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) says: Jun 7, 2010. 1:42 PM
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.
steveastrouk in reply to seanrobertsJun 7, 2010. 4:07 PM
Looks ideal to me.
seanroberts (author) in reply to steveastroukJun 7, 2010. 10:49 PM
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.
steveastrouk in reply to seanrobertsJun 8, 2010. 12:02 AM
I'll ask my father, who is an expert on ferrite properties. Steve
seanroberts (author) in reply to steveastroukJun 8, 2010. 12:08 AM
Thanks, that would be of great help!
steveastrouk in reply to seanrobertsJun 8, 2010. 6:30 AM
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
steveastrouk says: Jun 7, 2010. 2:11 AM
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) in reply to steveastroukJun 7, 2010. 2:16 AM
I can't find old core memory either. What do you mean by re-energizing it? Do the toroids become demagnetized or something?
steveastrouk in reply to seanrobertsJun 7, 2010. 3:21 AM
http://cgi.ebay.co.uk/USSR-Soviet-military-ferrite-core-memory-HUGE-CORES-/220616557908?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item335dc58554
Re-design in reply to steveastroukJun 7, 2010. 4:36 AM
Too bad that one appears to have been damaged.
steveastrouk in reply to Re-designJun 7, 2010. 6:04 AM
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
Re-design in reply to steveastroukJun 7, 2010. 6:46 AM
Yes, I forgot the original quest was for the cores.
steveastrouk in reply to Re-designJun 7, 2010. 11:24 AM
Re-design in reply to steveastroukJun 7, 2010. 12:34 PM
Gosh. Those are sure tiny little things. I'll bet the people sewing those things went bonkers after a while.
steveastrouk in reply to Re-designJun 7, 2010. 4:11 PM
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) in reply to steveastroukJun 7, 2010. 10:46 PM
Ya, I heard that on a discovery channel show about the apollo missions from someone being interviewed who actually worked on the mission.
Re-design in reply to steveastroukJun 7, 2010. 8:17 PM
I had heard something very similar.
kelseymh in reply to Re-designJun 7, 2010. 1:44 PM
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.
steveastrouk in reply to seanrobertsJun 7, 2010. 3:05 AM
I mean make the old electronics work, the core should work forever. Steve
Burf says: Jun 7, 2010. 11:24 AM
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.
steveastrouk says: Jun 7, 2010. 11:20 AM
steveastrouk says: Jun 7, 2010. 11:19 AM
Jayefuu says: Jun 7, 2010. 12:45 AM
Cor that sounds like a lot of work!
steveastrouk in reply to JayefuuJun 7, 2010. 2:06 AM
Do you mean core that sounds like a lot of work ? ! Steve
Jayefuu in reply to steveastroukJun 7, 2010. 2:29 AM
Yes but I was being coreful not to make the pun tooooooo obvious.
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