Multiple Transformers to power switch banks?

Discussion in 'Model Rail Operations' started by davera, Jan 16, 2005.

  1. davera

    davera New Member

    I have a layout that has 26 switch machines, 8 of which control 2 switches (for cross overs).

    I have 3 cabs, 2 for the main line (17 VA) and 1 for the yard (14VA).

    I have read that a switch machine, especially one controlling 2 switches, can draw significant power from the cab affecting the speed of the locos. I did a quick test on this and while not being able to measure the momentary power consumption of the switch, I did see the peak lamps light.

    I am wondering whether I can distribute the switch machines between the different cabs to reduce the effect on any one cab. If I do so, can I still connect all the center wires from each switch machine together beneath the layout or will I create ground loops or other such negative electronic effects?

    I still plan to connect the center wire of each bank of switch machines to the center wires of the switches in the layout but in this case, I am asking if they can all be shorted together?

  2. Tad

    Tad Member


    A simpler thing to do would be to get a seperate powerpack, an old one or a one from a trainset, such as a Bachmann or Life-Like, and dedicate it to powering just the switches. These can usually be found pretty cheaply and are adequate to power all of your switch machines.

    If you are going to wire them to the three powerpacks you currently have, I would set them up as three seperate banks wired independently.
  3. dhutch

    dhutch Member

    Does anyone know how much they draw on peak?

    - what rateing powerpack should i use

    - would a 200w PC PSU be ok? - thats 8amps continuasly rated on the 12v line, (with large smoothing caps)

  4. davera

    davera New Member

    Actually I did try a separate power pack, a Lifeline 7VA and it was not able to throw 2 switches on the same switch machine. It sounded like it was close but not enough. 8VA may be a bit close. I think 10VA would probably do it...
  5. 60103

    60103 Pooh Bah

    I would see if you could get at leat 24VA (2 amps @ 12 volts) if you're going to throw 2 at once.
    Do you expect to have several people throwing switches at the same time or just one? You might need extra oomph if a couple of operators throw 2 at once. One person is unlikely to hold down several buttons at one time.
    You could investigate a capacitor discharge unit (CDU). This a cicuit like the one that controls a camera flash unit.
  6. davera

    davera New Member


    8 A x 12 V = should be more than enough.

    i happen to have a couple of 200W PC PSUs lying around. for that reason I am very interested in the size of the smoothing caps. do you have a schematic that you could share?
  7. Fred_M

    Fred_M Guest

    A cdu is the way to go. It really is. They are cheap to build and work :thumb: . Fred
  8. davera

    davera New Member

    forgive my ignorance or naivete. can you point me to a how to guide to both size correctly and build a CDU? it sounds very interesting. would you do that or get another 14VA power pack. I know that works.
  9. dhutch

    dhutch Member

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