Electronics > Projects, Designs, and Technical Stuff
Core Memory
@rt:
Ok, I just read the other part of your post.
The curve of the initial magnetisation in your picture isn’t square.
That might be a problem for trying to detect even a half strength pulse.
I got done with my ROM last night. Any dirty old ferrite is ok for that.
This one is Australian Capital cities stored as a pair of 32 bit floats for latitude & longitude each.
For eight cities there were two zero values (in bytes), so only 62 of the 64 wires total.
@rt:
Well I had luck with the core ROM last night :)
eneuro:
--- Quote from: @rt on September 03, 2015, 01:34:30 pm ---My understanding of the core and the hysteresis loop is they are truly bistable and would not store a partial state.
--- End quote ---
When we perform demagnetisation Comparison of Stepwise Demagnetization Techniques , than ferromagnetic core should be in stable not magnetized state, so when we try to read not magnetized core maybe we could be able detect this? :-\
--- Quote ---To demagnetize small-scale objects (dimensions less
than 1 m) fabricated from ferromagnetic materials, it is standard
practice to expose the object to a continuous ac applied magnetic
field with a steadily decaying amplitude.
--- End quote ---
Anyway, maybe instead of using magnetic flux direction in the core, we could try use for logic zero (0) demagnetized core and for one (1) magnetized in any direction?
Of course those ferromagnetic cores will be exposed to Earth magnetic filed in the range of 5*10^(-5) T ~0.00005 T (0.5 Gauss).
Detection if ferromagnetic core was ever magnetized (we do not care about its direction) after demagnetisation might be interesting, so investigating this in spare time ;)
@rt:
Any luck with experimentation?
I finally got the rope ROM done :)
Not 100% success. The 74HC595 driving current for them I didn’t test with more cores.
If the byte value contains a lot of 1s there is not enough energy for every pulse to be recognised.
Now if a “C” version of 74HC595 was ever made it would be an easy solution.. just run them at higher voltage,
but I don’t think they were ever made “74C595” :(
Out of 512 bits I get typical 18 or so bit errors. demo video:
eneuro:
--- Quote from: @rt on September 21, 2015, 02:51:44 pm ---If the byte value contains a lot of 1s there is not enough energy for every pulse to be recognised.
--- End quote ---
Using this cut ferrite core with SS495A inside and by applying +/-5A current I was able create decent remanent magnetization in ferrite toroid core shown below, which I was able read in NOT DESTRUCTIVE way using... Hall effect current sensor and multimeter >:D
During calibration of this thing, I've noticed that this sensor is capable detect those small shift from the middle of ~2.5V @ 5Vcc, so using only voltmeter I was able to say in which direction it was magnetized, but didn't tested it what hapends after a few hour or when I change position in space in relation to North Pole, etc, however this was interesting finding, which could help build easy thunder lighting hit detector, just by using ferrite core with thick metal pipe inside to ground and then after storm check this core with the same sensor 8)
That is why I was interested in demagnetisation, since lighting might be sometimes unusual upward, not downward, so I'd like to be able detect three states of such ferrite toroid core, which was passed by lighting hit to/from ground :popcorn:
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