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How to Build an Electromagnetic Levitation Device

How to Build an Electromagnetic Levitation Device
Need to take some weight off? With some circuitry know-how, a magnet, and a Hall Effect sensor you can build you own electromagnetic levitation device

"Do not levitate the spoon; that's impossible. Instead, only try to realize the truth. There is no spoon." - para. The Matrix (1999)

But what if there is a spoon? Or some other object. You can't just rely on the power of your mind to levitate objects. This project from Drew Paul of Drew Paul Designs is a DIY electromagnetic levitation device that can lift a small metal object into the air. Use it for a centerpiece at your next dinner party...or trick your friends into thinking you have magical powers. Just remember the old saying, the only difference between a magician and an engineer is the engineer will tell you how it's done.

Watch the electromagnetic levitation device in action.
Parts List 
CIRCUIT COMPONENTS
(1) Small Circuit Board
(1) LM7805 Voltage Regulator
(1) MIC502 IC
(1) LMD18201 IC
(1) SS495 A Hall Effect Sensor
(1) 470uF Capacitor (electrolytic)
(1) 1uF Capacitor (ceramic)
(1) 0.1uF Capacitor (ceramic)
(1) 0.01uF Capacitor (ceramic)
(1) 2 Slot Input Jack (+/-)
(2) 2 Wire Connectors
 
(1) 12v/1a Power Supply
 
(1) LCD Voltage Display (optional)
(1) Green LED (optional)
(1) 10K Resistor
 
SOLENOID 
(20g 150-300 turns)
(1) Steel Bolt
 
Various Colored Wire (18-24g) 
 
(2-3) Neodymium Disc Magnets
 
(3) 8"x10" Plexiglass Sheets
(4) 12" x 5/15" Threaded Rod
(24) 5/16" Nuts
(24) 5/16" Washers
(8) 5/16" Rubber Caps (optional)

For tools you'll also need a soldering iron and solder, a drill and bits up to 5/16", some electrical tape or shrink wrap, glue, and a 5/16th wrench.

DOWNLOAD THE FULL SCHEMATIC HERE

For those who don't want to source the individual parts, Drew Paul has made a kit of all the components available as well. 

Core Components

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.

Mount and Secure Components

Now that we have a platform, we can build and install our components.

1.) This relatively simple circuit and solenoid pair can be built according to the diagram below. Note that the SS495 gets mounted to the bottom of the coil. Adding an LED allows you to verify power and a digital voltmeter allows you to detect a load for tuning purposes, both optional, they can be wired directly to the circuits 12v input with an in-line 10k resistor on the hot lead (+). 

2.) Wire the jack to the circuit's input, noting the circuit diagram and remember that the jack's case is the ground (-).

3.) Connect outputs 1 and 2 from the LMD18201 IC to the solenoid coil. Insert a steel bolt into the coil's center and to the head of the bolt mount the SS495 A Hall Effect Sensor to which will be connected to the leads according to the diagram. 

(It may be helpful at this point to secure everything temporarily, carefully connect power and test the solenoid's field with your magnet).

4.) Once satisfied, secure the components to the platform. The circuit should be upright to allow airflow and near the jack, the solenoid should have the side with the sensor facing down and the optional LED and LCD can be placed wherever is convenient. Adding some shrink wrap and wire covers at this point makes everything neat and helps avoid short circuits and tugged wires.

5.) To further secure and cover everything add the final plexiglass sheet. First add a nut and washer to each rod, then the last plexiglass sheet and adjust it down so that the top sheet makes contact with your solenoid, tightly holding it in place. Once in place and level, add four more washers and nuts and cap with your rubber end caps.

Tune and Test

1.) When mounting our solenoid, our orientation did not take polarity into consideration. Therefore, we will need to select the correct pole of our magnet to face our coil. To do this connect the power and begin bringing the magnet into the solenoid's field. One side of the magnet will attract continuously, the other will have a tendency to lock in place several inches from the coil. Make a note of this side of the magnet. Be careful not to get too close; both poles will attract violently if brought too near to the energized coil.

2.) Now that we know which pole of our magnet we are using, we will now determine how much weight it can hold. Too little weight and the load will attract without levitating, too much weight and the magnetic field will not be able to overcome gravity and the object will fall.

Trial and error should help you find the optimal weight by attaching random objects to your magnet. However you can also use a more precise approach:

Using small nuts and bolts, incrementally add them to your magnet and test. Once you find a balance point (you'll feel a slight click as it locks into place), note the weight of the load using a small scale. Then add or remove small weight to find your range and optimize for stability. You can then use this as a reference and start levitating anything within this weight range which is usually between 45-55 grams, not including the magnet itself.

3.) When everything is functioning correctly, connect an oscilloscope to see the fields in action! 

Inspire and Amaze!

Your electromagnetic levitation device should now be complete and functioning. It will levitate any item in the determined weight range. For non-metal objects try attacking nails or nuts to them.

[All images courtesy Drew Paul / Drew Paul Designs] 

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