DCC Circuit Breaker: PSX-1

[papajulietdelta]

Correction;  The PSX-1 is manufctured by DCC Specialities from the USA.

[RDS]

Hi

On my layout, I have two Hornby boosters, with 4.0A supply, providing power, together with my Elite.

If I get a short circuit, such as running into a point that is not set correctly, the Hornby booster shuts down.  To reset, I have to go under the baseboard and switch off the power pack, until the overload clears on the booster.  A pain!

I saw the PSX-1 manufactured by DCC Supplies advertised and thought it might be an easy solution - automatic circuit breaker.

I have purchased one and am extremely disappointed that it does not work.  If I short it in automatic mode, it also overloads the booster.  Even in manual mode (no automatic reset), it still overloads the booster, requiring a clearance as above.

It is currently set with a default trip current of 3.81 amps.  With a jumper, I could change this to 1.27 amps, which seems low.  There is another setting of 2.54 amps which can be programmed via a CV value.

Does anyone have any experience of the PSX-1?

Has anyone found a way to clear the overload from a Hornby booster, without removing the power to it?

Cheers

[Chrissaf]

In my view. The PSX-1 is an American designed and made product predominantly designed for the American market, where power boosters in excess of 6 or 8 Amps are common place. These high currents make circuit breakers near essential bits of kits to include on the layout to protect the layout, boosters and controllers. And as such, a circuit breaker trigger current of 3.81 Amps is totally appropriate when your booster is capable of 6 or 8 Amps or more. However in the UK, 4 Amps is more the maximum current norm, hence the issues you have found, as the default 3.81 Amp trip current is too high for the UK market track power products. The Hornby booster documents 3 Amps as being the nominal trip current in the user guide. This is less than the default 3.81 Amps of the PSX-1.

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If you continue to use the PSX-1 with the Hornby 4 Amp Power Booster supply, you will need to configure it to trip at the 1.27 Amp or 2.54 Amp setting, so that it trips before the Hornby booster trip current is reached. IIRC, the PSX-1 CV for setting the 2.54 Amp trip current is CV49.

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You may decide that you do not want to keep the PSX-1 in circuit, because it is downgrading the amount of current available to the 'booster' section of the layout. So in that case, why not re-route the power supply of the Hornby booster via your control position (extend as necessary) and fit an auxiliary 'on/off' switch in the DC supply feed that you can use to reset the booster without having to crawl about under the layout.

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[96RAF]

I installed a small mains type I/O rocker switch in the case of my 4-amp supply. This switched the output side only as there wasn’t room to put the switch on the mains input side.

 

Please note this modification was purely for my own convenience to be able to switch the power to my Elite on and off during repeated track testing. It does NOT switch off the mains side of the unit so it is not a true safety isolator switch as the transformer remains live all the time it is plugged into the mains.

 

Anyone contemplating making a similar modification should note that there is lethal UK mains voltage inside the 4-amp supply and work on such equipment should be carried out by a certified electrician.

 

Rob

[2e0dtoeric]

If you don't want to, or cannot, extend the mains supply to where you can reach it to operate the on-off switch, how about getting one of those remote switched mains breakers, such as the Energenie. (There are others).

I've got three sockets that can be switched independantly or all at once, via a tiny hand-held button thingy a bit bigger than a car electronic key.

www.energenie4u.co.uk

[BeanCWappre]

Hi, I have two layouts having the Hornby booster followed by the PSX1. The PSX1 is set to 2.54amps, setting 02.   It protects the Hornby Booster nicely as the Booster never overloads now so does not ever need the "switch off then back on" treatment. I often run 3 or 4 sound locos at the same time which is really quit enough to cope with.  I hope this helps. 

[Fishmanoz]

As a matter of interest PJD, how big is your layout and how many locos of what types do you run at once that you need 2 boosters?

[St1ngr4y]

I have a simple "push-to-break" switch between the power supply pack and my booster. Having cleared the cause of the short circuit, I just push the button for a second or two and the booster is reset.

 

Ray

[papajulietdelta]

Thanks BenC&W.  That is the same advice that I got from the supplier: CoastalDCC.

Also the others, who suggested putting a switch in the power lead to the booster.  It would save my knees but I would still need to move along the attic from my operating position.

I think I have managed to set CV49 to 2 (2.54A) using the single CV programmer in Decoderpro with a Sprog, directly connected to the PSX-1.

Unfortunately, I cannot read the CV to check with this set up.

Anyway, I have now connected it between the booster and track and it seems to work, cutting out when I short and resetting automatically, when I remove. 

Now there is no annoying delay powering off the booster and waiting for it to reset from overload mode, before repowering.

I have managed to have 6 locos with sound activated with 2 running and the turntable (Heljan) moving at the same time on that power district, without overloading circuit breaker.  So I guess, it is doing it's job.

I did notice a problem with one Seep point motor where I was using the inbuit switch to change the frog polarity. It was momentarily causing a short circuit when switched one way which caused a blip, long enough to restart the sounds.  I have disconnected the switch and now rely on the blades for power to the frog.  (I use peco 100 and had not DCCed the point).

I wonder how the circuit breaker will fare on another power district where I use frog juicers.

Cheers 

[papajulietdelta]

Hi Fishy

I am developing my layout in our loft.  I shall have a double track continuous loop in the room, which is 7.0m by 2.0m.

There is a five platform junction station, which is part of power district 1, together with the double track down one side..

Power district 2 is the other half of the double track plus storage and a reversing loop.

Power district 3, where I have now fitted the circuit breaker, is the branch, terminus station and motive power depot, including turntable.

Seperate boosters for each power district are probably over the top, but I did not want to go back if I was short of amps. 

Now to get two more PSX-1s cutouts as they seem to work.

Cheers

[Fishmanoz]

Thanks PJD. If you think you may exceed a single supply, wiring for but not necessarily with a booster is a good way to go.  A few IRJs and a little extra wire is cheap.  But boosters are expensive so can be worthwhile, having made allowance for a booster, to run without it for a start and see how you go.  Then you can install later if needed by separating the districts you've wired for.

[Phil_Spiegel.]

I use PSX;s on all our 00/H0 layouts to create 'sub-districts' where the maximum current possible is lower than the total capability of the central controler or booster.

Don't forget, that the larger your current capability, the lower the circuit resistance needs to be to ensure that the full current can flow with minimal voltage drop, AND THAT THE 'COIN TEST' [short circuit protection] works in all parts:  This is something which may be overlooked by those converting an existing 'sectioned' layout' to DCC  with a 'high capacity' controller [ie 3-5A and not 1A per loco/section as with analogue].

Eg a [select or similar 1A 'starter' dcc] Controller, as supplied comes with a 1A supply and (after removal of suppression capacitors in power feeders) could replace an existing analogie sectioned layout 'instantly': the wiring being able to take 1 A continuously. A short circuit anywhere on the track will probably cause enough current to flow to trip the power supply ( not the Select itself, as it can cope with the larger 4A supply..)

If the power is upgraded to 4A, then the wiring must be capable of supplying 4A continuously as normal - AND of low enough resistance to allow the short-circuit current to flow long enough ( a few milliseconds) to trip the Select/Power Supply protection  ... Simple ohms law  ...TEST IT with a coin or other metal object in all parts of your layout ... the controller should protect itself (and therefore you) almost instantly (faster than analogue controllers used to).

REMEMBER that a circuit with a 4A Supply/Controller NORMAL MAXIMUM will CONTINUE TO PROVIDE 4A if the circuit has low enough resisitance (and it should do!)  ... a SHORT CIRCUIT should produce a NOTICEABLY HIGHER CURRENT ... BUT this needs the resistance to be LOW ENOUGH for it to flow ( V=IR ohms law )

However, as with the equivalent philosophy of household wiring - where you may have a 100A supply, NOT ALL the wiring is designed to take 100! or even 30A or even 13A .... LOWER RATING (devices and) WIRING are protected by using CIRCUIT BREAKERS of lower ratings ...  wiring BEYOND those breakers only needs to be of the lower capability.....   Eg a Shower 40A, Kettle 13A, Bedsite Light 0.1A..

For MANY layout users, it is only Solenoid Point Motors which MIGHT need the 'full' or a large proportion of the current capability eg 3A+ ... and these are best powere dby their own 'accessory bus' .. which also presents a low risk to short circuits because it has no connection with the open, exposed rails of the track .... it can be fed directly from the Controller or Booster Output.

My TRACK AREAS are ALL fed through PSX's - limiting the current availabke in each area AND ALSO providing a useful Automatic-Reset Mode - where it tries to clear the fault every 2 seconds ... allowing me to go to where the problem is (eg a derailment) and clear it ... with the power coming back to that (sub-district) automatically .... and other parts of the layout, supplied through OTHER PSXs, have been continuing to run ... becaue the total current taken at any time never exceeded that of the supply.

BEYOND each PSX, because of the lower, locall current limit, the gaue of wiring can be smaller than if  I was trying to supply them all directly from the full current of the controller  ( which, in the garden with G Scale, can be as high as 8/10/12A !!! .    As a guide, with modern locos (ie excluding old Hornby Dublo and Triang X04 types), each loco only takes about 0.25-0.5A ON THE LEVEL (more needed on an incline!!!) ... and the 'quiescent current' in each of my Power-Districts/Sub Districts, as monitored by RRampneters, shows about 0.25A for any modules and LED coach lighting in that section - increasing to just over 1 Amp for my 'Storage Area' with about 6-8 illuminated trains + locos in 1 area.   So, although, for historical reaons, I have 4 power districts (ie controller+ 3 boosters each with their own Switched Mode Power Supply) I could use just 1 controller for all areas, and still be within my current limit - partly, if not mainly, because I use low-current point motors or CDU point modues or Point Modules which take theor power from a separate 16Vac supply - and not from the dcc signal.

So I strongly recommend the PSX or an equivalent electronic ciruit breaker (BUT NOT 'car headlamp bulbs ! - to slow to protect ) ... and the advantage of the PSX, and one original reason for my getting them, is the intelligent start up controlling a surge current it offers - to cope with sound-fitted (or perhaps stay alive fitted) locos and their cpacitor's inrush current.   A possible cauition - I believe the response speed of more recent PSX's has been changed - and may not match that of those bought some years before - which may affect compatibilty with some controllers - it may be worth checking if purchasing.

[Fishmanoz]

Can’t fault your logic Phil, except as below, but seems to me like a very long-winded way to say bus wiring must be appropriate to the circuit you are using it in.  It is certainly true that the higher the current capability the lower the internal resistance of the supply and so circuit resistance must also be lower if it is to not cause higher voltage drops.  And circuit breakers will offer an extra level of protection as you say.

 

With solenoid point motors, as long as you follow good practice and use a CDU, DC or DCC, your supply is not going to see the high current required to throw the solenoid, only the low CDU recharge current, the reason you use them in the first place.