Acoustic magnetic generator.

[itsu]

Hi Synchro1,

no, no bridge rectifier, its the old speaker bracket.

Regards Itsu

[MileHigh]

Itsu:

There is no need for you to cut the iron bar, it won't make any difference with respect to the amount of magnetic flux that flows through the magnetic circuit.

I think that your build is great.  From my perspective I don't see how beaming sound down the two rods will affect the amount of flux that flows through the circuit.  It's really a mystery to me.

It may be a bit preliminary to pass judgement, but we can see how your pickup coil barely generates any EMF.  It's possible that the EMF that is being picked up has very little or nothing to do with any possible flux modulation from the acoustic waves.

MileHigh

[itsu]

I momentarely upped the input power into the piezo to what is possible with my present setup (Fg + PA)
I used my x100 HV probe on CH1 to measure the voltage which was around 820V pp.

But even then no extraordinary EMF was picked up by the pick up coil.
This screenshot was taken at 11.790KHz where normally no audio was heard (by me), but there was again
this spurious 4-6KHz audible signal.
But as can be seen, it did not produce any high signal in the pickup coil (blue trace).

So brute force is probably not the way to go.

What puzzles me is the negative mean power of -600mW * 2 (for the current probe terminator) = -1.2W
Ch4 (current) is inverted, as it depends how i clip up the probe, but you can see that at this low frequency
the current is leading the voltage which i think is correct (capacitive/low side of the LC).


Regards Itsu

[synchro1]

@Itsu,


I think the ferrite rods are super saturated at this point, and that it would help to begin to reduce the number of magnets.


It would also help to rectify the output to DC to illuminate the LED.

[verpies]

From my perspective I don't see how beaming sound down the two rods will affect the amount of flux that flows through the circuit.  It's really a mystery to me.

When the sound affects the permeability of the ferrite (and it really does) its reluctance changes locally.
Your intuition probably tells you that the net flux does not change, because any decrease of reluctance in one segment of the core is offset by exactly the same increase in another segment of the core, leading to a zero net reluctance change.
And you would be correct, but only for series magnetic circuits and flux changes over integer acoustic wavelengths.

Parallel magnetic circuits circuits and non-integer acoustic wavelengths can and do produce significant reluctance and flux changes (see here).  If you muse over it, you'll immediately come up with multitude of magneto-acoustc configurations that will maximize reluctance&flux changes.
IMO if nodes of longitudinal acoustic standing waves in the ferrite are not determined accurately (e.g. by real time visualization) then it is very hard to properly tune and design a parallel magnetic circuit that will maximize these flux variations.

P.S.
I am not insisting that these reluctance changes are free or overly efficient, just because they are caused by acoustic compressions and rarefaction of the ferrite core.  The purpose of these experiments is to determine just that.  ..so let's leave the quantitative O/I discussion for later, when we have more data.