Swing Bridge Track Power Cut-off

dcsun Feb 12, 2016

  1. dcsun

    dcsun TrainBoard Member

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    Hello All,

    I did a search and didn't see anything to do with this so my apologies if it's already been covered somewhere. I'm building a new HO DCC (18V) around the room layout that will include a lift-out section (actually a powered swing bridge). I'd like to cut track power to a section on either side of the bridge when it's out of the closed position using a contact switch on the bridge structure. Just curious if anyone had any experience with what types of relays would work best that could save me some wasted money, waiting for parts, and of course hair pulling!


    Thanks,
    Dave
     
  2. TwinDad

    TwinDad TrainBoard Member

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    I simply used a SPST micro-switch like this one: https://www.sparkfun.com/products/9414

    I wired it to the bus/feeder that is powering the last section of track so that when the lift-out is down (in the "run trains" position), the switch is closed and when the lift-out is open ("don't run trains"), the switch is open. No relays or other fancy materials needed.

    These particular switches are rated for 3A, which should be fine for a short section of track leading up to a bridge.
     
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  3. Arctic Train

    Arctic Train TrainBoard Member

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    I used brass contact strips on the hinge side of my swing out gate. When the gate is opened, these cut the power to the gate track as well as about 2 feet of track that lead up to the gate. This keeps trains from falling into the abyss if you forget to close the gate. On the latch side of the swing gate I used a small micro switch to cut power to the lead tracks. When the gate is open more than a 16th of an inch power is cut to prevent a derailment.

    Brian
     
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  4. dcsun

    dcsun TrainBoard Member

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    Thanks for the replies guys. I did order some normally open momentary switches (more the push-button style but essentially the same as those SparkFun ones) that are rated for enough that the track could just run through them. It's going to be double tracked and one of those a reversing section, so I was hoping to get away with not having four contact switches on the thing, but I might start out with that route and see how it goes.

    Dave
     
  5. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    You don't want "momentary", you want it normally open, and then full close. A momentary switch will just "flicker" closed, then reopen (this is what you use for push button switch control, etc)
     
  6. dcsun

    dcsun TrainBoard Member

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    I was under the impression a "momentary" switch means that when you release the button it goes back to its previous state, rather than the "push on, push off" type that holds its state until pressed again. Further research required I guess, or I may just wait and play with whatever I bought from eBay when it arrives in 6 weeks!

    Dave
     
  7. acptulsa

    acptulsa TrainBoard Member

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    You're right. I expect either is called 'momentary'. But any switch that continues to make contact only as long as you continue to hold it has always been called a momentary switch in my experience.
     
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  8. TwinDad

    TwinDad TrainBoard Member

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    But this is just what you want... a normally open momentary switch. It stays closed only when the bridge is pressing on it, and as soon as the bridge is moved to release pressure on the button, the switch opens. Momentary is just the ticket for a lift bridge.
     
  9. acptulsa

    acptulsa TrainBoard Member

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    Mr. Brodzinsky was warning about switches that open the circuit before you release them, and are also called momentary switches. I was just saying that however it is that you can tell them apart, it isn't the word 'momentary'.
     
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  10. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    I stand corrected on the nomenclature
     
  11. TrainboySD40

    TrainboySD40 TrainBoard Member

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    dcsun likes this.
  12. dcsun

    dcsun TrainBoard Member

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