Z scale DCC circuit protection options

JoshMurrah Dec 23, 2019

  1. JoshMurrah

    JoshMurrah TrainBoard Member

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    OK, so I've done a search or two, and read up on the good info from Garth and Rob A regarding Z scale power although those threads are a few years old now... there's not a lot of great info about circuit breakers for Z scale.

    So my question here is, what's everyone been doing for DCC circuit protection?

    Are you relying on the booster for it? I know for a hard fact that's a bad idea with Digitrax's full size boosters, I got the N scale melted trucks to show for it haha.
     
  2. husafreak

    husafreak TrainBoard Member

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    I have been getting a lot of advice about this as well. Since I will be using the NCE system it boils down to: watch your trains, maybe use a 12v power supply instead of the slightly higher voltage factory supply, watch your trains, maybe put an automotive tail light bulb in the circuit to act as a fuse, watch your trains, and don't worry too much about it as it is pretty rare to damage a train. There may be more posts about this on the AZL forum as well.
     
  3. tjdreams

    tjdreams TrainBoard Member

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    I use the DCC Specialties PSX1 on my test track and we use the PSX-AR series of Circuit Breakers on the layout.

    David
     
  4. SJ Z-man

    SJ Z-man TrainBoard Member

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    The PSX default Trip Current is 3.8 Amps. It can be Jumper to a lower 1.3 amps by jumpering J6 1-2.
    NCE's EB1 is 2 amps but can be hacked down by paralleling a o.5 ohm resistor across the board mounted resistor to get it down to ~o.7 Amps. Their CP6 with light bulbs is 1A

    JUST SO YOU KNOW: *ALL* circuit breakers will deliver the DCC's system's FULL current (e.g 2+ Amps for NCE, Digitrax, etc) which comes from the Power Supply. The circuit breaker detects the short in ~.05 to .25 seconds and then disconnects the power. *But* then turns it back on again (to re-test for the short) in ~.25 seconds. This process repeats until you may notice you train is not running, that 'smell' or ...
    The Light bulb is a bit different but still the same max power supply current initially but as the bulb now begins to glow, the current will reduce but not to zero but to a somewhat lesser amount than the bulb's rating (e.g 1 Amp for NCE's CP6)
     
  5. tjdreams

    tjdreams TrainBoard Member

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    The PSX series has a place right on the board to add one of their buzzers which will sound when their's a short and their is a place to add indicator lights which will light in the event of a short. Their's also a setting that will keep the power off until a reset button is pushed.

    The PSX series is packed full of features. They may not be the cheapest option out there but they are cheaper than a new Loco and they do work. Take a few minutes and read through the instruction manual. It may be just the ticket your looking for.
     
  6. rray

    rray Staff Member

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    There you go, a PSX wired to a big red flashing light and a fire bell! :D (Smiles of utter JOY)
     
  7. Svein-Martin Holt

    Svein-Martin Holt TrainBoard Member

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    I have used an automotive tail light bulb connected in one of the power lines to the track, for many years. If you need more powerdistricts, you can use a bulb in each section. Then not the whole layout is shut down, only the section with problems.
    This is a cheap and good working solution. NCE have a product that uses lamps for protection: CP6.
     
    rray likes this.
  8. husafreak

    husafreak TrainBoard Member

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    Well, I really like the idea of a buzzer or fire bell ringing out to get your attention quickly, as long as you are in close proximity you should be good.
     
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  9. marmot

    marmot TrainBoard Supporter

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    I'm working on building my first Z-Bend module. What do you do for circuit protection when I'll use DC at home (for now) but the module is sure to be utilized as DCC at shows? That is, is there circuit protection available that is compatible with both types of power? I see one DCC circuit breaker that claims to be ideally suited to DCC.
     
  10. JoshMurrah

    JoshMurrah TrainBoard Member

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    OK, so I wanted to keep my original message simple and just ask the question... now that there are some most excellent answers, thanks guys!... I'm gonna post what I have built, and it seems to be pretty much in line with what you guys are saying... I just have to add the diodes, and I'll have what I'm showing below all done.

    DCC side has...
    13v supply
    Digitrax DCS240 + Digitrax LNWI
    RRampMeter (amperage display)
    two PSX-1's (two circuits), buzzers installed
    two diode reductions (4 sets of bi-directional, 4v drop, final voltage under 10v)
    track connector outlets (two sets)

    I have selector switches for each circuit, to allow for DC or DCC...

    The DC/accessory side has:
    12V 10A supply
    two Rokuhan RC-02's
    accessory bus connectors (two sets)
    USB charging outlet
    T-TRAK-Z_powerfrontupdate.png T-TRAK-Z_powerbackupdate.png
     
  11. JoshMurrah

    JoshMurrah TrainBoard Member

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    There is a question above asking about what circuit protection is available for DC... I have found, just by trial and error, that the Rokuhan RC02's are SUPER DUPER sensitive to trips and overloads... so I just use them alone when on DC, no additional protection on the DC side.
     
  12. SJ Z-man

    SJ Z-man TrainBoard Member

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    The light bulb is universal. The NCE EB1 and PSX require DCC as they reset on each polarity.

    Most all DC controllers are ~ 1 amp or less so fairly safe. Some of these controllers, like Rokuhan's will shut down (no current) but simple controllers like the MRC and similar will still deliver current. For stalled motors, this means HEAT. Same with wheels which carry the current still will get hot.

    In Josh's example images, there is a 10 amp power source. I don't care what circuit breaker use, you will have ~10 amps (x 12 Volts =120 Watts) for some period time, during the short. And, if you read the PSX Docs, you'll see that it turns right back on several times per second (unless you use the Trip Once which requires you to keep manually resetting the PSX). You need a much lower current supply and place additional Boosters (various sources like Tam Valley, Rail-Stars, etc.) that can supply the potential needed additional power farther away.

    With those large bus wires you are using, you won't have any issues over a large layout (like our BAZ BoyZ 10-15 Z-Bend modules).

    Ask Robert about the time we started with the only choice NCE Pro which was 5 Amps. A Märklin loco bridge an opposite polarity on a turnout and there was a flash of light from the loco truck with the following smoke whiff. Near completely disintegrated the wheel wiper that was trying to carry the 5 amps between the front and rear axle. Then there was the time that Rob was trying to clean the frog of a märklin turnout's frog wheel contacts. Poof, flash bulb.
     
  13. rray

    rray Staff Member

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    Yes, I remembert that. On my Timesaver module, I had built with all Marklin turnouts which in my opinion are a disaster on a timer. The Marklin frogs are pseudo powered by foil railhead material which makes electrical contact to the flanges. While cleaning muck from the frog on a DCC powered layout, those foil railheads touched and briefly glowed bright like a 100W bulb filament. The hot molten railhead stood straight up from the heat, and it was the end of that turnout. It happened so quick I didn't notice the any shutdown of DCC at all!

    Another time on a very DCC friendly Peter Wright turnout, Jeff noticed a loco stalled at the turnout frog. A wheel had jumped the rail before reaching the turnout, and when that loco wheel jumped the frog it shorted against the diverging rail. The DCC was pulsing on and off for a couple seconds and when I pulled the loco off the track, the hot plastic pinion axle dripped down with a wheel attached to it. The whole truck was a melted mess.

    The only true safe DCC breaker would be a trip and require a manual reset. Still, DCC is that much easier than DC block operation to use to justify the risk.

    Z Scale DCC Tips:
    *Always watch your trains run, if you can't watch them, park them.
    *Keep debris off your track, and keep your track clean.
    *Don't use an 8A or 10A booster with Z Scale, meltdowns can happen too fast with them.
    *Marklin turnouts can cause a fire on your layout! Don't walk away with trains running.
    *Did I mention to Always Watch Your Trains?

     
  14. JoshMurrah

    JoshMurrah TrainBoard Member

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    Good discussion guys, I really appreciate it!

    I totally agree that 8 amps (the amperage limit on my Digitrax DCS240) is overkill and can be dangerous... I’ve seen that much power de-sheath small feeder wires and melt passenger trucks. To make things worse, for Digitrax at least, the circuit protection included is just for the booster, not to save your rolling stock, it’s terrible.

    I will also say, however, that I have NEVER seen those issues for anyone that runs the PSX’s. They’re super sensitive. That’s just an opinion on my end but they’re some amazingly complex devices and I do put some faith in them.

    I have seen issues with Digitrax’s PM42 circuit protection and wouldn’t recommend them. They’re solid state / old tech and slower to trip, and I’ve seen them fail open without protection.

    What makes things worse for me personally is that the DCS240 that I own is the most feature rich, most compact command station Digitrax makes, even has USB programmer ability onboard. I just wish you could turn down the amperage.
     
  15. JoshMurrah

    JoshMurrah TrainBoard Member

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    After reading the manual again, there is one thing I can do - it says if I feed power via the barrel connector, the unit will self-limit to 5 amps. I should probably do that. The PSX’s are gonna limit that down anyway tho. The sampling rate is crazy on those so again I’m putting some level of faith in them.
     
  16. markm

    markm TrainBoard Supporter

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    The February issue of Model Railroader has a piece of this subject with references to previous articles (June 2017 & May 2019). They describe a product from a company called Voltscooter with an adjustable trip of .6-1.8 A, which to me would be ideal for the average Z scale layout. Unfortunately at this writing their website is trashed and I can't get further information.

    Correction, their home page is trashed, search took me to the product page directly:

    http://voltscooter.com/?page_id=343


    Mark
     
  17. rray

    rray Staff Member

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    Fair price, a non greedy outfit.
     
  18. markm

    markm TrainBoard Supporter

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    Quick update on Voltscooter. The website is working. I've ordered a unit to try out.
     
  19. marmot

    marmot TrainBoard Supporter

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    Wow. This looks very encouraging. I like the price, compact size, and a lot of features about this since it could really simplify the need for a switch between DC and DCC circuit protection (since the PSX isn't compatible with DC).

    The relatively low trip amperage values are great. After reading their instruction pages, I don't like the need for a soldering iron to tune the "jumpers" for the amperage amount. That makes it more complex for a module expected to be used at shows if you need to modify it quickly to avoid an issue.

    I still think I'll get some of these and use some trial and error for a reasonable trip setting.
     
    Last edited: Feb 4, 2020
  20. markm

    markm TrainBoard Supporter

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    The low current trip is what attracted my attention. From my DC measurements, the worst case I've seen for a non-Märklin locomotive is under 100 mA.

    If I were using it on a module, I think I'd remove both jumpers and bridge the gaps with a >=2 gang DIP switch.
     

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