the title says it all lol. im wondering if its possible to alternate the north and south poles of an electromagnet and how to do it? you would think changing direction of the current flow would do that if that's the case what would be the best way to change the flow rapidly and be able to control it thanks for your help

 

Google H-bridge.

Bob

 

thank you every time I tried to Google alternating an electromagnets poles I just got a bunch of end of the earth stuff

 

Double pole double throw switch

 

does anyone know of a place to get a core that is made especially for electromagnets so I can get the highest saturation iron possible

 

The highest saturation will likely come with a stack of insulated silicon-steel plates (thinner is better).

Other options are pressed iron powder cores (check Micrometals.com). Stick with iron powder and not permalloy or other similar alloys if saturation is key.

Also, to answer tour original post, a generator makes AC signals. What frequency and what load are you looking at? When you say "control" do you mean voltage, frequency or other? Are you trying to make a square wave, sine wave, or other?

 

im not sure sign I guess I need to be able to switch the polarity of two electromagnets at the same time and have them do it on there own without me physically switching them and I need to be able to time the switching to the movement of a another magnet

 

so basically I need to move a earth magnet back and forth across a bar with two electromagnets so I need an h bridge that all the switches are normally closed on so I can apply voltage to open them when the magnet hits a certain point in its path. I need to use a sensor of some kind to send a signal to the h bridge to switch directions and I need to be able advance the timing of the switching the faster the magnet moves back and forth. if that makes any sense

 

You are basically describing a degauser, something designed to remove magnetic fields from other material, such as audio tape.

 

I envisioned something more like an old style automotive distributor from the posters last description.

Hall effect switches and a rotating magnet 'geared' in a mechanical fashion to his oscillating magnet would give the OP the ability to set timing lead or lag to his operational speed and provide the signal to switch his electromagnets as well.

Whatever method is chosen, the use of Hall effect devices to provide switching signals is a good one, since we are dealing with moving magnets and want to syncronize a circuit by sensing their positions.

 

I think our OP is describing something more like a slide hammer, where the slide on the hammer is a permanent magnet which is attracted/repulsed by electromagnets.

 

ya kermit2 and sgtwookie you are correct I am pretty familiar with hall effect sensors sense im an automotive technician and was thinking that would be the best thing to use I just don't know how to use the signal to switch my h bridge I need to know how to turn the signal that the magnet is in the right spot into a command to switch polarity on my electromagnets

 

I cant find an example of one of these anywhere is that because its a stupid idea lol it seams to me there could be a lot torque produced but would prolly need a lot battery power not large voltage and amperage requirements but that it would run a battery dead really quickly

 

How much movement are you talking about? What distance between the electromagnets?

 

I was planning to play with it to try to find the best distance

 

So you don't have a real application for this? Is there any weight involved, other than the weight of the magnet?

The reason I'm asking is ,what it sounds like your trying to do is called a VCA, voice coil actuator. Here is a link to one company that makes them; http://www.beikimco.com/actuators_linear.php If you Google that term, if it's what your trying to make, you'll get more information.

But you kind of threw me off when you mentioned 'torque' in one post. Torque usually means a rotating motion, not a linear one. If you could describe what you want to do or post a sketch it would be better.

 

linear motion can be turned into rotational force pretty easily the magnet would be used to drive some sort of crankshaft via a connecting rod of some sort and no there's no real application or purpose just an experiment and the satisfaction of taking an idea and building a working example of it even if it isn't really a practical concept

 

im thinking a large neodymium magnet that will hold about 600 pounds and weighs about 10 pounds drug back and forth across maybe a bar of aluminum or a bar made of something that wont react with the magnet by some big electromagnets. I found some that run on 12 volts and have a max of 1.6 amps that will lift 450 pounds. I would like to build my own electromagnets but I don't think I could build any that would work as well as these would. I'm hoping that with one magnet pushing and the other pulling I can get the machine to do a little work. my main problem is I don't know how to make the poles switch on the electromagnets in time with the magnet sliding back and forth and how to advance the timing of the switching as the speed of the magnet increases.

 

can someone direct me to a part of this forum that might be able to help me with this

 

Yes! I can if you can prove the theory, "North polls attract South poles and South poles attract North poles" false.