Solar motor with floating rotor made of wood

Today we'd like to introduce you to a very impressive magnetic application: a solar motor with a floating wooden rotor.

There is no practical application for this motor. On the windowsill, it's a real eye-catcher that never fails to amaze guests.

Solar motor with floating rotor made of wood

Material list:

• Ring magnet Ø 18.0 x 10.0 x 4.0 mm N40 nickel - holds 4.4 kg - 4 pieces
• Disc magnet Ø 20.0 x 10.0 mm N40 nickel - holds 12 kg - 4 pieces
• Block magnet 20.0 x 20.0 x 3.0 mm N45 nickel - holds 4.3 kg - 4 pieces
• 8 solar cells 0.5 V / 150 mA - with solder connection (item number: 695-SM150L from EDUNIKUM)
• 60 g enameled copper wire Ø 0.25 mm
• Plywood 4 – 5 mm thick
• Solid wood 18.5 – 19 mm thick
• Round wood Ø 10 mm
• Glass pane approx. 70 x 80 mm, approx. 2 mm thick (in this case, from an old picture frame)
• Ballpoint pen refill
• Two-component adhesive
• Wood glue
• Solder
• Support

Levitating rotor

To make the rotor levitate, four magnets in the stator and at least two magnets on the shaft are required.
For the stator, I used four disc magnets measuring 20.0 x 10.0 mm and two ring magnets measuring 18.0 x 10.0 x 4.0 mm for the rotor.

To make the rotor levitate, the magnets must be arranged according to the drawing.

To prevent the rotor from spinning, one degree of freedom must be restricted. This was achieved by inserting a ballpoint pen refill.
By supporting the ball against the rear glass pane, an illusion is created. This represents a completely freely levitating rotor.

Rotation of the rotor (motor operation)

This is where the Lorentz force comes into play. This is the force experienced by a current-carrying conductor (or coil) in a magnetic field. For this purpose, four coils of enameled copper wire were wound onto the coil carrier below the rotor's solar cells.

Each coil is electrically connected to two solar cells offset by 180°. When light hits, a continuous current flows through the coil. The coil's solar cell faces the light source.

The field magnets are located below the rotor in the center of the stator. Here I would have used 4 block magnets 20.0 x 20.0 x 3.0 mm N45, but I had older, slightly larger block magnets from another project in stock, so I used those.

The current in the coils in conjunction with the field of the block magnets generates the Lorentz force, which in turn generates a torque on the rotor. The rotor rotates continuously when light hits the solar cells.

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