoy your detailed and honest reviews, and I seem to hear about a lot of items here first, so that’s a big plus. I’m in S scale and have really been impressed with your non-prejudiced attitude toward my less-popular scale. Thanks for a great magazine and for being what the “others” aren’t.,
Roger W. Huber
Pasadena, TX
The Atlas N Scale Articulated Auto Carrier featured in the February issue of MRN requires only two screws for assembly. The third screw is an extra. For complete instructions and a diagramvisit our web site:
www.atlasrr.com/NFreight/nartautocarrier1.htm/
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