Where can i get small toroids for magnetic core memory?

I have really wanted to do this but I could never find those pesky rings!

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seanroberts (author) 7 years ago
I think i am going to get: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330433810462&rvr_id=&crlp=1_263602_263622&UA=WVS%3F&GUID=bb6efd981260a0aad2c2bf02fff80f71&itemid=330433810462&ff4=263602_263622#ht_500wt_1154 This will work right? It will change states when current running through wire magnetizes it.
Looks ideal to me.
seanroberts (author)  steveastrouk7 years ago
What I am worried about though is if the will change the polarity of their magnetic field in the way necessary for magnetic core memory. I don't know if cores were purpose built with specific material properties but I am hoping they weren't and that all small ferrite toroids will work.
I'll ask my father, who is an expert on ferrite properties. Steve
seanroberts (author)  steveastrouk7 years ago
Thanks, that would be of great help!
Right, I asked. "Only HARD ferrites are used for core memory - they have a virtually square BH curve. Hard ferrites exhibit permanent magnetism, soft ones don't." Steve
If I were you, I'd look at buying some old core memory and re-energising it, rather than sewing my own. Steve
seanroberts (author)  steveastrouk7 years ago
I can't find old core memory either. What do you mean by re-energizing it? Do the toroids become demagnetized or something?
Too bad that one appears to have been damaged.
Yes, but its got cores on it. The one the same guys had sold that was intact went for over 150 USD ! That means the 4 boards I have from a computer that was broken up at University must be worth a fortune by now. Steve
Yes, I forgot the original quest was for the cores.
Gosh. Those are sure tiny little things. I'll bet the people sewing those things went bonkers after a while.
According to some of the sources about the Apollo guidance computer, the core rope memory of the AGC was know as LOL memory, for Little OId Lady memory - it was hand stitched by, well, little ol d ladies who could follow a knitting pattern !
seanroberts (author)  steveastrouk7 years ago
Ya, I heard that on a discovery channel show about the apollo missions from someone being interviewed who actually worked on the mission.
I had heard something very similar.
Fascinating. From the picture, I calculate that they're exactly 1/33 inch in diameter (1/13 cm). That seems a slightly non-obvious form factor to choose.
I mean make the old electronics work, the core should work forever. Steve
Burf7 years ago
All of the new fluorescent bulbs I've opened up have one in the circuit board. I once saw an Instructable for opening the things up. I presume it is still available through the Search function above.
Jayefuu7 years ago
Cor that sounds like a lot of work!
Do you mean core that sounds like a lot of work ? ! Steve
Yes but I was being coreful not to make the pun tooooooo obvious.