Permanent magnetic memory

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  • #1
arivel
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Hi everyone .
Since I do not have all the necessary knowledge to do what I am about to explain, I ask you for help if you feel like it.

I would like to understand if it is possible and how to make an elementary and completely transparent permanent memory using a small toroidal core with a high magnetic permeability value combined with a Hall effect magnetic sensor. After making a cut in the toroid, the sensor must be inserted into the resulting slot as shown in fig. 1. Naturally, the toroid must be wound by coils of copper wire to be calculated, in which to make a current pulse flow. The idea is to exploit the magnetic remanence (Br-Br) after the coil power is removed.
When the current flows in one direction, the remanence Br is created and when it flows in the opposite direction, the remanence -Br is created.

There are Hall effect sensors that do not behave in a linear way but as an electrical diverter, that is, it supplies the positive or negative voltage on the output depending on which sign is the applied magnetic field, they have 3 terminals of which 2 go to the power supply , the rest is the exit. There are 4 types of Hall sensors that might interest me: unipolar, latch, omnipolar, bipolar. In my opinion the most suitable is the latch but I leave it to you. They also have a hysteresis because in this way when the magnetic field is close to zero there can be no fluctuations in the output voltage, in other words the uncertainty is eliminated as well as in schmit triggers.

The toroids can be composed of many different materials, I attach rows (materials).
The amorphous 2605 metglass caught my attention but you have to choose the right one if there is a better one, it is logical to choose the one with narrow hysteresis.
If there is something that is not clear please ask me. For those who want to read there are attachments.

https://it.wikipedia.org/wiki/Coercitività
https://it.wikipedia.org/wiki/Induttore
https://it.wikipedia.org/wiki/Isteresi#:~:text=L'isteresi è anche una,si somma con quella ohmica.
https://www.allegromicro.com/en/ins...cations/latching-switch-hall-effect-ic-basics
https://coefs.uncc.edu/mnoras/files/2013/03/Transformer-and-Inductor-Design-Handbook_Chapter_2.pdf
https://it.wikipedia.org/wiki/Permeabilità_magnetica
https://it.wikipedia.org/wiki/Rimanenza

bye thank you
 

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  • fig.1.jpg
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  • Latch-Switch-Sensors-Application-Note-Melexis.PDF
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Answers and Replies

  • #2
hutchphd
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I assume you are aware of the rope core memory for Apollo spacecraft ?
 
  • #3
davenn
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I assume you are aware of the rope core memory for Apollo spacecraft ?


I had a beautiful stack of core memory years ago, sadly it got lost in the move to Australia :frown:

very similar to this

Clipboard01.jpg


was 2 double sided boards
 
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  • #4
hutchphd
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I never quite understood the rope core memory. They were apparently ROM and used permanently magnetized beads to carry the important subroutines...apparently smaller than any other method. Needed to be physically rewoven to change anything. OK
Here is an article that does explain it( I guess I understand it now):
http://www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html
Pretty similar to the RAM I guess but error proof.
 
  • #5
Baluncore
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There are 4 types of Hall sensors that might interest me: unipolar, latch, omnipolar, bipolar. In my opinion the most suitable is the latch but I leave it to you.
You must cut a slot in the toroid, wide enough to house the sensor. How hard is the core material?

You must calculate the amp*turns needed to change the direction of remanence in the modified core having what is a relatively wide air gap housing the sensor.

You will need to verify the current required to ensure a change of state in the core. You can do that by initially using a linear analogue sensor, without hysteresis or latch. You need to be able to tell if the remanence has changed, or if it is the hysteresis or latch that is remembering the state.
 
  • #6
Vanadium 50
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I don't see the advantage over core memory, which has similar density (much less than anything available today) and is also kinda-sorta persistent, but not as good as flash.

An MIT computer man got drunk one fateful night
He opened up the console and smashed everything in sight
When they finally subdued him, the judge he stood before,
Said, "Lock him up for twenty years, he's rotten to the core!"
 
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  • #7
arivel
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I don't know how your proposed magnetic memory works.
what interests me is the extreme simplicity of piloting and in my case it is an impulse in one direction or the other after which the sensor works automatically.
we can solve it in the following way, tell me which material to choose for the toroid, I'll take care of the magnetic sensor.
I only have to memorize six bits
 
  • #8
Vanadium 50
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tell me which material to choose for the toroid, I'll take care of the magnetic sensor.

What problem are you trying to solve? A USB flash drive is a million times better along any metric.
 
  • #9
Baluncore
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I only have to memorize six bits
Then six CMOS RS flip-flops, with a 3V lithium battery, will last for tens of years.
It will not consume power when it is waiting, being read or written.
 
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  • #10
256bits
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I had a beautiful stack of core memory years ago, sadly it got lost in the move to Australia :frown:

very similar to this

was 2 double sided boards
Up front, that stuff seems so primitive now, due to its size maybe.

But it was in fact, ingenious.!
And still is ( hate to sound so contradictory )
 
  • #11
Baluncore
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tell me which material to choose for the toroid, I'll take care of the magnetic sensor.
Toroidal cores are designed to minimise hysteresis. You need to find a material that has high hysteresis, which will be the challenge. I forget the type, but I have only seen one material recommended and I was unable to buy it at the time. I will try to remember what it was.

I have a couple of megabit of core here that came out of a Burroughs 6800, retired in the 1980s. The cores are too small to see with the naked eye, so they probably cannot be cut.

The size of the active area of the hall-effect sensor you select will probably be less than 1 mm across. The core should have a similar cross section as there is no advantage in having flux that passes outside the sensor, since that would require a greater current to switch the core, and you would have to cut more material.

Have you considered using six mechanically latching relays? They would have the same interface requirements as your proposed memory, but without the hall-effect sensors.

PS Edit.
The cores that are used for toroidal transformers are magnetically soft cores. They do not have high hysteresis and will not remember the magnetic field well.

Magnetically hard ferrites are used for core memory because they have a more square BH curve. Hard ferrites exhibit permanent magnetism. High carbon steel also satisfies that memory requirement. Soft iron does not.

Maybe you could cut a turn from a helical coil spring, or make a 'C' core from heavy piano wire, or from springy high tensile fencing wire.
 
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  • #12
arivel
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I would like to ask you something about the attached image. in particular on the amorphous material 2605-sc.
on the ordinate axis there is the quantity B which corresponds to the amount of magnetic flux in tesla when the material is in saturation. well I do not understand if they are tesla if they are a thousand tesla or micro tesla.
you think ?
 

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  • #13
Baluncore
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... on the ordinate axis there is the quantity B which corresponds to the amount of magnetic flux in tesla when the material is in saturation.
Not quite. The SI unit of magnetic flux, B, is the weber, Wb.
The SI unit of flux density is the tesla, T, which has dimension of Wb / m².
The area of the magnetic path through which B flows is important, as it is the flux density through the material that determines the point where the material saturates.

Since the ordinate is labelled, B, it suggests the sectional area of the material under test has been standardised. If the numbers on the vertical axis are to make sense, then I think you must treat them as being flux density, simply tesla.

Where is the Fig 2-27 from? Maybe examination of the original document will explain the situation.
 
  • #14
arivel
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