capacitor transformer

[Jamie Morken]

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie

 

[john jardine]

"Jamie Morken" <jmorken@shaw.ca> wrote in message
news:EPnoe.1569435$Xk.504797@pd7tw3no...

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie

The Colpitts oscillator make good use of this effect. For general use
though, capacitors (unlike inductors) are pretty crap at storing energy. For
reasonable powers you either need shed sized caps or terrifying working
voltages (or both).
regards
john

 

[Mac]

On Sat, 04 Jun 2005 20:04:52 +0000, Jamie Morken wrote:

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie

I believe the energy density in a "charged up" iron core is much higher,
even on a mass basis, than the energy density in a capacitor.

I also believe it is quite common to build high-frequency (microwave)
circuits which rely on coupling through a dielectric. I'm thinking of
waveguide filters and such. I'm not sure if this is exactly what you are
talking about or not, but it is certainly similar. Of course for
waveguides, it is probably wrong-headed to think only of the E-field and
neglect the H-field.

--Mac

 

[Pooh Bear]

Jamie Morken wrote:

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

You mean one of these ? Only good up to certain powers though.

http://www.fuji-piezo.com/piezo.htm

Graham

 

[Pooh Bear]

Jamie Morken wrote:

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

Here's an interesting overview.

http://www.worldandi.com/newhome/public/2004/april/nspub1.asp

Graham

 

[Mebart]

I'm not sure I totally understand your question. But, I think you are
talking about the modern piezotransformer. It is a resonant circuit
based on inductance and capacitance, which has to be driven at or near
it's resonant frequency to get any output. It is largely capacitive
however.

It's method of transferring energy from the input to the output is
MECHANICAL in nature however, the ceramic piezo body moves as the
electrical input varies in applied voltage, which induces a change in
output of the output voltage.

It is more like an electrical to mechanical energy converter on the
input side. This mechanical energy is applied to the output side,
where it is converted back to electrical energy.

Step up voltages range from 10 to 200 and the output voltage is only
limited by the dielectric thickness that separates the transformer
elements. If the absolute maximum output voltage rating is exceeded,
the device shatters from voltage arcing. It is probably possible to
build these units to produce 200 kV (or more), but the present
manufacturers of the devices only make them in configurations that
limit the output voltage to around 6 kV p-p.

There are 2 basic types of devices, one is rectangular and is the more
common Rosen type, used in backlight inverters and personal ozone
generators (also known as piezo air purifiers). The less common round
type is easier to drive and has more output power, but is virtually
unavailable as it is being developed in labs at the moment.

If these are the devices you are looking for, there is a large
collection of piezotransformer technical materials posted on the web
(18 MB, zipped). Let me know if you want the URL.

Regards,

M





On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca>
wrote:

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie

 

[Scott Stephens]

Jamie Morken wrote:

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios?

The role of mechanical force in a magnetic transformer's core isn't
obvious, I can see where you'd have trouble imagining a metaphor.

Consider how levers and gears transforms force/displacement ratios. Now
think of a capacitor as an energy transducer. How does force act on the
plates of a capacitor? How could you put a lever between the plates of
two capacitors to make a transformer?

Teaching piezo-transformers theory before magnetic transformer theory
would lead to better appreciation of magnetic transformers as mechanical
and not merely electrical devices.

Scott

--
**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!
http://home.comcast.net/~scottxs/

POLITICS, n.
A strife of interests masquerading as a contest of principles.
The conduct of public affairs for private advantage. - Ambrose Bierce

There is no giant behind the devastation of the world—only a shriveled
creature with the wizened
face of a child who is out to blow up the kitchen because he cannot
steal his cookies and eat them, too. - Ayn Rand
**********************************

 

[Scott Stephens]

Mebart wrote:

I think you are
talking about the modern piezotransformer. It is a resonant circuit
based on inductance and capacitance, which has to be driven at or near
it's resonant frequency to get any output. It is largely capacitive
however.

Inductance doesn't have anything to do with it, unless it is the
fictional "motional inductance", a term I've read used in modeling watch
crystals, which can have thousands of "Henries". This "motional
inductance" refers momentum as if it were flux in an inductor so spice
can deal with the component.

It's method of transferring energy from the input to the output is
MECHANICAL in nature however

Don't you think magnetic transformers are MECHANICAL in nature? Go take
an iron transformer apart, delaminate then relaminate the core so you
can move the "I" section away from the "E" section. I did this with a
200W transformer. You can hardly pull it off. If you put cardboard
between, you'll notice the MECHANICAL FORCE making sawdust of it.

Electrostatic and magnetic forces themselves can be modeled as a
compactified dimension in 3-space. Charge (Coulombs) measured in meters
displacement.

It is more like an electrical to mechanical energy converter on the
input side. This mechanical energy is applied to the output side,
where it is converted back to electrical energy.

You can model a magnetic transformer similarly.

Step up voltages range from 10 to 200 and the output voltage is only
limited by the dielectric thickness that separates the transformer
elements. If the absolute maximum output voltage rating is exceeded,
the device shatters from voltage arcing. It is probably possible to
build these units to produce 200 kV (or more), but the present
manufacturers of the devices only make them in configurations that
limit the output voltage to around 6 kV p-p.

I'd like to see a 200kV transformer! I took a cheap piezo disk, etched
the electrode surface (see my web page) and found occasionally I could
get twice the voltage out I put in. If I tried putting over 50-100V
(IIRC) on the disk, around 5W, it would begin glowing blue from corona
on the surface, and eventually fracture, glowing bright blue at the
fracture sites. They can use piezo disks in ionizers too.

If these are the devices you are looking for, there is a large
collection of piezotransformer technical materials posted on the web
(18 MB, zipped). Let me know if you want the URL.

Where?

Scott

--
**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!
http://home.comcast.net/~scottxs/

POLITICS, n.
A strife of interests masquerading as a contest of principles.
The conduct of public affairs for private advantage. - Ambrose Bierce

There is no giant behind the devastation of the world—only a shriveled
creature with the wizened
face of a child who is out to blow up the kitchen because he cannot
steal his cookies and eat them, too. - Ayn Rand
**********************************

 

[Mebart]

On Sun, 05 Jun 2005 10:28:47 -0600, Scott Stephens
<scottxs@comcast.net> wrote:

Mebart wrote:

I think you are
talking about the modern piezotransformer. It is a resonant circuit
based on inductance and capacitance, which has to be driven at or near
it's resonant frequency to get any output. It is largely capacitive
however.

Inductance doesn't have anything to do with it, unless it is the
fictional "motional inductance", a term I've read used in modeling watch
crystals, which can have thousands of "Henries". This "motional
inductance" refers momentum as if it were flux in an inductor so spice
can deal with the component.

It's method of transferring energy from the input to the output is
MECHANICAL in nature however

Don't you think magnetic transformers are MECHANICAL in nature? Go take
an iron transformer apart, delaminate then relaminate the core so you
can move the "I" section away from the "E" section. I did this with a
200W transformer. You can hardly pull it off. If you put cardboard
between, you'll notice the MECHANICAL FORCE making sawdust of it.
Thanks Scott,

No, I don't normally think of a conventional copper and magnetic
transformer as functioning as the result of a mechanical movement of
the coils or the core. Perhaps this is wrong, if so, thanks for the
information.

I do imagine the coils as being fixed and the magnetic field pushing
against the core...and in doing so, transferring the electrical energy
into magnetic energy. The secondary senses the build up of magnetic
flux, and of course, it tried to neutralize the build up, so it
removes energy from the magnetic energy stored in the core.

Again, this might be wrong, or perhaps understated is a better word.

I agree 100 percent however that you could model a transformer as an
electrical to magnetic to electrical conversion...or, as an electrical
to mechanical to electrical conversion and get the same results.

You can model a magnetic transformer similarly.

Step up voltages range from 10 to 200 and the output voltage is only
limited by the dielectric thickness that separates the transformer
elements. If the absolute maximum output voltage rating is exceeded,
the device shatters from voltage arcing. It is probably possible to
build these units to produce 200 kV (or more), but the present
manufacturers of the devices only make them in configurations that
limit the output voltage to around 6 kV p-p.

I'd like to see a 200kV transformer! I took a cheap piezo disk, etched
the electrode surface (see my web page) and found occasionally I could
get twice the voltage out I put in. If I tried putting over 50-100V
(IIRC) on the disk, around 5W, it would begin glowing blue from corona
on the surface, and eventually fracture, glowing bright blue at the
fracture sites. They can use piezo disks in ionizers too.

You are either talking about extracting voltage from a piezo sensor,
or I think you aren't aware of the piezotransformer specifically.

All piezo materials output a voltage when you stress them
mechanically. The common application is quartz crystals and piezobased
sensors. Yes, you would have problems getting anywhere near the
multiple kV output from these.

However, a piezotransformer is a specialized beast, even when made in
small versions, it outputs 6 kV p-p, and if operated with a high value
resistive load, they can exhibit gains of 500 or more. In this case,
100 volts in would give 50 kV out.

The piezotransformers currently manufactured will shatter if operated
with high output voltages however as the ceramic material will break
down and arc.

If a piezo manufacturer chose to make a device that was physically
larger, it could produce higher voltages.... The possibility probably
exists to mount them in a vacuum tube enclosure to minimize the
possibility of high voltage arcing around the device and to provide a
means of extracting the high voltage output.

Take a look at the many technical papers that deal with the
piezotransformer specifically. You will see that the thickess of the
materiel and physical dimensions determine the output voltage gain.
These factors are discussed in great detail in many of the documents
in the piezotransformer data archive.

If these are the devices you are looking for, there is a large
collection of piezotransformer technical materials posted on the web
(18 MB, zipped). Let me know if you want the URL.

Where?

The archive can be found at:

http://oregonstate.edu/~kolstadj/

Click on the PiezoXfrmrs.zip link and save to disk.

I am the collector of the material contained in the archive, which all
came from www searches over the years. Some is recent and some is
older. Joel had access to the web space, and agreed to post it. There
are pictures, a couple of thesis papers, many theory of operation
papers, some practical examples of non-typical piezotransformer usage,
various sources of piezotransformer vendors and my Spice model (which
works well in Spice).

Enjoy the reading.

M

 

[Mebart]

I'd like to see a 200kV transformer! I took a cheap piezo disk, etched
the electrode surface (see my web page) and found occasionally I could
get twice the voltage out I put in. If I tried putting over 50-100V
(IIRC) on the disk, around 5W, it would begin glowing blue from corona
on the surface, and eventually fracture, glowing bright blue at the
fracture sites. They can use piezo disks in ionizers too.

Scott,

I did take a look at your website.

You used a piezo sensor to do your experimentation...........

I think you would see quite a bit of difference if you duplicated your
work with an actual piezotransformer designed and optimized to put out
higher voltages and power levels.

I agree that even piezotransformers made today won't go to mega kV
outputs, but only because no one designed a device to withstand the
higher voltages and because no one ever enclosed their high voltage
capable device in a vacuum in order to extract the highest possible
voltages without corona arcing problems.

You might want to order one to the TI evaluation modules that come
with multiple layer PZtransformers. The archive has the full technical
specs for the EVM module. You can also obtain them on ebay from
steminc, steminc uses ebay as a means to sell samples. If you want a
unit without specs, you can find them in used ccfl inverter boards or
in 'piezo air purifiers' sold on ebay.

I would comment on your driver. In a properly designed piezo
transformer, your driver would fail immediately. In real life, the
voltage on the output of cmos gate exceeds Vcc and Vdd by some number
of tenths of volts. This exceeds the capacity of the chips output as
Vcc and Vdd typically define how much voltage you can apply to the
input. For this reason, it is common practice to use a higher output
voltage transistors set...which can withstand the higher voltage
swings. Yes, you can clamp the PZtransformer to prevent the gate
inputs from being driven to far negative or positive...but, in doing
so, your efficiency go to hell. See the TI UCC3977 driver spec sheet
in the archive for better info on this.

Enjoy the reading and please let me know if you do additional work
with PZtransaformers.

M

 

[John Larkin]

On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca>
wrote:

Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie

If by 'transformer' you mean a gadget that transfers power efficiently
between source and load of different impedance, there's no direct
capacitive equivalent of a transformer.

The closest thing is a charge-pump inverter. You need at least two
capacitors: charge them in parallel and discharge them in series, and
you get the equivalent of a step-up transformer. There are lots of ICs
that do this for you. There's a newish part, TI or LTC maybe, that
adapts the number of caps dynamically to make a variable-ratio
inverter, which allows efficiency to be kept up, sort of like an
automatic transmission.

John

 

[Fred Bloggs]

John Larkin wrote:

On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca
wrote:


Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie




If by 'transformer' you mean a gadget that transfers power efficiently
between source and load of different impedance, there's no direct
capacitive equivalent of a transformer.

The closest thing is a charge-pump inverter. You need at least two
capacitors: charge them in parallel and discharge them in series, and
you get the equivalent of a step-up transformer. There are lots of ICs
that do this for you. There's a newish part, TI or LTC maybe, that
adapts the number of caps dynamically to make a variable-ratio
inverter, which allows efficiency to be kept up, sort of like an
automatic transmission.

John

There's that little thing about putting the power source in series with
the load that cause the most trouble.

 

[Jamie Morken]

John Larkin wrote:

On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca
wrote:


Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie




If by 'transformer' you mean a gadget that transfers power efficiently
between source and load of different impedance, there's no direct
capacitive equivalent of a transformer.

In the simplest case I am really just thinking of a capacitor that has 4
sheets seperated by dielectric, and the first and third sheet make one
capacitor and the second and fourth sheet make the second capacitor, and
this is all rolled up like a radial electrolytic cap, but with 4
terminals instead of 2, corresponding to two seperate capacitors that
are electrostatically coupled.

If you can run AC into the "primary", ie. charging and discharging it at
an average current of 1Amp over a 50volt range, then should you also not
be able to extract a large portion of this power from the "secondary",
if it is electrostatically coupled very well to the primary?

The Colpitts oscillator make good use of this effect. For general use
though, capacitors (unlike inductors) are pretty crap at storing
energy. For
reasonable powers you either need shed sized caps or terrifying working
voltages (or both).
regards
john

So a capacitor transformer isn't good at storing energy compared to an
iron core transformer, but it is good at moving energy, so if you keep
the primary charging and discharging quickly that may work well?

cheers,
Jamie

The closest thing is a charge-pump inverter. You need at least two
capacitors: charge them in parallel and discharge them in series, and
you get the equivalent of a step-up transformer. There are lots of ICs
that do this for you. There's a newish part, TI or LTC maybe, that
adapts the number of caps dynamically to make a variable-ratio
inverter, which allows efficiency to be kept up, sort of like an
automatic transmission.

John

 

[John Larkin]

On Sun, 05 Jun 2005 19:19:33 GMT, Jamie Morken <jmorken@shaw.ca>
wrote:

John Larkin wrote:
On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca
wrote:


Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie




If by 'transformer' you mean a gadget that transfers power efficiently
between source and load of different impedance, there's no direct
capacitive equivalent of a transformer.

In the simplest case I am really just thinking of a capacitor that has 4
sheets seperated by dielectric, and the first and third sheet make one
capacitor and the second and fourth sheet make the second capacitor, and
this is all rolled up like a radial electrolytic cap, but with 4
terminals instead of 2, corresponding to two seperate capacitors that
are electrostatically coupled.

The "electrostatic coupling" is just more capacitance. So the whole
thing, circuit-wise, reduces to an array of capacitors, which doesn't
make a very useful transformer.

If you can run AC into the "primary", ie. charging and discharging it at
an average current of 1Amp over a 50volt range, then should you also not
be able to extract a large portion of this power from the "secondary",
if it is electrostatically coupled very well to the primary?

If the circuit reduces to a big cap connecting the source to the load,
sure you can get current to flow through it. But it's not a
transformer.

John

 

[Jamie Morken]

John Larkin wrote:

On Sun, 05 Jun 2005 19:19:33 GMT, Jamie Morken <jmorken@shaw.ca
wrote:


John Larkin wrote:

On Sat, 04 Jun 2005 20:04:52 GMT, Jamie Morken <jmorken@shaw.ca
wrote:



Hi,

Is there any application for using two electrostatically coupled
capacitors to make a transformer? Would changing the ratio of plate
area and plate seperation from the primary to secondary capacitor plates
be able to control the voltage input and output ratios? This
transformer would only be able to work with AC input just like an
inductor based transformer, the main benefit I can see is that it works
electrostatically so may not need an iron core to hold the EMF, and
should be good for high frequency?

cheers,
Jamie




If by 'transformer' you mean a gadget that transfers power efficiently
between source and load of different impedance, there's no direct
capacitive equivalent of a transformer.

In the simplest case I am really just thinking of a capacitor that has 4
sheets seperated by dielectric, and the first and third sheet make one
capacitor and the second and fourth sheet make the second capacitor, and
this is all rolled up like a radial electrolytic cap, but with 4
terminals instead of 2, corresponding to two seperate capacitors that
are electrostatically coupled.



The "electrostatic coupling" is just more capacitance. So the whole
thing, circuit-wise, reduces to an array of capacitors, which doesn't
make a very useful transformer.


If you can run AC into the "primary", ie. charging and discharging it at
an average current of 1Amp over a 50volt range, then should you also not
be able to extract a large portion of this power from the "secondary",
if it is electrostatically coupled very well to the primary?


If the circuit reduces to a big cap connecting the source to the load,
sure you can get current to flow through it. But it's not a
transformer.

I forgot about AC coupling a load. (much simpler!)

cheers,
Jamie

John

 

[Mebart]

Scott,


Scott,

I've read your DIY page a couple of times now and I have to admit I
skipped over alot of 'worthless' technical material on piezo
transducers in my quest to learn more about piezotransformers. Reading
your page today, I think I might have discovered the missing
link.....so to speak.

Piezo transducers do come in BIG sizes, for instance the hull of ships
below the waterline and the nose cone of submarines are both
transmitters and receivers for sonar. A physically large piezo device
is just what we need to make a really high voltage piezotransformer
because of the physical spacing between the terminals provides a
higher breakdown voltage.

The breakdown voltage is essentially the limiting factor in the
voltage output amplitude, so a piezo material with a longer dimension
between the electrodes should enable higher output voltages.

I know some piezo sensors are large and already come with metal
electrodes bonded to the material, mounting structure and attached
leads. I'm wondering if a box stock piezo sensor can be used to make a
piezotransformer. The primary difference between a sensor and a
transformer is the presence of a part of the crystal that is polled in
a different direction. If I take a piezo sensor and remove part of the
electrode and then mount it between 2 plates on the end axis, I can
apply a dc voltage and change the polling for a portion of the
crystal.

If I can get a third electrode bonded properly to the newly polled
axis, the newly built device should exhibit the properties of a
piezotransformer, with voltage gain and a resonant frequency!

I have to admit, despite all the research I did on piezotransformers,
I never thought about making them myself from a piezo sensor.

I might just have a crack at this. I already have a significant
knowledge of lasers, which can be used to quantify the physical
movement of the piezo transformer with a varied voltage applied.

I'm psyched.

Are piezo sensors available cheaply or free?? I know piezo actuators
are horribly expensive:>:

Thanks for the nudge in this direction.

M

 

[Scott Stephens]

Mebart wrote:

No, I don't normally think of a conventional copper and magnetic
transformer as functioning as the result of a mechanical movement of
the coils or the core. Perhaps this is wrong, if so, thanks for the
information.

Its not desired the core move or vibrate, but since it isn't infinitely
stiff, the energy of the flux it is conducting must cause it to deform.
Looking at the electron spins, atomic bonding and crystal lattice, it
looks like a composite electro-mechanical system, not just a perfect
electronic component.

I agree 100 percent however that you could model a transformer as an
electrical to magnetic to electrical conversion...or, as an electrical
to mechanical to electrical conversion and get the same results.

Charge is charge. If it isn't changing relative to your reference frame,
it appears as an electric field. If its changing relative to your frame,
its appears to be a magnetic field. Or something in between.

Where?

The archive can be found at:

http://oregonstate.edu/~kolstadj/

Thanks, sounds familiar.

Scott

--
**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!
http://home.comcast.net/~scottxs/

POLITICS, n.
A strife of interests masquerading as a contest of principles.
The conduct of public affairs for private advantage. - Ambrose Bierce

There is no giant behind the devastation of the world—only a shriveled
creature with the wizened
face of a child who is out to blow up the kitchen because he cannot
steal his cookies and eat them, too. - Ayn Rand
**********************************

 

[Scott Stephens]

Mebart wrote:

A physically large piezo device
is just what we need to make a really high voltage piezotransformer
because of the physical spacing between the terminals provides a
higher breakdown voltage.

Somewhere I read about a Russian EMP HERF gun used to zap perimeter
security devices, which featured a crank that wound up a spiral spring
on a ratchet. When the trigger was pulled, the spring unwinds,
accelerating a hammer and hitting a substantial piezo-stack.

After that I surmise (the article didn't say) the pulse, probably in the
microsecond regime, either fires a spark gap or GaAs-type impulse device
to create a ~10 Ghz impulse.

Googled, but couldn't find it.

The breakdown voltage is essentially the limiting factor in the
voltage output amplitude, so a piezo material with a longer dimension
between the electrodes should enable higher output voltages.

Of course. Also consider some VanDeGraaf generators have "equipotential"
conductive wire rings going up the length of the belt tube, to equalize
and average the voltage gradient so hot zones wont form if dust begins
to accumulate. And high voltage caps, the self-healing ones, have layers
of aluminized mylar floating between sheets of dielectric. Not only do
the equalize and prevent inconsistencies/inhomogeneity of the dielectric
from forming a hot spot to break down, but even if a cosmic ray happens
to ionize a path, the aluminum vaporizes if an arc forms, reducing the
field in that spot, thus the cap is "self-healing".

So it might help to deliberately reduce the resistance of the ceramic,
if possible without ruining the crystal structure. Perhaps poly rather
than monocrystaline material?

I'm wondering if a box stock piezo sensor can be used to make a
piezotransformer. The primary difference between a sensor and a
transformer is the presence of a part of the crystal that is polled in
a different direction.

I read one article that described that. I was thinking (being ignorant
of transformer design) that you'd have a donut shaped pattern on a disk.
The large outer ring is the high-capacitance, low voltage primary, that
mechanically, vibrates with a higher mass and lower velocity than the
center. The center has low capacitance, high voltage secondary, that is
vibrating with a high velocity and lower mass.

I can
apply a dc voltage and change the polling for a portion of the
crystal.

I suppose you could bake and repoll the ceramic. Don't know if the epoxy
could stand the baking.

I have to admit, despite all the research I did on piezotransformers,
I never thought about making them myself from a piezo sensor.

I did a double-take when I measured more voltage out than I was putting
in! I worked with high-Q saw filters that had 20dB loss, and didn't
expect to see it in a cheap disk.

Are piezo sensors available cheaply or free?? I know piezo actuators
are horribly expensive:>:

I don't know what you mean by "piezo sensors", but the buzzer-disks you
can get those disks for a $1/ea at Electronics Goldmine, All
Electronics, et.

Scott

--
**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!
http://home.comcast.net/~scottxs/

POLITICS, n.
A strife of interests masquerading as a contest of principles.
The conduct of public affairs for private advantage. - Ambrose Bierce

There is no giant behind the devastation of the world—only a shriveled
creature with the wizened
face of a child who is out to blow up the kitchen because he cannot
steal his cookies and eat them, too. - Ayn Rand
**********************************

 

[Scott Stephens]

Mebart wrote:

I'd like to see a 200kV transformer! I took a cheap piezo disk, etched
the electrode surface (see my web page) and found occasionally I could
get twice the voltage out I put in. If I tried putting over 50-100V
(IIRC) on the disk, around 5W, it would begin glowing blue from corona
on the surface, and eventually fracture, glowing bright blue at the
fracture sites. They can use piezo disks in ionizers too.


I agree that even piezotransformers made today won't go to mega kV
outputs, but only because no one designed a device to withstand the
higher voltages and because no one ever enclosed their high voltage
capable device in a vacuum in order to extract the highest possible
voltages without corona arcing problems.

A tube full of transformer oil, like a car coil, would probably be the
cheapest and most effective unless its for some kind of satellite or
expensive application.

I would comment on your driver. In a properly designed piezo
transformer, your driver would fail immediately. In real life, the
voltage on the output of cmos gate exceeds Vcc and Vdd by some number
of tenths of volts.

Of course, transformers are power devices and require protected drivers.
Piezo-gyros and are low-power applications, but they, like
accelerometers, if they got a good hit, could knock a chip into latching
up without protection diodes.

Enjoy the reading and please let me know if you do additional work
with PZtransaformers.

Thanks for the info, I let you know if I do.

Scott

--
**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!
http://home.comcast.net/~scottxs/

POLITICS, n.
A strife of interests masquerading as a contest of principles.
The conduct of public affairs for private advantage. - Ambrose Bierce

There is no giant behind the devastation of the world—only a shriveled
creature with the wizened
face of a child who is out to blow up the kitchen because he cannot
steal his cookies and eat them, too. - Ayn Rand
**********************************

 

[Mebart]

Hey Scott, I'll email you so we can take this dicussion out of the
public domain.

TTFN.

M

On Mon, 06 Jun 2005 01:59:19 -0600, Scott Stephens
<scottxs@comcast.net> wrote:

Mebart wrote:

I'd like to see a 200kV transformer! I took a cheap piezo disk, etched
the electrode surface (see my web page) and found occasionally I could
get twice the voltage out I put in. If I tried putting over 50-100V
(IIRC) on the disk, around 5W, it would begin glowing blue from corona
on the surface, and eventually fracture, glowing bright blue at the
fracture sites. They can use piezo disks in ionizers too.


I agree that even piezotransformers made today won't go to mega kV
outputs, but only because no one designed a device to withstand the
higher voltages and because no one ever enclosed their high voltage
capable device in a vacuum in order to extract the highest possible
voltages without corona arcing problems.

A tube full of transformer oil, like a car coil, would probably be the
cheapest and most effective unless its for some kind of satellite or
expensive application.

I would comment on your driver. In a properly designed piezo
transformer, your driver would fail immediately. In real life, the
voltage on the output of cmos gate exceeds Vcc and Vdd by some number
of tenths of volts.

Of course, transformers are power devices and require protected drivers.
Piezo-gyros and are low-power applications, but they, like
accelerometers, if they got a good hit, could knock a chip into latching
up without protection diodes.

Enjoy the reading and please let me know if you do additional work
with PZtransaformers.

Thanks for the info, I let you know if I do.

Scott