Experiment on neodymium - changing the magnetic field at home

ShlomoShtudi

Joined Aug 31, 2020
11
neodymium lose it magnetic field at aprox. 80C i want to change the original field... but making a electromagnetic field with batteries or a transformer is a little dangerous, i need to plug this electromagnet for about 3 minutes with a 9 v source at 1 amp at least, how it can be done in a safe and easy way?

shortbus

Joined Sep 30, 2009
7,926

With all of the different types and pole configurations out there today I wondered the same thing. Never in any time have there been so many great strength magnets available.

And don't think it will be as easy as the TS thinks to change a neodymium magnet pole configuration at home.

Sal Shtudy

Joined Feb 25, 2019
13
Why, 7 U$C for a simple one, 50 U$C for a custom field magnet that is the reason

Delta prime

Joined Nov 15, 2019
487

MisterBill2

Joined Jan 23, 2018
6,998
neodymium lose it magnetic field at aprox. 80C i want to change the original field... but making a electromagnetic field with batteries or a transformer is a little dangerous, i need to plug this electromagnet for about 3 minutes with a 9 v source at 1 amp at least, how it can be done in a safe and easy way?
You will not get it done with 9 volts from a batter in 3 minutes, 3 seconds, or 3 weeks, because that is not how it works. You can wish that it would, but still it will not.Magnetizing thakes a burst of very high magnetic intensity to have a lasting effect. You may be able to do it with a simple coil and the current of an automotive battery, since the big current pulse is less than a second.

ShlomoShtudi

Joined Aug 31, 2020
11
You will not get it done with 9 volts from a batter in 3 minutes, 3 seconds, or 3 weeks, because that is not how it works. You can wish that it would, but still it will not.Magnetizing thakes a burst of very high magnetic intensity to have a lasting effect. You may be able to do it with a simple coil and the current of an automotive battery, since the big current pulse is less than a second.
if you look how the magnetization of this kind of magnet is done, i think i'm not wrong, that includes heat magnetic field and fast cooling... exactly what i want to replicate

Alec_t

Joined Sep 17, 2013
11,639
How do you plan to sustain an extremely high magnetic field for the whole time necessary for the magnet to cool from some way above its Curie point to well below that? I can't see how you'd cool the magnet in MisterBill's 'less than a second', and I'd expect the magnetic field to be lost if the applied pulse finished while the magnet was still above the Curie tmperature.

Last edited:

MisterBill2

Joined Jan 23, 2018
6,998
First of all, ANY power source used MUST have isolation from the mains. As almost all commercially available supplies meet this requirement isolation should not even be an issue. Even with the voltages needed to produce the high current pulses needed for conventional magnet production, an isolated supply is ALWAYS used.
Quick chilling of a small magnet can be done very rapidly with a chilled water flood system, as dropping with some small temperature reduction, say from 95C to 65C will not mandate that much heat removal. But to sustain the high current may require a larger capacitor bank, and possibly higher voltages.

MisterBill2

Joined Jan 23, 2018
6,998
Note that in step @6 of that rather excellent description the magnetizing field is 3X the desired field strength. So to know what you need to provide, determine the desired magnet strength, and the convert that into units of ampere-turns. THAT is where you discover that what I stated was correct.

ShlomoShtudi

Joined Aug 31, 2020
11
Note that in step @6 of that rather excellent description the magnetizing field is 3X the desired field strength. So to know what you need to provide, determine the desired magnet strength, and the convert that into units of ampere-turns. THAT is where you discover that what I stated was correct.
Cool, i can make it with the club car batteries... but it's a little risky, so high gauge copper coil, plug to a power supply... that's it... so some tips about security measures?

Alec_t

Joined Sep 17, 2013
11,639
so some tips about security measures?
Big electromagnets plus car batteries = risk of impressive arcing, which can damage eyesight.

MisterBill2

Joined Jan 23, 2018
6,998
I was going to caution that indeed, high current practices should be used, along with cautions to avoid burns and fires. One way to end the current pulse would be to include a fuse in the circuit, which hopefully would open and stop the current before any other parts failed.
The one challenge that has not been discussed is the arrangement to direct the magnetic flux through the part being magnetized. That is not a simple matter at all.

ShlomoShtudi

Joined Aug 31, 2020
11
I was going to caution that indeed, high current practices should be used, along with cautions to avoid burns and fires. One way to end the current pulse would be to include a fuse in the circuit, which hopefully would open and stop the current before any other parts failed.
The one challenge that has not been discussed is the arrangement to direct the magnetic flux through the part being magnetized. That is not a simple matter at all.
in my case, maybe that is the simple part, i want to know what happen when you configure the magnet in a circular path, a coil along a ring... very simple, but what will be the polarity on each place...

ShlomoShtudi

Joined Aug 31, 2020
11
Big electromagnets plus car batteries = risk of impressive arcing, which can damage eyesight.
maybe i can use an old big resistor from a microwave?

MisterBill2

Joined Jan 23, 2018
6,998
Given that the high current is what does the magnetizing, limiting the current will not work. Certainly adequate preparation must be made, and having an adequate understanding of what will happen is certainly needed.

The fears of those who are not willing to understand what they would be doing are unfortunate. Therefore the ones who are unable or unwilling to understand things should not bother those of us willing to learn, understand, and take adequate care and precautions.

For this project certainly safety precautions must be taken. That includes assuring that the weak link selected to disconnect the current can open in a manner that is safe. It also includes adequate measures to assure that no overheated wires will cause injury or damage. But none of those measures are so difficult as to halt the experiment.
But Alec must stand at least 500 feet away.

Alec_t

Joined Sep 17, 2013
11,639
But Alec must stand at least 500 feet away
.... and I'll make sure I have my flak-jacket and UV-proof shades on .

MisterBill2

Joined Jan 23, 2018
6,998
I am serious that you do need to wear eye protection, more against splatter than against UV, but that is a good choice indeed.

ShlomoShtudi

Joined Aug 31, 2020
11
lets make the recipe simple:
Heat your Neodymium at pre-heated oven at +80C for a couple minutes
let the piece cool down
make a coil around/inside/over/ through (as your desired magnetic config) it with thick copper, the more winding the best...

12v at 1+ amp will give some noticeable magnetic field? (from disassembled old laptop batts)???

I will try to do that today, if it succeeded, the next step will be with those club cart batteries, big resistor, and i try to get a strong gaseous fuse (interesting...can it blow? lit up?) .