LED Discussion Revisited
Just read your article in the February issue of Model Railroad News [The Real Story Behind Resistor Values and LEDs], it couldn’t have come at a better time. I have been tasked with building the control panel for our club’s new layout, so there are a few questions I need answering, if you will bear with me.
First off, your article does not make any mention of driving voltage for LEDs, is there a preferred voltage range that LEDs can be safely operated? We are considering a 6 volt to 12 volt, 2 to 3 amp regulated DC power supply for Bipolar red/ green LEDs for switch position indicators. Would this be suitable, or should we be considering another approach? Would the Bipolar LEDs work or should we use separate Red and Green LEDs? I have built a resistor switchable selection box ranging from 1k ohm to 120 ohm, so I should be able to select the appropriate resistor required. Your comments would be much appreciated.
Thank you.
Denby Isaac
Cocoa Beach, FL
Thanks for your letter, Denby. I shared your question with Jim Hinds of Richmond Controls. What follows is his response. — P. Scandura
The article addresses LED voltage in the last paragraph of the sidebar on page 51: LED Colors and VLED.
For LEDs, it is the current and not the voltage that must be controlled. The LED will exhibit whatever voltage drop it wants, and it is a function of the LEDs color. This is the LEDs choice, not the user’s. When using LEDs, you need to examine how you think about driving lamps and then totally reverse that thinking, as follows:
For a lamp, for example, you should start with a power supply capable of supplying at least whatever current the lamp decides to draw when operating “normally,” and then you adjust the applied voltage to get the brightness you want. For an LED, you should start with a power supply capable of supplying at least whatever voltage the LED decides to take when operating “normally,” and then you adjust the current to get the brightness you want. Note that the lamp current and the LED voltage are not things you control in the normal operating regions; it is the lamp voltage and LED current you control. The easiest way to control an LED’s current is via a series current-limiting resistor.
Be sure to read the first bullet in the Summary — that describes what happens if you apply just a bit too much voltage to an LED without controlling the current. If you apply still more voltage you get a flashbulb response (one time only, very brief and very bright).
For most LEDs, the best question to ask would be “is there a safe current range in which LEDs can be safely operated?”. For the type of 3 mm LEDs normally encountered in model railroading, the maximum current limit is normally 30 mA. For highly efficient LEDs like the Golden White and Sunny White varieties, people have been known to complain about painful brightness at currents of 10 mA and greater. I consider 3 mA to be ideal for these. For surface mount LEDs, which have less mass for use in dissipating heat, typical maximum current ratings are around 20 mA, and 3 mA looks quite bright. With your 3 Amp supply, this means you could drive 1,000 of them at one time.
In my opinion, your 6 to 12 volt power supply is ideal. Bipolar LEDs can also be ideal, but you have to be careful to get one that works properly with the type of switch you plan to use. The bipolar LEDs with two leads are wired back-to-back internally, so you need to reverse the polarity to change the color. This should be great if you plan to use Tortoise switch motors, because they generally need a polarity change to reverse positions. The two-color LEDs with three leads generally share a common cathode (negative terminal, in the center), so you need to switch one anode off while switching the other on to change the color. Separate LEDs could also work.
With two-color (red/green) LEDs, sometimes you can get something that looks yellow by driving the red and green at the same time (for the common cathode type) or using AC (for the two-pin type).
In case you don’t already know, you can buy low-cost plastic lenses that are ideal for mounting 3 mm and 5 mm LEDs in control panels. They hold the LED in place, give the panel a finished look, and scatter the light over a wider angle. — Jim Hinds of Richmond Controls
Power Supply Quandary
I am considering purchasing a DCC starter set such as the Digitrax Super Chief 8 amp. Would I need to purchase their 20 amp power supply also? Could I use my old Lionel ZW transformer as a power supply for DCC? It has adjustable AC accessory voltage terminals. I don’t know how many amps it puts out, but I imagine it’s plenty.
John Wegner
Roeland Park, KS
Thanks for your question, John. In my experience the power source for your DCC Command Station/Booster can be an old power pack, a bench power supply, an official Digitrax supply, etc. Any one of these will work, provided you adhere to the input voltage and current ratings of your DCC system. In the case of the DCS200 Command Station 8 amp Booster, Digitrax specifies either 50/60Hz AC or DC input, with a minimum input voltage of 12V AC or DC and maximum input voltage of 22V AC or 28V DC. The power supply should include overload protection as well. If your old Lionel ZW can be adjusted within those limits you should be fine.
Also don’t forget about keeping the power supply and DCS200 cool; I recommend using an inexpensive 6-inch or 8-inch desk fan (you can pick one up at K-Mart, Target, Wal-Mart, etc.) to blow air across the DCS200 heat sink. It you don’t keep the booster cool it will eventually reach an over temperature state and shut down. This is very important if you operate several locomotives simultaneously causing the booster to run near its 8 amp maximum rating. One easy way to ensure the fan operates whenever the system is powered on is to plug the fan and the power supply into the same power strip. — P. Scandura
DCC Anomalies
Hopefully you are still addressing “anomalies” about DCC (Jan 2004 issue). If so, I have a LokSound XL V3.5; a Lenz LH100 and LZV100 to operate it. I have tried to install it in a Bachmann G-scale Spectrum Mogul 2-6-0 (Bachmann #81496). Here are my current problems doing this. (Actually, I have now turned the engine over to my Lenz dealer — Hobby Gauge, Melbourne, FL — for help, and he has worked on it for over 4 hours and cannot figure it out yet, either.) The sound works fine, however, the engine motor does not respond to the LH100 and LZV100 control. If you apply power to the engine from the LH100 and then switch the NMRA direction switch rapidly back and forth the (apparent) pulse gets the motor running, however, it will not stay running or start again after stopping it. In other words hooking up the LokSound decoder XL V3.5 as directed does not operate the Bachmann engine motor. (There is nothing easy or specific about hooking up the smoke unit or the firebox leads either). So Bachmann/Lenz/LokSound implied “DCC ready and easy to hook up,” is far from the truth. Any suggestions would be appreciated. I’m copying this to Bachmann, Lenz, and LokSound too.
Pete Engel
Cocoa, FL
Hi, Pete. It sounds like you’ve taken all the right steps to address the problem. Your local Lenz dealer should be the first line of defense, as he can see and touch the locomotive. Keeping Bachmann and LokSound in the loop is also essential. While I have not had the opportunity to work with this particular locomotive or decoder, I have experienced strange things after installing hardwired decoders. After several hours of troubleshooting my wiring, soldering, etc., I’ve had to remove the decoder completely and return the locomotive to its factory-wired state. On at least one occasion the locomotive still didn’t work; the eventual problem turned out to be a stray piece of wire had found its way into the motor. If your dealer is unable to figure out the problem, you might try removing the decoder to see if the locomotive still works under normal DC. — P. Scandura
DCC Brand Comparison
I have been reading your column on DCC from the beginning. I have found it to be informative and I like the way you break the subject down into easily digestible bites. I have read a lot about DCC and think it’s the way to go, but at my age I am not looking to take on any more hassles. (I have three PCs that give me plenty of that.) However, I am about ready to take the plunge into DCC and I have a number of DCC engines, most with sound, so that is not the drawback. My biggest issue is what system to go with that is fairly user friendly. I want to have radio control, so that poses some limits as I understand some brands only offer tethered systems at the present time. I think it was you who said once that a way to learn about a particular system was to operate with it, and it would be beneficial to use a system that your associates use as they can be a source of assistance. I have been operating on a friend’s layout for about six months and he uses Digitrax. There are some things I don’t like about it, although, it and your column have convinced me to take the plunge. I am leaning towards the NCE system as it has duplex communication and I think that would be useful. I also belong to a module group and we are planning to adopt DCC for our switching line. (We plan to keep the mainlines DC for the present time, but there are many benefits to using it on the switching line.) I want to use the same system that we adopt as a group and since I am leading the committee to pick a system I can have an impact. There is one fellow in the group who uses Digitrax at a local club and has a tethered system for his home use, but I am not sold on Digitrax. Not that it is not a good system, but I am not sure it is what I want.
Now to the point of all of this rambling. Have you ever considered publishing an article comparing the various brands, listing the pros and cons of each and some evaluation of the features of each? I know you have done some limited comparisons in the past, but I can’t recall anything recent, plus the systems are rapidly evolving so anything a year or more old would not be 100 percent current.
Just some of my thoughts. Keep up the good work.
Thanks,
Wil Davis
via e-mail
Thanks for writing Wil, and thanks for your support of our DCC coverage here at Model Railroad News. More than once we have discussed publishing a system comparison article, and while we are currently working a series that will do so in a limited way, it is still far from a full-blown system comparison. There are already several articles and how-to books in the model railroading press that provide DCC system comparisons, but they are typically limited to functional comparisons only and don’t say much about pros and cons of each system. The reason for this is simple; choosing a DCC system is more than picking features, it’s about picking an operating philosophy that works for you and serves your needs. Just because a system has the features you want, it still may not suit your needs. For example, many DCC systems support functions F0 through F12, enabling them to support sound decoders that typically use the higher function numbers. However, not all systems make it easy to access those function buttons. Some give “one-button” access only to F0-F9, requiring a shift-key or other sequence to get to F10-F12, while other systems give all functions one-button access. Depending upon how often you use the upper functions, one-button access may not be that important to you (especially if having it means a larger throttle with lots of buttons!). As a product reviewer, we can point out the differences between systems but really can’t say which the right system is for you.
I’ve had the opportunity to use systems from Bachmann, Digitrax, Lenz, and ZIMO. Some are “full-featured” systems while others are beginner systems. While there is some commonality between them, each of them implements a design strategy espoused by their manufacturer. In my opinion there is no right or wrong strategy; all companies follow the approach they’ve determined best for their customers. The important thing is to judge for yourself the approach that works best for you.
Your letter says that you are leading a committee to choose the DCC for your club. One suggested way of approaching this is to first determine your list of “must have” features, then your list of “nice to have” features. Once you can agree on those, make arrangements to visit clubs, hobby shops, or other layouts that use the various DCC systems available. It sounds like you’ve done some of this already and quite frankly, that’s the best way to go. Reading a system comparison article is only the first step; it may help you narrow down the field. But you can’t pick a system just by reading about it; you have to pick it up and try it out.
Good luck with your selection committee.
— P. Scandura
Installing LokSound Decoders in Athearn Ready-To-Roll Locos
Before my question, I’d like to say you have probably the best model railroad publication; although, you have forced me to buy more products than I really need. I probably wouldn’t have even known about them if it weren’t for your publication. At any rate I’m enjoying them, so keep up the good work.
Now for the DCC question, how would one go about wiring the NMRA 8-pin socket on an Athearn Ready-To-Roll Locomotive? I know it is very simple to use the 9-pin plug, but I want to install LokSound decoders in these engines. In my opinion they are the best sound decoders out there. Hope it’s not as much work as I think it is.
George Stanko
Lakewood, CO
Thanks for the kudos, George; we appreciate them. I feel the same way; not only about the magazine, but the number of items that get added to my wish list. There isn’t an issue that doesn’t tempt me to change era, scale, or any of a number of other things.
According to Athearn, installing an eight-pin decoder in Ready-To-Roll locomotives is a bit more difficult than using the nine-pin, but it’s still very doable. There are holes for decoder installation in the locomotive’s adaptor board. Please note these holes are not a plug but merely holes. You will need to do one of two things. First, you could solder the plug from the decoder directly into the holes in the board (be careful to note that one hole has a square solder tab around the hole where the others are round; this is the #1 pin). The second option is to purchase the plug socket from one of the DCC manufacturers, solder the plug into the holes, and simply plug the decoder into the socket. Either way, be sure to remove the nine-pin jumper board from the nine-pin pigtail. It is not used in any DCC application regardless of whether you use an eight-pin or nine-pin socket.
A big tip ‘o the hat to Athearn for the information. — B. Cawthon
Have you been to the toy department at your local Wal-Mart? At ours there is a nice selection of 1/87th vehicles. In the price range of $3.97 there are several truck tractors and cars with campers; in the $1.97 price range there are two different groups of cars — one type comes in a black box and another set which is called Cherries. The Cherry set of individual cars are: 1972 AMC Pacer, 1972 AMC Gremlin, 1976 Ford Pinto Wagon, 1979 Mercury Bobcat, 1981 Ford Escort, and a 1984 Ford Tempo.
The above mentioned vehicles come in individual display cases. Also offered is a nice selection of 1/87th scale construction equipment consisting of a bull dozer, motor grader, back hoe crane, front end loader, and a water wagon for the price of $5.97.
Steve Hubbard
Litchfield, MI
And there’s more coming: Real Rides is a new brand about which little is known other than there’s space for it on Wal-Mart’s shelf plans. In addition, I recently heard a well-known major toy maker is planning to test the HO-scale waters.
I’ve had toy makers tell me for years there was no market for 1/87 scale in America. In reply I would tell them the market was there; all that was needed was the products. Nice to be right now and then. — B. Cawthon
Athearn’s Fabulous ‘55 Fords: Wow! I got out of the Army in late summer 1954 and, with my Idaho-born wife of 15 months, took-off on a transcontinental trip (in my ‘51 Ford Tudor sedan) to visit my parents and to show her where I was born in northeastern Pennsylvania.
Returning to the west coast in early October, I went back to work at the same ranch that I had left two-and-a-half years earlier. My new job entitled me to have a company pickup and since all but one of the company trucks was a Ford, it was logical that I would get one, also.
My 1955 Ford F-100 came straight from the local dealer’s new car lot with only the ranch’s brand and name custom-painted on the doors and with a dealer-supplied rear bumper (rear bumpers would not become standard for at least another 20 years): a simple 4-inch channel painted Ford “Argent” (silver). Owners added their own trailer hitches. It was dark Forest Green, with factory-painted white wheels. The front, spring bumper was painted a flat black. The grille was painted white with the Ford emblem in the center. Although I drove that pickup for nine years I don’t recall if there was a passenger side arm rest and sun visor or not. The driver’s side did have them.
Now, a couple of discrepancies with the review. Standard equipment was one, driver’s side only, rear view mirror. If it was chromed I don’t remember but I’d guess it was not. Also, the brake-tail light was a single, left side only, and certainly no turn signals. After being rear-ended in a dense fog one morning I got a second rear view mirror, and a second brake/tail light and turn signals.
Air conditioning? Why, of course. Just open the wing windows to catch the breeze.
Thanks, too, for the article about the Red Ball AAR converted boxcar/troop cars. My companion and I stayed in the Railroad-owned Denali Park Hotel in 1997. I knew that the wings were ex-railroad cars but didn’t know anything of their history. I do now. Also, I keep reading here in MRN and other publications about people riding behind and in steam locomotives. I have ridden behind a UP Challenger, the DL’s “Phoebe Snow,” behind a Pocono, the ATSF’s Grand Canyon behind one of their big Northerns, and even went off to Army Basic Training at Ft. Ord aboard the SP’s “Owl” behind a GS Class; and back when I was a kid I got a cab-ride in one of the D&H’s Class J Challengers in the Carbondale, PA yard. Gee, am I that old?
Sincerely,
Chuck Coleville
Moses Lake, WA
The mid-50s Ford pickups have been among my favorite vehicles since they were new and I really am very pleased with the Athearn replicas. While you’re correct in saying passenger-side mirrors and turn signals were both factory options in those days, that doesn’t mean the Athearn trucks are incorrect. Athearn never said they were making a base-model truck, so it’s not an error that their F-100s have a couple of options like the extra mirror and taillight. After all, some of the Athearn trucks have the optional chrome bumper, too.
In addition, the so-called optional turn signals weren’t entirely optional. By 1955, dual rear lights and turn signals were mandatory in some areas. New York State, for example, required both on all new motor vehicles manufactured after January 1, 1952 and Virginia required electric turn signals on vehicles manufactured after January 1, 1955, just a couple of months after the 1955 F-100s were introduced. Just think of the Athearn Fords as “forty-eight-state” trucks, legal for registration in every state.
The optional passenger-side mirror would have been chrome because it was identical to the driver’s side mirror. The same basic mirror, which had a swiveling base, was used on both sides of all Ford light pickups from 1953 until the mid 1960s.
You didn’t note it as a discrepancy, but you remembered the front bumper on your 1955 Ford pickup was black. That is a blooper that was covered in the review. The standard front bumper on all first and second-generation F-series pickups was black. I mentioned this to Athearn and they said they would try to correct this error in future runs.
As I wrote in the review, the passenger-side armrest and sun visor became standard equipment in the 1955 model year. Even with these luxuries, pickups were still fairly Spartan. We both kidded about air-conditioning but even a heater was an option. And it would take another year for Ford to provide electric windshield wipers that would work even while the vehicle was accelerating.
I am guessing your truck would have been technically Meadow Green as Forest Green wasn’t one of the standard Ford, Lincoln, or Mercury colors in 1955. The other standard pickup colors offered were Raven Black, Banner Blue, Aquatone Blue, Waterfall Blue, Snowshoe White, Sea Sprite Green, Vermilion, and Goldenrod Yellow. As close as I can tell, the tan used on the Athearn models is what Ford called Sandalwood Tan, a passenger car color that would have been a special order on a pickup. Since the models painted in this color also have matching wheels instead of the standard white, another special-order item, it’s safe to assume these would have been special-production trucks. That might even explain the white bumper.
With all this in mind, I think there is plenty of justification for giving Athearn very high marks for producing nice models of classic American light trucks that can be used on layouts set in any period from the mid-1950s to today. — B. Cawthon
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