White Noise Source

[chiron613]

Yeah, well, as I was saying, it's an interesting question, but not one
I feel up to answering.

I've listened to recorded samples where people thought they heard a
voice, but I never got anything other than the noise. So I figured
I'd just try it myself and see what happens. Since I am doubtful, I
didn't want to invest a whole lot of effort building a circuit.

Thanks for your offer. I don't think I can use it, because I'm not
using Windows. But I do appreciate the offer, and I again apologize
for seeming to ignore you.

-B

 

[Bob Masta]

On Fri, 10 Feb 2012 00:03:15 -0800 (PST), chiron613
<chiron613@gmail.com> wrote:

Yeah, well, as I was saying, it's an interesting question, but not one
I feel up to answering.

I've listened to recorded samples where people thought they heard a
voice, but I never got anything other than the noise. So I figured
I'd just try it myself and see what happens. Since I am doubtful, I
didn't want to invest a whole lot of effort building a circuit.

Thanks for your offer. I don't think I can use it, because I'm not
using Windows. But I do appreciate the offer, and I again apologize
for seeming to ignore you.

No apology needed. If you go with a hardware solution you
will need to be able to convince yourself that it is not
picking up an AM station, so be sure to compare one-ear
listrening to two-ear listening if you get an effect.

As for Zeners, I haven't tried the 20V units George
mentioned... but that sounds like a good aproach if it
avoids the need for a lot of gain. I used a reversed-bias
EB junction from an NPN back in the "olden days"... I think
this was pretty common. You ground the base and feed the
collector through 100k from +15, and tap off the noise via a
big cap (0.47 or whatever) and a bunch of gain.

If you go with a pseudo-random generator, you have to be
careful: "Back in the day" the single-chip units were
notorious for having a short repeat pattern. They were
designed for transient uses like snare drums, and if you ran
them continuously you'd hear "shoop, shoop, shoop" from the
repeats. Make sure whatever you use has at least a minute
or more, and for your purpose best if it's hours or beyond.


In the past, when computers had easily-controlled hardware,
it was fairly easy to do this with code that drove the
printer port. Alas, no more.

Best regards,


Bob Masta

DAQARTA v6.02
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!

 

[Chiron]

On Fri, 10 Feb 2012 13:37:29 +0000, Bob Masta wrote:

On Fri, 10 Feb 2012 00:03:15 -0800 (PST), chiron613
chiron613@gmail.com> wrote:

snip

No apology needed. If you go with a hardware solution you will need to
be able to convince yourself that it is not picking up an AM station, so
be sure to compare one-ear listrening to two-ear listening if you get an
effect.

You know, you reminded me that my system has a random function built into
it - not sure exactly how it works, but it spews out (pseudo)random bytes
at a pretty fast rate (A few seconds worth created a file > 100M). Now
the trick is to convert that to sound... I suppose I can figure that
out. I might pass it through an FFT program just to see whether it's
even close to being white noise... I just don't know how this "random"
function works. As John von Neumann said, "Anyone who attempts to
generate random numbers by deterministic means is, of course, living in a
state of sin."

As for Zeners, I haven't tried the 20V units George mentioned... but
that sounds like a good aproach if it avoids the need for a lot of gain.
I used a reversed-bias EB junction from an NPN back in the "olden
days"... I think this was pretty common. You ground the base and feed
the collector through 100k from +15, and tap off the noise via a big cap
(0.47 or whatever) and a bunch of gain.

I don't see much problem with gain - if I can't do it with a few
transistors (maybe in a Darlington arrangement?), then I can always use a
couple of op amps.

If you go with a pseudo-random generator, you have to be careful: "Back
in the day" the single-chip units were notorious for having a short
repeat pattern. They were designed for transient uses like snare drums,
and if you ran them continuously you'd hear "shoop, shoop, shoop" from
the repeats. Make sure whatever you use has at least a minute or more,
and for your purpose best if it's hours or beyond.

I'm probably not going to try this. I don't have the parts handy.

In the past, when computers had easily-controlled hardware, it was
fairly easy to do this with code that drove the printer port. Alas, no
more.

Sure, back when you just about had to write your own drivers for
everything. I had a lot of fun back then, but I wouldn't really want to
go back to it now.



--
Fortune's current rates:

Answers .10
Long answers .25
Answers requiring thought .50
Correct answers $1.00

Dumb looks are still free.

 

[ehsjr]

stratus46@yahoo.com wrote:

On Feb 9, 11:44 pm, Chiron <chiron...@gmail.com> wrote:

On Thu, 09 Feb 2012 21:58:06 -0800, stratus46 wrote:

You give them a solution - and for free that they can use right now -
and they continue to talk about using Zeners to make noise. I have a
horse. I showed him where the water is and he drinks it. Not sure about
these people though.

G˛

How about, I ask for a cheeseburger; someone offers me a free glass of
water; but I keep talking about the cheeseburger, because I'm hungry, not
thirsty. Besides, your horse is drinking out of the glass, and that's
just plain gross.

To be honest, I never saw the post you quoted. It didn't get past the
killfile - too many lines. Unfortunately, one of the problems with a
killfile is that you may wind up blocking perfectly legitimate posts, as
you try to get rid of all the crap.

OK, I'll have a look on Google and see what he said...

--
You can always tell luck from ability by its duration.


You asked for an audio noise source and mentioned Zeners but you have
to build something to actually use Zeners. You obviously have a
computer which very likely has audio capabilities. You can build
something in a few days or you can have your noise source in minutes.
You were offered a noise source. What's your time worth?

G˛

Sometimes you want (or need) to use a noise source (or whatever)
when there is no computer close enough. A laptop solves that
problem - but the zener source solves it a whole lot cheaper.

Ed

 

[Michael Black]

On Fri, 10 Feb 2012, Chiron wrote:

As for Zeners, I haven't tried the 20V units George mentioned... but
that sounds like a good aproach if it avoids the need for a lot of gain.
I used a reversed-bias EB junction from an NPN back in the "olden
days"... I think this was pretty common. You ground the base and feed
the collector through 100k from +15, and tap off the noise via a big cap
(0.47 or whatever) and a bunch of gain.

I don't see much problem with gain - if I can't do it with a few
transistors (maybe in a Darlington arrangement?), then I can always use a
couple of op amps.

Then there was the circuit in "Electronics", Designer's Casebook or

Engineer's notebook, that just used a noisy op-amp and amplified it, as a
noise source. No diode needed.

Michael

 

[Jasen Betts]

On 2012-02-10, Chiron <chiron613@gmail.com> wrote:

On Thu, 09 Feb 2012 21:58:06 -0800, stratus46 wrote:

To be honest, I never saw the post you quoted. It didn't get past the
killfile - too many lines. Unfortunately, one of the problems with a
killfile is that you may wind up blocking perfectly legitimate posts, as
you try to get rid of all the crap.

Your filter blocked a noise source,
kind of ironic.

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Jasen Betts]

On 2012-02-10, Chiron <chiron613@gmail.com> wrote:

On Fri, 10 Feb 2012 13:37:29 +0000, Bob Masta wrote:

You know, you reminded me that my system has a random function built into
it - not sure exactly how it works, but it spews out (pseudo)random bytes
at a pretty fast rate (A few seconds worth created a file > 100M). Now
the trick is to convert that to sound... I suppose I can figure that
out. I might pass it through an FFT program just to see whether it's
even close to being white noise... I just don't know how this "random"
function works. As John von Neumann said, "Anyone who attempts to
generate random numbers by deterministic means is, of course, living in a
state of sin."

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate
of about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

--
⚂⚃ 100% natural

 

[Baron]

Jasen Betts Inscribed thus:

On 2012-02-10, Chiron <chiron613@gmail.com> wrote:
On Fri, 10 Feb 2012 13:37:29 +0000, Bob Masta wrote:

You know, you reminded me that my system has a random function built
into it - not sure exactly how it works, but it spews out
(pseudo)random bytes
at a pretty fast rate (A few seconds worth created a file > 100M).
Now the trick is to convert that to sound... I suppose I can figure
that
out. I might pass it through an FFT program just to see whether it's
even close to being white noise... I just don't know how this
"random" function works. As John von Neumann said, "Anyone who
attempts to generate random numbers by deterministic means is, of
course, living in a state of sin."

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate
of about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

Well, I'll be... ! One to put in the vade mecum.

--
Best Regards:
Baron.

 

[Chiron]

On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

<snip>

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile. Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave. Just a little
*too* perfect. I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise). As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
<sel> need help: my first packet to my provider gets lost :-(
<netgod> sel: dont send the first one, start with #2

 

[Jamie]

George Herold wrote:

On Feb 10, 4:16 pm, Chiron <chiron...@gmail.com> wrote:

On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip



if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile. Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave. Just a little
*too* perfect. I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise). As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel: dont send the first one, start with #2


With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.


+15
|
1 Meg
|
+--0.1uF--+---->scope (use x10 probe,
| | not a crappy clip lead.)
Z 100k
^ |
| GND
-15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

George H.
You know that is strange, I have some 39V zeners and when applying 50

50 volts with a test like above, I don't see what I would say is noise
being generated from the node of the zener and R ?

I tried this with my Tek 350mhz scope and the 100 DSO one.

Maybe I have different zeners ? Of course, these are 2 watt zeners
I tried, they were left overs from a job .

Jamie

 

[George Herold]

On Feb 10, 4:16 pm, Chiron <chiron...@gmail.com> wrote:

On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip



if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples  per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile.  Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave.  Just a little
*too* perfect.  I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise).  As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel:  dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.


+15
|
1 Meg
|
+--0.1uF--+---->scope (use x10 probe,
| | not a crappy clip lead.)
Z 100k
^ |
| GND
-15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

George H.

 

[George Herold]

On Feb 10, 6:43 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

George Herold wrote:
On Feb 10, 4:16 pm, Chiron <chiron...@gmail.com> wrote:

On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples  per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile.  Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave.  Just a little
*too* perfect.  I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise).  As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel:  dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.

    +15
     |
    1 Meg
     |
     +--0.1uF--+---->scope (use x10 probe,
     |         |            not a crappy clip lead.)
     Z        100k
     ^         |
     |        GND
    -15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

 George H.

   You know that is strange, I have some 39V zeners and when applying 50
50 volts with a test like above, I don't see what I would say is noise
being generated from the node of the zener and R ?

   I tried this with my Tek 350mhz scope and the 100 DSO one.

  Maybe I have different zeners ? Of course, these are 2 watt zeners
I tried, they were left overs from a job .

Jamie- Hide quoted text -

- Show quoted text -

Yeah, for other Zeners.. "I know na's'inggg".
(In the voice of Sergeant Shultz.)

But higher power means more area, and that will change things.
"Give 'er a bit more power Scotty."
20V 1/2 Watt zeners with black tape, surface mount should be similar,
but I haven't looked.

I'll post pics' Monday, with a x10 probe.

George H.

 

[Bob Masta]

On Fri, 10 Feb 2012 21:16:06 GMT, Chiron
<chiron613@gmail.com> wrote:

On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.


That's very close to what I did - cat /dev/urandom > randomfile. Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave. Just a little
*too* perfect. I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Actually, the spectrum of random-amplitude samples should be
flat. So I'd be more suspicious of the roll-off above 20
kHz. I haven't delved into ogg format, but my guess is
that it may be rolling things off above the audio range.

Note that when an FFT generates a spectrum, it doesn't
really know anything about frequency... it just operates on
a set of numbers. If the numbers are random, the resulting
spectrum is flat. The frequency interpretation comes by
knowing the sample rate of the raw data values.

If audacity can't look at the spectrum of the raw data, can
you convert to WAV instead of ogg? WAV is just a simple
header in front of the raw data... it doesn't actually
convert anything. The header holds the sample rate info and
related stuff.

Best regards,


Bob Masta

DAQARTA v6.02
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!

 

[fungus]

On Feb 11, 1:20 pm, N0S...@daqarta.com (Bob Masta) wrote:

On Fri, 10 Feb 2012 21:16:06 GMT, Chiron









chiron...@gmail.com> wrote:
On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples  per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile.  Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave.  Just a little
*too* perfect.  I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Actually, the spectrum of random-amplitude samples should be
flat.   So I'd be more suspicious of the roll-off above 20
kHz.    I haven't delved into ogg format, but my guess is
that it may be rolling things off above the audio range.

*Any* lossy compressor will do that.

Use an uncompressed format (.wav).

 

[George Herold]

On Feb 10, 6:16 pm, George Herold <gher...@teachspin.com> wrote:

On Feb 10, 4:16 pm, Chiron <chiron...@gmail.com> wrote:





On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip

if linux, this is easy:

cat /dev/urandom > /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples  per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom > randomfile.  Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at > 30 dB per octave.  Just a little
*too* perfect.  I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise).  As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel:  dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.

    +15
     |
    1 Meg
     |
     +--0.1uF--+---->scope (use x10 probe,
     |         |            not a crappy clip lead.)
     Z        100k
     ^         |
     |        GND
    -15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

 George H.- Hide quoted text -

- Show quoted text -

A bit more on Zener noise. (20 V zener 1N5250)

So here’s a few ‘scope shot with 1 Meg Ohm bias resistor. And a x10
scope probe (C = 16pF)
The step is ~10ns or so... But I may be hitting the limit of the 40MHz
scope.

http://bayimg.com/HamjLAaDj

The same at slower time base.. showing the RC ‘recharging’
http://bayimg.com/HamJPAaDj

You can average the FFT when watching on the ‘scope but a single FFT
trace is pretty noisy... but it looks flat to about 500kHz.

If you reduce the bias resistor to 100k you can get improve the
bandwidth.
http://bayimg.com/IaMjFaADj
The FFT looks flat out to near 10MHz!

and a fast shot still with 100k ohm
http://bayimg.com/iaMjHaADj

From the slope (1 volt in ~170ns) (at a current of 100uA) I get a C of
17pf... I’m still looking at the C of my probe!

Any ideas on reverse biased zener capacitance? This is the best data
sheet I could find.

http://61.222.192.61/mccsemi/up_pdf/1N5221-1N5267(DO-35).pdf

Low C, high speed...it’s like a photodiode front end.

As a side note,
There are some I-V curves (22V) that do look like a bit of negative
resistance... as someone else posted.


George H.

(Bayimag looks like a nice hosting site... no fluff!)

 

[Ben / SM0KBW]

George Herold skrev 2012-02-11 00:16:

On Feb 10, 4:16 pm, Chiron<chiron...@gmail.com> wrote:
On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip



if linux, this is easy:

cat /dev/urandom> /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom> randomfile. Then I
imported that as a raw file into audacity, converted it to ogg format.
When I looked at its spectrum, it was suspiciously flat all the way from
zero to 20kHz, where it fell off at> 30 dB per octave. Just a little
*too* perfect. I go by the maxim that, if everything goes according to
plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the other
one just for fun (amplified diode noise). As someone pointed out, having
a quick noise source around could be handy for other reasons besides
talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel: dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.


+15
|
1 Meg
|
+--0.1uF--+---->scope (use x10 probe,
| | not a crappy clip lead.)
Z 100k
^ |
| GND
-15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

George H.

One trick, at least at RF is to use the Zener breakthrough in a regular
transistor, the base - emitter diode backwards can give a very good
noise source ranging upp to 1GHz and even above.

/Ben - SM0KBW

 

[Baron]

Ben / SM0KBW Inscribed thus:

George Herold skrev 2012-02-11 00:16:
On Feb 10, 4:16 pm, Chiron<chiron...@gmail.com> wrote:
On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip



if linux, this is easy:

cat /dev/urandom> /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample
rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom> randomfile.
Then I imported that as a raw file into audacity, converted it to
ogg format. When I looked at its spectrum, it was suspiciously flat
all the way from
zero to 20kHz, where it fell off at> 30 dB per octave. Just a
little
*too* perfect. I go by the maxim that, if everything goes according
to plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the
other
one just for fun (amplified diode noise). As someone pointed out,
having a quick noise source around could be handy for other reasons
besides talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel: dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.


+15
|
1 Meg
|
+--0.1uF--+---->scope (use x10 probe,
| | not a crappy clip lead.)
Z 100k
^ |
| GND
-15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

George H.

One trick, at least at RF is to use the Zener breakthrough in a
regular transistor, the base - emitter diode backwards can give a very
good noise source ranging upp to 1GHz and even above.

/Ben - SM0KBW

Has anybody tried LEDs as noise sources ?

--
Best Regards:
Baron.

 

[krw@att.bizzzzzzzzzzzz]

On Sat, 18 Feb 2012 21:20:26 +0000, Baron <baron@linuxmaniac.net> wrote:

Ben / SM0KBW Inscribed thus:

George Herold skrev 2012-02-11 00:16:
On Feb 10, 4:16 pm, Chiron<chiron...@gmail.com> wrote:
On Fri, 10 Feb 2012 19:22:39 +0000, Jasen Betts wrote:

snip



if linux, this is easy:

cat /dev/urandom> /dev/audio

(dev/audio is (IIRC) mono 8 bit Ulaw and runs at a fixed sample
rate of
about 8000 samples per second so it's not propper white noise.

for something better try sox or audacity.

That's very close to what I did - cat /dev/urandom> randomfile.
Then I imported that as a raw file into audacity, converted it to
ogg format. When I looked at its spectrum, it was suspiciously flat
all the way from
zero to 20kHz, where it fell off at> 30 dB per octave. Just a
little
*too* perfect. I go by the maxim that, if everything goes according
to plan, you've obviously overlooked something.

Anyway, it's a nice, noisy signal, but I'm still going to do the
other
one just for fun (amplified diode noise). As someone pointed out,
having a quick noise source around could be handy for other reasons
besides talking to ghosts.

--
sel> need help: my first packet to my provider gets lost :-(
netgod> sel: dont send the first one, start with #2

With the a 20V zener you don't need any amplifictaion, just a
buffer.
I wrapped this together on the top of a power supply.


+15
|
1 Meg
|
+--0.1uF--+---->scope (use x10 probe,
| | not a crappy clip lead.)
Z 100k
^ |
| GND
-15V

I saw a random RC step response with a time constant of ~2us.
With something like a few hundred mV step size (on average)
(Driving home I realized that the ~80pf in the clip lead I used to
connect to the scope was my RC.. so I can't pull any 'real' numbers
out.)
You can try it yourself with a x10 probe and report results.
You should do better than two micro seconds.

George H.

One trick, at least at RF is to use the Zener breakthrough in a
regular transistor, the base - emitter diode backwards can give a very
good noise source ranging upp to 1GHz and even above.

/Ben - SM0KBW

Has anybody tried LEDs as noise sources ?

Wouldn't there be correlation problems with any light sources around? Seems
like it's needlessly asking for trouble.

 

[Michael Black]

On Sat, 18 Feb 2012, krw@att.bizzzzzzzzzzzz wrote:

Has anybody tried LEDs as noise sources ?

Wouldn't there be correlation problems with any light sources around? Seems
like it's needlessly asking for trouble.

Yes, and someone's already warned about that, but the issue isn't because

of it's an LED but because of the seethrough casing.

I remember one article about a VCO where the author suggested trying
different types of diodes for the varactor. And he mentioned trying some
small signal diodes and having AC hum on the output, until he realized the
hum was coming from the desk lamp that was shining on the clear-cased
diode.

I've seen other mentions of problems because of light. I recall one
article warning about it, but not because of hum, but because the external
light was affecting diodes, and they were biased wrong or something, or
maybe turning on when they shouldn't.

Since LEDs have been used as low voltage zeners, perhaps they do have some
ability to better generate noise at a lower voltage or something. With a
breadboard, it costs very little to try. If it works, simply paint the
LED, get rid of any external problem.

Michael

 

[Phil Hobbs]

Michael Black wrote:

On Sat, 18 Feb 2012, krw@att.bizzzzzzzzzzzz wrote:

Has anybody tried LEDs as noise sources ?

Wouldn't there be correlation problems with any light sources around? Seems
like it's needlessly asking for trouble.

Yes, and someone's already warned about that, but the issue isn't because
of it's an LED but because of the seethrough casing.

I remember one article about a VCO where the author suggested trying
different types of diodes for the varactor. And he mentioned trying some
small signal diodes and having AC hum on the output, until he realized the
hum was coming from the desk lamp that was shining on the clear-cased
diode.

I've seen other mentions of problems because of light. I recall one
article warning about it, but not because of hum, but because the external
light was affecting diodes, and they were biased wrong or something, or
maybe turning on when they shouldn't.

Since LEDs have been used as low voltage zeners, perhaps they do have some
ability to better generate noise at a lower voltage or something. With a
breadboard, it costs very little to try. If it works, simply paint the
LED, get rid of any external problem.

Michael

LEDs make great current switches--the garden variety ones I used in
Footprints had leakage is down in the femtoamps from ~-5V to +0.5V. The
photosensitivity can be a feature as well as a bug, when you use it to
supply DC bias for a capacitive sensor such as a pyroelectric. (See
http://electrooptical.net/#footprints, especially the paper with the
gory technical details.)

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net