Why can't we just position a magnet at the right distance to levitate metal objects? It's because as a ferrous material nears a magnetic field the force increases exponentially. This is described by what is called the magnetic inverse square law:
Intensity1 / Intensity2 = Distance1 / Distance2
So, there is no point in space where a magnet or electromagnet will naturally suspend an object without making contact. Once in the field, there is no turning back!... Unless...
A propagating magnetic field can be shown in 2D diagrams or on magnetic viewing film as lines of force emanating from the poles. Even with an oscilloscope it is impossible to tell much about the movement and direction of the field with only snapshots in two dimensions (like this notorious illusion). When observed in 3D this field can be seen and felt to be toroidal and in respect to time we begin to see that a propagating helical field emerges. This is the same in the case of an electromagnet, and when the field collapses it does so in the opposite direction. This is described by what is usually referred to as Flemings Right and Left Hand Rules.
So, in theory, it would be possible to create alternating vortices/helices in order to adjust an object to a desired position. After doing some calculations based on the formula above we find that it is only possible by alternating these fields precisely and quickly (50,000 times per second or more!)
With a few components we can create a propagating and collapsing electromagnetic field controlled by a sensor which detects the field strength and a circuit which applies the appropriate field to an electromagnet.
Building the Enclosure
When complete, the enclosure should measure 8 x 10 x 12 inches.
1.) First, stack and secure our plexiglass and measure and drill four holes near the corners being sure to leave space from the edges and to drill with incrementally larger bits to avoid cracking. You should end up with four 5/16-inch holes in the corners of all three plexiglass sheets. Be sure to note the orientation so that you have a symmetrical fit.
2.) Next, drill a hole or holes for our input jack on one of the sheets. This may vary depending on your jack but should be near the rear of the enclosure.
3.) To build the enclosure, start by inserting the four 5/16-inch threaded rods into the holes of one of the sheets. Secure the sheet about 1.5-2 inches from the bottom of the rods with one washer and nut on each side of the plexiglass and add a rubber foot on the bottom of each rod. Make sure everything is level before continuing.
4.) Next, insert a nut and washer about 3-4 inches from the top of our rods and place the sheet with the hole for the jack on top.
5.) The last step to our enclosure is to secure the last sheet of plexiglass to the top once you've add the components from the next section.