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Special type of switch needed

Discussion in 'Electronic Components' started by smpaladin, Sep 18, 2004.

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  1. smpaladin

    smpaladin Guest

    I am new to electronics and I need to know if there is a type of
    switch that will assist me in reversing the polarity of an
    electromagnet, as in the picture here

    I've asked this question before in a different group, but I keep
    getting unclear answers about a relay or a DPDT switch.

    What I want is a switch, like the green switch in the picture, that
    will alternate the input/output currents between two wires, as long as
    an outside current is applied to the switch. This way, I will be able
    to reverse the polarity of an electromagnet as long as the outside
    current is applied to the green switch. Is there any specific type of
    switch that will accomplish this?
  2. You can either use a DPDT switch, or use a DPDT relay, with an SPST
    switch to control the relay.

    If the wiring from the battery to the electromagnet is located where
    you can easily reach it, I would use a simple DPDT switch.

    If you want to be able to switch polarity while you are some distance
    from the battery and electromagnet, then the relay and SPST switch
    might be more appropriate.

    What you have shown in that drawing is a relay and SPST switch.

    Peter Bennett, VE7CEI
    peterbb4 (at)
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  3. You do indeed need a DPDT relay, the normally closed contacts wired
    straight through and the normally closed contacts wired in reverse.

    Is this for a class? If not, (how) are you planning on implementing
    this circuit?
  4. It's called a polarity reversal switch. See the diagram at the bottom
    under double pole double throw switch.

    You can wire a double pole, double throw relay similarly.
  5. You forgot 'normally open'.
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