Ratings on products

Discussion in 'Homework Help' started by amano001, Nov 11, 2012.

  1. amano001

    Thread Starter Member

    Sep 7, 2012
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    0
    Hello,

    Just a quick question about ratings on packaging. I am trying to find a switch for a project of mine.

    The packaging states .5A at 200VDC, does this mean at lower Voltages it will be able to handle higher currents?

    Thanks.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    yes and no.

    due to the size and composition of the contacts, there is a limit on how far you can lower voltage and raise current.

    The I(sq)R losses appear as heat in the metal contact, and due to physical constraints such as size and surface area, an increase in current will produce a greater rise in temperature when passing the larger current. You will MELT the contacts if you raise the current too high.
     
  3. amano001

    Thread Starter Member

    Sep 7, 2012
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    0
    Ah gotcha thank you!
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,962
    1,097
    No, voltage rating has nothing to do with the current that can flow through the switch.
     
  5. amano001

    Thread Starter Member

    Sep 7, 2012
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    One more question,

    I bought a DPDT switch that seems to be rated for VAC, and the diagram for wiring from what I have found looks like this where + signs means there connected.

    Switch up

    1 2
    + +
    3 4

    5 6

    Switch down

    1 2

    3 4
    ++
    5 6

    Can I use it to just run a rectified DC voltage through it like this with just one wire?

    Switch up

    1 2
    +
    3 4

    5 6

    Switch down

    1 2

    3 4
    +
    5 6
    Thanks
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I don't understand your 'number switch' stuff, but, A switch doesn't care if its AC or DC anymore than a copper wire cares what kind of voltage it carries.

    A switch is basically a piece of wire that can be broken and reconnected multiple times.
     
  7. amano001

    Thread Starter Member

    Sep 7, 2012
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  8. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I respectfully disagree. breaking direct current can be much harder on a switch than breaking alternating current.
     
  9. amano001

    Thread Starter Member

    Sep 7, 2012
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    0
    So does anyone know if I can hook it up with just one of the terminals being used instead of having both hooked up? as in the diagram above i posted with numbers?

    Thank You.
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    Yes

    The two 'poles' refered to by the DPDT label(Double Pole Double Throw) means it has two seperate poles, or two sets of contacts.

    You do not have to use both sets of contacts for the switch to work.

    I didn't want to get to deep into the 'physics' of switches and arcing at the contacts. It seems just knowing if he can use the switch was taxing his understanding already, but I agree Stantor. Dc does have a greater tendency to draw an arc and do damage to the contact surfaces.
     
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