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The Magic Cafe Forum Index » » The workshop » » Info on electromagnets? (0 Likes) Printer Friendly Version

Ed_Millis
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Yuma, AZ
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So there's a plastic peanut butter jar on the magician's table. Suddenly, it begins to rise and float a few inches off the surface.

Where might I find information on an electromagnet sufficient for something like this? How much power is needed for how much weight pushed a few inches? Is it feasable without wiring your table for 220? I'm thinking also of a variable control and a timer - set the jar down, walk away, and a few seconds later things happen.

Ed
AGMagic
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Cailf.
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Ed,
I am no expert on this, but I suspect that you will have a major problem trying to get anything to hover magnetically. I have played with the toys that they sell at museum shops that have a hovering piece and they are a royal pain to get the piece hovering. However, once it is, they tend to be fairly stable.

That said, it should not require much power to levitate an empty plastic peanut butter jar. There are basically two make an electro-magnet stronger, increase the current flow through the wire, or increase the number of windings in the coil. For this application, you will want a coil with many wraps of fine magnet wire. You can make this yourself, but the cost may get pretty high as you are paying for new copper wire. I would guess that you would want several hundred to perhaps a couple of thousand windings, of 24Ga or smaller wire, around an iron core.

Stay away from AC for power. You need direct current to control the polarity of the electro-magnet. 6 to 12 VDC should be sufficient for what you are trying to accomplish. Watch for heat buildup as your magnet is powered on. It can happen quickly if there is not enough resistance in the circuit. Watch out for the high voltage arc when you remove the power. As the magnetic field collapses through the coil of wire it becomes a generator capable of producing a voltage of hundreds to thousands of volts, depending on the number of wraps in the coil. A flyback diode across the coil can protect you and your equipment.

Finally, you will need a magnet of opposite polarity on the bottom of your peanut butter jar. I suspect the stronger and lighter this magnet is the better the whole thing will work. You might want to try this with regular magnets to see if you can get the jar to hover before you spend a lot of time and money on building the electro-magnet.
Tim Silver - http://www.facebook.com/pages/Magic-Woodshop/122578214436546

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Anverdi-museum
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Electro - magnets are very cool, it takes a lot of experimentation to get what you want unfortunately. For your purposes there is a concern about stability....I cannot imagine your peanut butter jar rising/lowering under control no matter what coil you use. Possibly placing the jar in a cylindrical glass or plexiglass tube would add the stability you would need.

If you go that route there are other ways to make the jar both rise and descend...possibly the same principle of the Anverdi Floating Cube.


Below is a brief clip of myself with the Anverdi cube effect:


http://www.youtube.com/watch?v=wC-zAJXyIys



Chuck Caputo
Ed_Millis
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Yuma, AZ
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Well -- so much for that thought.
Time for more thinking.

Thanks for all the info.
Ed
Peter McMillan
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St. George, Utah
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I've ordered a number of these and have been happy with the product and service.

Started with the 5.5 and 11 pound. moved to the 12v 90 pound and and am trying out the 24v ones next.

Go to http://www.suntekstore.com and search for "Holding Electromagnet Lift Solenoid" for the list of 6 selections.

Hope this helps.

Pete
Spiritus Dictum Artifacts ~ Tools of the Craft for Serious Workers http://petemcmillan.wixsite.com/sd-artifacts/artifacts
jolyonjenkins
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United Kingdom
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Using an electromagnet to repel is tricky. The core of the electromagnet is iron, and if you use the EM to repel a permanent magnet, the PM will in fact be attracted strongly to the iron core of the EM, and that attraction is stronger than the repelling forces of the EM. I have not managed to solve that problem myself although clearly others have.
Jolyon Jenkins
seforeman
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I was thinking about doing a floating candle using magnets, and I abandoned the idea. This site has a plethora of good information about magnets in general. They even have some "levitation" type experiments for sale. But more importantly, they show why a magnet does not work for any real levitation (due to weight and the magnetic field disapating). Some neat information though: http://www.kjmagnetics.com/categories.as......od2VAAsQ

Stuart
Stuart Foreman
BenHFarrar
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There is a trick where a block of wood levitates inside a perspex tube, sealed with paper on either end. At the end, the tube is still sealed and examinable. I believe that it was originated by Peter Warlock and was called Pentablock (from memory.. ???). I see no reason why this couldn't be adapted and done with a very light plastic jar instead. It really is a cool trick and quite baffling. The levitation has the same sort of feel as an electromagnet actually. Originally it used an offstage assistant, but it would be very simple to make an electronic device to do the job.

Just a thought...
slowdini
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I think making something sort of like an air hockey table is a safer bet. Let air lift it up. You'll spend hours and dollars feddling with the magnets for very little return.
A.J.Drake
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Germany
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Yeah, magnets are very difficult to handle.
I think you need two magnetic fields to hold an object in one place.
Otherwise it would drop on one or the other side of the magnetic field.
Magic is everywhere ...



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