White Noise Source

[Chiron]

I need a source of white noise (audio). It doesn't have to be perfect.

I seem to recall that you could use a zener diode as a white noise
source. Is this true? Are there any other possibilities? I anticipate
using a 9-V battery for my power, and a few transistors to amplify the
signal to drive earphones.

You may ask, "why the heck would he want to do that?" Good question:

http://en.wikipedia.org/wiki/Electronic_voice_phenomenon

Since I believe that the chances of there being anything to this are just
about zero, I don't want to invest a whole lot of effort in doing it.



--
Do not apply to broken skin.

[Phil Allison]

"Chiron"

>I need a source of white noise (audio). It doesn't have to be perfect.

** I think you will find this microwave sauce recipe most satisfactory:

http://allrecipes.com.au/recipe/10834/cheesy-white-sauce.aspx

Not to mention tasty too.

And may I supply a word of advice -

leave the imaginary voices to the experts -

ie the genuine schizophrenics.




... Phil

[Bob Masta]

Download my Daqarta software... it's free for signal
generation use. Midway down the Generator dialog, click the
left Waveform Controls button. Click Wave on the dialog that
appears and select Noise: White. Toggle the Generator
button on in the main toolbar. The first time the Generator
goes on the volume control dialog will pop up, plus a
cautionary message about loud levels. You'll need to cancel
the message before the sound starts. (In WinXP you may also
need to unMute, at the bottom of that dialog.) Later, you
can open the volume dialog via the F9 key at any time.

Now I'm going to give away a secret: In the next version of
Daqarta (v7.00, in a month or so) there will be a whole Help
section on EVP-related stuff, and a demo on how to hear it
for yourself. Well, not exactly what the woo-woo folks are
talking about, but a phenomenon I call "Phantom Signals"
that I think is at the root of the EVP nonsense... as well
as "dental radio".

The trick for phantom signals is to use headphones and put
the white noise in *one ear only*. The loudness should be
about 30-40 dB above your detection threshold. (You'll need
to be in a fairly quiet room, with no music, TV, or voices.)


I'll provide a simple way to set that level. Let me know if
you want me to explain a manual approach here. It's not
super-critical, but it needs to be loud enough to hear
easily, but not too loud.

Listen for a few minutes, and you will start to hear a
"radio station". You might hear music or voices, but you
won't be able to tell exactly what the song is, or
understand what they are talking about... nevertheless
you'll be convinced there is a "signal" there. You might
categorize the station as "Country", or "Talk Radio", or
whatever, based on what you hear. You'll probably have an
overpowering feeling that if only you could just improve the
S/N a *teeny* bit you would understand everything. But you
can't.

And if you switch the noise source to *both* ears, the
phantom signal vanishes and you just hear noise. (Sometimes
you can get the effect with both ears, but it may take a
*lot* of listening.)

I actually discovered this a long time ago, while designing
a diode-based noise generator. Since that sort of circuit
involves a lot of gain, when I heard the "radio station" I
naturally assumed that's *exactly* what it was hearing. I
tried all kinds of filtering before I finally got rid of
it... coincidentally having switched from a single-ear
lineman's test set to stereo phones. Problem solved!

Then I built a completely digital version, which doesn't
involve gain and is not susceptible to AM pickup... or so I
assumed. Yet it was back again, but only with the mono
headset, not stereo or speakers. Took a lot of testing to
convince myself that it wasn't a circuit problem... at least
not in my hardware circuit, only the "wetware" between my
ears!

Then when I showed the phantom signals effect to others they
were absolutely convinced it was a real radio station, and
that there was some defect in my hardware. Had to go
through all the steps with them to prove it was only in
their heads. The really convincing proof was that it
vanished instantly when heard through both ears... hard to
explain if it was AM pick-up!

For a long time I didn't want to announce this to the
general public because I hoped to recruit subjects for an
unbiased test. But that got put on the back burner for so
long that I've given up on it.

So enjoy!

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!

[Oppie]

"Chiron" <chir...@gmail.com> wrote in message
news:weLYq.15012$Au5....@newsfe23.iad...

Zeners do work. I had used a 6V zener feeding it through a 1 meg resistor
from 15V. The spectrum was lacking in much of the audio range though. I had
better success reverse biasing the base-emitter junction of any garden
variety transistor. The NPNs that I tried break down in the range of 8
volts, so again, a 1 Meg feed from 15V is a good starting point.

the '15V' can be either from two 9V batteries or a boost converter.

OR you can look up "white noise schematic"

Pseudo Random Noise can be digitally generated with a recirculating shift
register that has the feedback tapped at a few points and XORed as shown in
this diagram
http://www.discovercircuits.com/DJ-Circuits/noisegen.htm
It shows 12V power but modern logic elements will work at lower voltages. I
used a similar circuit for calibrating a sonar system (signal of interest
burried in 90 db of noise).

[Chiron]

On Thu, 09 Feb 2012 09:32:55 -0500, Oppie wrote:

<snip>

Thanks, Oppie. I might try the idea with the transistor. Seems like it
might be what I'm looking for...




--
Exercise caution in your daily affairs.

[George Herold]

I really like 20V 1/2 watt zeners for this... bias from +/-15 volts
through a 1 meg resistor. Lotsa noise and flat out to ~500kHz or so.
The voltage is a bit asymmetric, but that can be fixed..... by adding
two of opposite polarity.

George H.

[Chiron]

On Thu, 09 Feb 2012 13:28:04 -0800, George Herold wrote:

<snip>

>
> I really like 20V 1/2 watt zeners for this... bias from +/-15 volts
> through a 1 meg resistor. Lotsa noise and flat out to ~500kHz or so.
> The voltage is a bit asymmetric, but that can be fixed..... by adding
> two of opposite polarity.
>

Thanks, George. Is there anything special about the zener being 20V? In
other words, would a 20V zener be better than using, say, a 5.1V?


--
Tart words make no friends; a spoonful of honey will catch more flies than
a gallon of vinegar.
-- B. Franklin

[BeeJ]

on 2/9/2012, Chiron supposed :

> On Thu, 09 Feb 2012 13:28:04 -0800, George Herold wrote:
>
> <snip>
>>
>> I really like 20V 1/2 watt zeners for this... bias from +/-15 volts
>> through a 1 meg resistor. Lotsa noise and flat out to ~500kHz or so.
>> The voltage is a bit asymmetric, but that can be fixed..... by adding
>> two of opposite polarity.
>>
>
> Thanks, George. Is there anything special about the zener being 20V? In
> other words, would a 20V zener be better than using, say, a 5.1V?

Yes, the higher voltage zeners have a little negative resistance in
part of their curve. That is why you can build an oscillator using
just the diode a capacitor and resistor. Try it. Fun.
Look closely at the curves on the higher voltage zeners.

[George Herold]

Yeah a big difference. In low voltage Zeners the current is from
tunneling electrons (one at a time) and only have shot noise. (Which
is pretty small). High voltage 'Zeners' do this avalanche break
down...big random current pulses.
Lot's more noise 'amplitude'.
I looked at a bunch of different voltages. (Above somethiing like 6V
is where you start to get some avalanching.) 10 and 12 Volt Zeners
showed more than shot noise, but there was a lot of part to part
variation in the amount of noise. For some reason* 20V zeners all
give about the same signal levels... I posted a 'scope shot some time
back.
If you use glass encapsulated diodes then wrap some black electrical
tape around them... else the room lights leak in and ruin everthing.

George H.

* So here's a WAG as to why 20V (or there abouts) has uniform noise
piece to piece.
At lower volatage the break down is at some channel in the diode.
There's a lot of variation in the 'golden' channel for different
diodes. So different sizes of current pulses... (different
capacitances in each channel).

But at some voltage, (20V?) the whole diode breaks down and you get a
current pulse that is the whole diode capacitance. Since this is
pretty constant, you get about the same size of pulses piece to
piece. (I'll mave to 'measure' the pulse size and see if that
fits...)

[George Herold]

Interesting, can you post a schematic? It may not be negative
resistance.... With a long enough time constant, you may be seeing the
random 'firing' of the zeners discharging the RC, then waiting a few
RC for the voltage to rise. Once above some 'thershold' you only
have to wait about a micro second till the next random firing.

George H.

[Chiron]

On Thu, 09 Feb 2012 17:46:23 -0800, George Herold wrote:

> Yeah a big difference. In low voltage Zeners the current is from
> tunneling electrons (one at a time) and only have shot noise. (Which is
> pretty small). High voltage 'Zeners' do this avalanche break down...big
> random current pulses.
> Lot's more noise 'amplitude'.
> I looked at a bunch of different voltages. (Above somethiing like 6V is
> where you start to get some avalanching.) 10 and 12 Volt Zeners showed
> more than shot noise, but there was a lot of part to part variation in
> the amount of noise. For some reason* 20V zeners all give about the
> same signal levels... I posted a 'scope shot some time back.
> If you use glass encapsulated diodes then wrap some black electrical
> tape around them... else the room lights leak in and ruin everthing.

<snip>

This is interesting. Who knew there was so much to something as
(seemingly) simple as a zener diode? Not me, anyway.

Thanks for the info.


--
Afternoon, n.:
That part of the day we spend worrying about how we wasted the
morning.






--
I'm a soldier, not a diplomat. I can only tell the truth.
-- Kirk, "Errand of Mercy", stardate 3198.9

[Chiron]

On Thu, 09 Feb 2012 09:32:55 -0500, Oppie wrote:

<snip>

>

> OR you can look up "white noise schematic"

Never even thought of that; I'll do it.

>
> Pseudo Random Noise can be digitally generated with a recirculating
> shift register that has the feedback tapped at a few points and XORed as
> shown in this diagram
> http://www.discovercircuits.com/DJ-Circuits/noisegen.htm It shows 12V
> power but modern logic elements will work at lower voltages. I used a
> similar circuit for calibrating a sonar system (signal of interest
> burried in 90 db of noise).

I think I recall something similar from Don Lancaster's CMOS Cookbook...
but IIRC, the "noise" repeated. Not sure whether that would be a
problem, though...

Anyway, thanks for the ideas.


--
Some of us are becoming the men we wanted to marry.
-- Gloria Steinem

[George Herold]

On Feb 9, 9:04 pm, Chiron <chiron...@gmail.com> wrote:
> On Thu, 09 Feb 2012 17:46:23 -0800, George Herold wrote:
> > Yeah a big difference.  In low voltage Zeners the current is from
> > tunneling electrons (one at a time) and only have shot noise.  (Which is
> > pretty small).  High voltage 'Zeners' do this avalanche break down...big
> > random current pulses.
> > Lot's more noise 'amplitude'.
> > I looked at a bunch of different voltages.  (Above somethiing like 6V is
> > where you start to get some avalanching.)  10 and 12 Volt Zeners showed
> > more than shot noise, but there was a lot of part to part variation in
> > the amount of noise.  For some reason* 20V zeners all give about the
> > same signal levels... I posted a 'scope shot some time back.
> > If you use glass encapsulated diodes then wrap some black electrical
> > tape around them... else the room lights leak in and ruin everthing.
>
> <snip>
>
> This is interesting.  Who knew there was so much to something as
> (seemingly) simple as a zener diode?  Not me, anyway.

Grin... You caught me at golden moment, I'm waiting for a pcb with a
Zener noise source on it to come back from the board house.

Diodes look simple, but there is lots of nice physics to be got out of
them.
Decent thermometers for instance.

George H.

[Michael Black]

On Fri, 10 Feb 2012, Chiron wrote:

> On Thu, 09 Feb 2012 09:32:55 -0500, Oppie wrote:
>
> <snip>
>
>>
>> OR you can look up "white noise schematic"
>
> Never even thought of that; I'll do it.
>>
>> Pseudo Random Noise can be digitally generated with a recirculating
>> shift register that has the feedback tapped at a few points and XORed as
>> shown in this diagram
>> http://www.discovercircuits.com/DJ-Circuits/noisegen.htm It shows 12V
>> power but modern logic elements will work at lower voltages. I used a
>> similar circuit for calibrating a sonar system (signal of interest
>> burried in 90 db of noise).
>
> I think I recall something similar from Don Lancaster's CMOS Cookbook...
> but IIRC, the "noise" repeated. Not sure whether that would be a
> problem, though...
>

It depends on what you want, and how long the sequence is.

Sound generator ICs like the AY-5-8910 (I think I got that number right)
or those from Texas Instruments used that scheme. If the sound generator
in the Commodore 64 included a white noise source (I can't remember), then
it used that scheme.

For a while in the seventies, National Semiconductor had an IC that
generated noise using that scheme, it was sold as a "pink noise
generator", where you'd add an external filter to make the noise "pink".
Another company had a similar device.

Of course, PAIA just used a 2N2712 for the noie source in their projects.
It was never clear if they found that device was better at it, or if they
just found a cheap device.

Michael

[Chiron]

On Thu, 09 Feb 2012 22:49:29 -0500, Michael Black wrote:

<snip>

>>
> It depends on what you want, and how long the sequence is.
>
> Sound generator ICs like the AY-5-8910 (I think I got that number right)
> or those from Texas Instruments used that scheme. If the sound
> generator in the Commodore 64 included a white noise source (I can't
> remember), then it used that scheme.
>
> For a while in the seventies, National Semiconductor had an IC that
> generated noise using that scheme, it was sold as a "pink noise
> generator", where you'd add an external filter to make the noise "pink".
> Another company had a similar device.
>
> Of course, PAIA just used a 2N2712 for the noie source in their
> projects. It was never clear if they found that device was better at it,
> or if they just found a cheap device.
>
> Michael

IIRC, the C-64 did have some sort of noise function... we're going back a
ways now. That was about the last time I played around with electronics,
too. Things have changed a wee bit since then - what, 1988 or so?

I found a circuit that looks promising. I'll have to refer you to the
Website, since I don't yet know how to draw schematics using ASCII:

http://www.seekic.com/uploadfile/ic-circuit/2009624223240862.gif

This circuit uses 2 resistors, 2 capacitors, a diode and a 2N3904. I
doubt I'm going to find anything simpler, unless it's an IC like you
described.

I think my main problem was I didn't hit upon the right Google search
words, so I was chasing down all kinds of stuff that had nothing to do
with what I wanted.

Thanks, all, for your help.



--
The profession of book writing makes horse racing seem like a solid,
stable business.
-- John Steinbeck
[Horse racing *is* a stable business ...]

[stra...@yahoo.com]

On Feb 9, 6:09 am, N0S...@daqarta.com (Bob Masta) wrote:

> Download my Daqarta software... it's free for signal
> generation use.  Midway down the Generator dialog, click the
> left Waveform Controls button. Click Wave on the dialog that
> appears and select Noise: White.  Toggle the Generator
> button on in the main toolbar.  The first time the Generator
> goes on the volume control dialog will pop up, plus a
> cautionary message about loud levels.  You'll need to cancel
> the message before the sound starts.  (In WinXP you may also
> need to unMute, at the bottom of that dialog.)  Later, you
> can open the volume dialog via the F9 key at any time.

<snip>

> Bob Masta

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.

G²

[Chiron]

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.
>
> G²

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.

[stra...@yahoo.com]

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?

G²

[chiron613]

On Feb 9, 8:09 am, N0S...@daqarta.com (Bob Masta) wrote:

A whole lot that I missed...

<snip>

Bob, I apologize for not responding to your thoughtful post. I keep a
fairly stringent killfile, and one of the things I filter on is the
length of the post. Unfortunately, the filter doesn't distinguish
between someone endlessly ranting, and someone who has troubled to
write a lengthy response. I'll have to rework the filter somehow to
make sure you don't get blocked again.

Your suggestion to use only a single ear is intriguing, and something
I'd not heard about before. Had you not mentioned it, I'd have used
both earphones; but now I will follow your idea and use only one.

To be honest, I am highly doubtful of this EVP. My guess is that
people, when encountering auditory or visual "noise." tend to perceive
patterns where none exist. Of course, then you get into the question
of whether someone is hearing voices that don't exist, or whether
someone is simply deaf to those voices. An interesting philosophical

[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

[Chiron]

On Thu, 09 Feb 2012 23:58:58 -0800, stratus46 wrote:

<snip>

>
> 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?
>
> G²

Yes, of course you're right. However, there are several considerations
here. First, as I said, I had no idea Bob Masta had responded to my
post- a problem I hope to fix very soon. Second, I don't use Windows,
which is the OS he writes programs for. Third, I do this stuff for fun,
so I have not the slightest objection to reinventing the wheel or doing
things the "hard" way.

The circuit I found contains six parts. If I had the zener I could slap
it together in about ten minutes.

But mostly I just didn't see Bob's post. Even if I didn't like his idea
(and I do like it), I'd have been courteous enough to reply, had I seen
the post.

--
Start the day with a smile. After that you can be your nasty old self
again.






--
When I was 16, I thought there was no hope for my father. By the time I
was
20, he had made great improvement.

[Bob Masta]

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.

[Chiron]

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

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

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]

You can throw together something that will generate white noise in
minutes. Yes, longer if you need to put it in a box, but it's a very
simple circuit, a dioded to generate the noise, and then amplification.
It won't take "days".

On the other hand, having a little circuit can be pretty useful. If one
is using it for testing, it kind of beats trying to balance that laptop on
your knee as you kneel behind the stereo system. You can take the noise
source to the problem, rather than bringing the problem to the noise
source.

It really depends on what is needed.

But these are discussion groups, to debate what someone has said, to offer
other solutions. The discussion can go on long after various things have
been offered, it doesn't negate the validity of those solutions offered.

But lots of times, people ask questions that are too vague to get an
absolute answer, so while a computer generated white noise source is a
valid answer, it may not be what's actually needed.

Michael

[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 <chir...@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 ne...@netfront.net ---

[Jasen Betts]

On 2012-02-10, Chiron <chir...@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:

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

[George Herold]

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.

[Jamie]

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, 6:43 pm, Jamie

> 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
<chir...@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.

[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]

>  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]

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:

Has anybody tried LEDs as noise sources ?

--
Best Regards:
Baron.

[k...@att.bizzzzzzzzzzzz]

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, k...@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]

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

[George Herold]

> /Ben - SM0KBW- Hide quoted text -

>
> - Show quoted text -

Thanks Ben, I've heard that, but never tried it.

George H.

[Baron]

Phil Hobbs Inscribed thus:

Seems most of the photos are missing !

--
Best Regards:
Baron.

[Ben / SM0KBW]

I've only used that kind of noise source when i'm aligning VHF and UHF
preamps. The zener breakthrough is at around 6V for ordinary
transistors as the 2N2222. You have to test a handful to find the best
noise source ;)

/Ben - SM0KBW

[Phil Hobbs]

Right! Thanks. Fixed now.

[Baron]

Phil Hobbs Inscribed thus:

> Baron wrote:

>> > 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
>>
>> Seems most of the photos are missing !
>>
>> --
>> Best Regards:
>> Baron.
>
> Right! Thanks. Fixed now.
>
> Cheers
>
> Phil Hobbs

Looks fine now. Thanks.

--
Best Regards:
Baron.

[George Herold]

What are you going to paint it with?

I discovered over the weekend, that black electrical tape is not as
good as I thought it was. (I'll have to do some testing, when I have
time.)
I was tweaking the gain of my zener noise source and turned on the
overhead lamp to get some more light for soldering. The noise dropped
by a factor of ten or more.... and this is with black electrical tape
wrapped around the zeners! Putting my hand over the zeners to shade
them... noise went back up.

I've perhaps made an anvalanche photodiode out of my zener?

George H.
>
>    Michael

[Michael A. Terrell]

It's well known that black vinyl tape is translucent to some light.


--
You can't have a sense of humor, if you have no sense.

[Phil Hobbs]

Yup. Many black-looking things are coloured with organic dyes, which
become transparent in the near IR. Silicon doesn't really cut off till
about 1100 nm, so there's frequently a detectable leak.

Novolac epoxy (used for chip packages) is opaque at all wavelengths from
the mid-IR to soft X-rays, so it's not an issue with plastic-packaged
chips.

[Michael A. Terrell]

I saw several reels of optical sensors on Ebay this morning, but
probaly nothing of interest to you. I did win a reel of 3,000 UHF
transistors last night, though. I see the seller posted another reel:
"Reel of 3000 UHF 9GHz NPN Transistors Philips/NXP"

http://www.nxp.com/documents/data_sheet/PRF949.pdf

Now, to see what trouble I get into with them. ;-)

[JW]

On Mon, 20 Feb 2012 08:46:38 -0800 (PST) George Herold
<ghe...@teachspin.com> wrote in Message id:
<db84ada7-d3a7-4673...@l16g2000vbl.googlegroups.com>:

>On Feb 19, 12:07 am, Michael Black <et...@ncf.ca> wrote:
>> On Sat, 18 Feb 2012, k...@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.
>
>What are you going to paint it with?
>
>I discovered over the weekend, that black electrical tape is not as
>good as I thought it was. (I'll have to do some testing, when I have
>time.)

Try using some heat-shrink tubing, then pinch the ends closed while still
hot.

[Phil Hobbs]

Carbon paint is pretty good, e.g. ultraflat black Krylon. It's somewhat
electrically conductive, though, so you have to be careful with it.

[George Herold]

On Feb 20, 12:22 pm, Phil Hobbs

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

>
> - Show quoted text -

Thanks Phil, Time to order some more parts.
Say can you buy Novolac epoxy?
(for less than a bottle of good Scotch.)

I figured it might be something out past ~800nm. I've mostly looked
at how the tape blocks the Rb D line's (780 and 795 nm)

I've got a bit of time today and will do a few measurments. I've got
this old Jarrel Ash spectrometer and PAR 1205 multichannel analyzer.
(I'm not sure what the detector is...)

George H.

[George Herold]

On Feb 21, 8:11 am, JW <n...@dev.null> wrote:
> On Mon, 20 Feb 2012 08:46:38 -0800 (PST) George Herold

> <gher...@teachspin.com> wrote in Message id:
> <db84ada7-d3a7-4673-8067-71e6e02ac...@l16g2000vbl.googlegroups.com>:

> hot.- Hide quoted text -

>
> - Show quoted text -

OK I can look at that too.

George H.

[George Herold]

On Feb 21, 9:29 am, Phil Hobbs

<pcdhSpamMeSensel...@electrooptical.net> wrote:
> JW wrote:
>
> > On Mon, 20 Feb 2012 08:46:38 -0800 (PST) George Herold

> > <gher...@teachspin.com> wrote in Message id:
> > <db84ada7-d3a7-4673-8067-71e6e02ac...@l16g2000vbl.googlegroups.com>:
>

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

>
> - Show quoted text -

I use to paint Aquadag on the radiation baffles in the pumping lines
of low temperature probes.

George H.

[et...@whidbey.com]

So use black paint for white noise?
Eric

[Phil Hobbs]

> > - Show quoted text -
>
> I use to paint Aquadag on the radiation baffles in the pumping lines
> of low temperature probes.
>
> George H.

Hmm, interesting, I'd have thought you'd get a lot of outgassing even
from dried DAG, just on account of all that surface area.

And you weren't worried about flakes of DAG getting into the turbo? Or
was it diffusion-pumped?

[Phil Hobbs]

Absolutely. Use it and like it. ;)

Cheers

Phil Hobbs

[George Herold]

On Feb 21, 8:11 am, JW <n...@dev.null> wrote:

> On Mon, 20 Feb 2012 08:46:38 -0800 (PST) George Herold

> <gher...@teachspin.com> wrote in Message id:
> <db84ada7-d3a7-4673-8067-71e6e02ac...@l16g2000vbl.googlegroups.com>:
>
>
>
>
>

> hot.- Hide quoted text -
>

> - Show quoted text -

Black electrical tape.

3M Scotch Super 33+ Vinyl electrical tape made in USA (2007)

I’m also posting this on sci.optics too. (So a bit of a recap)

So I was testing a noise source made with some glass encapsulated
Zener diodes (1N5250). The Zeners are wrapped in the above electrical
tape to keep out the light. I found that light was still leaking in.
(The noise amplitude goes down dramatically when exposed to
light.)

I tried to measure the transmission of the above tape with a Si PIN
photodiode.
I first used a diode laser at 780 nm. The laser was producing a bit
more than 10mW of power (8mA of photo current) and I could see no
signal leaking through one layer of tape (PD gain = 10Meg ohm, DC
offset = 0.1 mV.. no change at 10uV level.)

I then put the same photodiode under a 60 Watt incandescent lamp.
Which when stuck right in front of the PD produced about 2.5mA of
photo-current. Again with the tape, at the highest gain setting I
could see no change at the 10uV level.

10uV/ 10 M ohm, about 1pA of current vs a few mA’s. Attenuation of at
least10^9!

I’m stuck wondering what the heck is going on?
Is the Zener also a ‘very’ sensitive photodetector?
Or does it respond to some longer wavelength photons than the Si
photodiode that is leaking through the tape?

The PD is a square about 0.25” on a side (0.0625 sq. in area).
It’s a bit hard to know the zener active area. Looking under a
microscope there’s gap about 0.01” (inches) between copper colored
electrodes. Maybe 0.06” wide, so an area of maybe 6x10^-4 sq in.

George (confused again) Herold

[George Herold]

On Feb 21, 11:39 am, Phil Hobbs

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -
>

> - Show quoted text -

No this was in the big ass pumping lines.... Mechanical pumps. going
down into a He4 pot. Some piece of low temperature lore said to use
aquadag.. and I just followed that advice, no idea how much it reduced
the heat load. If at all.

George H.

[Phil Hobbs]

That suggests that it isn't photocurrent, all right. Could it be pickup
from an electronic ballast? Does putting aluminum foil over the tape
help?

[Michael A. Terrell]

It needs a tinfoil beanie! :)

[George Herold]

On Feb 21, 7:52 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

> You can't have a sense of humor, if you have no sense.- Hide quoted text -

>
> - Show quoted text -

Oh, It's fine as is. I just find it weird, somet'ing is triggering
the zener.
I 'smells' like a photon making electron hole pairs... shallow trap
states?
I need to know more about what's inside.

George H.

[George Herold]

On Feb 21, 4:48 pm, Phil Hobbs

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

>
> - Show quoted text -

Yeah but the specturm is still pretty flat. No signs of some
frequency.
(on a Tek 'scope FFT))*
And it was the same 60 Watt incandesent that caused the "through
tape" leakeage.
Pretty much DC with some nice gentle 120 on the top.

I was also thinking about some pinhole in the tape...
but I've got two diodes, a pin hole in one, would make the amplitude
asymmetric... no signs of that.

The front panel was being 'made pretty' today. But tomorrow, I can
measure some numbers. (I should post a pic. The Audio Amp has a
gain of eleven!)

George H.
*Which is pretty good at picking out siganls at the ~1% level... If
you average and trigger near the tippy top of the noise.

[Phil Hobbs]

It's probably a pretty good thermometer.

[George Herold]

On Feb 21, 10:56 pm, Phil Hobbs

> > > hobbs at electrooptical dot nethttp://electrooptical.net-Hide quoted text -

>
> > > - Show quoted text -
>
> > Yeah but the specturm is still pretty flat.  No signs of some
> > frequency.
> > (on a Tek 'scope FFT))*
> >  And it was the same 60 Watt incandesent that caused the "through
> > tape" leakeage.
> > Pretty much DC with some nice gentle 120 on the top.
>
> > I was also thinking about some pinhole in the tape...
> > but I've got two diodes, a pin hole in one, would make the amplitude
> > asymmetric... no signs of that.
>
> > The front panel was being 'made pretty' today.  But tomorrow, I can
> > measure some numbers.       (I should post a pic.  The Audio Amp has a
> > gain of eleven!)
>
> > George H.
> > *Which is pretty good at picking out siganls at the ~1% level... If
> > you average and trigger near the tippy top of the noise.
>
> It's probably a pretty good thermometer.

Opps, "Mystery Managed". Operater error... I've got a two sets of
diode on the pcb. I had the wrong set covered with tape. The Zeners
were still 'wide open'.

Moving the tape to cover the 'noise diodes' fixes the light
sensitivity problem...
Duh!

George H.

[Phil Hobbs]

That's the sort of thing that never happens without a large and
appreciative audience. Been there.

[George Herold]

On Feb 22, 10:46 am, Phil Hobbs

> > > > > hobbs at electrooptical dot nethttp://electrooptical.net-Hidequoted text -

Grin... I had this whole list of different experiments I wanted to try
today.

Now I can do something productive.

George H.

>
> 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 nethttp://electrooptical.net- Hide quoted text -

[Chiron]

I hate when I do that... and it's not a rare occurrence.


--
Breakpoint 1, main (argc=1, argv=0xbffffc40) at main.c:29
29 printf ("Welcome to GNU Hell!\n");
-- "GNU Libtool documentation"

[Chiron]

On Wed, 22 Feb 2012 06:15:11 -0800, George Herold wrote:

> Opps, "Mystery Managed". Operater error... I've got a two sets of
> diode on the pcb. I had the wrong set covered with tape. The Zeners
> were still 'wide open'.
>
> Moving the tape to cover the 'noise diodes' fixes the light sensitivity
> problem...
> Duh!
>
> George H.

Darn... I was thinking that it might be fun to investigate stuff in the
IR range using your technique of masking the diodes with visually opaque
tape that passed IR. A whole new area to check out...

Oh, well. Better luck next time.

BTW, after all this, I opted to just use software-generated noise for my
brief experiment. I'll put together a hardware version that I'll likely
use for testing circuits (amps and such).

Thanks again for all the great ideas. You guys sure taught me a lot
about all this stuff - which I guess is the idea.



--
What sane person could live in this world and not be crazy?
-- Ursula K. LeGuin

[George Herold]

On Feb 22, 10:47 pm, Chiron <chiron...@gmail.com> wrote:
> On Wed, 22 Feb 2012 06:15:11 -0800, George Herold wrote:
> > Opps,  "Mystery Managed".  Operater error...  I've got a two sets of
> > diode on the pcb.  I had the wrong set covered with tape.  The Zeners
> > were still 'wide open'.
>
> > Moving the tape to cover the 'noise diodes' fixes the light sensitivity
> > problem...
> > Duh!
>
> > George H.
>
> Darn... I was thinking that it might be fun to investigate stuff in the
> IR range using your technique of masking the diodes with visually opaque
> tape that passed IR.  A whole new area to check out...

Yup, I had an exciting morning driving in to work thinking about
different things I might try... Then reality punches you in the
nose.

>
> Oh, well.  Better luck next time.

Well it might not be a complete waste. I 'someday' want to make a
variable noise source that shows how shot noise depends on the size of
the electron. Current noise density i sub n = sqrt(2*e*I), (amps/sqrt
Hz). Where I is the average current. So if you could turn a knob and
make electrons four times bigger, (while keeping the average current
the same.) Then the noise density would go up by a factor of 2.
In my model this is exactly what's going in in the zener. With no
light I get big pulses but not very often. With the light on you get
less noise. Because an absorbed photon makes an e-h pair and this
can cause the zener to discharge sooner than it would have without the
photon. The average current is kept roughly constant by the zener
bias resistor.

>
> BTW, after all this, I opted to just use software-generated noise for my
> brief experiment.  I'll put together a hardware version that I'll likely
> use for testing circuits (amps and such).

Digital sources are nice, because (in theory) you should know exactly
how much noise you are making.

George H.

[Chiron]

On Thu, 23 Feb 2012 07:18:34 -0800, George Herold wrote:

> Well it might not be a complete waste. I 'someday' want to make a
> variable noise source that shows how shot noise depends on the size of
> the electron. Current noise density i sub n = sqrt(2*e*I), (amps/sqrt
> Hz). Where I is the average current. So if you could turn a knob and
> make electrons four times bigger, (while keeping the average current the
> same.) Then the noise density would go up by a factor of 2. In my model
> this is exactly what's going in in the zener. With no light I get big
> pulses but not very often. With the light on you get less noise.
> Because an absorbed photon makes an e-h pair and this can cause the
> zener to discharge sooner than it would have without the photon. The
> average current is kept roughly constant by the zener bias resistor.
>

Sounds interesting... never would have thought of it.

Personally, I don't feel most of my mistakes (in electronics) are a
waste. If nothing else, I wind up learning something.

For example: I learned to make sure there's nothing between me and the
door when I power up a circuit I've built. Also, try not to be the high-
value resistor that discharges high voltage capacitors. There are
endless opportunities for learning, if you don't incinerate yourself.






--
Your good nature will bring unbounded happiness.

[George Herold]

> >                 -- Ursula K. LeGuin- Hide quoted text -

>
> - Show quoted text -

I just wanted to cross the final Zed on the 20V Zener noise source run
off the +/-15 V power rails.

I had other circuit 'stuff' leaking into the noise source. Turns out
it has about zero PSRR.
(As I should have guessed since this particular mistake has bitten me
before.)
I threw a cap multiplier at it, and that worked fine... though perhaps
overkill.
So for clean noise, well filtered power is important.

The light sensitivity of the zener was useful, I could turn on an
incandescent and kill the noise by 40dB... that made it easy to see
what was underneath.

George H.