Atlas Snap Relay

Discussion in 'Track Planning' started by thedowneaster, Jul 1, 2007.

  1. thedowneaster

    thedowneaster Brakeman

    Hi all,
    I'm interested in using Atlas Snap Relays to control Atlas switch machines and staging operations. I've not used an HO switch machine in a very long time. The ones I had 15 years ago were toggled by a momentary contact switch and were powered using the AC terminal on my transformer.

    The snap relay is not a momentary contact switch. Will this not burn out my switch machine?

    In large scale the switch machines run on DC, but you can leave the power to them on constantly since they automatically shut off after the switch is completely thrown.

  2. YmeBP

    YmeBP Member

    Snap relays are exactly like switch machines, they use the same solenoid and require the same voltage. They are powered by the ac accessory terminal on your power supply.

    Here is a thread w/ great info about atlas snap relays in specific.

    I also scanned the instructions from the snap relay and posted a link to it.

    Do you have a particular effect you want to achieve w/ the relays?

  3. thedowneaster

    thedowneaster Brakeman


    Thanks for the link! My application is a little bit different though.

    Automated "Shuffle Yard"...
    I have a large single track loop that splits into 4 tracks for 15ft or so. I want that every time a train enters the yard another replaces it. (like a relay race)
    Before the train enters the yard it will trigger 4 snap relays through a momentary reed switch (specific to each of the 4 trains magnets placed to left, right, top, + bottom) The snap relays will align the turnouts to the train's dedicated siding, start up the next train, and also shut power to a section of the previous train's siding to stop it. The whole thing will continuously repeat itself until the power is cut out.

    The snap relay will easily turn on and off the sidings, but I do not know how to trigger turnouts with them unless I use a turnout that will shut off after being completly thrown.
  4. rogerw

    rogerw Active Member

    How about using a tortise switch machine?
  5. YmeBP

    YmeBP Member

    Hmm o.k. i'm going to take a stab at this .. i'm not an expert yet but i've been doing alllooooot of reading since i've started w/ the trains :) oh and i stayed at a holiday inn once hehe.

    There are things like the snapper (link) and other capacitance discharge devices that will send a high voltage/amperage out when you send only a small voltage in. Coupled w/ a snapper you can use an occupancy detector (link) (any type) far enough away from the mouth of your yard or frog of your turn out to send the input signal to your snapper which would then discharge and throw your turnouts.

    So train crawls through detector => detector sends signal => snapper throws turnout => train crawls throw other end => detector sends signal => snapper throws turn outs back => operator grins w/ glee :mrgreen:.

    You can also have the same snapper throw your relays at the same time.

  6. 60103

    60103 Pooh Bah

    Jeff: your first proposal will cook your switch machines. Atlas type twin-coil machines require/only tolerate a momentary burst of current.
    I think that the snap-relay would work a Tortoise type machine, which is a low-current DC motor that requires a constant current. But they're expensive.
    I'm not sure about the CDU -- it probably wouldn't recharge if was draining continuously through the switch machine.

Share This Page