Magnetic Levitation System
A feed-back control system is employed to balance a ferromagnetic substance or a magnet in mid-air
The setup consists of an electromagnet, ir emitter and receiver for position sensing, electromagnet driving MOSFET, 555 IC PWM signal generator, and op-amp feedback control circuit employing lead-lag compensator. When the suspended object goes a little down, the output voltage from the ir sensor will go up which is fed to the op-amp circuit. After a network of circuitry this finally results in the PWM duty cycle being increased and hence the increased electromagnet current will pull the object back and a bit more. So, there is this micro oscillation going on all the time and the object remains stable at its average position.
When levitating a magnet instead of a piece of iron, the magnet aids to the attraction force and helps decrease the electromagnet current requirement. When you are trying tyo suspend a magnet below an iron bolt, there is this point called the magnetic neutral point. If you try to hover the magnet above this magnetic neutral point it will snap up into the bolt. If you try tyo hover it below this magnetic neutral point, the force will be insufficient to support the weight of the magnet and it will fall. Although theoretically you should be able tyo balance it at the magnetic neutral point, practically, due to disturbances, it's impossible. Its like trying to balance a pencil on it's tip. But, when the magnet is very near the neutral point, it takes very little force to stabilize it there; energy I'd required only to overcome the disturbances, the magnet supports itself. Just like, you can balance a stationary bicycle on two wheels with your pinky finger as long as it's fairly upright.