Motionless Induction

[RalfM]

Hi,
let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?
Could an oszillator (or resonator?) or a similar electronic method
help here to generate induction?

 

[Jasen Betts]

On 2010-03-22, RalfM <rm@invalid.invalid> wrote:

Hi,
let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?

Yes. eg by moving paramagnetic or conductive materials nearby.
this is the principle of operation of most automotive ABS sensors.

Could an oszillator (or resonator?) or a similar electronic method
help here to generate induction?

???

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Francois Grieu]

RalfM wrote :

let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?

Yes; one option is to change current in another nearby coil.
Another option (suggested in another post) is to move a piece
of ferromagnetic material near the magnet or coil.

Could an oscillator (or resonator?) or a similar electronic method
help here to generate induction?

According to the acknowledged laws of physics, there is no hope to
"generate" anything out of a permanent magnet and a coil without
injecting energy in some way.


Francois Grieu

 

[Michael Robinson]

"RalfM" <rm@invalid.invalid> wrote in message
news:ho72hm$mab$1@speranza.aioe.org...

Hi,
let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?
Could an oszillator (or resonator?) or a similar electronic method
help here to generate induction?

The crankshaft posiition sensor in my old Jeep worked that way.
The cps contains a permanent magnet and a coil. It sits very close to the
flywheel or flex plate, which has gear teeth.
When the engine runs the flex plate spins, and each time a tooth moves past
the crank position sensor, the iron in the tooth "grabs" the magnetic field
of the permanent magnet and jerks it around (or the magnetic field grabs the
gear tooth, same difference). The movement of the magnetic field induces a
voltage pulse in the coil, which goes to the car's central computer for
controlling the ignition and whatnot.

This is a bit off the subject, but the Jeep cps in particular is prone to
wearing out -- over time, heat and vibration cause the little magnet to
weaken. Eventually the magnetic field in the cps gets so weak that it
simply won't induce enough of a pulse in the coil for the computer to
detect.
A simple fix is to put a small cap in parallel with the coil. When the cps
in my Jeep wore out I found that .01uF got it running properly again.

 

[JeffM]

RalfM wrote:
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?

Jasen Betts wrote:
Yes. eg by moving paramagnetic or conductive materials nearby.
this is the principle of operation of most automotive ABS sensors.

Electric guitar strings too.

 

[Jamie]

Francois Grieu wrote:

RalfM wrote :

let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?


Yes; one option is to change current in another nearby coil.
Another option (suggested in another post) is to move a piece
of ferromagnetic material near the magnet or coil.

Could an oscillator (or resonator?) or a similar electronic method
help here to generate induction?


According to the acknowledged laws of physics, there is no hope to
"generate" anything out of a permanent magnet and a coil without
injecting energy in some way.


Francois Grieu
If the coil and magnet remands in a steady state, you can use

a near by moving ferrous object that will disturb the reluctance
of the field and thus, the static coil will generate a pulse from the
field being shifted.

These are known as VRS'es "Variable Reluctance Sensors"

 

[terryS]

On Mar 22, 3:29 pm, "Michael Robinson" <nos...@billburg.com> wrote:

"RalfM" <r...@invalid.invalid> wrote in message

news:ho72hm$mab$1@speranza.aioe.org...

Hi,
let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?
Could an oszillator (or resonator?) or a similar electronic method
help here to generate induction?

The crankshaft posiition sensor in my old Jeep worked that way.
The cps contains a permanent magnet and a coil.  It sits very close to the
flywheel or flex plate, which has gear teeth.
When the engine runs the flex plate spins, and each time a tooth moves past
the crank position sensor, the iron in the tooth "grabs" the magnetic field
of the permanent magnet and jerks it around (or the magnetic field grabs the
gear tooth, same difference).  The movement of the magnetic field induces a
voltage pulse in the coil, which goes to the car's central computer for
controlling the ignition and whatnot.

This is a bit off the subject, but the Jeep cps in particular is prone to
wearing out -- over time, heat and vibration cause the little magnet to
weaken.  Eventually the magnetic field in the cps gets so weak that it
simply won't induce enough of a pulse in the coil for the computer to
detect.
A simple fix is to put a small cap in parallel with the coil.  When the cps
in my Jeep wore out I found that .01uF got it running properly again.

Thanks for the tip. We fastened a small magnet to the semi flex
coupling of our boat's motor. Never hooked it up; but the idea was
that using some sort of pickup coil the pulses, as the propeller shaft
rotated, rectified, would give some kind of idea on a DC meter or
small solid state circuit driving a meter of how fast the prop was
turning.

 

[terryS]

On Mar 22, 9:16 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

Francois Grieu wrote:
RalfM wrote :

let's say there is a magnetic field of a _permanent magnet_,
and a fixed/nonmovable induction coil is placed into field.
Is it possible periodically to change (ie. "disturb") the intensity
of the said magnetic field so that an induction happens
without moving the coil and the magnet?

Yes; one option is to change current in another nearby coil.
Another option (suggested in another post) is to move a piece
of ferromagnetic material near the magnet or coil.

Could an oscillator (or resonator?) or a similar electronic method
help here to generate induction?

According to the acknowledged laws of physics, there is no hope to
"generate" anything out of a permanent magnet and a coil without
injecting energy in some way.

  Francois Grieu

  If the coil and magnet remands in a steady state, you can use
a near by moving ferrous object that will disturb the reluctance
of the field and thus, the static coil will generate a pulse from the
field  being shifted.

    These are known as VRS'es "Variable Reluctance Sensors"- Hide quoted text -

- Show quoted text -

Something has to 'change' to cause electric current (from cutting
lines of force etc.) to flow. For example if a metal door swung or
moved between a magnet and a sensor the magnetic field would change.
That change could cause electric current to flow in the sensor coil.