White Noise Source

George Herold wrote:
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
Click to expand...

It needs a tinfoil beanie! :)


--
You can't have a sense of humor, if you have no sense.
 
On Feb 21, 7:52 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
George Herold wrote:

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

   It needs a tinfoil beanie! :)

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

- Show quoted text -
Click to expand...
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.
 
On Feb 21, 4:48 pm, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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 -

- Show quoted text -
Click to expand...
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.
 
George Herold wrote:
On Feb 21, 4:48 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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 -

- 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.
Click to expand...
It's probably a pretty good thermometer.

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
 
On Feb 21, 10:56 pm, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

On Feb 21, 4:48 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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 -

- 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.
Click to expand...
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.

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 -

- Show quoted text -
Click to expand...
 
George Herold wrote:
On Feb 21, 10:56 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

On Feb 21, 4:48 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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 -

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

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
 
On Feb 22, 10:46 am, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

On Feb 21, 10:56 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

On Feb 21, 4:48 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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-Hidequoted 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.

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

- Show quoted text -
Click to expand...
 
On Wed, 22 Feb 2012 06:15:11 -0800, George Herold wrote:

On Feb 21, 10:56 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

On Feb 21, 4:48 pm, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
George Herold wrote:

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>:

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.- 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

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?

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 -

- 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.


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 -

- Show quoted text -
Click to expand...

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

George H.
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
Click to expand...
 
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.
Click to expand...

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.
 
On Feb 23, 10:18 am, George Herold <gher...@teachspin.com> wrote:
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.





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- Hide quoted text -

- Show quoted text -
Click to expand...
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.
 
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