Non polar electromechanical relay?

Discussion in 'General Electronics Chat' started by Skeebopstop, Feb 17, 2010.

  1. Skeebopstop

    Thread Starter Active Member

    Jan 9, 2009
    Dear all,

    I recently designed using a relay where the datasheet was unclear to me which polarity the coil had to be in to drive the switch out of its default position. So I put it to the test. An image is attached from the datasheet.

    When I applied voltage in either polarity to the coil, the relay would switch the contact over. I am a bit at odds with this. Obviously there is an explanation for this that extends beyond my assumption that this sort of relay was permanent magnet driven.

  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Most relays do not have a permanent magnet in them. They use a coil to induce a magnetic flux in a ferrous armature with a gap. The induced magnetic attaction causes the armature to move to close the gap. A spring pulls the gap open when the current is removed.

    e.g. think about an AC relay.
  3. BillB3857

    Senior Member

    Feb 28, 2009
    When you do think about an AC relay, also think about the copper D ring at the top of the coil pole piece and why it is there.
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    There is also a latching relay that does use a magnet. It latches with one polarity & releases on polarity reversal.