Electromagnetic Floater

step 1-Materials
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


step 2-Prepare The Base
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.


step 3-Install the Magnets and Sensor
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.


step 4-Build the Electronics
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.


step 5-Make Some Objects To Float
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.