The Levitating World Globe from With Design In Mind. Licensed by Pacific
Levitation Systems, Inc. Manufactured in Taiwan. The 9 inch world globe is made
by Replogle Globes Inc., 2801 S. 25th Ave., Broadview, IL, USA 60153-4589.
I purchased this wonderful electromagnetic levitation device at The St. Louis Missouri Science Museum. With Design In Mind could not be found at their warranty card address. I could not locate Pacific Levitation Systems Inc., either. Both may be out of business. When this article was written, they did not have a presence on the internet. I opened the bottom cover plate to see inside this awesome science toy. I could not see everything as I would have had to destroy it to get it apart.
The 9 inch world globe contains a large magnet inside the top and a small
magnet inside the bottom. The top of the stand contains a large iron core
electromagnet. The bottom of the stand contains a Hall effect magnetic field
strength sensor. This senses the position of the globe by sensing the field
strength from the small magnet in the bottom of the globe. The sensor provides
input to the feedback circuit which controls the current provided to the
electromagnet in the top of the stand. This feedback control circuit holds the
globe in mid air. It provides rock stable levitation and will take a good hard spin because the circuit uses about 30 watts. Some newer cheap levitation globes use only about 7 watts and will just barely hold their globe in the air.
The base of the stand is a large heat sink with some power transistors and parts I could not see without breaking the welded plastic. I could not see the Hall effect sensor. I will not break my $170. toy to try to see it! If you are a smart electrical engineer, you may be able to build this wonderful stable levitation system. It is no longer sold as far as I can tell. When you place the globe in the stand (in mid air), there is a solid notch it stays in. If you pull down on the globe, you can hear the circuit transformer hum as it sends more current to the top electromagnet to pull the globe up. This is a very good, very stable feedback control circuit. I have left it on for at least 8 hours at a time. The base gets warm. If you give the globe a good spin, it will spin for about 20 minutes before it slows down from air friction and the friction of the magnetic field itself. When you unplug the stand, the globe drops. The large magnet in the top of the globe will hold the globe hanging from the stand top when the power is off.
This thing is really neat !!!
The label and cover plate.
The circuit board top. (enlarged)
The circuit board bottom. (enlarged)
A very large full color scan of the board components.
Most visible parts are available at Radio Shack at low cost. For example:
TL082, Dual op amp DIP-8 case quantity 3 at $1.89 each
2N3906 PNP transistor TO-92 case at $.89
MC7815C +15 V DC 1 amp voltage regulator TO-220 case at $1.49
I heard from another globe owner that the variable resistor on circuit board
controls the levitation height, and the stand head includes a thermal cutoff
protection device with the electromagnetic coil. The current to the coil seems
to be pulsed. (This may be a pulse width modulation circuit.) The globe came with a 10 inch plastic rod to calibrate the gap
length of the stand.
This same type levitating globe was once featured in Tim Allen's great comic television show "Home Improvement".
Magnetic Levitation - Science is Fun