Push/Pull Electromagnet

Thread Starter

Azez

Joined Jan 16, 2012
13
Hello!

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 :)
 

gerty

Joined Aug 30, 2007
1,287
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).
 

luvv

Joined May 26, 2011
186
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.

-luvv-
 

Bernard

Joined Aug 7, 2008
5,559
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.
 

crutschow

Joined Mar 14, 2008
25,126
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.
 

Thread Starter

Azez

Joined Jan 16, 2012
13
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 :)
 

Thread Starter

Azez

Joined Jan 16, 2012
13
How about using suction? Any smooth object would be able to be picked up and release with this method. There is a company that makes a complete kit that is be controlled by a servo (Lynxmotion)

http://www.lynxmotion.com/p-788-vacuum-gripper-kit.aspx
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 :)
 
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