Motionless Induction

Started by RalfM March 22, 2010
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?
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 ---
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
"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.
>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.
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"
On Mar 22, 3:29=A0pm, "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. =A0It 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 pa=
st
> the crank position sensor, the iron in the tooth "grabs" the magnetic fie=
ld
> of the permanent magnet and jerks it around (or the magnetic field grabs =
the
> gear tooth, same difference). =A0The movement of the magnetic field induc=
es 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. =A0Eventually 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. =A0When 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.
On Mar 22, 9:16=A0pm, 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. > > > =A0 Francois Grieu > > =A0 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 =A0being shifted. > > =A0 =A0 These are known as VRS'es "Variable Reluctance Sensors"- Hide quo=
ted 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.