DCC Dilemma, Electrical Shorts – Defined

Since shorts seem to be present and  at the heart of each and every layout.  The question is how do we eliminate the majority of them?  Answer that and you will be a hero among-est the model railroad and toy train set.

Suspect to DCC operators, is/are shorts responsible for decoder failure?  The Question is what causes the decoder to fail?   As in having to set it back to factory default.   Are shorts  killing the memory in our decoders?

Right about now I need to refer you to DCC Guy.  He has some interesting answers.
In the meantime let’s start at the beginning.  How about a definition?

Short defined:
“A low-resistance connection between two points in an electric circuit through which the current tends to flow rather than along the intended path. A short circuit can damage the circuit by overheating”, courtesy of Free Dictionary.

See: http://www.thefreedictionary.com/short+circuit

Why should we be concerned about short’s? Well, short’s just aren’t fun. They disrupt the train operations and are frustrating to deal with, especially for those “Hog Heads,” manning the throttles. Once a short occurs the whole layout goes down as in non-operational. Not Good!

There have been times on my Analog DC model railroads and on others I’ve visited. When the power dropped out from underneath us and the trains ground to a halt. Sure enough the little red light on the power supply and/or the meter’s attached, all indicate a “Short”. Where? Here’s a hint, look under the locomotive. You guessed it, in the switch mechanism. Finding it can become a real source of frustration. Not fun! And when a number of us finally narrowed it down we discovered the following:

  • It was the live points  (opposite polarity)  making contact with the metal wheels causing a short.
  • The rails that come together on the diverging side of the switch mechanism at the frog and metal wheels that overlap making contact resulting in  a short.
  • Then there’s how the power routes or doesn’t route through the switches.  How we did or didn’t we wire things in?
  • Isolation Gaps: The way we did or didn’t …cut in the gaps?

Do I dare say an age old problem that doesn’t want to go away.

Do we want to take into account what the Gremlins and Mr. Murphy have up their sleeve, for the next operations night? I could swear, I’ve heard him laughing his @$$ off at the cute disruptions he’s created. I’m with you….we don’t need that… I don’t think so!

Problems Manifested and/or Anomalies:

As I’ve worked on others layouts and watched decoders die on line, I’m convinced there is a problem. The cause and affect isn’t obvious. The proof we are all looking for is lacking. This anomaly is haunting just about every DCC operator out there. It appears the decoder will work one day and when you go to crank everything up the next day, nothing works. Requiring the owner to reset the decoder back to factory default. Something and we aren’t sure what is negatively affecting our decoders.  Requiring us to reset them back to factory default and start all over again. Not what we are looking from our DCC equipment.

And, the guy in back responded “Not Good.” You are so right! Not good and not something I’m very patient with. Causing me to ask, can we compromise a decoder or is there some human fallibility built into the decoder?

Decoder Shuts Down:

This appears to be the number one problem with DCC and the decoders. Most of the time you can recover the decoder by going back to factory default. As of this writing those of us who aren’t electrical guru’s (engineers) believe the cause of such is attributed to shorts.

More About Short’s, A look at how and why they occur.

I need to clarify, the type of shorts that have given me so much trouble pre-DCC. This is where it gets technical and I’m not sure a word picture, verbal description is going to get the job done. I agree with Alan Gartner., as a picture or schematic says much.

Shorts in the switches/turnouts where to look for them. An ongoing discussion that’s been going on forever.

  1. Operator Error: The first one here is due to operator error. A train engine tries to run through a closed switch, (coming in from the diverging end of the switch) resulting in a SHORT! Did the dispatcher forget to throw the switch and/or align the points? Gosh how many times have I done that?  Forgetting to align the points in the switch mechanism to allow the train through. This is purely operator error.
  2. Peco and Kato both make power routed switches that if your isolation gaps are cut in properly…IE., For block wiring.   Approaching the switch on the diverging end.   It will prevent the locomotive from moving forward into the closed switch.
  3. Metal Wheels contact non-movable points: A short happens when one metal wheel rolls across the diverging end of the frog and makes contact (overlaps the two rails) with both non-movable points, the rails leaving the frog resulting in a SHORT! This can happen before and after the frog. And they blame the frog. Sigh!
  4. Isolation Gaps: Another short can occur when you have wire drops in a siding and you forgot to install isolation gaps and the positive meets the negative coming out of the switch and you have a SHORT!  Not easy to find. Not fun!
  5. Contact with hot aka live open movable points: Metal wheels because of a lack of a standard may have wider tires and deeper flanges especially the older ones and they may come in contact with the live open movable points as the wheels pass by them. If the polarity isn’t the same, you have it….you guessed it…a SHORT!
  6. Derailments: The last one I will mention here you can’t, as in can not blame it on the switch mechanism. A derailment that occurs before the train car arrives at the switch. The metal wheels come in contact with the open, hot aka live movable points and the outside rail. This is when all the fun starts.  ZZZIT!  Short!

Track Switches/Turnouts:

“Keep in mind you should never depend on a track switch to be an electrical switch,” as we are reminded by Greg M. For example power routed switches. Although set up to transfer power through out the switch mechanism there is way to much resistance in the switch causing line drop or power loose. Which can negatively effect operations disrupting the performance as in slowing the train down.  Powereing up from the opposite end may not be the answer as the direction the points are set will dictate the polarity moving through the live rails of the switch.

Now with all that said, I do use power routed switches only because I prefer to us a “Hot” frog or better said “Peco’s Electrofrog”.

Kato’s frog’s are hot and the polarity is governed by a sliding switch built into the switch mechanism.

Power Routed Switches:

Where the idea came from that power routed switches is undesirable escapes me. Perhaps a little myth management is in order. I have power routed and non-power routed switches and have yet to experience any real problems. Did I say? With any of them! I’ll share how I did that in resolution #2, just down the page a ways

What Are Power Routed Switches? My first reaction and response to the above question is and always has been … every switch routes power through them by various ways and means of point contact, rail connectors and jumper wires that can be found built into and on the bottom side of the switch mechanism.

Let’s start with establishing that not all track switches /turnouts are power routed. Oh they route power but they aren’t power routed. Isn’t that an oxymoron?

“Power Routing,” Power Routed Defined: It is where the switch shuts off power to the rails in the track, depending on the direction the points are aligned on the switch.

One thing I’m not afraid to use and actually prefer them on my layout is the power routed switches. No problems operating DCC on my layout. Is that a kicker or what? Especially when other authors are dogging them out.

The reason I like them, they are the simplest way to route power to a hot frog with the correct polarity. Yes, the points can get dirty but I don’t know of a switch mechanism that doesn’t. The Frog: The short legged metal kind. One example is power routed switches with Insulated frogs and a very age old short that can occur at both ends of the frog and the rails leading away from the frog. All set off by an over sized tire or metal wheels. Even so the darn frog gets blamed for everything. What’s a frog to do? One of the reasons you find manufacturers producing switches/turnouts with dead frogs. When a live or Electrofrog would be by far better. No stuttering or hiccuping locomotives as they move through the switch mechanism. One of the reasons Alan Gartner wires them up to a reversing toggle. Thus we get, a nice smooth performance of the locomotives or diesels as they crawl through them.

FYI:

It’s important you hear me when I say:

It’s counter productive to cut gaps in before and after the frog because  you end up with a dead forg uhh…err frog. You’ll find yourself going right back to hand pulling your locomotives across those darn dead frogs. Not a Rick approved method of advancing a locomotive.   Or a safe procedure when dealing with the switch.   The (turnout) Switch becomes a maintenance nightmare.

On the other hand the following is Rick Approved. I do not alter or change a switch mechanism. After an inspection. It gets installed as is. By now you’ve read or seen an article or two where they recommend you cut in gaps on both ends of a Peco Electrofrog. The whole purpose of an Electrofrog is to have live current in the frog and the correct polarity flowing through it.

  • Caution: Soldering wires to a switch mechanism, in inexperienced hands as in yours or mine, can damage a switch. You can ask me how I know. I’ve been there and I didn’t like the results.
  • Caution: A word about operating DCC and Analog DC at the same time.   Short version is, “Not a good idea.”

If you’ve been following along here you know that I operate with Analog DC and DCC. With the flip of a DPDT, or a cut off switch, we are good to go. I don’t recommend this for the newbies who might be tagging along here. You don’t want to mix AC power on the tracks with DC power, at the same time. Unless you like sparks, fire works and your train equipment looking like you’ve installed smoke generators. Resulting in: Do I dare say dead decoders? It takes a considerable amount of awareness and self discipline to accomplish operating both at the same time. Not recommended.

Here in this posting we’ve looked at the physical causes for shorts in our switches and the proposed resolutions to solve such.

  • You will want to review Joe Fugate’s, Short Circuit Control/Management.
  • You will want to review how Alan Gartner’s, DCC Friendly procedures will resolve most problems identified.
  • You will learn more about him and the ideas he shares by reviewing his blog. I will leave you to choose whether or not his suggestions are a viable option for you and your layout.

Research, Research and more Research: It just seems endless. Here’s where it gets interesting. I want you to take full advantage of the research I’ve done. Please note the links I’ve provided. Take whatever time you need to visit them and read the information shared. Then find your way back to BarstowRick.com as we aren’t finished….yet! You know click for a box to appear and then click on the return arrow.

This has been an overview of the basic causes of shorts.

More on decoder killing shorts in other posts that can be found here on BarstowRick.com.  See Category that can be found in the sidebar.

RickH.

This is a work in progress so do come back to see what’s changed.

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