Push/Pull Electromagnet

Discussion in 'The Projects Forum' started by Azez, Feb 20, 2012.

  1. Azez

    Thread Starter New Member

    Jan 16, 2012

    I want to use an electromagnet in a project I'm doing but I'm confused about what the difference between a push/pull electromagnet is?

    If anyone could sorta give me a definition of them it'd be really helpful!

    Thank you :)
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
    Think of an electric door lock on a car. When you push the lock button the door locks and the locking lever goes one way, when you push the unlock button the door unlocks and the lever goes the other way. All the buttons do is change the polarity to the locking coil (electromagnet).
  3. luvv


    May 26, 2011
    Did a project that required reversing polarity of a E- magnet and found because of residual magnetism it's nearly impossible to do fast switching .

    Only the purest soft iron cores can be fast switched and they are hard to find and expensive when you do.

    Furthermore, if you plan to do the switching w/ transistors, mosfets or a IC you have to use a flyback diode to protect it and that can be a bit challenging considering the constant polarity change.

    In the end this is what i came up w/http://forum.allaboutcircuits.com/attachment.php?attachmentid=39500&d=1328223319

    Two coils instead of one means no need to reverse polarity and deal w/ the problems associated w/ it.

    Used a 555 in astable mode to trigger the gates pnp/npn combo which energized the two coils wired in opposite polarity.

    It wasn't perfect for numerous reasons but did the job well.

    Don't know if any of this applies to the project you are working on but hope it helps.

  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Must solenoids are open on only one end so that when energised, the armature is pulled into the solenoid- hence pull type. If a hole is drilled in closed end & a rod is attached to armature, when energised, rod is pushed out- hence push type, so there can be both push & pull in one solenoid.
  5. crutschow


    Mar 14, 2008
    An electromagnet will normally "pull" towards any nearby magnetic material, but you can get it to "push" or repel a permanent magnet if the two have the same magnetic pole polarity.
  6. Azez

    Thread Starter New Member

    Jan 16, 2012
    Thank you every one for replying!!!

    The project is to build a battery powered rover and a task it has to complete is to drop/release an object so say a ping pong ball or something using a re-deployable method.

    I thought of an electro-magnet would be the best thing to use, so I think its a push magnet I'd have to use? I don't want it to have to stay energised the entire time so is the push one the right one?

    Also does it need a relay driver within the circuit?

    Thank you again every one :)
  7. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
  8. Azez

    Thread Starter New Member

    Jan 16, 2012
    I wouldve looked at that but one issue is size of the rover so the electromagnet was a good choice because it can be small enough to fit onto the rover without being much of a hinderance. Thank you for your suggestion tho :)