Atlas snap switches

Discussion in 'N / Z Scale Model Trains' started by SR39, Jun 23, 2009.

  1. SR39

    SR39 Member

    Does anyone know what the neutral wire is on an Atlas snap switch machine. I am changing to DCC and need to know for wiring a stationary decoder. The wires are green, black and red. The black is in the middle but I don't want to assume that it is the neutral.
  2. ytter_man

    ytter_man Member

    Your assumption was correct, the middle screw is ground. :thumb:
  3. mjm

    mjm New Member

    Turn outs

    Your turn outs will all work with the Black neutral. I have to warn you and others that have had a scary experiance with Atlas turn outs, for some reason when closing two to the turn outs they melted, without warning two more melted. My layout is abut 1 1/2 years old, I pulled the motors and talked to my dealer, he had no answer and said to call Atlas, I did and they wanted the turn out, so Isent then to them. I just recieved new onew with no explanation to what happen. I beieve the switches stuck open when moving from one side to the other causing a reverse flow of current and a short, other then that I have never had any problems with Atlas turnout on my N scale and HO scale layouts. If someone has a answer, tell me.
  4. pgandw

    pgandw Active Member

    The usual failure mode for Atlas switch machines is a sticking button on the controller - Atlas controllers are known for this. The switch machines can only tolerate the current being on for a second or so - then they start to melt.

    Failure is more likely with a marginal power supply and/or trying to throw 2 turnouts simultaneously. The power supply can't give quite enough current/voltage to snap the switch machine(s) over, so the buttons are held down slightly longer than they should be to get the turnout thrown completely.

    The solution is to install a Capacitive Discharge Unit (CDU). A CDU provides a big jolt of energy to the switch machine from a charged capacitor that allows the switch machine to "snap" over. The jolt tapers off very quickly as the capacitor discharges, protecting the switch machine from overheating. The CDU recharges in a second or two, and then is ready to throw another turnout. Most CDUs will easily throw several switch machines at once. A CDU is very similar to the electronic flash unit in your camera.

    Circuits for building your own CDU can be found here - - and elsewhere on the web. A CDU is a particularly simple electronics project, but you can also buy commercial units from Circuitron.

    hope this helps
  5. mjm

    mjm New Member

    Atlas turnouts

    Hey thank you for your help, as I said, Atlas replaced the turn outs, and I do believe you are right.
    Sorry it took me so long to get back to you, this is all new to me, I can do about anything with the trains, but to find where I was here, I'm lost.

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