Levitron Design


Posted on Feb 5, 2014

When an electric current is passed through a wire, it creates a magnetic field around it. The wire is wound into a coil to concentrate the magnetic field. Iron is a ferromagnetic material and when placed into the centre of the coil results in a much stronger magnetic field being produced. In order to acheive levitation, a magnet must first be attracted upwards towards the


Levitron Design
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electromagnet. This happens when an electric current is passed through the electromagnet. If the electromagnet is turned off, the static magnet descends again. When the magnet falls too far down, the electromagnet turns back on again in order to make the magnet rise once more. If this process is continuously repeated at a high enough frequency then the static magnet will appear as if it is floating in mid-air. A hall effect sensor detects magnetic field strength. If placed under the electromagnet, as shown on the right, it will detect how close the static magnet is to the frame. The output of the sensor controls the height of the static magnet by determining when the electromagnet should turn on and off. The hall effect sensor requires an input of 5V, therefore a 5V regulator is used to limit the voltage. The 5V is also used as a reference voltage for the 741 Op-amp. The coil is connected to a high-power driver P-channel MOSFET which amplifies the output of the 741. To protect the MOSFET from the coils kickback voltage a protection diode is placed in parallel with it. Kickback voltage can happen when the electromagnet is turned off. In the schematic there are two diodes, but only one is necessary for a 40mm electromagnetic. The circuit on veroboard is shown below: The legs were made first. The design was sketched onto a piece of Light Ply and cut out with a knife. This was then reapeated using Balsa. The Balsa was...




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