Using an STM32 to levitate/suspend tiny neodymium magnet at 12" or so…

Holes Flow Mon Nov 13, 2017 1:41 am

You see, suspending common objects as desk fodder with a short range Hall effect sensor is common-place.

But I want to find out what would be required to suspend/levitate a tiny neodymium magnet (NM) up to 12″ distant. Too big a magnet, and you fight gravity, and too small, and the electromagnet (EM) would need to be too big. I’m using 1mm to 3mm NMs, and winding my own coils around my own soft iron cores, and so far I can’t influence the magnets past a few inches… It doesn’t seem detecting the magnet & polarity needed is the issue; not when compared to the feat of suspending/levitating the NM from so far away.

I already know that a single EM can’t do the trick if the NM is not attached to a tether or restraint due to, well, the obvious reasons. If it helps to think of a NM sliding up & down inside a plastic tube, then use that to frame a use case.

TIA!

Replies

ahull Mon Nov 13, 2017 6:04 pm

I don’t have an answer to your problem, but I do know how to slow down a large magnet .

I suspect you need a far more energetic magnetic field than you might imagine… or maybe you need to spin your magnet at high speed…

Holes Flow Tue Nov 14, 2017 12:43 am

Standard Disclaimer: I hope the moderators know that I realize this is not an STM32 question or problem. I love those little buggers!

Thanks Andy (@ahull) for writing!

I suspect you need a far more energetic magnetic field than you might imagine

Well, I can imagine enough to tear a hole in the fabric of space & time-and just for noble/honorable/honest purposes, mind you! Instead I’m hoping it doesn’t come to that (and by that, I mean the last part of every MythBusters experiment/segment involving explosions or high voltage)…

This is more of a post regarding “Projects” for the µCs, and as far away from the actual µC as you can get is PMs vs EMs… As for the video, the PMs I’m talking about would likely never make it through, they just have so little mass, being in the low millimeters in size. But I’m beginning to think that is also the issue. There is going to be a curve coming out of my experiments where suspending/levitating a tiny PM (NM for neodymium magnet if you’d rather) becomes a function of it’s mass exerting force via gravity vs it’s mass too small to be acted upon ‘forcefully’ enough by an EM. In other words:

if NM Mass v = EM Effectieness v = Gravity‘s Influence v
…and of course:
if NM Mass ^ = EM Effectieness ^ = Gravity‘s Influence ^

where ^ is more, and v is less

I fully realize this is not a magnetism forum, or anything close… It was just a post about a project I’m doing where I’m trying to determine just how much I can influence a tiny NM with batteries, and not a Tesla coil!

Thanks for the reply!

Pito Tue Nov 14, 2017 8:36 am

The force/intensity of the magnetic field of such setup drops with the cube of the distance usually.

For example: if you need “1” unit of power to levitate at 1 inch distance, you would need “1728” units of power in order to levitate at 12 inch distance..

Say with the same coil and magnet you levitate at 1 inch with 1 Ampere current into the coil, you would need 1728 Amperes to levitate at 12 inch..

All that plus/minus, as the gravity decreases with the altitude over Earth’s surface (not an important decrease at 12 inch though), and the magnetic field of your coil may not be symmetrical/homogeneous.

Holes Flow Wed Nov 15, 2017 7:22 am

Pito,

So all i need is a 1728 ampere battery? And here i naively thought this would be difficult! I have more options for suspension than detection, so I’ll do some graphing with that to find the sweet spot for magnet size.

Thank you for running the numbers i was subliminally too frightened to do!

Pito Wed Nov 15, 2017 8:21 am

So all i need is a 1728 ampere battery?
Nope, I have not said that

Anyhow, in order to control the levitation by stm32 you first have to know with how much current you need to feed your coil in order to get your magnet at the required height..
I do not know, you have to measure.
Knowing that you may start discussing how to control that current with an MCU like stm32.

RogerClark Wed Nov 15, 2017 9:00 am

Time of flight detector distance module may be a good option for height detection

zmemw16 Wed Nov 15, 2017 3:38 pm

way back in 4th form(68/69??), physics teacher said Saturn V used a pp9 ‘sized’ battery to supply 1000A !
only question was mine, for how long ?
1mS
a brief levitation then

Pito Wed Nov 15, 2017 5:42 pm

The rail guns use 5-10 million Amperes to fire a projectile w/ 2miles/sec muzzle velocity and 100miles range..

RogerClark Wed Nov 15, 2017 7:43 pm

Depends on what voltage you need

PC power supplies are a cheap ( often free) way to get quite a lot of amps at 5V or at 12V ( I am using one to power a HF transmitter that needs 20A at 12V )

If you need low voltage but lots of current, it is possible to modify an transformer by removing the secondary coil, and replacing the winding with a few turns of very thick wire.

Also I suggest taking a look at those home made battery connector welders, or perhaps get hold of a second hand arc welder.

zmemw16 Wed Nov 15, 2017 11:04 pm

[Pito – Wed Nov 15, 2017 5:42 pm] –
The rail guns use 5-10 million Amperes to fire a projectile w/ 2miles/sec muzzle velocity and 100miles range..

googled,
https://www.wired.com/2010/12/video-nav … es-record/
albeit only 1.5-2MAmp, shell is a brick shape, visibly drops in its very short flight.
i’m surprised it got that far without tumbling
srp

Holes Flow Fri Nov 17, 2017 3:51 am

Me = Stewie Gilligan Griffin with a rail gun…