Electromagnetic Floater

This Instructable will show you how to make a device that can float almost any object with a magnet in it.

It is much like the floating globes you can buy, except it works by balancing the forces of permanent magnets with electromagnets, rather then simply using combinations of permanent magnets.
This is done by using a microcontroller and an IR sensor to detect where an object is floating below. Then based on a set value, the microcontroller uses the electromagnets to to hold the floating object at a given height.

The place the object floats at depends on the weight of the object and the power of the magnets in the object. The height is set by holding the object under the magnets and sensor and pushing the button.
The object floats at the point where the force of gravity down equals the force of the magnets pulling up, which allows it to use non-industrial electromagnets and less power to float. The program also dynamically adjusts so the object is always at the perfect height.

I decided to make the electromagnetic floater because I have always been fascinated by the floating globes in the store, but I never wanted to pay their prices, and I never liked how they only floated objects that you had to buy or came with it. So, I decided to make my own that could float anything with a magnet. The results are what you see here.

Materials:
- ATMega168 Microcontroller
- 1 16-20 MHz Crystal
- 28 Pin Socket
- Dual Full H Bridge IC
- 1 Power NPN
- 2 Electromagnets
- 1 Bicolour LED
- 2 IR LED
- 1 IR Photodiode
- 1 5V Regulator
- 2 Leveling Capacitors
- 1 SPST Switch
- 1 NO Button
- 1, 470 Ohm Resistor
- 1, 5 Ohm Resistor
- 1 Universal Breadboard
- 2 Cases
- Plexiglas
- Solder
- Hot Glue
- Steel Wire
- Vinyl Tubing
- 3 or more 1/4" diameter x 1/4" thick rare earth magnets (for the base)
- 2 or more 1/2" diameter x 1/8" thick rare earth magnets (for the objects)

Tools:
- Soldering Iron
- Hot Glue Gun
- Desoldering Pump
- 3rd Hand
- Plexiglas cutter

Once the materials are gathered, the cases needs to be prepared. For my base I used a project box from The Source (Radio Shack in U.S.) to house the electronics, and a ring box to house the magnets and sensor assembly.

First you need to drill a hole in the back of each box for the support wire to go through. Also cut holes for the power switch, power input, set height button and LED indicator. You also need to cut most of the bottom of the ring box out, just leaving a lip on the bottom.

Support the ring box above the base box by using some heavy gauge steel wire, bent to the shape and height you want. Next, wrap the electrical wire around the steel wire, then cover all of it with the vinyl tubing (optional) as seen below.

Next, bend the bottom end of the support in a zig zag pattern and use hot glue to secure it to the inside of the bottom case (see second picture below). I secured the ring box to the top of the support wire by using a magnet, but it could also stuck on by hot glue.

This step is pretty straight forward, first solder the electromagnets to 4 of the wires. As you attach the parts be sure to use a continuity tester to find and label the corresponding wires on the other end. At this point it is not too important which way the electromagnet coils around the magnet, it can be adjusted later. But be sure to connect both electromagnets the same way.

When you put the electromagnets in the box when finished, put the permanent magnets inside the coil.

Next cut a piece of Plexiglas to fit inside the bottom of the ring box but so the bottom lip holds it up. The next step is to attach the IR emitters and sensor to the Plexiglas as seen in the pictures below using hot glue then finish attaching and labeling the wires.

For this step you probably should assemble the electronics on a solderless breadboard before soldering them together. The schematic to build the circuit is attached along with the hex file to load on the microcontroller. The Arduino - 0007 code file is in the introduction so you can tweak it or make changes as you need.

It is very important to plan where all of the parts go, so all of the electronics will fit in the box the first time, If not it could be very frustrating and cause much grief.

It is also important to note that the NPN power transistor(s) will heat up, to overcome this I mounted them to contact the aluminum base of my project box, This way it acts as a heat sink, preventing a spectacular fire. You will also need to come up with something similar to remove most of the heat from the box.

Once the electronics are built, there is a section of code in the program to uncomment and and then load onto the chip to test the orientation of the coils. It pulses the coils off, pulling up, and pushing down, also indicated by the LED. If you hold a magnet under the electromagnets and it doesn't follow the pattern, reverse the wires.

This part is only limited by your imagination. I have found that if the objects to float are too small, or two short relative to the width, are harder to get to float.

The object shown here is a heavy cardboard tube covered in electrical tape with 2 1/2" diameter x 1/4" thick rare earth metal magnets (from Digi-Key). I have also successfully floated a die I crocheted using a granny square pattern, and a ruby made from construction paper.

All that is left to do is start floating the objects.
This is done by holding the object under the magnets and slowly bringing it up. When It nears the point where it wants to float up, push the button. This will set the level to float at to the current height.

Next, hold it just below where you set the hold height, so the LED lights up. Hold it there until it simply floats out of your hand. This happens because the microcontroller slowly adjusts the hold height up, to where the electromagnets have enough power to control the object.

You may also notice some buzzing coming from the electromagnets. This can be easily fixed by inserting some padding around the electromagnets.

If you do make this I would love to see some photos. It would also be great to hear any comments you have.