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Phil Hobbs
Guest

Sat Feb 09, 2019 7:45 pm   



So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Jan Panteltje
Guest

Sat Feb 09, 2019 7:45 pm   



On a sunny day (Sat, 9 Feb 2019 13:28:27 -0500) it happened Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote in
<q3n64d$p25$1_at_dont-email.me>:

Quote:
So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)

Cheers

Phil Hobbs


Use your sensor or whatever it is to change the VCO input of a 4046
that runs in the audio range?
Offset voltage from sensor subtracted by opamp, some gain,
2 chips: opamp and 4046?

Or
digtal output from sensor to Linux PC running sgen,
any math you line in between.


Or
sensor voltage -> PIC ADC -> any math you like in asm -> PIC PWM -> audio amp..
or PIC PWM into small speaker:
http://panteltje.com/panteltje/pic/audio_pic/

Or
NTC in 1 MHz oscillator, beat against medium wave broadcast station Smile

Well the list of ways to do that is endless...

John Larkin
Guest

Sat Feb 09, 2019 8:45 pm   



On Sat, 9 Feb 2019 13:28:27 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.


What supports the isolated object?

I guess the oscillator could be battery powered and output its signal
magnetically or optically. Otherwise there would have to be lead wires
which would conduct heat. Or just suspend an LC tank that has a very
bad capacitor. I have some N4700s, but you can do much worse.

Hey, you're an optics guy: do something optical! Interference fringes
maybe.

Send us a link to the patent application after it's filed. Sounds
interesting.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Sat Feb 09, 2019 8:45 pm   



On 2/9/19 1:46 PM, John Larkin wrote:
Quote:
On Sat, 9 Feb 2019 13:28:27 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

What supports the isolated object?


I'm expecting it to be battery powered and just sit there on a table.
The thermal conduction isn't a serious limitation as long as there's
enough power available.

Quote:

I guess the oscillator could be battery powered and output its signal
magnetically or optically. Otherwise there would have to be lead wires
which would conduct heat. Or just suspend an LC tank that has a very
bad capacitor. I have some N4700s, but you can do much worse.


I'm thinking about just using a ceramic cell phone speaker. Doesn't
have to be too loud. Making it super temperature sensitive would be
good--like some audible shift when you pass your hand over it without
touching.

Quote:
Hey, you're an optics guy: do something optical! Interference fringes
maybe.


That's an interesting idea, but it would have to be self-contained.
Stabilized lasers, PCR reactors, sensors for road icing, and stuff like
that are among the potential applications.

Quote:

Send us a link to the patent application after it's filed. Sounds
interesting.


Yeah, it's pretty fun. I'll show you the demo sometime. (It has an
analogue square-rooter in the loop.)

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Larkin
Guest

Sat Feb 09, 2019 9:45 pm   



On Sat, 9 Feb 2019 14:26:35 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
On 2/9/19 1:46 PM, John Larkin wrote:
On Sat, 9 Feb 2019 13:28:27 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

What supports the isolated object?

I'm expecting it to be battery powered and just sit there on a table.
The thermal conduction isn't a serious limitation as long as there's
enough power available.


I guess the oscillator could be battery powered and output its signal
magnetically or optically. Otherwise there would have to be lead wires
which would conduct heat. Or just suspend an LC tank that has a very
bad capacitor. I have some N4700s, but you can do much worse.

I'm thinking about just using a ceramic cell phone speaker. Doesn't
have to be too loud. Making it super temperature sensitive would be
good--like some audible shift when you pass your hand over it without
touching.

Hey, you're an optics guy: do something optical! Interference fringes
maybe.

That's an interesting idea, but it would have to be self-contained.
Stabilized lasers, PCR reactors, sensors for road icing, and stuff like
that are among the potential applications.


Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime. (It has an
analogue square-rooter in the loop.)

Cheers

Phil Hobbs


For a demo, I was thinking about parallel mirrors at the ends of a
little tube made out of something with a terrible expansion tempco,
plastic even. Shine a laser at it and change the temp and watch the
fringes squirm. Make a movie.

https://cdn.britannica.com/s:300x300/11/147311-004-613FB85F.jpg

That might be too intellectual for some of your prospects.



I'm busy Spicing a new pin driver; that circuit is sort of my lifetime
hobby. Just when I had a wonderful circuit, two critical parts (RF PNP
and big PHEMT) went EOL.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Sat Feb 09, 2019 9:45 pm   



On 2/9/19 3:24 PM, Winfield Hill wrote:
Quote:
Phil Hobbs wrote...

Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime.
(It has an analogue square-rooter in the loop.)

I've made servos with square-root functions included.
In one case I was servoing both a supply voltage and
a PWM signal, that made the result go by the square
of the servo output, so I added a square-root. It
worked very well, over three decades of linear output
range. (I didn't try removing the square root, to
see how badly it'd do.) BTW, analog multiplier ICs,
to make the square root, are pretty scarce, and none
work at the low voltages we like to use now.


This one uses a power device, a dual BJT and a few resistors. In the
SPICE spherical-cow universe, it's +-5% of a real square root in the
region of interest.

As long as the BJTs are at reasonably similar temperatures, the errors
are mainly offsets, so the overall FB loop can compensate.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Phil Hobbs
Guest

Sat Feb 09, 2019 9:45 pm   



On 2/9/19 3:00 PM, John Larkin wrote:
Quote:
On Sat, 9 Feb 2019 14:26:35 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/9/19 1:46 PM, John Larkin wrote:
On Sat, 9 Feb 2019 13:28:27 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

What supports the isolated object?

I'm expecting it to be battery powered and just sit there on a table.
The thermal conduction isn't a serious limitation as long as there's
enough power available.


I guess the oscillator could be battery powered and output its signal
magnetically or optically. Otherwise there would have to be lead wires
which would conduct heat. Or just suspend an LC tank that has a very
bad capacitor. I have some N4700s, but you can do much worse.

I'm thinking about just using a ceramic cell phone speaker. Doesn't
have to be too loud. Making it super temperature sensitive would be
good--like some audible shift when you pass your hand over it without
touching.

Hey, you're an optics guy: do something optical! Interference fringes
maybe.

That's an interesting idea, but it would have to be self-contained.
Stabilized lasers, PCR reactors, sensors for road icing, and stuff like
that are among the potential applications.


Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime. (It has an
analogue square-rooter in the loop.)

Cheers

Phil Hobbs

For a demo, I was thinking about parallel mirrors at the ends of a
little tube made out of something with a terrible expansion tempco,
plastic even. Shine a laser at it and change the temp and watch the
fringes squirm. Make a movie.

https://cdn.britannica.com/s:300x300/11/147311-004-613FB85F.jpg

That might be too intellectual for some of your prospects.



I'm busy Spicing a new pin driver; that circuit is sort of my lifetime
hobby. Just when I had a wonderful circuit, two critical parts (RF PNP
and big PHEMT) went EOL.


Yah, I know. Broadcom and NXP have a lot to answer for.


Fortunately Mini-Circuits is trying to help, and Infineon still makes
fast PNP arrays.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Winfield Hill
Guest

Sat Feb 09, 2019 9:45 pm   



Phil Hobbs wrote...
Quote:

Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime.
(It has an analogue square-rooter in the loop.)


I've made servos with square-root functions included.
In one case I was servoing both a supply voltage and
a PWM signal, that made the result go by the square
of the servo output, so I added a square-root. It
worked very well, over three decades of linear output
range. (I didn't try removing the square root, to
see how badly it'd do.) BTW, analog multiplier ICs,
to make the square root, are pretty scarce, and none
work at the low voltages we like to use now.


--
Thanks,
- Win

Joseph Gwinn
Guest

Sat Feb 09, 2019 10:45 pm   



On Feb 9, 2019, Phil Hobbs wrote
(in article <q3n64d$p25$1_at_dont-email.me>):

Quote:
So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)


Sounds ideal for controlling the temperature of the crystal in a reference
oscillator. Such things are offered commercially, called an oven controlled
crystal oscillator (OCXO). ppb frequency stability is obtainable.

The theory of such ovens was laid out by Richard Karlquist of HP, back in the
day.

"THE THEORY OF ZERO-GRADIENT CRYSTAL OVENS", Richard Karlquist et al,
and
Cutler, Karlquist, et. al, "High Thermal Gain Oven with Reduced Probability
of Temperature Gradient Formation for the Operation of a Thermally Stable
Oscillator," U. S. Patent 5,729,181.

Joe Gwinn

George Herold
Guest

Sat Feb 09, 2019 11:45 pm   



On Saturday, February 9, 2019 at 1:28:34 PM UTC-5, Phil Hobbs wrote:
Quote:
So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)

Huh, well my first thought for thermal control was a diode laser.
As for a demo maybe an unequal arm Michelson, as the wavelength
changes you can watch the nice fringe pattern change.

Then lock your gizmo in and it stops changing...
(except for the thermal expansion of the optic table
holding the interferometer.)

George H.


Quote:
Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com


John Larkin
Guest

Sun Feb 10, 2019 12:45 am   



On Sat, 09 Feb 2019 16:27:32 -0500, Joseph Gwinn
<joegwinn_at_comcast.net> wrote:

Quote:
On Feb 9, 2019, Phil Hobbs wrote
(in article <q3n64d$p25$1_at_dont-email.me>):

So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)

Sounds ideal for controlling the temperature of the crystal in a reference
oscillator. Such things are offered commercially, called an oven controlled
crystal oscillator (OCXO). ppb frequency stability is obtainable.

The theory of such ovens was laid out by Richard Karlquist of HP, back in the
day.

"THE THEORY OF ZERO-GRADIENT CRYSTAL OVENS", Richard Karlquist et al,
and
Cutler, Karlquist, et. al, "High Thermal Gain Oven with Reduced Probability
of Temperature Gradient Formation for the Operation of a Thermally Stable
Oscillator," U. S. Patent 5,729,181.

Joe Gwinn


1998, back when HP still had something to do with electronics.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

John Larkin
Guest

Sun Feb 10, 2019 12:45 am   



On Sat, 9 Feb 2019 15:32:31 -0500, Phil Hobbs
<pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Quote:
On 2/9/19 3:00 PM, John Larkin wrote:
On Sat, 9 Feb 2019 14:26:35 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

On 2/9/19 1:46 PM, John Larkin wrote:
On Sat, 9 Feb 2019 13:28:27 -0500, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate. The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC. That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun. I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

What supports the isolated object?

I'm expecting it to be battery powered and just sit there on a table.
The thermal conduction isn't a serious limitation as long as there's
enough power available.


I guess the oscillator could be battery powered and output its signal
magnetically or optically. Otherwise there would have to be lead wires
which would conduct heat. Or just suspend an LC tank that has a very
bad capacitor. I have some N4700s, but you can do much worse.

I'm thinking about just using a ceramic cell phone speaker. Doesn't
have to be too loud. Making it super temperature sensitive would be
good--like some audible shift when you pass your hand over it without
touching.

Hey, you're an optics guy: do something optical! Interference fringes
maybe.

That's an interesting idea, but it would have to be self-contained.
Stabilized lasers, PCR reactors, sensors for road icing, and stuff like
that are among the potential applications.


Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime. (It has an
analogue square-rooter in the loop.)

Cheers

Phil Hobbs

For a demo, I was thinking about parallel mirrors at the ends of a
little tube made out of something with a terrible expansion tempco,
plastic even. Shine a laser at it and change the temp and watch the
fringes squirm. Make a movie.

https://cdn.britannica.com/s:300x300/11/147311-004-613FB85F.jpg

That might be too intellectual for some of your prospects.



I'm busy Spicing a new pin driver; that circuit is sort of my lifetime
hobby. Just when I had a wonderful circuit, two critical parts (RF PNP
and big PHEMT) went EOL.


Yah, I know. Broadcom and NXP have a lot to answer for.

Fortunately Mini-Circuits is trying to help, and Infineon still makes
fast PNP arrays.

Cheers

Phil Hobbs


I've moved on with my life, to GaN and SiC. I wonder how long they
will last.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics


Guest

Sun Feb 10, 2019 3:45 am   



On Sunday, February 10, 2019 at 7:24:34 AM UTC+11, Winfield Hill wrote:
Quote:
Phil Hobbs wrote...

Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime.
(It has an analogue square-rooter in the loop.)

I've made servos with square-root functions included.
In one case I was servoing both a supply voltage and
a PWM signal, that made the result go by the square
of the servo output, so I added a square-root. It
worked very well, over three decades of linear output
range. (I didn't try removing the square root, to
see how badly it'd do.) BTW, analog multiplier ICs,
to make the square root, are pretty scarce, and none
work at the low voltages we like to use now.


The Thaler THAT 2181 is a possible alternative to the Analog Devices AD734, and could be used at lower supply voltages - down to +/-4V

http://www.thatcorp.com/datashts/THAT_2181-Series_Datasheet.pdf

It's not touted as a multiplier but does seem to depend on a Gilbert cell.

--
Bill Sloman

bitrex
Guest

Sun Feb 10, 2019 6:45 am   



On 02/09/2019 09:31 PM, bill.sloman_at_ieee.org wrote:
Quote:
On Sunday, February 10, 2019 at 7:24:34 AM UTC+11, Winfield Hill wrote:
Phil Hobbs wrote...

Send us a link to the patent application after it's filed. Sounds
interesting.

Yeah, it's pretty fun. I'll show you the demo sometime.
(It has an analogue square-rooter in the loop.)

I've made servos with square-root functions included.
In one case I was servoing both a supply voltage and
a PWM signal, that made the result go by the square
of the servo output, so I added a square-root. It
worked very well, over three decades of linear output
range. (I didn't try removing the square root, to
see how badly it'd do.) BTW, analog multiplier ICs,
to make the square root, are pretty scarce, and none
work at the low voltages we like to use now.

The Thaler THAT 2181 is a possible alternative to the Analog Devices AD734, and could be used at lower supply voltages - down to +/-4V

http://www.thatcorp.com/datashts/THAT_2181-Series_Datasheet.pdf

It's not touted as a multiplier but does seem to depend on a Gilbert cell.


There's a second source for them now via "CoolAudio" electronics in
China, $3 each in small quantity:

<http://smallbear-electronics.mybigcommerce.com/ic-v2181l/>

bitrex
Guest

Sun Feb 10, 2019 6:45 am   



On 02/09/2019 01:28 PM, Phil Hobbs wrote:
Quote:
So.

I have this effectively-infinitely-fast temperature control gizmo that
I've been dying to make a good demo for. The gizmo produces a volume
which is essentially immune to external thermal forcing, and that's what
I want to demonstrate.  The idea would be to show what temperature does
to some unprotected thing, then turn on the controller which will make
it completely immune.

I'm thinking of building a sort of thermal Theremin with a crystal
oscillator beating with an LC.  That ought to give a nice audible
woo-woo sound when I heat it with a hair dryer or a small heat gun.   I
might try dividing the XO down to 10 kHz or so and using a sample-hold
to do the downconversion, so that the signal would never leave the audio
range.

That will sound interesting, but might not be the most compelling demo.

Any alternatives?

(Sorry for the teaser--I'll happily say more about it when the patent
has been filed.)

Cheers

Phil Hobbs


Yeah needs to be more dramatic.

Put some kind of thermally-activated triggering device in the volume
that fires a huge volume of pink glitter and fart-scent spray around the
conference room if it hits a certain temperature and put the whole
apparatus on a hot plate with a dramatic RED 7-segment display like the
show "24" showing the temperature rising to the critical temperature.

The attendees have to agree to sign off on a purchase order if their
activating your device saves the day/their suits. Tell them it's a
really nasty-smelling fart-spray, too, the worst there is. Lock the doors.

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