Motionless Induction
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From: Jamie on 22 Mar 2010 20:16 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"
From: terryS on 26 Mar 2010 15:49 On Mar 22, 3:29 pm, "Michael Robinson" <nos...(a)billburg.com> wrote: > "RalfM" <r...(a)invalid.invalid> wrote in message > > news:ho72hm$mab$1(a)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.
From: terryS on 26 Mar 2010 15:53
On Mar 22, 9:16 pm, Jamie <jamie_ka1lpa_not_valid_after_ka1l...(a)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. |