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Magnetic levitation

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Petezel

Tue Jul 18 2006, 02:58PM

Registered Member #211 Joined: Sun Feb 19 2006, 05:33PM
Location:
Posts: 27

Hey, nice work!

< have a poke at that, a clock where the display section 'floats'
Regards,
Pete

uzzors2k

Sun Oct 15 2006, 07:27PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

I just built one of these except I chose to use an infrared beam for object detection. One photo-transistor detects background and LED light while another detects whether the beam is broken. These two are compared and the result goes through a lead compensation circuit much like cjk2s. This signal then gets amplified and this controls the electro-magnet. Quite simple but once I got it running it was very stable with both heavy and light objects.

Things I can improve on it are the need for dual supply, overheating of drive transistor and make a proper housing. Otherwise it would be mantelpiece worthy!

1160940466 95 FT9059 Magnetic Levitation Uzzors

teravolt

Sun Nov 12 2006, 03:29AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Tesla Down Under what does the rest of your levitating shaded pole motor look like

Tesladownunder

Sun Nov 12 2006, 05:51AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

teravolt wrote ...

Tesla Down Under what does the rest of your levitating shaded pole motor look like

Nothing shady about my poles.
Not quite sure what you mean? Details here.

I now have an electromagnet that will support a NIB magnet at 17cm height with about 500W input power. This is compared with about 10cm max with the old magnet pictured below.
The new one is based on a cut down 2KVA 250 to 110V transformer.

Pic below is the old one.

Peter

Dr. Dark Current

Wed Nov 15 2006, 04:13PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Here is a circuit I designed, do you think it will work?

Steve Conner

Fri Nov 17 2006, 04:18PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Due to the lack of catch diode across the magnet, I expect it would "A splode". Also that stuff about the TL494 needing pull-up or pull-down resistors on its outputs (can't remember which) and you forgot to put bypass capacitors on the supply rail too.

uzzors2k

Fri Nov 17 2006, 06:13PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Jmartis wrote ...

do you think it will work?

The quickest way is to simply try it.

Dr. Dark Current

Fri Nov 17 2006, 08:28PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Steve Conner wrote ...

Due to the lack of catch diode across the magnet, I expect it would "A splode". Also that stuff about the TL494 needing pull-up or pull-down resistors on its outputs (can't remember which) and you forgot to put bypass capacitors on the supply rail too.

thanks, so I built a circuit with these modifications, and by principle it works, but it is not stable (the levitated object sticks to the electromagnet above it)

Marko

Fri Nov 17 2006, 08:32PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

With such 'flyback-ish' drive mosfet is surely going to absorb some HV spikes and heat up, but it probably won't blow up unless you push the frequency very high and power hard.

Putting diode or TVS across mosfet will just move the heat to another place, but that's probably the point.
Halfbridge drive would be much more efficient solution fr this.

Regarding pullups, with just one mosfet they aren't needed; just connect pin 10 to ground and pin 8 to mosfet, so you use TL's output transistors in push-pull.

Steve Conner

Sat Nov 18 2006, 09:14PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Jmartis wrote ...

it is not stable (the levitated object sticks to the electromagnet above it)

Did you see the earlier posts that mention the need for a lead compensation circuit to keep it stable?

BTW, merovingian mentioned the risk of "Flux Walking" in the magnet. Flux walking is exactly what you want in this system! It's the DC magnetic field that does the levitation. The controller walks the flux up to whatever level is needed to keep your object hovering at the desired height.

Any AC ripple at the switching frequency is just a nuisance. In practice due to the high frequency and high coil inductance, I expect there would be hardly any ripple, which explains why it's hard to extract power by magnetic coupling.

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