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DCC Circuit breakers - what to look for when buying


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As the title really.

 

I am looking to protect my booster,  but mainly I want to be able to continue throwing points after a short - usually caused by operator error - you know the sort of thing driving into wrongly set points and what have you.  I understand the principles but see that there are a few different products with quite a wide range of prices.

 

What sort of facilities should I be looking for, what pitfalls should I avoid and does any one have any particular recommendations?

Would simply splitting the track from the accessory decoders on different circuit breakers allow me to fire points once there is a short on the track circuit?  Do I need a circuit breaker on the Accessory decoder feed or would just one on the Track feed suffice?

 

Thanks for any help

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Minimum is one on the track feed, thus splitting the accessory bus from track shorts.  As accessory bus shorts should be extremely rare that ought to be sufficient.

 

Beyond that:

current rating - appropriate for the locos you are running on the track, and lower than the current rating of your command station.

cutout speed - faster than the cutout in your command station, otherwise the command station shuts down before the track cutout.

RailCom compatibility - if you currently use it, or think you might use it, or have a system which is using it (even though you're not paying any attention to it). 

compatibility with your system - I've know individuals run into problems, possibly with cutouts attempting to reset which seemed to be associated with a command station failure.  Proving that association is very hard without doing a repeat (which could get very expensive!). 

 

 

I've recently fitted six MERG kit built cutouts, with modified firmware (for RailCom compatibility) to a large layout as part of a wider wiring robustness upgrade.  Too early to say that they definitively solve things, but testing looks promising. 

 

On a fairly simple home layout for someone, I installed a car indicator bulb in series with the track feed.   That's done enough for that layout - drive into an incorrectly set frog and the "Idiot Indicator Indicator" lights up, trains stop, but rest of system stays operational.   It was cheap, simple, reliable  - in use for at least six years.

 

 

 

- Nigel

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4 minutes ago, Nigelcliffe said:

I've recently fitted six MERG kit built cutouts, with modified firmware (for RailCom compatibility) to a large layout as part of a wider wiring robustness upgrade.  Too early to say that they definitively solve things, but testing looks promising. 

 

Another vote for the MERG cutout, but then I did help in it's design doing initial testing and getting it to work with Bachmann Dynamis ;)  Most if not all ones that came before would not react fast enough to protect the Dynamis.

 

I fit one to each baseboard on my layouts in between the track and the controller/booster. Accessory feeds go direct from the controller/booster so points can be changed when I drive a loco into an incorrectly set point :)

 

At around a tenner (plus annual membership) they are very good value and easy to assemble if you can wield a soldering iron

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I bought a DCC Specialities PSX-1 for exactly this purpose. I like it because it means the layout recovers itself after a short, but it hasn't actually solved the problem with my accessories shutting down (and all the point servos cycling), despite being 'downstream' of it. I suspect that's my implementation, but I can't fathom why!

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11 minutes ago, njee20 said:

I bought a DCC Specialities PSX-1 for exactly this purpose. I like it because it means the layout recovers itself after a short, but it hasn't actually solved the problem with my accessories shutting down (and all the point servos cycling), despite being 'downstream' of it. I suspect that's my implementation, but I can't fathom why!

Another fan of the PSX breaker. In general you need to set your booster to the slowest possible shut down time and the PSX to a faster time so it triggers first. Accessories need to be upstream of the breaker, ie connected to the booster itself. For my implementation I don't have an accessory bus but power all the accessory decoders from a dc supply and the DCC commands are fed through Loconet. That way I don't have an issue if there is a loss of booster power. 

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I tried that too and it didn't make a difference, but you should be able to put it in place downstream too IIRC, where the next PSX would go if you had multiple power zones.

 

I'll re-wire it one day and work out why, it's nothing obvious, it's still a good product! I did have to slow down the delay slightly as I found you could get momentary shorts from some stock over pointwork which were not enough to interrupt continuity, but were enough to cause the PSX to shutdown.

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54 minutes ago, njee20 said:

I tried that too and it didn't make a difference, but you should be able to put it in place downstream too IIRC, where the next PSX would go if you had multiple power zones.

 

I'll re-wire it one day and work out why, it's nothing obvious, it's still a good product! I did have to slow down the delay slightly as I found you could get momentary shorts from some stock over pointwork which were not enough to interrupt continuity, but were enough to cause the PSX to shutdown.

Multiple PSX units should all be in parallel and fed directly from the booster. If you are using a Digikeijs DR5000 then forget it. That thing shuts down too fast even for a PSX. Been there, done that, gave up. I now only power the track from boosters that have their loconet messaging switched off. 

 

If you are getting wheel shorts on your pointwork you need to look at some gapping and rewiring. I'm assuming you are using insulfrog points without insulated rail joiners. This is not DCC friendly. The only time you should ever get a short is when going through a wrongly set point or a derailment. 

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'Multiple PSX's would be in parallel not series !!!

Compare to your household mains fuse box/breakers - incoming 100A or so,  32A 16A and 5A circuits for various parts IN PARALLEL ...  ie when 1 trips, the others are still working.

 

So with 1 central unit ---------dcc output---------------------------------------------------------------------------------------- Accessories......

                                                                                             !                                    !                                !

                                                                                       PSX A                            PSX B                      PSX C

                                                                                            !                                     !                                !

                                                                                       TRACK A                      TRACK B                     TRACK C

Example: 3A-5A from central unit    1-2A for each PSX  (ie less than central unit

 

Accessories might include your programming track - or this can be a separate feed - it MUST NOT go via a PSX

PSXs will automatically attempt to reset every 2 seconds .... useful when the 'reset' button is not near the derailement

PSXs ONLY break 1 rail connecttion:  USE PSX-AR if you want or need to break BOTH RAILS connections

It can be useful to position the 'diagnostic LEDs' where they can be seen easily  - not hidden beneath the layout.

 

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1 minute ago, njee20 said:

The PSX manual tells you to wire them in series, although obviously you can wire them in parallel.

I see the confusion. It looks like series but if you wire multiple units you are actually wiring in parallel as the input on J1 is directly connected to the output on J1. Effectively you are taking the output from the booster, connecting to J1 (3,4) then connecting J1(1,2) to the next one's J1(3,4)  Wiring in series would mean connecting the J2 track output of the first unit to the J1 input of the second. 

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I just have a NCE EB1 breaker in the track circuit. It means accessories still work after an overload on the track. It has plenty of setting options available with lots of CVs.

I've also got a couple of boosters (not yet connected) which can be also reset with a CV.

Edit I thought this had been posted hours ago but when I turned the device on it said posted just now so is now irrelevant!

Edited by melmerby
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3 hours ago, njee20 said:

I bought a DCC Specialities PSX-1 for exactly this purpose. I like it because it means the layout recovers itself after a short, but it hasn't actually solved the problem with my accessories shutting down (and all the point servos cycling), despite being 'downstream' of it. I suspect that's my implementation, but I can't fathom why!

 

I take upstream to be the input side of the PSX, connected to the booster, and downstream to be the output of the PSX.

 

Accessories should be connected upstream of the PSX (nearer the booster), the main track downstream of it. That way the PSX works if there is a short on the main track but the accessories remain powered.

 

If you wire the accessories downstream of the PSX then the PSX is protecting for shorts on the accessory bus, which are far less likely to occur.

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Thanks for the replies. 

Pointers about current ratings and timings have been very useful.

 

I had envisaged splitting the dcc feed from the booster into two parallel busses (by bus here I mean both wires from the booster in my case both J and K from the Lenz system) and putting just one breaker in the pair that goes to the tracks.  The other would go directly to the accessory decoders.  From what I have read above this would appear to do what I require.

 

 

 

                  Lenz command    J _______________________________________________________________________________________    

                  station/booster                         |                                                                                                                                    Track bus via circuit breaker

                                                 K __________ |___________________________________________________________________________

                                                                      |         |

                                                                      |_____|______________________________________________________________       

                                                                                 |                                                                                                                 Direct bus to accessory decoders

                                                                                 |____________________________________________________________

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@Nigelcliffe is this software update for Railcom compatibility to the MERG DCO something in the past 6 months? 

 

I ask ask because I tested 2 last year and they failed catastrophically if a Railcom signal was present on the track. I was told that they were Railcom compatible but they most definitely were not  :(

 

Th only one one I have found that doesn’t fall over with Railcom is the NCE EB1 but you can’t read CVS on main with it - however at least it doesn’t fall over with Railcom present :)

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32 minutes ago, WIMorrison said:

@Nigelcliffe is this software update for Railcom compatibility to the MERG DCO something in the past 6 months? 

 

I ask ask because I tested 2 last year and they failed catastrophically if a Railcom signal was present on the track. I was told that they were Railcom compatible but they most definitely were not  :(

 

 

I can't give you a date on the firmware, but its three or four years. 
It is *not* the standard firmware in the kits, it has to be found (its moderately difficult to find on the MERG website) and flashed into the PIC used in the DCO before assembly.    The kit-supplied firmware does not work with RailCom.

 

 

My Railcom testing was very limited as we're not currently using Railcom on the layout.   I turned RailCom on at the command station (Lenz), and checked that I could read things at the track (Hans De Loof reader, Zimo decoder, Lenz decoder).  Repeated the reading tests downstream of a DCO, and checked the DCO still functioned if track was shorted.   With the Zimo decoder, I got loco ID, loco speed (different to throttle speed), and other decoder parameters.  With the Lenz decoder there is less information, but did include loco ID.    

Railcom was then turned off again as it causes serious running problems with some locos fitted with older decoders.  

 

If we were to turn RailCom on for actual running, we only need to read loco address, either in fiddle yard or in the roundhouse.  In all cases it will be a single loco within a detection/reading block.   But before any decision about turning on RailCom, all the locos with old RailCom-hostile decoders have their decoders replaced.

 

 

Independently of the big layout, I've used the modified firmware MERG DCO on my own setup, using a short pre-amble cutout from a DCC4PC cutout generator on my Digitrax system.  I get loco identification with it, which is all one can get from a short pre-amble.

 

 

 

- Nigel

 

 

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@Nigelcliffe - that is interesting as that is what I was told *should* happen but it most definitely did not. Both units showed short circuits when Railcom was present and I was assured that they had the latest Railcom enabled firmware present.

 

If I could guarantee that it worked then I would consider trying one again .

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17 hours ago, Crosland said:

 

I take upstream to be the input side of the PSX, connected to the booster, and downstream to be the output of the PSX.

 

 Accessories should be connected upstream of the PSX (nearer the booster), the main track downstream of it. That way the PSX works if there is a short on the main track but the accessories remain powered.

  

If you wire the accessories downstream of the PSX then the PSX is protecting for shorts on the accessory bus, which are far less likely to occur.

Yes I think my terminology was at fault! I've tried connecting my accessory bus direct to the booster, and using the J1 output on the PSX (which is essentially the same thing, but what I was referring to as downstream), after a couple of seconds of a short my servos all cycle in unison, which is usually more destructive than the original short, as anything sat astride any pointwork then gets derailed! I must have wired it wrongly somewhere, but I certainly can't see where, there aren't exactly many connections!

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5 minutes ago, njee20 said:

Yes I think my terminology was at fault! I've tried connecting my accessory bus direct to the booster, and using the J1 output on the PSX (which is essentially the same thing, but what I was referring to as downstream), after a couple of seconds of a short my servos all cycle in unison, which is usually more destructive than the original short, as anything sat astride any pointwork then gets derailed! I must have wired it wrongly somewhere, but I certainly can't see where, there aren't exactly many connections!

That says to me your booster is still shutting down during the short, or the current output is being pulled down as the PSX tries to "test the waters" before resetting. What is your command station/booster model? You will likely need to adjust the short timing settings. One other thing to consider is the current rating of your power supply, booster, and current setting of your PSX.  What you should have is current of power supply > current output of booster > current trip setting of PSX. If you have a 5a booster but only a 4.5a power supply, the current supplied by the power supply will drop before either the booster or PSX can trigger. This dip can cause your servo decoders to cycle. 

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When I used a small (G scale portable) shunting puzzle layout with Servo-controlled points, we experienced the large current demand of all the servos starting up (or after any 'emergency stop' removing track power) ... these were being driven from just 2off  4 output Bachmann/ESU ServoPilots.  One of the reasons we reverted that layout to conventional LGB 1/2 turn motors. 

 

On another of our portable layouts, I also decided to add a ' conventional ' resettable fuse on the accessory bus - as it could otherwise be fed 3-5A continuously when it rarely used  1 Amp  ( in this case all point motors were now driven from TrainTech CDU point modules - so only controlled current flow, BUT I also added some other 'power consumers'  on the accessory bus ... and it was sensible to provide some degree of protection to the rest of the layout (ie keeping trains running on the track busses) if there was any fault on the accessory bus - they cost very little, and are relatively 'slow acting'  - and as they are a push-button reset, they cannot be ignored in the event of a fault. 

 

When responding about loco decoder problems, I usually suggest the use of a multimeter - and here too, I would recommend an ammeter to monitor how much current is being drawn from the central unit ... in many cases, this is available on a menu screen of the controller or central unit (eg ZTC511, Roco MCP or Z21/+multimaus, Massoth Dimax and many more).  I use Rrampmeters on my loft layout (readable across the room).    My recollection from Zero-1 days is of Peco (original type) point motors taking 6A and a 'larger'  H&M taking 'only' 4 Amps... for example ....  Servos take most power when changing position.

 

On the PSX's - do double check the same phase is being cut by each one - otherwise a fault at a boundary between 2 PSXs on the track can bypass the cut-out ...   using their 'loop through' connections can make this error more likely, from the way they are arranged, as I recall ??  .... if in doubt use the AR version which isolates both rails.

 

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1 hour ago, AndrewC said:

That says to me your booster is still shutting down during the short, or the current output is being pulled down as the PSX tries to "test the waters" before resetting. What is your command station/booster model? You will likely need to adjust the short timing settings. One other thing to consider is the current rating of your power supply, booster, and current setting of your PSX.  What you should have is current of power supply > current output of booster > current trip setting of PSX. If you have a 5a booster but only a 4.5a power supply, the current supplied by the power supply will drop before either the booster or PSX can trigger. This dip can cause your servo decoders to cycle. 

Yes, that is rather what it feels like. It's an ECoS 50200, which is 4A? Accessory power supply is 10A IIRC. I've not touched the PSX current settings (apparently it's "about 4A" by default, but presumably if the current trip setting of PSX was greater than than the ECoS output it just wouldn't be tripping, the ECoS would get there first? I could try adjusting it down slightly. I don't think you can adjust the short timing settings on the ECoS; but the PSX definitely does its job, the ECoS isn't cutting out (requiring manual intervention to restart), but it's like the current still fluctuates enough to freak the accessories out.

 

I apologise, I've somewhat hijacked this thread!

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2 hours ago, njee20 said:

 

I apologise, I've somewhat hijacked this thread!

 

‘No worries, my queries have, mostly, been answered and if you find a solution as a spin off then it’s win win.

 

I am now just deciding which make/model to go for.  If I were going for more than one section I would consider MERG but as I want just one, I will probably go for a  proprietary make.

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2 minutes ago, BoD said:

 

‘No worries, my queries have, mostly, been answered and if you find a solution as a spin off then it’s win win.

 

I am now just deciding which make/model to go for.  If I were going for more than one section I would consider MERG but as I want just one, I will probably go for a  proprietary make.

Just avoid ones like the Digitrax PM42 that use relays. Again the PSX is my recommendation. Coastal DCC has them in stock. BTW the PSX2,3,4 are just the same devices that haven't been split. Ie, the PSX4 is 4 units on a single board without the perforation in the circuit board being cut. 

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I have exactly the same question as the original poster.  I note when reading the data on the PSX it states "Very Low Voltage Drop: Total breaker on resistance is less than 0.060 ohms, so the PSX has a very low voltage drop even at high currents. Better than detectors that use a diode voltage drop".

 

Does anyone know whether the NCE EB1 has similar resistance / voltage drop characteristics or if it uses a diode to drop voltage?  I couldn't see that information. For the PSX, I'm assuming with a 5 Amp system drawing the full 5 Amps the potential difference across the output terminals to the track will be less that 0.3 volts less than the track voltage output by the command station.

 

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My recollection, for the benefit of those using multiple sound-equipped locos, is that the PSX was developed from the original and successful PS specifically to allow the current in-rush that occurs when sound decoders boot up. Whether other modern breakers offer the same intelligent facility I know not. 

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1 hour ago, Oldddudders said:

My recollection, for the benefit of those using multiple sound-equipped locos, is that the PSX was developed from the original and successful PS specifically to allow the current in-rush that occurs when sound decoders boot up. Whether other modern breakers offer the same intelligent facility I know not. 

The NCE EB-1 has adjustable trip time 16mS -512mS to allow for power up surges.

The EB-1 has been around a long time > 7 years.

 

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