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Obscure Electronics Topics

J

John Larkin

I'd rather say I my obscurity was enlightened by the brilliant ideas:

IIR filters with perfectly linear phase, random sampling as long as
Nyquist condition is satisfied at the average, FDLS, thermal noise in
capacitors, compensation of hard nonlinearities in control loops,
3-dimensional FFTs, WI method for sound analysis.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

What's an FDLS?

John
 
F

Frank Buss

Tim said:
While sitting on the pot this evening, I idly wondered: what's the most
obscure facet of electronics you've learned recently?

The most obscure facet of electronics I've learned recently is the PWM
output of the NS9360, see PDF page 145 (document page 121) :

http://ftp1.digi.com/support/documentation/90000675_b.pdf

If you concatenate the timers, you can control the pulse with and the
period with both timers, but this allows 1:1, 1:2, 1:3... duty cycles,
only. I wonder for what this obscure PWM output can be used for.

There is an "alternative" described in the datasheet: Just stop all
interrupts, use the same frequency for both timers and start the second
timer after some manual programmed delay loop. Ok, WindowsCE might crash
and it might be not so fast, if you do it too often, but at least the PWM
works, with a whopping precision of 1% !
 
F

Fred Bloggs

:
While sitting on the pot this evening, I idly wondered: what's the most
obscure facet of electronics you've learned recently?

It's a sorry state of affairs when defecating is the only time you're
able to think...and if you're there *that* long, you might consider a
fiber laxative such as Metamucil or something.
 
T

Tim Williams

John Fields said:
Hmmm... that anally controlled variable resistors are available?

Literally, sphincter tension?

Strange things have been made... Behavioral scientists need to measure
sexual arousal somehow, for instance!

Tim
 
F

Fred Bloggs

Tim said:
Literally, sphincter tension?

Strange things have been made... Behavioral scientists need to measure
sexual arousal somehow, for instance!

This is already being done with CAT scans...
 
F

Fred Bloggs

Tim said:
Literally, sphincter tension?

Strange things have been made... Behavioral scientists need to measure
sexual arousal somehow, for instance!

Oh I get it, your sexual arousal manifests as sphincter tension, that is
not a good sign...
 
S

Spehro Pefhany

Oh I get it, your sexual arousal manifests as sphincter tension, that is
not a good sign...

You'd prefer just the opposite, I suppose.


Best regards,
Spehro Pefhany
 
V

Vladimir Vassilevsky

John Larkin said:
What's an FDLS?

FDLS (Frequency Domain Least Squares) is an elegant universal method for
approximation of an analog transfer function by a digital filter. You can
get as accurate approximation as you need. FDLS was invented by Greg
Berchin. You can see him quite often in comp.dsp.

Vladimir Vassilevsky
DSP and Mixed Signal Consultant
www.abvolt.com
 
T

Tom Del Rosso

John Larkin said:
But recently? Double-edge-clocked flops in Xilinx FPGAs, wave digital
filters, running DDS synthesizers backwards, running SRDs in series,
various bizarre aircraft serial busses, mach sensors and airplane
crashes, Legendre filters.

Running a DDS backwards?
 
J

John Larkin

Running a DDS backwards?


Yup. As you clock it faster and cross the Nyquist rate, it runs
backwards. So the signal phases reverse.

Well, I thought it was cool.

John
 
P

Phil Hobbs

Photomultiplier non-linearity.

Sloman, A.W. "Comment on 'Computer aided simulation study of
photomultiplier tubes'", IEEE Transactions on Electron Devices, ED-38
679-680 (1991) doesn't even show up on Google Scholar.

I was commenting on a paper by Zaghloul and Ree - professor and
graduate student - who claimed that nothing had been published on the
subject. I cited five papers and an application note, and pointed out
that a couple of the papers I'd cited did include fairly comprehensive
reviews of what literature there is.

The 1978 paper I cited, by Aspnes and Studna, had made the same claim,
but Rev.Sci Instrum refused to publish my comment addressing that
point, amongst others.

I got started on the subject when Lush publishe his paper in 1965, so
I'm falling short on the recently, but I expect to stay way ahead on
obscurity.
If you can get a copy of "Methods of Experimental Physics", volume 12,
there's an astonishingly good discussion of how to make accurate
measurements with PMTs.

Cheers,

Phil Hobbs
 
T

Tim Williams

John Larkin said:
Yup. As you clock it faster and cross the Nyquist rate, it runs
backwards. So the signal phases reverse.

So, out of, say, 4096 entries in the lookup table, you're skipping 4095 or
4097 each pass? (Or any other integral fraction of the length.)

Tim
 
:


It's a sorry state of affairs when defecating is the only time you're
able to think...and if you're there *that* long, you might consider a
fiber laxative such as Metamucil or something.

It's not so much that you get time to think there, it is more that it
offers the sub-conscious an opportunity to bring the results of the
last few hours of background processing to your concious attention.
 
Hey! A house that Slowman can afford ;-)

Jim's Alzheimer's seems to have gotten worse - why else would he
confuse a mobile stage with a house? Maybe he's reverting to a time
when he was trailer trash, and his homes all had wheels.
 
F

Fred Bloggs

It's not so much that you get time to think there, it is more that it
offers the sub-conscious an opportunity to bring the results of the
last few hours of background processing to your concious attention.

I thought that was what a good night's sleep was for?
 
J

John Larkin

So, out of, say, 4096 entries in the lookup table, you're skipping 4095 or
4097 each pass? (Or any other integral fraction of the length.)

Tim

Yup. Suppose you have a 4096 point waveform table, and the system
clock is 128 MHz. If the phase accumulator value is, say, 7FF00000,
you're skipping 2047 points every clock, and the sinewave is just a
hair under Nyquist, 63.9... MHz. At 80000000, the output is zero. At
80100000, you're skipping 2049 points every clock, equivalent to
-2047, so you're over Nyquist and walking the table backwards.

John
 
J

JosephKK

D from BC [email protected] posted to sci.electronics.design:
I haven't looked very much...but suspect it's a nonexistent animal.
I have to add one more detail...
That would be a tapped SMD chip inductor sharing the same core..
It's like a chip autotransformer.
Not 2 individual inductors in series.


D from BC

I don't suppose that you have tried looking for three or four winding
SMD transformers?
 
J

JosephKK

Vladimir Vassilevsky [email protected] posted to
sci.electronics.design:
I'd rather say I my obscurity was enlightened by the brilliant
ideas:

IIR filters with perfectly linear phase, random sampling as long as
Nyquist condition is satisfied at the average, FDLS, thermal noise
in capacitors, compensation of hard nonlinearities in control loops,
3-dimensional FFTs, WI method for sound analysis.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

I am pretty curious about the physical understanding / application of
the 3D FFT.
 
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