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DC Block Wiring - SPST or DPDT switches?

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  • Member since
    January 2013
  • 89 posts
DC Block Wiring - SPST or DPDT switches?
Posted by kgill on Sunday, May 26, 2013 11:01 AM

I got a great deal on a bulk supply of switches so I bought a bunch of great toggle switches that are just on and off. No middle position.

Does it matter which type I use? I cant seem to get a clear discussion of that topic.

I am wiring blocks in my 4x8 layout and thought all i need to do it turn power on or off to each block.

Please enlighten me :)

  • Member since
    October 2005
  • From: Detroit, Michigan
  • 2,284 posts
Posted by Soo Line fan on Sunday, May 26, 2013 11:14 AM

If you are only using one pack, they will allow you to park or power down engines in each block.

If you want to use more than one power pack they will not work. You need the center off pole switch as shown:

Jim

  • Member since
    January 2013
  • 89 posts
Posted by kgill on Sunday, May 26, 2013 11:52 AM

Sensei,

Please tell me more. I want to use more than one power pack. so the center off switch is needed, why do i need power on-off-on feature of the switch?

thanks,

Grasshoper

  • Member since
    October 2005
  • From: Detroit, Michigan
  • 2,284 posts
Posted by Soo Line fan on Sunday, May 26, 2013 12:32 PM

The center off position allows you to park engines anywhere on the layout and still use both power packs  elsewhere.

Jim

  • Member since
    October 2004
  • From: Colorful Colorado
  • 8,639 posts
Posted by Texas Zepher on Sunday, May 26, 2013 8:24 PM

You can also use DPDT switches.  The difference is that there would not be a "common" wire.  There would be two wires from each switch to each section of track.  And two wires from each power pack to each switch.

  • Member since
    January 2013
  • 89 posts
Posted by kgill on Sunday, May 26, 2013 9:15 PM
Ok what does it mean if I don't have a common wire?
  • Member since
    January 2010
  • From: Chi-Town
  • 7,712 posts
Posted by zstripe on Monday, May 27, 2013 8:00 AM

KGILL,

Look at SOO,Lines diagram,,study it,,,,,,then read TZ's response,,,your answer for your question,has already been explained..

Cheers,

Frank

  • Member since
    December 2006
  • From: Lancaster, PA
  • 512 posts
Posted by claymore1977 on Wednesday, May 29, 2013 7:21 AM

Side note: I actually prefer DPDT, since it allows for complete circuit isolation.  While i know that SPDT + common wire allows for lower overall costs, it does present a bit of a complicating factor when troubleshooting a short comes into play.

To the OP though:  Lacking center off *may* be an issue if switches are the "make-before-break" type.  This could cause a power pack to power pack short :/

If the switches are "break-before-make" type, then you can over come the lack of center off by using one of the switches as an ON/OFF for the block, and then a second switch for the CAB select.  

I'm away from my home computer or I'd whip up a quick schematic.

Cheers!

Dave Loman

My site: The Rusty Spike

"It's a penny for your thoughts, but you have to put your 2 cents in.... hey, someone's making a penny!"

  • Member since
    October 2004
  • From: Colorful Colorado
  • 8,639 posts
Posted by Texas Zepher on Friday, May 31, 2013 11:00 PM

Actually there is a third option.   One can use the common wire arrangement and just use 1/2 of the DPDT switch, in effect making it a SPDT.

  • Member since
    October 2005
  • From: Detroit, Michigan
  • 2,284 posts
Posted by Soo Line fan on Saturday, June 1, 2013 8:54 AM

Here is a diagram using Atlas Selectors:

Jim

  • Member since
    January 2010
  • 2,616 posts
Posted by peahrens on Saturday, June 1, 2013 9:12 AM

Jim, your diagrams are terrific!  Nice of you to take the trouble to so clearly illustrate the systems.  Pic's are worth 1K words.

Paul

Modeling HO with a transition era UP bent

  • Member since
    October 2005
  • From: Detroit, Michigan
  • 2,284 posts
Posted by Soo Line fan on Saturday, June 1, 2013 9:22 AM

Paul,

Thanks for the kind words. They were done using a program called Visio professional.

Jim

  • Member since
    September 2007
  • 90 posts
Posted by RetGM on Sunday, June 9, 2013 5:19 PM

Jim,   PLEASE change the turnout to place the short rail ABOVE the  longer one so that any car or engine's wheels could actually be routed to the side track.  Thanks, JWH 

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