so this is what im trying to do.

Im trying to take and electro magnet and have it repell something then after a certain amount of time have the pic controller switch over and attract.
Can this be done using the same electromagnet by switching polarities?

 

Yes, as long as what you are attracting/repelling is itself a magnet. Try googling "H bridge" .

 

Just for kicks. what are you trying to do? I once set up a solenoid that moved both directions on the same electromagnet. It was as much mechanical, with detents and springs as anything. The results was the armature was almost out of the coil on each end after the pulse.

 

Just a dumb thought here, How are you going to deal with the 'inductive kick' (don't know the correct term) of the coil? When you charge the coil in one polarity there will be a EMF in the coil that will have to be over come before the polarity is changed. Right?

A coil that is large enough to attract some thing is going to be the equivalent to a large inductor. If you could modify a circuit similar to a 'buck boost' converter the EMF that you would have to dump into a resistor could recycle back into the winding of the reverse polarity.

The coil would have to be wound in a "biflar' type winding. Two sets of windings at the same time, on the same coil. One for one polarity and one for the opposite polarity.

The coil will also have to have an "E" type core. With out a core it won't attract or repel with much power. Here is a link to a project, while not what your doing, tells how to figure the winding of a pretty powerful magnet that may help you with your project. http://aaybee.com.au/Magnabend/Building%20Your%20Own%20Magnabend.html

 

Do you know how the speaker in a radio works?

 

Do you know how the speaker in a radio works?

@BillB- This directed at me? I do know and were not talking about the same levels of current with attracting something. The ampere turns on a speaker are nothing compared to an electromagnet. The amount of weight in a speaker is almost nothing due to the cone shape and suspension surround on a speaker.

 

No, Shortbus, the comment was directed to the OP. Speakers do exactly what he is asking. It is really hard to tell what exposure level a Junior Member has and sometimes they just need a little jog to see a relationship of existing real world items to what they are asking. If he does understand how a speaker works, he will know that a magnet must be involved to perform both the attract and repel function he wants, but would not be needed for simple attraction.

 

@BillB- (in Rosana Rosana Dana voice) OK, never mind