My magnetic levitation display keeping a magnet spinning in mid-air.
After my earlier proof of concept Magnetic Levitation 1 it was time for a serious setup.
“Continue reading” for full display set-up in a science museum. 8 photos, video and links…
This was made from an x-ray ballast transformer. The rectangular core was taken apart and changed to a solenoid core with enlarged ends. Fortunately the laminations weren’t fixed and were suitable to do this. The iron core at 4 x 4 x 17 cm has about 20 times the volume as the previous coil and with the much higher number of windings, gives a much more efficient coil.
It runs at 60 V at 1 amp (= 60 W) at rest supporting a NIB magnet 3 inches (8 cm) below the electromagnet coil. At full power it draws 40 V 6 A (= 240 W). This power is supplied from a separate mains transformer. Total weight is 10 pounds (4 kg). Total levitating lifting power is around 2 pounds (1 kg). It will be supporting a NIB magnet weighing 160 g measuring 1.3 inches (3 cm) diameter x 1.3 inches (3 cm) deep.
Mounted on the coil are the two Hall effect devices (one end is shown on the right connected to shielded cable). There is a thermal cut-out not shown (microwave ovens have lots of these rated at 145 – 160 degrees C). Also not well shown are a 0.22 uF 250 V polyester capacitor and a freewheeling BYV29 500 V, 9 A, 60 nS diode and heatsink to constrain the RF hash locally.
This shows the mounting inside a 12 inch (30 cm) acrylic sphere. There is a high flow centrifugal fan supplying airflow through the PVC above it. Without the copper block beneath it, the magnet tends to oscillate and become unstable after perhaps 10 seconds or so. Despite my best efforts to counter this electronically, the most effective way to dampen it is to have a heavy aluminium or copper block beneath it about 1 inch (2-3 cm). This still gives an effective display. You can spin the NIB magnet or have it completely in your hand still levitated and resisting being moved away. Giving the magnet a simple spin with the fingers will keep it rotating for 1 1/2 hours limited by friction and eddy currents. It will also support an iron object such as a spanner without a magnet as above.
In a working display it is of advantage to have a lower stop anyway. The magnet then doesn’t drop to the ground when it is turned off.
The control electronics are essentially the same but I now use two paralleled MOSFET’s on a larger heat sink for extra power handling. The single control is for control of power and hence position.
The magnetic levitation demonstrated by Sylvia at the GDS. This (the mag-lev, not Sylvia) has been on constant hands on public display since November 2004. No-one has pinched the magnet yet. The alarm that sounds as the magnet is pulled away helps….
Related pages
Try something else
Exploding wire lightning simulation
External links
Rick Hoadleys article and links on suspended objects
cjk2 from the 4HV forum with another maglev circuit which is simpler.
Flyingmagnet An impressive French site with some nice vertical levitation.
Bill Beatty’s maglev with extensive links.
Photo Date: 2004