Continuously Rotating Sphere in a Glass Jar

The best place for a rotating sphere, driven by solar energy, is in a glass jar. Moving things are an ideal toy for cats or other pets and a jar gives some protection, or not? The project looks simple but it took me several weeks to find the right design. The electronic driver circuit and the mechanics consists of just a few components. The styrofoam sphere with a sharp needle as axis, rotates under a magnet bearing. The needle rests above against a small glass plate. Four magnets on top of the sphere, a solarpanel, a supercapacitor, a coil and a sensor are all the essential parts to keep the sphere spinning for a very long time.

• Glass storage jar 12cm diameter 20cm high.
• Styrofoam ball 8cm diameter

• Mattress needle 15cm long

• Aluminium strip 1.5x2x100cm
• Solarpanel 5V - 90mA
• Supercapacitor 22F 2.5 - 3V
• Coil out of a 220V mirror ball motor
• Electronic components, see circuit scheme.

The electronic circuit consists of a Hall IC, with a very low current consumption. This chip drives the pulse coil. Only this sensor, the pulse coil and a 3V lithiumcell can power this pulse motor for a year. I use a solar panel that has to supply 3 Vmax for the 3V supercapacitor. The SMD voltage regulator soldered below the supercap is doing that job. When using a 2.7V supercap, a 300mV schottky diode after the XC6206 decreases the voltage. The hall sensor Is soldered on a small board is connected on a corner below the solarpanel. The pulsecoil, from a mirror ball motor, is connected on the frame. Getting all the parts in the right position is not easy. Double check all the (solder)connections. This pulse motor has to run for a very long time.

Start with the rotor. Push the needle 'perfectly' trough the middle of the sphere. Warning: this is not an easy job! Connect with second glue the 4 magnets to the styrofoam sphere, perfect distributed over the upper part. Next is the frame. Look to the photo for the shape. Connect this to the wooden cap of the glass storage jar. Keep all within the size of the glass jar. Connect the magnet bearing on top. Glue the glass plate below and the magnets in the middle on top. Also securely attach the electronic components to the frame. Now testing and adjusting can start. The position of the hall sensor is the main adjustment point and not an easy one. When it runs, it keeps on going for a long time on the window sill.

To make a continouosly rotating sphere is not easy because jou have to rely on construction, connections, parts and skills to keep the thing going. All has to fit within a jar. Most of the time it is the mechanical part what makes, after some time, that something breaks and stops rotating . This pulse motor runs quite slowly. Slow and for a long time is my intention.