# NCE Power Cab short protection



## tkruger (Jan 18, 2009)

I have the NCE Power Cab. When there is a short (derail etc.) the Power Cab reboots. Should I add anything for short protection or is this enough for this system? 

I have read about using light bulbs in series to protect the DCC system, Is this a valid idea for this system. If so what are the pros and cons.

I am using the stock 2.5 amp power supply for this.


----------



## DonR (Oct 18, 2012)

The 12 volt auto tail light bulb in series with your DCC track
current does offer protection to your
controller. But, it is advisable to have a switchable shunt across
it. Various combinations of locos will get lower track voltage as
the in series bulb glows with the amp draw. That can affect 
train operations. It won't do any harm though. 

Don


----------



## gregc (Apr 25, 2015)

DonR said:


> The 12 volt auto tail light bulb in series with your DCC track current does offer protection to your controller.


i tried this. As the engine would start moving the bulb would glow, dropping the voltage and I believe cause the decoder to reset.

I had read that the bulb might not pass enough current and this would happen for an older locomotive that draws too much current.


----------



## fulsom56 (Sep 18, 2015)

I have the Power Cab also & am just starting to wire my layout. I've been researching circuit breaker protection besides what is inside the Power Cab. I plan on using a circuit breaker made by DCC Specialties called the PSX Power Shield. It gets wired in between the Power Cab & the track bus. I'm still waiting for it to arrive so I have no experience with it but what I've read is that it's a very good circuit breaker. You may want to check out this option which is considerably more expensive then a light bulb but offers great protection.


----------



## Brakeman Jake (Mar 8, 2009)

If your only concern is to avoid the Power Cab from re-booting,then go for the bulb.However,if you care about the potential damages a short can do,install a breaker.

In the advent of a short,the bulb will simply glow and will not cut the current supply to the shorted item,wether it be a wheel,a turnout point or a decoder.The bulb will draw two amps from the Power Cab witch it will supply without a sweat,but the bulb will also keep the same two amps applied to whatever is between it and the short.

I agree that two amps isn't much of a threat but in our world of miniature components,I believe it should be reckoned with.If a spotted wheel,a melted turnout or a fried decoder (not talking about fire hazard) doesn't matter,then go for the cheap bulb solution.

A fire hazard is next to impossible indeed while a layout is being attended,but what if a short occurs during a five minute visit to the restroom?A bulb isn't a breaker (or fuse) and will never be.


----------



## Magic (Jan 28, 2014)

I use those DCC Specialties breakers and they work great, wouldn't be without them.

Magic


----------



## Cycleops (Dec 6, 2014)

I would have thought it more important to protect the supply into  your system from the mains. Recently I had a problem with neutral in my domestic supply which blew all the bulbs and caused some appliances to become 'live'. It also took out my NCE power supply and I don't know if affected the controller as yet.


----------



## DonR (Oct 18, 2012)

Cycleops

I do have Surge protectors on my computer and Surround
Sound amp, but not on my DCC power supply. I wonder if
one of those would have protected your power supply. It
needs a good ground, and if your neutral was loose that
could have affected the ground. They are tied together in
my breaker box.

Greg

What kind of loco, or how many were you using that caused
the bulb to glow? Several will, but I haven't seen one do it.
The decoders have not reset. 

When the track is shorted, perhaps by a derail, all of the decoders
are shunted, the short is the route of least resistance
and sends most track current to the bulb and
it glows brightly. The DCC controller simply 'sees' the amp draw of
the bulb and does not 'see' a short circuit. And it automatically
restores track current when the short is eliminated.

This is not to argue against use of a breaker. They obviously
are desirable. It's simply that the bulb is cheaper and easily
available.

Don


----------



## gregc (Apr 25, 2015)

DonR said:


> What kind of loco, or how many were you using that caused
> the bulb to glow?


It's an older brass 0-6-0. But I was using a 3021 bulb rated at .24A. So when the loco draws a 100 ma, that's half the current the bulb normally draws and there's a relatively large voltage drop across the bulb.



DonR said:


> When the track is shorted, perhaps by a derail, all of the decoders
> are shunted, the short is the route of least resistance and sends most track current to the bulb and it glows brightly. The DCC controller simply 'sees' the amp draw of the bulb and does not 'see' a short circuit. And it automatically restores track current when the short is eliminated.


all current through the circuit goes through both the locomotive/decoder and bulb.

the 1156 bulb is rated at 27 W 12.8 V, so it normally draws about 2A. So a locomotive drawing 200 ma shouldn't drop much voltage across an 1156 bulb.

when there's a short between the rails, there is zero volts across the rails and the decoders are un-powered.


----------



## kayaker8 (Feb 5, 2016)

I have a NCE Power Cab 5 amp system and was strongly advised to include circuit protection which I did with PSX circuit breakers. I am happy I did because I am experiencing an odd situation with an American Models lighted caboose which causes a short after going through turnouts with a plastic frog. In any case the PSX seems to work great.


----------



## mesenteria (Oct 29, 2015)

I believe you are using the wrong bulb. You want an 1156 2.1 amp bulb that will halve the available amperage when you get a hard short in the location where you have that bulb wired _in series_ to the tracks providing the short. What you have listed, unless you have a typo, is about 1/10th of what you need if it is truly a 0.25 amp bulb.

I broke my second layout into four 'districts', but not for the sake of boosting, only for the sake of wiring a bulb in series in each of them, via a sub-bus. When I got a short, the light glowed brightly showing that the short was located in the 'district' that it served, but the rest of the layout stayed functional.


----------



## DonR (Oct 18, 2012)

Kayaker8

Look where the frog rails come together. There is a tiny sliver of
insulation keeping them apart. Possibly your lighted caboose wheel
is shorting across this point. You can check that by very slowly pulling
the caboose thru the turnout with a very close view. You would see
a tiny spark when the short occurs and if ambient light is low enough
you should be able to tell if it is as I suspect or something else.

You can eliminate the problem by carefully filing down one of the
frog rails so a wheel can't touch both at the same time. Another
way is to use a tiny dab of clear fingernail polish on the point.

Don


----------



## mesenteria (Oct 29, 2015)

If you are having shorting problems at the frog, there are several remedies, and each works if it is appropriate to the defect.

You can lay thin polystyrene shims against a guard rail to get a better run through the frog.

You can sever the frog point from the frog rails if the frog is live, and use a switch to electrify the frog. Or, if the frog is already isolated via plastic spacers, consider cutting one of the two rails another 5/16" outbound from the spacer. The problem is that the wide not-very-scale-realistic tires on the HO rolling stock are touching both energized rails for just a fraction of an inch before their diverging paths take the metal tire completely away. This takes place after the black plastic spacer. 

Or, as indicated by the previous poster, you can take clear nail polish and paint a couple of light coats over the rails where you know the short is taking place. Let the first coat dry thoroughly, say a whole hour, before you apply a second coat. Expect the coating to turn dark over time.


----------



## kayaker8 (Feb 5, 2016)

Here is a more complete description of what I have found. 
1) When the DCC loco is traveling slowly and the caboose rolls through a turnout the caboose light goes off when the rear truck hits the plastic frog. When the rear truck rolls and hits live rail the short occurs but shortly thereafter the engine restarts. Note that the loco has Keep Alive.
2) With the loco running slowly as in 1) above and I tilt the caboose so that half of each truck is off the rail the caboose light goes off as expected and loco continues to run. When both trucks are then replaced on both rails the short occurs, the loco stops and then restarts.
3) When the loco speed is increased significantly and the caboose goes through a turnout there is no short.
My guess is that there is a capacitor in the caboose that discharges when contact with the rail is lost and then recharges when contact with the rails is once again made. The recharge appears to somehow cause the appearance of a short. I spoke to the manufacturer who assures me that there is no capacitor in the caboose. I am having trouble opening the caboose to confirm without damaging it. Still working on it.


----------



## mesenteria (Oct 29, 2015)

kayaker8 said:


> Here is a more complete description of what I have found.
> 1) When the DCC loco is traveling slowly and the caboose rolls through a turnout the caboose light goes off when the rear truck hits the plastic frog. When the rear truck rolls and hits live rail the short occurs but shortly thereafter the engine restarts. Note that the loco has Keep Alive.
> 2) With the loco running slowly as in 1) above and I tilt the caboose so that half of each truck is off the rail the caboose light goes off as expected and loco continues to run. When both trucks are then replaced on both rails the short occurs, the loco stops and then restarts.
> 3) When the loco speed is increased significantly and the caboose goes through a turnout there is no short.
> My guess is that there is a capacitor in the caboose that discharges when contact with the rail is lost and then recharges when contact with the rails is once again made. The recharge appears to somehow cause the appearance of a short. I spoke to the manufacturer who assures me that there is no capacitor in the caboose. I am having trouble opening the caboose to confirm without damaging it. Still working on it.


Probably no capacitor in the caboose. I know of know rolling stock apart from locomotives that do have capacitors, but maybe they are out there.......

More likely your trip current in your DCC controller's shorts detection circuitry is set too low and it trips when the light inside your caboose draws a large inrush of amperage after both sets of rail wipers can pickup voltage from the metal tires once again as those tires regain connection with power.


----------



## kayaker8 (Feb 5, 2016)

The reason I originally hypothesize the presence of a capacitor is that the problem does not occur with a lighted post-war caboose having only a simple bulb. American Models indicated that there is an LED in their caboose which I assume means that the circuit includes a resistor. It could very well be that the LED-resistor combination is the issue.


----------



## DonR (Oct 18, 2012)

I doubt the LED/resistor circuit itself is the problem. If the LED is glowing
on tracks other than the turnout it is OK.

Did this caboose light work properly then fail, or has it always done
as you describe?

Now in your test 2, are you saying that the short occurs ANYWHERE on
the track when you tilt the caboose, or again, just on the turnout?

From your description
in test 2, it would appear the caboose does not have all wheel
power pickup. Inspect the trucks and determine whether they use
a metal strip pressing against the back side of the wheels, or
a metal strip pressing against the axles. If against the wheels,
is it against all 4 wheels on each truck?

Did you do the 'spark' test as I suggested in an earlier post?

Don


----------



## kayaker8 (Feb 5, 2016)

Don,
Answers are in the order of your questions.
The shorting issue with the caboose occurred from when I took it out of the box.
The short occurs when going through turnouts or when being tilted on straight track. In both cases the short is intermittent. I see the PSX LEDs come on indicating a short when contact is first remade with the rails and then a second or two later go out and the caboose lights go on.
The caboose circuit is made by wires attached to the axles. Previously I had placed a piece tape between the wire pickup and an axle and no short occurred anywhere on the rails.
I can see no spark when going through a turnout.


----------



## Lemonhawk (Sep 24, 2013)

If the caboose has a capacitor in it, it sounds like there is no resistor between the track and the cap, hence there is a large current spike that occurs when power is restored trying to restore the charge on the capacitor. Without seeing the circuit all we can do is guess, but your test of just tilting the caboose to one side and then putting it back down sure indicates an in-rush transient as being the problem. It just does not seem that a simple bridge-resistor-LED would cause much of a transient.


----------



## kayaker8 (Feb 5, 2016)

A capacitor was my original guess but negated by a conversation with the manufacturer. I won't know for sure until I am able to open the caboose up without damaging it.


----------



## gregc (Apr 25, 2015)

mesenteria said:


> I believe you are using the wrong bulb. You want an 1156 2.1 amp bulb that will halve the available amperage when you get a hard short in the location where you have that bulb wired _in series_ to the tracks providing the short. What you have listed, unless you have a typo, is about 1/10th of what you need if it is truly a 0.25 amp bulb.


yes, the 3021 bulb is rated at .25 amps. even two in parallel draw only .5A.

but I just tried an 1156 bulb which draws 2A with no success (hoping to prevent the PoweCab going thru a reset cycle). I believe the problem is that the wall supply for the PowerCab is only rated at 1.35A, not enough to power the 1156 bulb and making it look like a short to the PowerCab.


----------



## gregc (Apr 25, 2015)

gregc said:


> yes, the 3021 bulb is rated at .25 amps.


I chose festoon bulbs because I couldn't find panel mountable bulb holders for 1156 bulbs and I found mountable festoon bulb holders on ebay.

the NCE CP6  does what I want. They also have 1 amp bulbs that should serve my needs.


----------



## Ike8120 (Mar 5, 2016)

I use 2 1156 automotive bulbs, the only thing they do is act as current limiter. The circuit breakers are for short protection.
I have a Power Cab with SB 5 booster.


----------



## Ike8120 (Mar 5, 2016)

fulsom56 said:


> I have the Power Cab also & am just starting to wire my layout. I've been researching circuit breaker protection besides what is inside the Power Cab. I plan on using a circuit breaker made by DCC Specialties called the PSX Power Shield. It gets wired in between the Power Cab & the track bus. I'm still waiting for it to arrive so I have no experience with it but what I've read is that it's a very good circuit breaker. You may want to check out this option which is considerably more expensive then a light bulb but offers great protection.


Did you set up your power shield, if so any hints or tips??


----------



## Ike8120 (Mar 5, 2016)

fulsom56 said:


> I have the Power Cab also & am just starting to wire my layout. I've been researching circuit breaker protection besides what is inside the Power Cab. I plan on using a circuit breaker made by DCC Specialties called the PSX Power Shield. It gets wired in between the Power Cab & the track bus. I'm still waiting for it to arrive so I have no experience with it but what I've read is that it's a very good circuit breaker. You may want to check out this option which is considerably more expensive then a light bulb but offers great protection.


Did you connect your PSX yet? If so did you add an external LED or manual reset?


----------

