Crystals For Odd Frequencies?

[Sir Charles W. Shults III]

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk80im$qevq8$1@ID-43450.news.uni-berlin.de...

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.

You are chasing echoes. You have done something that many uninitiated do-
confuse the cause and the effect. Also, just because it's "on the net", that
does not lend credence to it. Far from it!
Brainwaves frequencies are composites of billions of tiny neural firing
events- statistical in nature and absolutely NOT tied to a narrow range of
frequencies. These frequencies do nothing- they are the end result of
processes, not the cause of those processes.
Driving a very specific frequency into your brain is not the key to amazing
things. In order for that to be the case, then your brain would have to have a
very precise clock source somewhere- but it clearly does not.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Roger Johansson]

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote:

There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different.

There is no scientific reason for such a difference, you are reading
those lists with far too much seriousness.

The frequencies we talk about are not constant, they are varying more
than heartbeats vary in frequence, it is only the part of the spectrum
they are within which is of interest, for example if it is somewhere
between 6 and 8 Hz the mind is in a certain mood, a certain state of
mind.

There is also a technical problem too consider.
This kind of unit should be powered by batteries for two reasons.
1: Safety reasons.
2: Noise reasons.

If we use only analog technology, active filters, we do not introduce
noise into the circuit, but if you put in logic circuits, crystal
oscillators and dividers, digital filters, etc.. you will have big
problems to isolate the digital parts from the sensor amplifier part.

We are already on the border of what is possible to perceive with
analog active filters, what is possible to dig out of the noise.
If you introduce a lot of digital noise anywhere near this unit it
will be a lot harder or simply impossible to keep noise out of the
input active filters.

If you insist on using digital technology and crystal oscillators you
will have to isolate the sensor amplifiers/active filters from the
digital equipment with optocouplers.
Make the sensor unit a battery driven analog unit, use optofiber to
send the signals to another unit which contains the digital circuits,
etc..

If you want to start with brainwave inducing methods I recommend
trying Cooledit from syntrillium.com.

Try its 7Hz theta function, mix with a tone (250Hz for example).
Use high volume on your stereo.
It works for me.
But I experience no difference between 6 and 7Hz.


--
Roger J.

 

[Michael A. Terrell]

Ron Hubbard wrote:

Bob Masta wrote in message
3f670746.3671296@news.itd.umich.edu>...
On Mon, 15 Sep 2003 16:22:22 -0700, "Ron Hubbard"
hubbard_ron@hotmail.com> wrote:

snip
But learning how to change your brainwaves is not like
learning to tie your shoes; it's bloody difficult. With my
original design that used analog filters, I could be sure
that
a specific frequency would be passed and others rejected.

With this digital filter being clock dependent, if there are
any slight frequency variations it makes it doubly hard to
learn how to reach whatever center frequency I may want to
learn. If I wanted to learn how to produce 5 Hz at will, a
slight deviation of .01 Hz isn't going to be constant with
anything but a crystal-based clock oscillator; using my
original CD4046 as an clock it would shift up and down maybe
1
Hz or maybe 2 Hz sporadically; other oscillators were even
worse.

For most applications a 1 or 2 Hz shift might not be a
problem, but in this case it would be shifting the center
frequency up and down— can you drive when sunlight is
flickering in your face unpredictably? Such a frequency
shift
would amount to the same thing in this application.

(snip)

My guess is that you can probably tolerate 5 or even 10%
drift in the center frequency before you will get a
perceptible
difference.

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.

But the LTC1164-8 is a 8th order, ultra-selective digital
bandpass filter,

http://www.linear.com/pdf/11648fa.pdf

whose center frequency depends only upon it's clock frequency,
which, as I said elsewhere, is in a 100:1 ratio: 500 Hz in to
get 5 Hz bandpass. With a few custom crystal oscillators and
few counters, I can get even fractional frequencies with a
high degree of accuracy out of the LTC1164-8 that I could
never achieve with analog filters even using 0.1% resistors
and matching caps to three places.

Ron

Then you should look into a DDS chip to generate the clock. It is a
programmable frequency source, and with a proper design, you can have a
stable and accurate clock to 1/1000 of a Hz.

<http://www.analog.com/Analog_Root/sitePage/mainSectionHome/0,2130,level4%253D%25252D1%2526level1%253D117%2526level2%253D137%2526level3%253D%25252D1,00.html>
--


Michael A. Terrell
Central Florida

 

[Robert Monsen]

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk80im$qevq8$1@ID-43450.news.uni-berlin.de...

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.

Are there any independent studies backing up the frequency to function
mapping claims here? Sounds much too precise to be plausible... However,
almost anything is possible...

Regards,
Bob Monsen

 

[Ron Hubbard]

I got news for you: you're wrong. Brainwaves do affect us in
many ways. I have fibromyalgia and as a result my tiny little
brain is producing nothing but alpha 24/7 as opposed to normal
beta. That results in a lack of time perception and other
problems.

I've had numerous EEGs, sleep studies, experience with
hypnosis, biofeedback, and altered states of consciousness.and
well aware of how brainwave frequencies relate to
physiological states as well as moods.

People have been studying brainwave activities since the first
EEG was made back in the 1970s and the collected, accumulated
information is available from many sources. Just because some
of it is on the Internet doesn't make it invalid.

But biofeedback is like ESP: you either believe in it or you
don't. Personally, I don't believe in taxes-- but I know the
efficacy of biofeedback and you can believe what you will.


Sir Charles W. Shults III wrote in message ...

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk80im$qevq8$1@ID-43450.news.uni-berlin.de...

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list
is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.

You are chasing echoes. You have done something that
many uninitiated do-
confuse the cause and the effect. Also, just because it's
"on the net", that
does not lend credence to it. Far from it!
Brainwaves frequencies are composites of billions of tiny
neural firing
events- statistical in nature and absolutely NOT tied to a
narrow range of
frequencies. These frequencies do nothing- they are the end
result of
processes, not the cause of those processes.
Driving a very specific frequency into your brain is not
the key to amazing
things. In order for that to be the case, then your brain
would have to have a
very precise clock source somewhere- but it clearly does not.

Cheers!

Chip Shults
My robotics, space and CGI web page -
http://home.cfl.rr.com/aichip

 

[Sir Charles W. Shults III]

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk942k$qnt6d$1@ID-43450.news.uni-berlin.de...

I got news for you: you're wrong. Brainwaves do affect us in
many ways. I have fibromyalgia and as a result my tiny little
brain is producing nothing but alpha 24/7 as opposed to normal
beta. That results in a lack of time perception and other
problems.

Okay, fact #1- you are not making brainwaves with a machine! Let's get that
straight from the outset. You are making an external signal that is NOT a
brainwave. Brainwaves are made by brains.

I've had numerous EEGs, sleep studies, experience with
hypnosis, biofeedback, and altered states of consciousness.and
well aware of how brainwave frequencies relate to
physiological states as well as moods.

Once again, these frequencies are INDICATORS, not CAUSES.
Fact #2- your brain CANNOT distinguish these frequencies to that degree of
accuracy. If it could, we would not need frequency counters. The fact that we
DO need and use frequency counters supports the position that we cannot
distinguish between 3.6 hertz and 3.84 hertz without support equipment.

People have been studying brainwave activities since the first
EEG was made back in the 1970s and the collected, accumulated
information is available from many sources. Just because some
of it is on the Internet doesn't make it invalid.

Nor does it make it true.

But biofeedback is like ESP: you either believe in it or you
don't. Personally, I don't believe in taxes-- but I know the
efficacy of biofeedback and you can believe what you will.

Fact #3- we all are familiar with the placebo effect. If you believe that
something will affect you in a certain way, you are probably conditioning
yourself to respond to that thing in the way you expect. In a nutshell, that
will sum up the effect of this very precise frequency.
If you think otherwise, then find references with a respectable
bibliography, and start your career selling medical devices. You cannot truly,
honestly believe that you have found out something that all the neurosurgeons
and researchers have blindly stepped over and around. And don't even start with
the conspiracy ideas.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[Michael Black]

"Sir Charles W. Shults III" (aichipREM@OVEcfl.THISrr.com) writes:

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk942k$qnt6d$1@ID-43450.news.uni-berlin.de...
I got news for you: you're wrong. Brainwaves do affect us in
many ways. I have fibromyalgia and as a result my tiny little
brain is producing nothing but alpha 24/7 as opposed to normal
beta. That results in a lack of time perception and other
problems.

Okay, fact #1- you are not making brainwaves with a machine! Let's get that
straight from the outset. You are making an external signal that is NOT a
brainwave. Brainwaves are made by brains.

I think you've misread him at some point. He talked of "producing"

brainwaves, and I think you mistook that for feeding external signals into
the brain. I thought he was using "produce" in terms of the whole biofeedback
process. Have an external unit that detects the desired frequencies, which
gives you some sort of feedback, which helps you to get your brain into the
right mode to continue generating those frequencies.

Whether or not this works, and whether or not the filters have to be so
accurate is a completely different matter. But this seems to be a misreading
that is sidetracking the issue.


Michael

 

[Wade Hassler]

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message news:<bk80im$qevq8$1@ID-43450.news.uni-berlin.de>...

<snip>

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.
snip

Just wondering: are human bodies so similar (using the same clock
generator, maybe) that frequencies specified to +/- .1% are widely
applicable?
Wade Hassler

 

[Ron Hubbard]

Roger, you have a fixation on heart beats. And there is a very
vast difference between what is essentially a biological pump
and an infinitely more sophisticated biological computer The
brain)

But as it stands, I understand what goes on in my brain, and I
know both what I want and what I'm doing; I've had over
thirty years of accumulated experience in this area. When was
the last time *you* had an a clinical EEG or studied neurology
& electroencephalography?

Roger Johansson wrote in message ...

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote:

There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different.

There is no scientific reason for such a difference, you are
reading
those lists with far too much seriousness.

The frequencies we talk about are not constant, they are
varying more
than heartbeats vary in frequence, it is only the part of the
spectrum
they are within which is of interest, for example if it is
somewhere
between 6 and 8 Hz the mind is in a certain mood, a certain
state of
mind.

There is also a technical problem too consider.
This kind of unit should be powered by batteries for two
reasons.
1: Safety reasons.
2: Noise reasons.

If we use only analog technology, active filters, we do not
introduce
noise into the circuit, but if you put in logic circuits,
crystal
oscillators and dividers, digital filters, etc.. you will
have big
problems to isolate the digital parts from the sensor
amplifier part.

We are already on the border of what is possible to perceive
with
analog active filters, what is possible to dig out of the
noise.
If you introduce a lot of digital noise anywhere near this
unit it
will be a lot harder or simply impossible to keep noise out
of the
input active filters.

If you insist on using digital technology and crystal
oscillators you
will have to isolate the sensor amplifiers/active filters
from the
digital equipment with optocouplers.
Make the sensor unit a battery driven analog unit, use
optofiber to
send the signals to another unit which contains the digital
circuits,
etc..

If you want to start with brainwave inducing methods I
recommend
trying Cooledit from syntrillium.com.

Try its 7Hz theta function, mix with a tone (250Hz for
example).
Use high volume on your stereo.
It works for me.
But I experience no difference between 6 and 7Hz.


--
Roger J.

 

[Ron Hubbard]

There have been studies with the aim towards curing such
conditions as alcoholism and ADD/ADHD using
neurofeedback.There has also been military and other studies
into some fascinating, but non-mainstream areas that link
specific brainwaves with specific activities. But hey, just
you trying to solve a problem is very likely to elicit what's
called Fm Theta (Frontal midline theta) at 6.2-6.7 Hz and
reaching anywhere from 50 to 100 micro-Volts amplitude.

Those are precise measurements. You have to consider that
there has been almost seventy years of ongoing neurological
research. How many studies do you want


Robert Monsen wrote in message
<9lS9b.369601$Oz4.148414@rwcrnsc54>...

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote in message
news:bk80im$qevq8$1@ID-43450.news.uni-berlin.de...

In this one particular application, neither a 5 nor 10 per
cent drift is acceptable. If you just want to learn how to
produce alpha or theta-- yeah, it don't matter. But I have
reasons for very precise, very specific frequencies +/- no
more than 1% and that's being generous. There's a list of
brainwave frequencies available on the "Net and that list
is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different. That's less
than a 7% difference, but there are other frequencies even
closer together than that that do very different things. So
there are no allowances for drift of any kind.


Are there any independent studies backing up the frequency to
function
mapping claims here? Sounds much too precise to be
plausible... However,
almost anything is possible...

Regards,
Bob Monsen

 

[Bob Masta]

Ron:

Just had another thought. If I understand you correctly, you
are monitoring brainwaves and want to know when certain
frequencies are being produced, to high accuracy. But if you
make the filter so accurate, narrow, and sharp that only
a narrow band is detected, you don't know when you get
low or no filter output whether you are too high or too low,
which might make a difference for biofeedback.

Instead, could you simply use a filter to remove high-frequency
noise and then measure the output frequency directly?
You would need an excellent high-pass to reject near-DC
drift from your electrodes, etc. And of course a steep low-pass
to block 60 Hz and above. But in between, you could measure
the frequency to as many decimal places as you wanted.

The trick is to measure period, not frequency, so you get
a reading on every cycle. You just count the pulses from a
1 MHz or 10 MHz crystal clock (say) between positive
zero crossings, and display the period directly. You don't
even need to convert to frequency, since you can decide
what target period your target frequency corresponds to, and
use period directly.

To create a test setup, many lab-type frequency counters
have a period counter mode. So if you have or can borrow
one, you can try this out before investing in an elaborate
readout system. If you are handy with programming in DOS,
you can even use the PCs printer port to do the period counts.

Just a thought.






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
Shareware from Interstellar Research
www.daqarta.com

 

[Keith R. Williams]

In article <3f69aaeb.2965202@news.itd.umich.edu>, no_spam@aol.com
says...

Ron:

Just had another thought. If I understand you correctly, you
are monitoring brainwaves and want to know when certain
frequencies are being produced, to high accuracy. But if you
make the filter so accurate, narrow, and sharp that only
a narrow band is detected, you don't know when you get
low or no filter output whether you are too high or too low,
which might make a difference for biofeedback.

Instead, could you simply use a filter to remove high-frequency
noise and then measure the output frequency directly?
You would need an excellent high-pass to reject near-DC
drift from your electrodes, etc. And of course a steep low-pass
to block 60 Hz and above. But in between, you could measure
the frequency to as many decimal places as you wanted.

WHat happens if there is more than one wave? Measuring a single sine
wave is easy. My solution would be to use a micro to do a Forier
transform on the signal and then look at the peaks.

--
Keith

 

[Chris1]

In article <bkaujl$r4gnk$1@ID-43450.news.uni-berlin.de>, "Ron Hubbard" <hubbard_ron@hotmail.com> wrote:

Roger, you have a fixation on heart beats. And there is a very
vast difference between what is essentially a biological pump
and an infinitely more sophisticated biological computer The
brain)

But as it stands, I understand what goes on in my brain,

This is an incredible claim. If you understand it, then you should be able
to duplicate it in a machine. You'll be famous (if you're not already).

and I
know both what I want and what I'm doing; I've had over
thirty years of accumulated experience in this area. When was
the last time *you* had an a clinical EEG or studied neurology
& electroencephalography?

I've never studied numerology either.

Chris

 

[Robert Monsen]

"Keith R. Williams" <krw@attglobal.net> wrote in message
news:MPG.19d38e6bf759d4ac989a6e@enews.newsguy.com...

In article <3f69aaeb.2965202@news.itd.umich.edu>, no_spam@aol.com
Instead, could you simply use a filter to remove high-frequency
noise and then measure the output frequency directly?
You would need an excellent high-pass to reject near-DC
drift from your electrodes, etc. And of course a steep low-pass
to block 60 Hz and above. But in between, you could measure
the frequency to as many decimal places as you wanted.

WHat happens if there is more than one wave? Measuring a single sine
wave is easy. My solution would be to use a micro to do a Forier
transform on the signal and then look at the peaks.

--
Keith

Try using a digital filter; without looking too hard, I found this:

http://www-users.cs.york.ac.uk/~fisher/mkfilter/

It'll write you a digital filter in C, given the specifications. I created a
fairly good bandpass filter for 4Hz += .1Hz with samples at 100Hz in a
couple of minutes.

Unfortunately, I'm in agreement with the folks that say that digital noise
will swamp your signal unless you take extraordinary precautions.

Regards,
Bob Monsen

 

[Chris1]

In article <bkaujm$r4gnk$2@ID-43450.news.uni-berlin.de>, "Ron Hubbard" <hubbard_ron@hotmail.com> wrote:

There have been studies with the aim towards curing such
conditions as alcoholism and ADD/ADHD using
neurofeedback.There has also been military and other studies
into some fascinating, but non-mainstream areas that link
specific brainwaves with specific activities. But hey, just
you trying to solve a problem is very likely to elicit what's
called Fm Theta (Frontal midline theta) at 6.2-6.7 Hz and
reaching anywhere from 50 to 100 micro-Volts amplitude.

Those are precise measurements. You have to consider that
there has been almost seventy years of ongoing neurological
research. How many studies do you want

6.2 - 6.7 Hz is a 7% range. Not too terribly precise in my book.

Chris

 

[Ron Hubbard]

I'm relying on the specs for the TLC1164-8 which as digital
filters go, seems very impressive. With a gain from anywhere
between 0 and 1000, not to mention the gain of all the
preceding stages. I'm not sure there will be a problem.
Besides the output from the filter only has to modulate a
frequency modulated oscillator; it does not have to be a
"clean" signal.

But because that filter is so easily tunable, I'm gonna give
it try anyway. It beats trying to find 0.1% resistors and
matching caps...


Robert Monsen wrote in message ...

"Keith R. Williams" <krw@attglobal.net> wrote in message
news:MPG.19d38e6bf759d4ac989a6e@enews.newsguy.com...
In article <3f69aaeb.2965202@news.itd.umich.edu>,
no_spam@aol.com
Instead, could you simply use a filter to remove
high-frequency
noise and then measure the output frequency directly?
You would need an excellent high-pass to reject near-DC
drift from your electrodes, etc. And of course a steep
low-pass
to block 60 Hz and above. But in between, you could
measure
the frequency to as many decimal places as you wanted.

WHat happens if there is more than one wave? Measuring a
single sine
wave is easy. My solution would be to use a micro to do a
Forier
transform on the signal and then look at the peaks.

--
Keith

Try using a digital filter; without looking too hard, I found
this:

http://www-users.cs.york.ac.uk/~fisher/mkfilter/

It'll write you a digital filter in C, given the
specifications. I created a
fairly good bandpass filter for 4Hz += .1Hz with samples at
100Hz in a
couple of minutes.

Unfortunately, I'm in agreement with the folks that say that
digital noise
will swamp your signal unless you take extraordinary
precautions.

Regards,
Bob Monsen

 

[Ron Hubbard]

Roger Johansson wrote in message ...

"Ron Hubbard" <hubbard_ron@hotmail.com> wrote:

There's a list of
brainwave frequencies available on the "Net and that list is
quite clear where a frequency like 3.6 Hz may do one thing,
but 3.84 Hz does something entirely different.
(snip)

If you want to start with brainwave inducing methods I
recommend
trying Cooledit from syntrillium.com.

Try its 7Hz theta function, mix with a tone (250Hz for
example).
Use high volume on your stereo.
It works for me.
But I experience no difference between 6 and 7Hz.

Oh, by the way, Cool Edit has one fatal flaw: when you use it
for so-called brainwave entrainment, you never actually *know*
when or if you have altered your brainwaves. What you "think"
may not be reality. This is the same flaw with the Brainwave
Generator
program and also light&sound goggles.

The effects vary with people, and some are happy merely
because of a placebo effect. Without an EEG or biofeedback to
tell what's going on the brain, Cool Edit and similar programs
are pretty much useless except as entertainment.

the other side of the coin is, can you produce theta at will
without listening to a Cool Edit set of tones? My brain
produces short trains of 4 Hz theta, and when on "auto-pilot"
I can walk around in theta for quite some time, but willingly
entering theta is a fairly difficult without knowing if there
has been a real change when I want it. That's also the problem
anyone using such entrainment programs [or goggles] face.

 

[Robert Monsen]

Well, good luck to you, and I'll look forward to seeing the circuit on
alt.binaries.schematics.electronics if you get it working to your
satisfaction.

Regards,
Bob Monsen

 

[Bob Masta]

On Thu, 18 Sep 2003 10:42:40 -0400, Keith R. Williams
<krw@attglobal.net> wrote:

WHat happens if there is more than one wave? Measuring a single sine
wave is easy. My solution would be to use a micro to do a Forier
transform on the signal and then look at the peaks.

--
Keith

Yours is the best idea I've heard so far, and by far the easiest
to actually use. It will require an ADC with response
down to very low frequencies, which may rule out a lot of sound
cards. But there are some with bottom ends around 2 Hz or so
(maybe lower, it's been a while since I looked), so this should be
easy to get going.

There are a couple of caveats. You will need an FFT that covers
the range of interest with the desired resolution. You can do that
using really huge FFTs at the usual audio sample rates, or you
can try to slow the sample rate with sample rate conversion. Either
way you need a lot of time to get enough data for each FFT, so
to prevent slow, jerky screen updates you would want to do
overlap processing. Just maintain a big data buffer and run your FFT
and display refresh as fast as possible, always taking the most
recent N samples from the buffer, even if some of them were used
for the previous FFT. This gives a nice smooth response, assuming
your FFT and display code are fast enough.

The big advantage of the FFT approach is that you can have an
effective huge array of narrow filters, and see all their outputs at
once. So you not only know if you are at your target, but also how
far off you are, and how strong each component is. And you get
immediate information if the noise floor increases due to electrodes
getting loose, etc. Nice!





Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[Keith R. Williams]

In article <3f6b09ed.6265615@news.itd.umich.edu>, no_spam@aol.com
says...

On Thu, 18 Sep 2003 10:42:40 -0400, Keith R. Williams
krw@attglobal.net> wrote:



WHat happens if there is more than one wave? Measuring a single sine
wave is easy. My solution would be to use a micro to do a Forier
transform on the signal and then look at the peaks.

--
Keith

Yours is the best idea I've heard so far, and by far the easiest
to actually use. It will require an ADC with response
down to very low frequencies, which may rule out a lot of sound
cards. But there are some with bottom ends around 2 Hz or so
(maybe lower, it's been a while since I looked), so this should be
easy to get going.

There are a couple of caveats. You will need an FFT that covers
the range of interest with the desired resolution. You can do that
using really huge FFTs at the usual audio sample rates, or you
can try to slow the sample rate with sample rate conversion. Either
way you need a lot of time to get enough data for each FFT, so
to prevent slow, jerky screen updates you would want to do
overlap processing. Just maintain a big data buffer and run your FFT
and display refresh as fast as possible, always taking the most
recent N samples from the buffer, even if some of them were used
for the previous FFT. This gives a nice smooth response, assuming
your FFT and display code are fast enough.

I don't think it's going to be a huge problem at these
frequencies. One should look up some algorithms for a
"continuous" FFT. I know of someone who does this stuff at RADAR
frequencies (using FPGAs), so at a few Hz things should be
simple. One thing you're going to need is a good filter on the
input to prevent aliasing, which will also help with noise.

The big advantage of the FFT approach is that you can have an
effective huge array of narrow filters, and see all their outputs at
once. So you not only know if you are at your target, but also how
far off you are, and how strong each component is. And you get
immediate information if the noise floor increases due to electrodes
getting loose, etc. Nice!

--
Keith