gwyn@smoke.BRL.MIL (Doug Gwyn) (10/07/89)
In article <35357@apple.Apple.COM> kchen@Apple.COM (Kok Chen) writes: > Solomon W. Golomb, "Shift Register Sequences," > Holden Day, San Francisco. 1967. This is indeed a classic book (reprinted by Aegean Park Press), but it is NOT what the requestor asked for, which was a genuine (not pseudo) random noise source.
mark@mips.COM (Mark G. Johnson) (10/07/89)
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}
eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) (10/08/89)
There is a good discussion of the basics of digital pseudo-random noise
generators in chapter 9 of "The Art of Electronics," by Horowitz and Hill
(I have the 1st edition, have not checked the new one).
They include a complete schematic for an adjustable bandwidth p-r noise
source, and claim that it is similar to the method used in the Hewlett
Packard 3722A.
--
Julian Vrieslander
Neurobiology & Behavior, W250 Mudd Hall, Cornell University, Ithaca NY 14853
UUCP: {cmcl2,decvax,rochester,uw-beaver}!cornell!batcomputer!eacj
INTERNET: eacj@tcgould.tn.cornell.edu BITNET: eacj@CRNLTHRYkchen@Apple.COM (Kok Chen) (10/08/89)
eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) writes: >There is a good discussion of the basics of digital pseudo-random noise >generators in chapter 9 of "The Art of Electronics," by Horowitz and Hill >(I have the 1st edition, have not checked the new one). >They include a complete schematic for an adjustable bandwidth p-r noise >source, and claim that it is similar to the method used in the Hewlett >Packard 3722A. >-- >Julian Vrieslander For the "bible" on PN Generators (PN = Pseudo-noise), take a look at Solomon W. Golomb, "Shift Register Sequences," Holden Day, San Francisco. 1967. Sorry, no ISBN number on my copy of the book (preceeded the introduction of ISBNs :-). I have used this method to generate a noise comb for an antenna resistance noise-bridge pretty successfully, instead of using the standard zener knee method. The biggest advantages are 1) it generates a *huge* signal compared to the zener, and 2) a simple D.C. voltmeter [measuring the TTL voltage level at the load when the PN sequence is not running] is all it takes to get a very good estimate of the noise density. (Well, it takes a calculator too, because there is a sin(x)/x envelope :-) But, since it was for a home project, and I don't own an oscilloscope, this became the most convenient noise generator to build. Caveat: Take great care if you want to use this as a pseudo-random number generator for image dithering, for example. You have been warned :-). -- ---- Kok Chen kchen@apple.COM Apple Computer, Inc.