Experts,
I'm rolling my own EMs, and thought a core material would be a snap-soft iron. I was reading on this U of Surrey web site how different materials perform. Iron is naturally a good magnifier of the field produced, but then I wondered about how a coil would retain a field if switched in polarity, and whether hysteresis of an iron core would make it worse.
Here is the application: Simple 'levitation' of neodymium magnet by 3 coils (triangle underneath). In this case, the fields in the same polarity can be adjusted in strength. But the intention is to have the same electromagnets (EMs) be pulled away from each other, and have the permanent magnet (PM) be suspended between the 3, on the same plane. So if the PM is level with the other 3, there can be both repulsion and attraction switching quickly.
I've made years past 'shock boxes' that utilized the collapsing of the DC magnetic field across an audio transformer to zap the holder via a mercury switch, so I know the field of a DC EM will retain the field for a time-even when the polarity is switched.
So one question is: Which core material will allow a high degree of magnification of the EM's field, while still allowing the polarity-even the magnitude-of the field changing very quickly?
I'm driving these coils with an STM32 processor at 72MHz, using hall sensors, batteries, hand-rolled coils that are about 1" long and about 1/2" at their widest in diameter, so these won't be huge. But if the nearest pole of the PM presents itself to one coil as another polarity (spinning/flipping in place), even if the magnet is being levitated/suspended, the nearest EM would have to switch polarity fast. It is entirely feasible that the PM could spin rapidly.
Since the PMs are from 2mm to 8mm in size, does this really sound like it will be an issue? I'm stocking up on spools of various gauges and core materials, but I lack an o-scope Thanks in advance for your thoughts...
I'm rolling my own EMs, and thought a core material would be a snap-soft iron. I was reading on this U of Surrey web site how different materials perform. Iron is naturally a good magnifier of the field produced, but then I wondered about how a coil would retain a field if switched in polarity, and whether hysteresis of an iron core would make it worse.
Here is the application: Simple 'levitation' of neodymium magnet by 3 coils (triangle underneath). In this case, the fields in the same polarity can be adjusted in strength. But the intention is to have the same electromagnets (EMs) be pulled away from each other, and have the permanent magnet (PM) be suspended between the 3, on the same plane. So if the PM is level with the other 3, there can be both repulsion and attraction switching quickly.
I've made years past 'shock boxes' that utilized the collapsing of the DC magnetic field across an audio transformer to zap the holder via a mercury switch, so I know the field of a DC EM will retain the field for a time-even when the polarity is switched.
So one question is: Which core material will allow a high degree of magnification of the EM's field, while still allowing the polarity-even the magnitude-of the field changing very quickly?
I'm driving these coils with an STM32 processor at 72MHz, using hall sensors, batteries, hand-rolled coils that are about 1" long and about 1/2" at their widest in diameter, so these won't be huge. But if the nearest pole of the PM presents itself to one coil as another polarity (spinning/flipping in place), even if the magnet is being levitated/suspended, the nearest EM would have to switch polarity fast. It is entirely feasible that the PM could spin rapidly.
Since the PMs are from 2mm to 8mm in size, does this really sound like it will be an issue? I'm stocking up on spools of various gauges and core materials, but I lack an o-scope Thanks in advance for your thoughts...