Z scale DCC circuit protection options

JoshMurrah Dec 23, 2019

  1. marmot

    marmot TrainBoard Supporter

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    Good idea!
     
  2. RobertAllbritton

    RobertAllbritton TrainBoard Member

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    My current solution (no pun intended) for DCC short circuit protection is four zones of PSX protection. They all have buzzers attached to them, and when under computer control, they report back to the PC. If there is a short, then the PC plays a voice recording announcing which zone is impacted: "Short Circuit Track 4!" A few years back, I got a pair of decommissioned crossing lights, mounted them to the rafters, and now they flash back and forth when there is a short circuit. Its all pretty hard to miss.

    Why all the fancy stuff? Well, if I'm operating the layout solo, it can take a while for me to walk / run from one side to the other. 20-30 seconds is a long time when something is shorting, and even longer if I'm not sure exactly where the problem is. Jeff's advice is exactly correct: the best way to prevent damage is to Watch Your Trains! My problem is I have the Alps in the way, and tons of spiral tunnels (5 to be exact) and as many as 20 trains running at once. It's impossible for me to watch them all constantly - so I need another solution.

    Some folks are looking for a DC / DCC combined solution, but since I always run DCC, that's not an issue for me. I also think that if you are running DC, then your layout is probably small enough that you can use the Jeff M solution (Watch Your Trains!) and Rokuhan makes an excellent shutdown / manual reset DC power pack to prevent damage.

    On my layout, I'm also running something like 50+ turnouts (Tortoise stall motors) through the DCC system, so the base draw from the command station is almost 1/2 amp. Because of that, I found the best setting on the PSX boards was the factory defaults. Lower amperage would trip far too quickly when there was not an actual short. I think the lower amperage setting would work fine with a smaller layout. My main bus wires are also over 100 feet long, so that may have something to do with it too. I don't have a scientific answer, I can only tell you what works in my case.

    Speaking of results, since installing the PSX boards I have had ZERO damage to any train. I'm sure it's still possible to cause harm - I just have not experienced it. And remember, thats running up to 20 trains for hours and hours essentially unattended. Not too bad!
     
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  3. husafreak

    husafreak TrainBoard Member

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    The Voltscooter looks great at that price but I already bought a PSX1, buzzer, and reset button. I just love the idea of a buzzer, even for a small layout. The PSX1 is a complicated device, I don’t think the reset button will be necessary though.
     
  4. shamoo737

    shamoo737 Staff Member TrainBoard Supporter

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    Don’t waste your money on a voltage reducer, but don’t run dcc without short protection. I never ran into a problem with high voltage, but short protection save couple of my locomotives.
     
  5. markm

    markm TrainBoard Supporter

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    I've been thinking for a while that the time has come for me to upgrade from my "most reliable" protection: a drawer of glass fuses; to something better, particularly since I'm upgrading to DCC. I've been watching this thread, plus a few others and reviewed the Model Railroading issues I've mentioned as well as their DCC books. I thank everyone here for the input, although I must admit I'd like to hear more of the bad experiences beyond Jeff and Robert.

    I've pretty much discounted the use of the taillight bulb. The standard taillight bulb, the 30W #1156, will still pass several amps into a short. The bulb used in garden lights, #194.

    Most of the throttles and electronic circuit breakers suffer from two problems. First trip currents are just too high. I figure 1-2 Amps is all I'll really need to operate the trains. Second, the mode of recovery: using voltage as a probe for shorts as this allows for excessive current flow as Jeff describes.

    I had been considering, and may still, design a circuit that would trip in the sub-Ampere range and use a current probe to detect short recovery. That's why I've been attracted to the voltscooter unit. In a discussion with the designer, it uses a current pulse to detect the short after the the initial trip.

    I have to admit I really haven't looked into the PSX. I'e found the user's guide online with some retailers, but I'm looking more for the technical aspects
    and the only website I can find: http://dccspecialties.com/ is coming up as being parked on GoDaddy. So if anyone has a better link, I'd appreciate it.

    Mark
     
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  6. SJ Z-man

    SJ Z-man TrainBoard Member

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    I have some of his earlier products from two years ago that are a simple “Varistor”, similar to an electronic (semiconductor) light bulb. http://voltscooter.com/?page_id=134
    It has a finite amount of resistance so higher currents make it heat up and change (higher) resistance. As said, it leaves a reasonably safe amount of current to track. These do not have a need for external power (like the new one with the switch and LED).
    This newer product appears the same, just adding an LED and Switch (nice) but required an external DC power supply. Unless this external DC supply is somehow optically-isolated form the DCC circuitry, there could be some serious issues when wiring the breakers in (most always be on the same buss wire) and should NOT Be used across Booster districts.
    While the earlier basic circuit and apparently the new advanced circuit have the semiconductor fuse, they will still supply the full Booster current for a finite amount of time.
    And, trip action will be likely be different (more sensitive) when running Permanent Magnet motors like märklin and especially MTL as they draw much more current than the AZL motors.
     
  7. SJ Z-man

    SJ Z-man TrainBoard Member

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    I have some of his earlier products from two years ago that are a simple “Varistor”, similar to an electronic (semiconductor) light bulb. http://voltscooter.com/?page_id=134
    It has a finite amount of resistance so higher currents make it heat up and change (higher) resistance. As said, it leaves a reasonably safe amount of current to track. These do not have a need for external power (like the new one with the switch and LED).
    This newer product appears the same, just adding an LED and Switch (nice) but required an external DC power supply. Unless this external DC supply is somehow optically-isolated form the DCC circuitry, there could be some serious issues when wiring the breakers in (most always be on the same buss wire) and should NOT Be used across Booster districts.
    While the earlier basic circuit and apparently the new advanced circuit have the semiconductor fuse, they will still supply the full Booster current for a finite amount of time.
    And, trip action will be likely be different (more sensitive) when running Permanent Magnet motors like märklin and especially MTL as they draw much more current than the AZL motors.
     
  8. rray

    rray Staff Member

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    I was on http://dccspecialties.com/ site in November, looking at autoreversers and hare manuals. I have about 100 hare generation 1 decoders I had collected for my retirement layout, and wanted to get a manual for the first gen before they disappear forever.
     
  9. markm

    markm TrainBoard Supporter

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    Well Jeff, that's why I only bought one and why I have a very large e-waste box in the garage.
     
  10. rray

    rray Staff Member

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    You should have seen the e-waste bin I had before I moved. It had probably 200-300 outdated gizmoes in it, and weighted hundreds of pounds. :D
    I had to hire a guy to take it 3 counties away because of the strict e-waste laws near where I lived, making it almost impossibe to get rid of. I learned my lesson... Now I immediately toss all old or unused electronics at first opportunity.
     
  11. shamoo737

    shamoo737 Staff Member TrainBoard Supporter

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    I am glad that I am not the only one that keeps old burnt out decoders. It’s not like it’s suddenly going to work after couple of years.
     

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