DPDT switching- two power supplies

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DPDT switching- two power supplies

Post by jkiker » Wed Mar 29, 2017 1:12 pm

Hi all,

I am working on a project and I want to use a DPDT switch and connect it up for two different power supplies. I want to be able to switch between "off," Battery power, and wall wart (from AC) power. The model is wired and I'm ready to connect the lights and power supplies. The stand will carry power to the model via a 1/8" RCA plug.

So; I think the wires from the model/plug will attach to the two center posts of the 6 pole toggle switch I have. That would mean no power from either source is connected. If that is correct, I cannot picture in my head how to connect the two sets of + and - wires from each power source.

What can you advise? Is there a diagram for such a setup? I have yet to find this particular combination on the internet, so I assume my google-fu to be weak! Thanks in advance for any light you can shed!

Cheers, Jim

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Post by zysurge » Wed Mar 29, 2017 3:40 pm

What you need is a DPDT switch that includes a center off position. Some don't.

With the correct switch, the load would be on the center contacts, and two two power supplies on the two outsides. Positive all along on edge, negative on the other.

It would look similar to this:

http://www.littelfuse.com/~/media/image ... .jpg?la=en

From that image:
1 Battery +
2 Load +
3 AC +
4 Battery -
5 Load -
6 AC -

Does that make sense?

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Post by jkiker » Wed Mar 29, 2017 5:47 pm

Hi Zysurge,

Yes indeed, that is just what I wanted to confirm. Technically, I think my load, the model, goes on the two middle terminals and the battery and wall wart go on the ends, with the +'s on one side of the switch and -'s on the other.

Thanks for the quick response and the image as well!

Cheers, Jim

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Post by DaveVan » Wed Mar 29, 2017 8:00 pm

I use the center off DPDT on my model railroad for all power routing. Each 'side' is isolated from the other. I use the center two as the 'output'....thus the bottom two terminals will be BATT and the top two will be TRANS. I pay about $2 online for GOOD center off switches.
30,000 miles on Amtrak in words and pics...

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Good to know...

Post by jkiker » Thu Mar 30, 2017 11:35 am

Hi Dave,

Thanks for the additional input; very helpful!

Cheers, Jim

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Post by Mr. Engineer » Sat Apr 01, 2017 4:12 am

D'oh! Why didn't think of that!

And I went o all the trouble of getting a relay which automatically connects to the battery once the wall adaptor plug is removed.
What can I take apart today?


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