Cheap and easy short protection for your DCC layout

[RonsTrainsNThings]

Before you spend $$$ on circuit breakers and extra high-tech equipment, here is a very easy and inexpensive way of managing short circuits on your DCC equipped layout that protects your locomotives and your DCC system as well as confines shorts to one district without shutting down your entire layout. I have been using this method for 15 years and it has worked great. Check it out and give it a try.

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[peteski]

While the video is amusing, this is just another rehash of the old automotive light bulb method which has been around for decades.  While I have seen it used several times, and it does a perfect job of keeping the DCC booster from shutting down, to me there is a downside when compared to the commercially made electronic breakers.  I also realize that, as your video shows, even DCC manufacturers do sell this type of breaker.

The downside is that while the short is present, the bulb will still be passing rather heavy current through the short. Here are the specs: 1156SC I/12.8V/2.1A/BA15S/S8/CL/1200H.  So, if there is a short on the protected side it will allow up to 2.1 Amps to pass through the short.  That is a fairly heavy current to be passing through many of the delicate power paths inside the small N scale model.  If you notice the short right away and remove it,  then there will be no damage done, but if you let the shorting loco sit in the shorting position for a while. depending where the short is, it can heat up the conductor passing current damaging (melting) some part of the model.  For example the side pickup strip on the new-design Kato 3-axle trucks (especially the center axle) are very delicate and will heat up and melt the sideframes under heavy current allowed bu the 1156 bulb. I have seen that type of damage few times.

Electronic breakers do not create that problem because when they short a heavy current draw, then cut the current completely of for short period, then attempt to turn  it on again. Then the cycle repeats until the short is removed. That IMO will cause less damage to the model than the light bulb breaker.

Of course this is just my opinion, but I choose not to utilize the light bulb circuit protection in N scale.

[Greg Elmassian]

I agree with Petski, and commented as such on your post on Trainboard.

The bulb lights up because there is voltage, and you "think" that the bulb is doing it's job, but as Peteski states, you still have short circuit current flowing through your loco.

There's other finer points for DCC... you show the NCE "bulb board", but did not notice that the filaments in those bulbs are straight, i.e. pretty much just a resistive load, that varies under current.

The bulbs chosen in the video are for cars, and to concentrate the light for a stop or tail light, the filament is wound in a small coil... well, that will cause inductance and it should be investigated if this inductance degrades the DCC signal. Inductance will degrade the signal for sure, but how much is the question.

At the very least, use the non-inductive type of bulbs the people at NCE have chosen.

Greg

p.s. the basis of the post is saving money apparently, (or that you hate high tech ha ha), but what is the cost of an electronic circuit breaker compared to ONE locomotive? I would submit if you have 5 power districts, you have more than 5 locos. To me the cost saving does not add up in the risk to my trains.

[Mark W]

Electronic breakers also have built in indicators, including LEDs or optional buzzers, so that covers the "where is the short?" part as well.  If we're talking novelty Lionel set-up that you find at many shows (which could mostly handle the current), maybe this would add to the experience; but as mentioned, definitely not my choice for N scale either.

[ednadolski]

So, if there is a short on the protected side it will allow up to 2.1 Amps to pass through the short.  That is a fairly heavy current to be passing through many of the delicate power paths inside the small N scale model.

Not sure I follow you here.  How does a short (across the rails I presume, not elsewhere) force any more current to flow thru any of the internal circuit paths of a DCC-equipped loco, aside from the normal current that flows when the rails are at full (non-short) voltage?

(I'm not talking about transient conditions, which presumably could induce a large voltage spike across the rails in some cases.  But it doesn't seem like a bulb should be of much help in that case.)

Ed

[John]

Yes . .the short is still there, but the bulb should be acting as a limiter to keep the whole 5 amps or whatever from being applied .. Not sure why this got downvoted .. its a legitimate way of doing the job .. maybe not the best, but also better than nothing

[wazzou]

.. Not sure why this got downvoted .. its a legitimate way of doing the job .. maybe not the best, but also better than nothing

The real shame of it is whomever downvoted it, only did that without any comment.

[Dave V]

The real shame of it is whomever downvoted it, only did that without any comment.

Seriously...  There's a difference between "that's not how I would do it" and "this post is profoundly negative, insulting, and detracts from the forum as a whole."  Count me in the former camp...it's nice to know the various ways of doing the job, and while I've known about this technique since I entered the world of DCC, I've never built a layout large enough to require power districts so this is an N/A for me.  So, like a good boy, I drove on.  Until I saw this downvote silliness.  Glad to see his respect is back on the plus side, but still...that's not what the respect vote downvote is really designed for.

[peteski]

Not sure I follow you here.  How does a short (across the rails I presume, not elsewhere) force any more current to flow thru any of the internal circuit paths of a DCC-equipped loco, aside from the normal current that flows when the rails are at full (non-short) voltage?

(I'm not talking about transient conditions, which presumably could induce a large voltage spike across the rails in some cases.  But it doesn't seem like a bulb should be of much help in that case.)

Ed

I'm not talking about shorts where the current path is strictly through the metal wheel (which is a robust piece of metal which can handle it no problem) but many times the current path of a short can be through the loco itself. Either between the front and rear truck or even between the same-side truck wheels.  In those cases the full current goes through delicate or thin conductors which will heat up and melt the surrounding plastic if the short persists for longer than a second or two.  Yes, the full booster current (5A, 8A, whatever) will be limited to only 2A, but I still think that 2A can do some damage if not immediately stopped.

Here is an example of such damage (upper right metal strip is melted into the sideframe).  I have seen this type of damage more than once. That is the kind of damage which can occur if a high current flows through fairly delicate parts of the model. 




I was not the down-voting member. I also agree that the votes should have user name tags associated with them so everybody could see who voted and how.  That would pretty much eliminate gratuitous votes.

[peteski]

Seriously...  There's a difference between "that's not how I would do it" and "this post is profoundly negative, insulting, and detracts from the forum as a whole."  Count me in the former camp...it's nice to know the various ways of doing the job, and while I've known about this technique since I entered the world of DCC, I've never built a layout large enough to require power districts so this is an N/A for me.  So, like a good boy, I drove on.  Until I saw this downvote silliness.  Glad to see his respect is back on the plus side, but still...that's not what the respect vote downvote is really designed for.

Don't you as a moderator have the ability to see who voted on the post and remove the vote if needed?

[Dave V]

Don't you as a moderator have the ability to see who voted on the post and remove the vote if needed?

Not as a moderator.  Only the forum admins...Tom and John.  But yes, there's a capability to attribute votes to members, and your overlords do monitor for voting abuse.

[RonsTrainsNThings]

I responded to these concerns on Trainboard, and I will reply here with a quote of the same reply.

"I would not suggest this or any other technique I demonstrate is the only war or is for everyone. I confess I have no G scale experience. What I do know is what has worked for me and others. I have used this technique on my N scale layouts under regular use for over 15 years and I have yet to experience a problem with DCC signal or cause damage to a single locomotive or my DCC system--the same one I have use for all of those 15 years. I learned about it initially from Joe Fugate who uses this method on his large HO layout with full success as well. I am aware of the theoretical problems with signal drop off, but I have yet to see this problem in practice on a layout. I am not saying it has never happened. I am saying that of all the people I know who have tried this method it worked efficiently."

[John]

Keep making them Ron .. someone will learn something from them ..

[peteski]

As I stated in my initial post here: Of course this is just my opinion, but I choose not to utilize the light bulb circuit protection in N scale.

I also provided tangible reasons for my opinion. My post was simply to serve as a warning about possible issues with a fairly high current present, while using this type of a circuit during a short.

[C855B]

I agree with @peteski , and will raise him an "Oh, I'm not all that sure this is such a good idea for N". HO, sort of maybe, tinplate, OK, but I abandoned taillight bulbs as MRR track protection around 40 years ago after frying an Atlas E8. (No big loss, but that's another discussion. )

The modern problem is hard-wired decoders typically use #30 or #32 wire. #30 is rated for 0.8A, #32 is 0.5A. If, heaven forbid, you would experience a hard short between the wheels and decoder, with that bulb passing 2+ amps you are all but certain to melt insulation, further reinforcing any short, and probably generating enough heat in the closed space to deform the shell before the wire(s) eventually melt apart. Like Pete said. And he brought up the potential for truck damage from simple derailment shorts, rightly so.

... I have used this technique on my N scale layouts under regular use for over 15 years and I have yet to experience a problem with DCC signal or cause damage to a single locomotive or my DCC system...

Don't dismiss good luck as a component of your experience here. It doesn't mean it hasn't happened to others. Count me firmly in the "electronic protection" camp as well.