Add fuses to models, from factory?

Every time a topic like this comes up I have to wonder how often people are having derailments that cause shorts. In the last 5 years I think I've had maybe one derailment on my layout that tripped an external breaker. Granted I don't have a really complex track plan with multiple switches. For the average hobbyist this extra fuse protection may be overkill, hence why manufacturers don't bother with them or TVS protection in each individual locomotive. 

I'll give you my guess, and that is that anything you add to an engine's design adds complexity (yes, granted, a fuse or circuit breaker is not a big deal conceptually, very simple wiring) , which in turn adds some cost, it also requires taking space there might not be. If an engine has multiple circuit boards in it, would you fuse each one's power connector? Would you fuse a circuit on the board? Would you have some sort of button for each breaker, or an access panel (let's say in the tender) to be able to change the fuse or reset the breaker? It isn't that simple. 

Then, too, if you look at the cause of what fries a board, the odds are it is likely to be something not involving internal issues with the engine.  The biggest issues likely are things like derailment or a short caused by something conductive on the tracks, and  modern transformer/power source or an older one equipped with fast blow breaker/fuse and a tvs would likely handle that kind of situation. In the end, it likely just doesn't pay, that the few cases you can trace internally to the engine don't justify adding fuses into the unit.  The other cause of boards frying are likely to be electrostatic, which a breaker or fuse won't help (for example, someone opens up the engine to work on it, touches a circuit board without grounding themselves, and zap). 

bigkid posted:

I'll give you my guess, and that is that anything you add to an engine's design adds complexity (yes, granted, a fuse or circuit breaker is not a big deal conceptually, very simple wiring) , which in turn adds some cost, it also requires taking space there might not be. If an engine has multiple circuit boards in it, would you fuse each one's power connector? Would you fuse a circuit on the board? Would you have some sort of button for each breaker, or an access panel (let's say in the tender) to be able to change the fuse or reset the breaker? It isn't that simple. 

Yeah that's understandable it will make the product a bit more expensive, but I would be fine paying a bit more if they added extra over-current protection. And yes, adding a fuse on everything is overkill. What I was going at is adding fuses onto motors only, since if a motor jams it will become a short circuit and then your motor driver board get's fried.

So for diesel locomotives; that would be 1 - 2 fuses for each motor and 1 fuse for the smoke unit motor. That would ensure that if any of the motors would jam, it would only take out the fuse and not the main board of the model.

Of course it doesn't have to be the old fuse type that needs to be replaced when it blows. There are fuses that trip when they get hot from too much current, and then reset when they cool down. Adding those to one side of the motor will also provide protection.

A simple solution would be a properly rated PTC.  I use them in the motor leads of Cruise Commander Lite installations to avoid cooking the board if you have a motor stall.  I also use them between a locomotive and tender in case of a derailment that puts a roller on an outside rail.  Finally, for passenger car lighting upgrades, I put one between the two pickups.  I've received a number of cars for repair where the lighting wiring was smoked by that very problem.

The beauty of the PTC is it resets itself, so there's no intervention required when you remove the issue that caused the overload.

Lou1985 posted:

Every time a topic like this comes up I have to wonder how often people are having derailments that cause shorts. In the last 5 years I think I've had maybe one derailment on my layout that tripped an external breaker. Granted I don't have a really complex track plan with multiple switches. For the average hobbyist this extra fuse protection may be overkill, hence why manufacturers don't bother with them or TVS protection in each individual locomotive. 

Over the last 15 years, I've had two such incidents. The most recent was a couple of months ago, when I forgot about some objects I had left on the track. Direct short, and lots of smoke. It was one of my best runners too. I've been afraid to open it up, My guess is all the wires are fried, which was what happened the first time, when an engine split a switch. Not sure about the boards.

GRJ's suggestion of PTC's is the way to go. I would like to put them on both rollers of all so equipped pieces. My experience is that the wire is the weak link. The track is protected by PTC's rated for 6A, but they are a little slow. Something faster acting and smaller in the locomotive, would solve the problem.

For a locomotive, you can use a PTC that has a trip rating of around 1.5-2.0 amps.  It'll take a significant overload for many seconds, so the amount of false trips is pretty low.  For my CC-Lite installations, I use a .75A trip PTC, and I've never had an issue, of course they're small locomotives as a rule.

Thanks John. that's pretty much what I was thinking for rating. I'd probably go with 2A for dual can motors. The trick for me is opening up all those engines, and installing them. A buddy of mine suggested using the surface mount style, but he's in On3 and space is limited, so he thinks small. I'll just stick to he classic style that look like capacitors.

Oh yes, to the OP's comment, for as expensive as locomotives are, and as cheap PTC's are, they should be manufactured that way, now and forever!

Not to resurrect this thread from the dead, but @gunrunnerjohn do you have any suggestions for a PTC inline on lets say a typical MTH subway car or diesel engine? Just an initial starting point?

I'm assuming id put one on the red wire between the roller and the PS2/PS3 boards?

Thanks,
Dan

Ran an MTH Z-4000 with DCS computer devices and engines over 20 years now, never had a failure during any sessions.

P.S. my remote thumbwheel and 75 power units still work as well!

Your fuse idea is not practical nor necessary. God bless those overthinkers...

In the case of a short or overload, the current goes up in the circuit everywhere at the same time. A modern high speed circuit breaker at the transformer will protect your locomotive just as well as a fuse in the locomotive.  TVS protection in the loco makes since, but not current protection.

I am not addressing fuses that are placed on boards to protect traces or individual components.  But a blown fuse on a board will kill the loco just as dead as any other blown component.  For most operators a loco with a blown board fuse is just another dead loco that either needs to go to the shop or on the shelf. Therefore, the value of on board fuses is questionable for most people. .  

@SIRT posted:

Ran an MTH Z-4000 with DCS computer devices and engines over 20 years now, never had a failure during any sessions.

God bless those overthinkers...

@SIRT

I hear ya, but ...

Neither you, nor anyone else, can extrapolate a lone experience to a much larger statistical population without a high probability of being dead wrong.  Now, if I take your observation, and thousands of others, as a set, and in that set there are absolutely no failures then I can agree with you.  Otherwise, no way.

There is a problem with the impression of "robust" based on individual experience.   In your specific case you may be the most lucky person in the world, in which case your avoidance of disaster has little to do with your choice not to add protection.  (Maybe it's time for you to buy a PowerBall ticket?)

Statistics are the name of the game when trying to estimate failures coming from exposure to the events that cause them.  They are compiled by including including everyone, not just you.  With electronics in general, and this holds true in our hobby, stats have indicated over the years that these devices are sensitive to excessive current travelling through them and high voltage spikes across them.

They can be made nearly bullet-proof but it costs money to do so.

There are quite a few people on this forum that can testify to their experience with electronics failures.

   Are there an excessive number of such failures?  No.

   Is the number close to zero?  It may be nearer than we think.

   Is is actually zero? No possible way, even though you seem to imply that it is, based on your experience.

My 2009 Ford Escape Hybrid, which I've had since it was brand new, has 260,000 miles on it.  I've taken it farther than the moon.  There has never been a single failure of any electronic device on this car in all that time.  Not one.  Zip.  Zilch.  Nada.  Nothing.  Yet I'll be the last one to imply, based upon my lone experience, that every one that Ford ever made is just as robust.

Mike