electromagnetic controls

[[email protected]]

Greetings Folks
New to these groups here, and have not checked out any of the
archives yet, so please forgive the simple question if the obvious is
already out there waiting for me... : )
I would like to scratch build one of those electromagnetic devices
that will float things under it. Maybe a steel ball bearing. While I
have an idea of the whats and whyfores, no reason to reinvent the
wheel if one of you already have the plans...
I've never seen one, but would it be possible to do this in
reverse, I mean like having the ball floating above the surface of the
device???
I've been daydreaming of making a miniture solor system with
various steel balls sitting on the glass of a smooth running clock
that would act like those skaters on the glass ice rink music boxes.
Anyone know how I could speed up one of those clocks??? I've been
looking for a DC that runs smooth rather then the harsh clicking per
second, and know they are out there, but not at the cheap stores that
I've been haunting for the goodies... Any hints on these subjects
would be appreciated.
Thanks in advance
Bill

 

[Stephen J. Rush]

Greetings Folks
New to these groups here, and have not checked out any of the
archives yet, so please forgive the simple question if the obvious is
already out there waiting for me... : )
I would like to scratch build one of those electromagnetic devices
that will float things under it. Maybe a steel ball bearing. While I
have an idea of the whats and whyfores, no reason to reinvent the
wheel if one of you already have the plans...
I've never seen one, but would it be possible to do this in
reverse, I mean like having the ball floating above the surface of the
device???
I've been daydreaming of making a miniture solor system with
various steel balls sitting on the glass of a smooth running clock
that would act like those skaters on the glass ice rink music boxes.
Anyone know how I could speed up one of those clocks??? I've been
looking for a DC that runs smooth rather then the harsh clicking per
second, and know they are out there, but not at the cheap stores that
I've been haunting for the goodies... Any hints on these subjects
would be appreciated.

The floating-ball gadget needs a feedback loop containing the magnet,
something to sense the position of the floating ball, and an amplifier to
drive the magnet. The sensor I remember from the days of Popular
Electronics was a photocell and lamp, set up so that the position of the
ball varied the amount of light reaching the cell.

The usual battery-powered clock has an oscillator, usually a quartz
crystal digitally divided down to 1 Hz, driving a stepping motor. The
stepper is used because it doesn't need much power, and because people
still expect clocks to 'tick'. Line powered analog clocks have
synchronous motors running at 3600 RPM (on my side of the Atlantic),
geared down to 1 RPM for the second hand, which gives very smooth motion.
You can get these motors with various gear ratios from the big supply
houses. If you need to run the system from DC, you could drive the motor
with an inverter locked to a precision frequency reference. Clock motors
draw less than five watts, so the inverter could be just an audio
amplifier and a transformer, driven by whatever precise 60-Hz source you
can come up with. I vaguely remember an article by an amateur astronomer
who built such a device to drive his telescope. Another approach would be
to control the speed of a high-speed DC motor that has some kind of
magnetic or optical pulse generator on its shaft. Compare the pulse rate
from the shaft with a quartz-crystal reference (after suitable processing
to match the frequencies), then use the difference to vary the voltage
supplied to the motor. That looks like more trouble than coming up with
5W at 60 Hz to drive an off-the-shelf synchronous motor.

 

[Esther & Fester Bestertester]

[email protected] sez:

I would like to scratch build one of those electromagnetic devices
that will float things under it.

Google "maglev" OR "magnetic levitation". One of the resulting hits took me
here:

http://www.coilgun.info/home.htm

Look in the left margin under "Levitation".