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From: mark@mips.COM (Mark G. Johnson)
Newsgroups: sci.crypt,sci.electronics
Subject: Noise generator (hardware)
Message-ID: <29071@obiwan.mips.COM>
Date: 7 Oct 89 14:46:35 GMT
References: <281@hhb.UUCP> <131@arinc.UUCP>
Reply-To: mark@mips.COM (Mark G. Johnson)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 35

In article <131@arinc.UUCP> tsp@arinc.UUCP (Tony S. Patti,4-100C,,,) writes:
>...  I would also be interested in compiling a list of random
>(noise) sources even if no schematic was available.
>
>I am aware of only ONE article which details how to build a noise-based RNG:
>
>     "Build a Noise-Based Random Number Generator" by Terry Mayhugh which
>     appeared in the May 1981 BYTE Magazine (pages 452-456).
>

A back issue of Audio Amateur magazine contains an article that may be of
interest.  1985 #1, p. 17: "A Digital Noise Generator".  Try (603) 924-6371;
that's Old Colony Sound Labs, who carries back issues.

The circuit uses four MM5837 chips.  Each 5837 contains a CMOS 17-stage
linear-feedback shift register running asynchronously (from its own
internal R-C relaxation oscillator clock).  The outputs of the four
5837 chips are analog-summed, to smooth out and schmear out the
behavior of the individual 5837's.

Of course, an eager experimenter could easily do a couple of stunts to
further randomize and noise-ify the output noise:

	1)  Use 10  5837's instead of 4.  Run them off different supply
	    voltages and/or put a resistor directly on top of (some)
	    5837's to change their temperature.  Different V+ voltages
	    and temeperatures affects the clock periods of the individual
	    oscillators, further uncorrelating their outputs.

	2)  At the analog summing point, add in the noise from a
	    diode or two (using the Byte ckt or others)
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
	(408) 991-0208    mark@mips.com  {or ...!decwrl!mips!mark}