impulse magnetizer

[surdopickups]

Messrs
with your questions and considerations,
with my answers,
has already been revealed much of the content of the magic box.

A few wise words

I like to have sparked some interest in you

[surdopickups]

Exactly. You need to turn energy stored in capacitors into a high peak current in a series resonant circuit with possible complicating factors such as eddy currents.

ousar.lib.okayama-u.ac.jp/file/30158/20061023224836/fulltext.pdf

We are here to university levels,

[surdopickups]

No, impulse magnetizers do not need iron yokes, although they can be designed with them, of course.
In fact sometimes iron yokes must NOT be used, as with all modern magnets , Neo and such, because it saturates at field values way lower than needed to saturate the magnets

So an air core coil is fine ... just put a couple thousand amperes through it.

This magnetizer is small, , I calculate 200uF caps (@360V) for that energy, but it may be more than enough for the pickup shown, which has a very low volume and to boot, Alnico is "easier".

And pickups use energy levels much lower than speakers.

Got any readings of a magnet chargd there?

Thanks.

PS: what David says is interesting: applying 360V to a, say 200 turn coil ... which coaxially has another with a few thousand turns "should" produce a huge voltage peak (think flyback or ignition coil)

I never worried or even thought about that, because my speakers have, say, 100 turn voice coils, so effect should be minimal, but pickups sure raise some red flags.

I guess the proof/test would be to connect the pickup outout to a scope.

Just in case, put a couple Zeners across it to protect the scope input.

a few years ago I had a notebook with copious notes,
including readings of the magnetic poles on the pickups.
Unfortunately this book I can not find it.
As soon as I at the time and repeat the readings.

[J M Fahey]

Quasi paesano , thanks for posting

Sent from La Boca, Buenos Aires' "Little Italy"

[surdopickups]

è un piacere caro sig. Juan Manuel Fahey

saluti dall'italia

[Joe Gwinn]

Exactly. You need to turn energy stored in capacitors into a high peak current in a series resonant circuit with possible complicating factors such as eddy currents.

http://ousar.lib.okayama-u.ac.jp/fil...6/fulltext.pdf

Not an easy read, but for the record, the gist is that if one abruptly increases the magnetic field around a bit of metal (like an alnico rod), eddy currents will initially prevent the field from penetrating into the interior of the rod, so if the impulse is too short, the core will remain unmagnetized. The solution is to use some combination of overwhelming power and long pulses, to allow complete saturation of the magnet material to happen.

[J M Fahey]

Just 2 small details:

1) although a capacitor and an inductor by definition do form a resonant circuit, you must never ever let it resonate !!!!!

a) because diminishing alternating field is the best guaranteed way to demagnetize.

b) if you use electrolytics, the strong inverting voltage and current will make them explode like grenades, no kidding.

2) so there are 2 solutions to this:

a) you calculate circuit constants, and add external resistance as needed to turn it into a critically damped circuit, , which by definition lets only one pulse pass, and only one way.

b) you put a big diode in parallel with the coil , so the initial large current peak keeps rolling as long as needed for the coil resistance to absorb it.

The big brother of what's used to damp relay pop and kickback.

3) my first magnetizer, brute force 3 x380V , 47A peak so some 25kW power used a Siemens "contactor", a brute force 3 phase relay typically used to start-stop big electric motors, elevators, etc.

And even so worked only on the AC side of things, before the full wave 3 phase rectifier.

Once while trying that machine prototype I tried to commute DC with a Frankenstein Movie type knife switch ... the blades opened but a huge arc kept shorting them ... and a small Sun started to form around it.

I had to run to the street and pull the 3 main 380V fuses, still under load of course.

Today all switching is done by replacing 3 rectifier diodes with large SCR ... but the main trick is the flywheel diode which keeps everything under control.

A similar trick is used on Capacitive/Impulse ones: an SCR grounds one end of the coil (the other one is always connected to +V) but again the flywheel diode helps.

[David King]

For more on snubber or flyback diodes Flyback diode - Wikipedia, the free encyclopedia
A Schottky diode is preferred.

[surdopickups]

Hello everyone
I am very fascinated by your thoughts and electrical systems,
despite having signed a preparation of electrical engineering, as I have done technical studies,
in the construction of the magic box, I have not made any kind of calculation, (beginner's luck).
I had the idea of mounting the circuit, the coil with the enamel made from recycled and it worked the first time.
As I said previously you had already a lot of detail to guess what it is, and you are very close.
Need more clues?

[surdopickups]

first clue
circuit costs very little

[surdopickups]

the electronic circuit used is in the public domain

[surdopickups]

most likely all you will have it used in the course of your life.

[surdopickups]

probably even your children will have it used

[surdopickups]

the electronic circuit is inserted in an object, such as its completion improvement

[surdopickups]

automatic operation sometimes required sometimes not necessary, reported on the subject matter in which it is mounted