by reparator, published
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This is a model of an Anti-Gravitator, sometimes also called Levitator or Levitron. It lets a small magnet spere levitate in a magnetic field.
Principle of the Anti-Gravitator:
Of course it is not possible to disable the gravity forces. The principle of the Anti-Gravitator is to compensate the gravity by a magnetic field generated in a copper coil. Referred to the Earnshaw´s Theorem (Samual Earnshaw, 1805-1888) it is not possible to get a stable magnetic levitation with permanet magnets. In this experiment the magnetic attraction force, generated by the electric coil, is controlled by a hall magnetic field sensor. If the floating magnet lifts up and approaches the sensor the current through the coil will be reduced leading to a lower magnetic force (and a drop down of the sphere). If the floating magnets descents, the hall sensor indicates a lower magnetic field to the OPAMP resulting in a higher coil current and a stronger magnetic force.
This sweep process takes place ~4.000.000 times a second resulting in a stable levitation state.
The case design of the levitron is adapted from the aluminium design of Andreas Titze
Thanks to the german Make Magazin for the inspiration to the topic.
What you need for this project:
1 x Hexagon socket head cap screw M6x40 mm as iron core
1x M6 nut and washer
100 g Cu wire Ø 0.28 mm
1 x electronic board as described in attachment
1x Power supply 15 V, 800 mA
1 x Hall sensor A1302 or simular.
2 x M4 Hexagon socket button head screws
4 x self-tapping screws ~2,5 mm
Nd-ball magnet (15 - 30 mm diameter) or similar Nd-magnet
First of all you have to print the carrier for the spool (Spule_Unterteil, Spule_Oberteil and Spule_Konus). These parts get sticked together with the M6 screw and fixed with the nut. The head of the screw fits in the part "Spule_Konus". Drill a 1 mm hole near the inner part of the spool so that the Cu-wire can be leaded through. After that you have to coil the copper wire on the spool. You need 120 m wire minimum so that the DC-resistance of the resulting coil is at least greater than 50 Ohms. If you need more wire to fill the spool this is not a problem. Fill the spool completely with wire. Solder a insulated copper wire on each end of the coil (approx. 20 cm is recommended).
Solder three isolated copper wires on the hall sensor legs, isolate the solder joints with heat shrink tubes.
After that glue the sensor with a big portion of hotmelt onto the top of the M6 screw head. If everything is solidified you can assemble the coil with the attached sensor into the "Cylinder"-part. Take care to lead the three wires from the sensor to one of the holes in the cylinder and the two wires from the coil to the other hole.
Print the other parts (in different colors would be nice) and build them together with hotmelt glue as you can see on the pictures. All parts are printed without support and with 20 % infill.
On the part "Sockel" four support sticks are included. They can easily be removed by breaking off. The inside of the "Sockel" needs some rework if you prefer a super finished surface. In principle it is not neccessary becaused it is covered by the electronic circuit board.
Assemble the two "Seitenteile" with the M4 screws on the "Sockel" part.
After that you mount the wires in the two small cable channels of the side parts. It is a good idea to secure the isolated wires with a small portion of glue. Solder the ends of the wires to the pads marked with "coil" and "Hallsensor" on the electronic board. Also add the cable for the power supply. I did not use the originally intended power supply chassis due to the oversize of that part, but soldered the wires for the supply directly onto the board. The pinhead connector called "Hall-control" is for future application and needs not to be soldered.
If everything is connected the electronic board can be assembled with the parts side downwards by use of four small self-tapping screws.
Glue the coil containing cylinder onto the side parts and cover the cable channels with the "Abdeckung_Kabelkanal" part.
Test and startup
Turn the precision potentiometer to the right end, hold the magnet sphere below the coil (approx. 15 mm), turn-on the power supply and turn the potentiometer screw slowly to the other end (as you can see in the video). If you reach the resonance point, the sphere will begin to levitate. If you turn further it will bounce to the coil cylinder above. Reduce the potentiometer than a small portion to get the system stable.
If you are not successful to get a stable levitation try at least to change the connections of the coil to the electronic board (exchanging the poles of the electromagnet).
Take in account that the power supply pulls a current of about 400 mA if the hall sensor does not detect a magnetic field (eg. because the floating sphere is falling down). This current leads to a slowly heatup of the coil. So don´t leave the instrument unattendet and turn off the power if no sphere is inside. During a stable levitation the current is much lower (< 100 mA).
NdFeB-magnets (Neodymium-magnets) are very strong and have to be handled carefully. If two of them collide they can break into small, sharp pieces. Also they are dangerous for people with heart peace-maker.
Keep children away from these magnets. Follow the instructions of the manufacturer.
Use this description at your own risk!
Added part V4_Sockel.stl in order to meet specific wishes :-)
This part has wider cylinders to give a better hold for the PCB (less fragile). I removed the support for the cylinders either. So you have to care for the support yourself by using the right parameter in your slicing software. Feel free to choose either V3 or V4 for the socket.
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Anti-Gravitator by reparator is licensed under the Creative Commons - Attribution - Share Alike license.
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