Levitron Design

Description: When an electric current flows through a wire, it generates a magnetic field around it. To enhance this magnetic field, the wire is coiled into a coil. Inserting iron, a ferromagnetic material, into the center of the coil significantly strengthens the magnetic field produced. For levitation to occur, a magnet must be attracted upward towards the electromagnet. This attraction occurs when an electric current is supplied to the electromagnet. When the electromagnet is deactivated, the static magnet descends. If the magnet falls too far, the electromagnet reactivates, causing the magnet to rise again. Repeating this process at a sufficiently high frequency creates the illusion of the static magnet floating in mid-air. A Hall effect sensor measures the magnetic field strength and, when positioned beneath the electromagnet, detects the proximity of the static magnet to the frame. The sensor's output regulates the height of the static magnet by controlling the activation of the electromagnet. A 5V input is required for the Hall effect sensor, necessitating the use of a 5V regulator to limit the voltage. This 5V is also employed as a reference voltage for the 741 operational amplifier. The coil connects to a high-power driver P-channel MOSFET, which amplifies the output from the 741. To safeguard the MOSFET from kickback voltage generated by the coil when the electromagnet is turned off, a protection diode is placed in parallel with it. While the schematic indicates two diodes, only one is needed for a 40mm electromagnetic. The circuit layout on a veroboard is depicted below. The legs were constructed first, with the design sketched onto Light Ply and cut out with a knife. This was repeated using Balsa wood, which was sandwiched between two pieces of Light Ply to enhance strength. A channel was carved into the Balsa section to allow wires to pass through. The cylindrical component was created next, with cuboid wood pieces cut and one edge sanded. These pieces were wrapped around a weight and secured with an elastic band, followed by extensive gluing. Once the glue cured, the weight was removed, and the wood was sanded. All components were spray-painted black. A protective shell for the sensor was carved and attached to the bottom of the cylinder, and LEDs were affixed to the top of the lid.

The described circuit operates on the principle of electromagnetic induction and feedback control. The system begins with an electric current flowing through a copper wire wound into a coil, which generates a magnetic field. The introduction of a ferromagnetic core, such as iron, amplifies this magnetic field, enhancing the overall electromagnetic effect. The levitation mechanism relies on the precise control of the electromagnet's current, which is modulated based on the feedback from the Hall effect sensor.

The Hall effect sensor, positioned strategically beneath the electromagnet, detects the presence and distance of the static magnet. Its output provides a voltage signal that is fed into the 741 operational amplifier, which functions to amplify this signal to a level suitable for controlling the P-channel MOSFET. The MOSFET acts as a switch, allowing high current to flow through the coil when the electromagnet is activated.

The inclusion of a protection diode is critical in safeguarding the MOSFET from potential damage due to inductive kickback, a phenomenon where a sudden change in current through the coil generates a high voltage spike. This diode provides a path for the kickback current, thereby protecting sensitive components within the circuit.

The physical assembly of the circuit involves careful construction of the support structure and housing. The legs, made from a combination of Light Ply and Balsa wood, provide stability and insulation for the wiring. The cylindrical housing not only serves as a protective enclosure for the electronics but also provides an aesthetic finish, as evidenced by the black spray paint. The integration of LEDs at the top of the lid adds a visual indicator of the system's operation. Overall, this design exemplifies the principles of electromagnetism, feedback control, and practical engineering in creating a levitation apparatus.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 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 sandwiched between two pieces of Light Ply to make a strong leg. In the middle of the Balsa section a channel was cut to allow wires to travel through the inside of the leg. The cylinder was made next. Many cuboid pieces of wood were cut and one edge of each piece was sanded. These pieces were then wrapped around a weight and held in place with an elastic band. Plenty of glue was used to join them together. Once the glue had dried the weight was removed and the wood was sanded. All the pieces were spray painted black. A protective shell for the sensor was carved out and stuck to the bottom of the cylinder. The LEDs were attached to the top of the lid.