Powered frog?

Discussion in 'DCC & Electronics' started by Nomad, Feb 10, 2008.

  1. Nomad

    Nomad Active Member

    Hello all.
    I am now building my own turnouts and would like to power the frog. I am using dcc and the frog is completely isolated. I have 2 way household light switches as my turnout controllers and would like to know if I can use those for powering the frog. If I can, how would I wire them? I checked the web but there is nothing about using light switches.
    Thanks in advance for any answers.

  2. Squidbait

    Squidbait Recovering ALCO-holic


    I believe someone in the Gauge here has done this already. You need to use the 3-pole switches (IIRC) to do power-routing for the frog.
  3. Squidbait

    Squidbait Recovering ALCO-holic

  4. Nomad

    Nomad Active Member

    Thanks Squidbait. I knew I should have looked there:v8:

  5. Nomad

    Nomad Active Member

    Anybody know how I would wire in a 3 way switch?

  6. steamhead

    steamhead Active Member

    Hi...Never actually having had one of these in my hands...I presume you've got 3 posts. If so, the two poles from the tracks would wire to the outside posts, and the output to the frog would come off the center post. Mind you...I'm just speculating here....:mrgreen:
    If they're not set up this way...use a voltmeter to check which posts connect to which other posts depending on the switch position...Good luck....:wave:
  7. Nomad

    Nomad Active Member

    Thanks Gus, I quess I'll have to experiment when it comes time to install them

  8. TCH

    TCH Member

    if the switches have 3 poles wire them as Steamhead has stated.

    I use 3 pole slide switches to operate my turnouts and wire them that way.
  9. pgandw

    pgandw Active Member

    I really don't like to nitpick, but the term "poles" has been misused in this thread, and has become confusing to me.

    In electrical switch terminology:
    • poles refer to the number of isolated circuits on the switch. A DPDT switch has 2 (D=Double) poles and 2 throws (2 positions). An SPST is an ordinary single pole, single throw switch like an everyday light switch - either on or off. For more than 2 poles, the number is used instead of a letter. 3P21T would be a 3 pole, 21 position rotary switch.
    • throws refer to the different positions for a given circuit or pole. ST means one position, the "ON" position". A SPDT switch or contact - which is what you want for powering turnout frogs - selects between 2 positions for a given circuit. In our frog powering case, you are selecting which polarity powers the frog. The 3P21T rotary switch would have 21 separate positions for each circuit or pole - but all 3 move together.
    • terminals are the screws or loops on the underside of the switch to which wires are attached. A SPDT switch will have 3 terminals - one for the pole or circuit feed wire, and one terminal for each of the 2 positions. In our case, the frog is wired to the center or pole terminal, and the stock rails are wired to the 2 "throw" (or outside) terminals.
    It sounds like you are already using the 2 way light switches (SPDT) for controlling the turnout motor. The frog power would have to be on a separate circuit. Therefore, you could use DPDT toggle or slide switches, but not the 2 way light switches, to control both switch machine and frog power.

    At the moment you throw the toggle switch, the frog changes polarity but the points have not yet thrown. Depending on how your points are wired, you may be setting up short circuits if a metal wheel set crosses the isolation gaps before the points are thrown. If the points are always opposite polarity to each other, and the same polarity as the adjoining stock rail, no problems (you have ideal wiring, Atlas turnouts are wired this way).

    Some Peco (perhaps all) turnouts (and some others) are not wired this way. The points are both of the same polarity, and change polarity when you throw the turnout. The problem with this point wiring and using the switch machine control toggle for frog power is that the switch machine does not operate instantaneously like the control switch does. So until the points move to the opposite position, the points and frog will be of opposite polarity, setting you up for short circuits. In this case, you need to use a separate contact on the switch machine or turnout throw for frog power so that the frog does not change polarity before the points do.

    Probably more than you wanted to know, but I hope this makes a little sense.
  10. Nomad

    Nomad Active Member

    Thanks Fred, actually the 2 way light switch I am using is the turnout motor.
    I used the design Gary S. has here
    There are only three terminals on the switch (actually two power terminals, ones a ground ) so I think I need to go to three way light switches.

  11. TCH

    TCH Member

    freds [w]right
    I should have said terminals or posts ,not poles.
  12. BigJim

    BigJim Member

    If you are using Tortoise "turnout motors" you can use the DPDT switch built into the Tortoise for the frog. I am assuming when you said building your own you mean Fast-tracks style with a cut in both points near the frog with the points always connected to the associated rail. If this is the case the "points" discussion above would not apply. If you are approaching the frog before the turnout is set to match the train direction you are cutting it a lot closer than I would :) Perhaps a short and DCC shutdown before the train derails might not be the worst thing.

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