2 switch and fuse join help

Discussion in 'The Projects Forum' started by minkey01, Nov 30, 2015.

  1. minkey01

    Thread Starter Member

    Jul 23, 2014
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    Hi, electro buddies!

    I want to have only one switch and one AC power cord for these two power supplies. See picture. What would be the best way to wire this?

    They are both going into the same housing and it would be a bit wasteful and annoying to have two power switches and two power cords.

    Thanks in advance for the help!

    join question.jpg
     
  2. minkey01

    Thread Starter Member

    Jul 23, 2014
    171
    0
    I came up with this. See pic rev2.

    Not sure if there is an easier way? Maybe there is another setup that only needs a SPST switch? What are the safest and best practices for something like this, setting up a switch and fuse?

    * Just read that you want to switch the hot side, so I moved the switch on that old transformer.

    join question_rev2.jpg
     
    Last edited: Nov 30, 2015
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    just put the fuse/switch on BEFORE you split into 2 wires...
    have fun.. be safe

    pictures worth 1000 words..
    remove red scratched out wire.. connect blue to it.. after the switch/fuse.. not before.
    mod2.JPG
     
    Last edited: Nov 30, 2015
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    If you move the fused wire to the second transformer to the right side of the switch, you will be able to turn both off with one switch. Your current design requires two switches (or a double-pole switch).
     
  5. minkey01

    Thread Starter Member

    Jul 23, 2014
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    I don't think the second transformer can have that 2A fuse before it. It draws more current than the first transformer. You can see the second transformer has that 10A fuse on the DC side. So I think my latest pic is the only way to do it??

    Thanks!
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Assuming this is a 12 volt transformer, 10 amps on the 12V secondary side is like 1 amp on the 120 V primary side.

    I would want a fuse on the primary side ( between the plug and switch).
     
  7. hp1729

    Well-Known Member

    Nov 23, 2015
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    You may want to move the fuse to the other side ofbSW1.
     
  8. minkey01

    Thread Starter Member

    Jul 23, 2014
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    Second power supply is 75 VDC (here is its specs attached if you need it). So you would add a third fuse before the second transformer on the AC side?
     
    Last edited: Nov 30, 2015
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes.
     
  10. minkey01

    Thread Starter Member

    Jul 23, 2014
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    Do you know what size and type it should be? thx
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    No. I don't know what load you are driving or what the transformer ratings are.
     
  12. minkey01

    Thread Starter Member

    Jul 23, 2014
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    Oh. I think it already has a fuse for the AC side built into the power supply. I just uploaded the spec sheet above. It says Fuse, 3AB, 2A, slow blow, 250VAC. If I'm reading it right. It won't be before the switch, but it is there on the circuit board.

    So probably my rev2 DPST circuit is the only option and looks good?

    Thanks GopherT!
     
  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    You only need a SPST switch (rated for both supplies current) and a single fuse on the primary for the supply that doesn't already have one..
    So no.. your DPST is not the only option and is more than needed..

    You just need one switch before you split the wire off to each supply and throw in a fuse if needed..
     
  14. minkey01

    Thread Starter Member

    Jul 23, 2014
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    Ok. I see. I was trying to keep that upper fuse before the switch, because I read the fuse would protect the switch. But since the second pole would be unprotected by a before-fuse anyways, it doesn't matter.

    The second power supply already has AC fuses on its board, so it would be redundant to put some more on them before the switch. I guess I will have to have the switch before the fuses. SPST switch and then branch off like you said.

    Here is what my rev3 looks like. Check it out:

    rev3.jpg
     
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