14 May
1999
14 May
'99
11:35 a.m.
At 10:43 PM 5/6/99 -0400, Allison wrote:
Well thanks to John D. I have a bunch of cores from
the early 60s.
They are roughly 50mils x 11 mils x 15mils. Cross section of the doughnut
is rectangular at 15x11 mils. The reason for such rough measurements is my
vernier is only good to .001" and I'd need somthing fancier to be more
accurate. By eyeball the 8e cores are smaller! Based on several articles
I've read theses will need about 400->600ma to switch and will do so in
under 4uS. I will have to test this in a jig. Since the hole is ~20mils
several #40 wires should pass through it easily.
The previous mentioned article in Byte is "Coincident Current Ferrite Core
Memories" and is in the July, 1976 Issue. It is very helpful. It describes
the support electronics too (x,y drivers, sense, inhibit, and diode
steering logic) as the author had an intact core plane assembly, so did the
tests for switching currents, etc. on the intact assembly. The x,y drivers
used were TI SN75325 H-bridge drivers, on both ends of the x,y lines.
Alternate ways of running the sense lines are shown. Typically both ends
were terminated with 100 Ohm resistors and fed to a comparator with an
adjustable threshold, such as a SN7524.
-Dave