Circuit knowledge

I was looking for something interesting about one of the projects of Tesla when I came across a very cool circuit, which referred to electromagnetic levitation. Levitation always aroused very human curiosity, since it was associated with magic and stuff besides. Magicians levitate objects or their Partners, not counting the flying saucers that levitating cows abduction them. Outside these "unbelievable" and supernatural phenomena there is the scientific side of levitation, where this supernatural phenomenon becomes simple when using the electro-electronics.




Of course we can not use electronics to levitate a cow, unless it is with a belly full of nails. But we can make relatively simple devices that allows the levitation of small metal objects. Called levitators, levitrons, anti-gravity devices or levitation device, there is no mystery nor magic, everything is pure physics. Who ever made ​​an electromagnet by wrapping wire in coil form on a nail. This is the principle that I found pretty cool device, it is very interesting since it is designed to actually levitate an object without touch anything. An electromagnet pulls the object levitates but not as the metal object tends to stick to the nail.


The basic electromagnet

With this circuit you can do with any ferromagnetic object levitate in the air, getting off without any visible thing to hold him. The secret is simple, a simple electromagnet was added a detector circuit passing that controls the current sent to the electromagnet. Every time the object passes through a given position the electromagnet receives less current and becomes weaker, and when the object falls the electromagnet receives more pulling on the object. By this he seems to be floating in the air without the aid of any device. The author of the project used as an optical sensor barrier formed by an infrared LED and an infrared photo diode and thus detects the position of the object.

The machine Levitate

The sensor operation is as follows, if the object climb, the LED will be illuminated and less circuit reduces the current in the coil of the electromagnet. If the object down, the LED will be illuminated and the current to the electromagnet will increase. The control circuit of the electromagnetic levitation device uses an integrated operational amplifier 1458 or 4558 as a voltage comparator circuit, but any other operating circuit can be used, such as a LM741.



What controls the charge to the electromagnet is a MOSFET power transistor, which may be a IRFZ44, or IRF3205 IRF540, which must have a heat sink. Have the electromagnet may be reused in any relay or large coil in the case, the author used a coil electromagnet with 1,200 laps with an enameled wire 0.4 mm in diameter in an iron core with 8 mm diameter. The coil has a resistance of about 8 ohms and is not designed for continuous operation at full 12V because it dissipates 18 watts. When operating the unit with the levitating object, the actual loss of coil power is much lower. Therefore one should not leave the unit turned on without anything to him levitate, as well as all the load goes to the coil and may burn it.

Adjustments Levitator

I would advise using a trim pot in place of R1 , photo diodes have different sensitivities , you may need to adjust the value of R1 . Measures of stress , when the photo diode is illuminated completely , its voltage should not be less than 6 Volts and 12 Volts almost electromagnet . When the photo diode is not illuminated , that is, when the light beam from the infrared LED is completely stopped, there must be more than 6 volts and the photo diode almost zero tension in the electromagnet.

If you have problems with the stability of the electromagnetic levitation device, ie , if the object starts to get very unstable or vibrating , you must change the time constant of the circuit . To do this , you must change the value of the capacitor C1 . This electrolytic capacitor 4.7 uF is originally from , but you can try lower values ​​like 2.2 uF to 1uF and larger values ​​like 10uF to 22uF . With a range of 1uF to 22uF will already be enough to settle the balance of the time constant , vary and test until the circuit enters a stable state as the video above .