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Magnetic levitation

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Dr. Dark Current

Sun Nov 26 2006, 09:48AM

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

well, today I finished a "final" version of my levitator, built a nice wooden base for it, and a nice small circuit board with exactly the came circuit I had before. It has just one small downside, and thats that it is not stable

. Even when I have everything the same except the base and the "frame" for the coil, when I turn the stabilisation pots on the circuit board in every possible direction and combination, I cannot get it stable. I think I will scrap it and build the hall sensor version, but the thing is I can't find any usable hall sensors. Crap.

Steve Conner

Sun Nov 26 2006, 03:15PM

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

You probably increased the gain of the system by moving the optics around. Maybe the target casts a sharper shadow on the photodiode now, or whatever.

uzzors2k

Sun Nov 26 2006, 03:41PM

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

You'll need to adjust it everytime you use it until you get a reference detector. Mine still works fine.

Dr. Dark Current

Sun Nov 26 2006, 06:18PM

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

After many hours of tweaking and adjusting, I have it finally working stable with the new base. In the process I designed a simple circuit that works quite stable for me. All components, especially in the phase lead compensation circuit, were selected experimentally so I think it will not work "as is" on a different setup. I have yet to test if it also works stable in a daylight.

Kipmans

Fri Dec 08 2006, 05:00PM

Registered Member #91 Joined: Thu Feb 09 2006, 03:03PM
Location: The Netherlands
Posts: 45

cjk2, what is the resistance of your coil?

I'm also constructing a levitating device like yours, but my electromagnet (18 AWG) currently draws over 16 A at 5 V, overheating the wires. Even if I use all my wire (about 70 meters) It'll draw about 6,5 A. Do you think it'll be ok when it's actually PWM'ed?

cjk2

Sat Dec 09 2006, 03:15PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Quite honestly, I have no idea if you will be alright with that type of coil. I think mine would draw something like 6 amps at 12v. I don't even think I ever measured the resistance, but i used something like 80' of 18awg wire. As long as the magnet does not actually have to provide that much force, the PWM circuit will be able to run with a low percentage of on time, so the magnet will not see that much power.

I'm about to have to leave, so I'm sorry I can't tell you any more. I'll back in a few hours, and Ill be happy to check the actual coil resistance, and tell you the percentage of on time the PWM tends to run at.

Kipmans

Sat Dec 09 2006, 06:27PM

Registered Member #91 Joined: Thu Feb 09 2006, 03:03PM
Location: The Netherlands
Posts: 45

Actually I made a mistake, I connected the coil to a 12 V source instead of 5 V when measuring the current

. I added some more layers and now it draws 4 - 4,5 A at 5 V. The coil still gets pretty warm though, so I am still interested in your measurements.

cjk2

Sat Dec 09 2006, 11:09PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

The resistance of my coil is about .5ohms. The on time is actually very low, usually under 20%. I bet this is due to the fact that the magnet is already strongly attracted to the core.

Kipmans

Wed Dec 13 2006, 12:58PM

Registered Member #91 Joined: Thu Feb 09 2006, 03:03PM
Location: The Netherlands
Posts: 45

I've been busy the past few days, hence the late reaction.

Thanks for the info, I'm pretty sure that my coil will be alright. It probably takes a lot of tweaking until the device eventually works, I will post here as soon as I made some progress.

Tesladownunder

Wed Dec 13 2006, 02:10PM

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

I have put my HV stuff to one side for a while and have started work back on magnetic levitation where I left off 2 years ago with a PIC controlled system.
I have been going back trying to relearn PIC stuff first. I think this is the best way to go particularly if multiple sensors or outputs are needed with true levitation rather than suspension. The options for flexibility should be greater particularly if you are to do clever stuff like active movement or stay where it is placed stuff.

Peter

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