| Electronics > Projects, Designs, and Technical Stuff |
| Core Memory |
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| Gavin Melville:
Just a few more bits.... https://www.flickr.com/photos/8788341@N05/ |
| jimdeane:
Now for a mercury delay line memory... |
| @rt:
Ah well actually next is a core rope ROM to match the RAM :D Just as elaborate in the end... the test version boards will get the hammer in the end. |
| eneuro:
--- Quote from: @rt on August 14, 2015, 03:57:41 am ---Unfortunately my favourite part (the sense pulse receiver) is hidden. --- End quote --- What kind of cores did you used for those tiny (1mm?) core memory? Low cost EMI ferite or something special with carefully choosen core material, etc? I'd like to use small toroid core in my discrete isolated DC-DC converter and it looks like even EMi feritte cores might work (100kHz-400kHz switching frequency in full-bridge SMPS) based on recent experiments, but I'd like to keep them as small as possible. However, probably bigger than 1mm outside diameter used in those core memories >:D I was strugeling use cores in my project, but now when saw what you did-no problem what so ever-I will do it at least for fun :-+ I've choosen for the moment 7mm ferrite toroidal RICHCO RT-79-40-70 core, but unfortunatelly in its datasheets it is mentioned ferrite material: K5B (RMS-303), but can't findout its hysteresis or even magnetic permability to estimate inductance at given number of turns-they specify 33 Ohm impedance @ 25MHz and 53 Ohm @ 100MHz :-// Update: Annyway I've found impedance of ferrite formulas there and at frequencies below 1MHz, probably linear estimation of Ls, while we know it for 25MHz (assuming 1 wire) might help guess what happends with this ferrite core at freaquency lets say 0.5MHz (400kHz), etc. Using Ferrites to Suppress EMI --- Code: ---Impedance – Z (ohm) The impedance of a ferrite may be expressed in terms of its complex permeability. Z = jwLs + Rs = jwLo(wu’- jwu”) (ohm) --- End code --- To get 33 Ohm @ 25 MHz Ls might be 250nH, when we assume XL>>Rs>>0, so when entered 10 turns, we have at 400kHz square switching frequency XL=w*250nH*(10^2)= 2*3.1415*400kHz*250nH*(10^2)= 51 Ohm which maybe is decent estimation, but I'm not sure if it can be done this way-we'll see in practice what we get....or maybe someone knows howto estimate this ferrite EMI cores inductances with a few turns better-I've not better idea for the moment....so probably I will need experiment more and test performance of a few ferrite cores and choose smallest one which fits my needs... |
| @rt:
Hi :) The ferrite I used (for the RAM) I ordered off eBay from a lady in Bulgaria. They are vintage, and made to use in core memory, and also relatively cheap, she was not being greedy. I don’t imagine many people are buying them, but I do imagine the supply of genuine beads will expire. The core from our local supplier in Australia “Jaycar Electronics” that I’m using in the ROM, I know nothing about them, and it’s just trial and error. They have interesting material names like “L8” for a ferrite, and “HY2” for an iron core, but I can’t find anything on the web, but the ROM operates within saturation region, and any old ferrite will do so long as they're all identical. But I am interested in rectangular loop ferrite, I would like to follow on Jeri Ellsworth’s experiment with core logic. She bypassed the RAM and ROM, and went straight for the gold I think. Core logic offers practical benefit today. A non-volatile shift register or flip-flop in modern times would require an EEPROM, and micro with software. It has to be hand wound... a nightmare for manufacture, but once it exists, it seems the simplest solution. |
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