W
Winfield Hill
Guest
I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?
--
Thanks,
- Win
drive. Anybody want to say anything about it?
--
Thanks,
- Win
W
Winfield Hill
Guest
Martin Riddle wrote...
Sorry, gang!
I should have said, piezo actuator.
OK, now you can carry on.
--
Thanks,
- Win
Sorry, gang!
I should have said, piezo actuator.
OK, now you can carry on.
--
Thanks,
- Win
M
Martin Riddle
Guest
On Sun, 14 Jul 2019 18:13:49 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:
The piezo is capacitive. I'm assuming Win is treating it like a Mosfet
gate (Qg), and designing the driver so that the piezo mechanically
oscillates in as little time as the driver can handle.
Cheers
<pNaOnStPeAlMtje@yahoo.com> wrote:
The piezo is capacitive. I'm assuming Win is treating it like a Mosfet
gate (Qg), and designing the driver so that the piezo mechanically
oscillates in as little time as the driver can handle.
Cheers
P
Phil Hobbs
Guest
On 7/14/19 1:37 PM, Winfield Hill wrote:
Turns out that the hysteresis is mainly in the capacitance and not in
the piezoelectric effect. Using charge control lets you take advantage
of the much higher piezoelectric sensitivity of 5H.
Another useful trick is that you can get the piezo to respond faster
than its lowest longitudinal resonance by launching pulses down the
stack--you get a wave of compression going down the stack, and the
launch end moves almost instantly by comparison. Not too much range,
but it makes a coarse-fine strategy possible.
A third thing is the utility of notch filters in PZT control loops. You
can get a 10x improvement in the loop bandwidth that way, by notching
out the huge resonant peak.
I did that on my atomic & magnetic force microscopes in 1988-9. Sped
the instrument up by a lot. The cantilever tip was driven by a PZT
bimorph, which had a first bending mode with a Q of about 30 at ~200 kHz
iirc. To avoid oscillation without a notch, you have to roll off the
loop gain by 30 dB at that frequency, making the loop schloooowww.
Notching it out let me run the loop up to about f_bend/3 with good
performance.
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
It's super helpful with high-hysteresis piezo materials, e.g. PZT-5H.
Turns out that the hysteresis is mainly in the capacitance and not in
the piezoelectric effect. Using charge control lets you take advantage
of the much higher piezoelectric sensitivity of 5H.
Another useful trick is that you can get the piezo to respond faster
than its lowest longitudinal resonance by launching pulses down the
stack--you get a wave of compression going down the stack, and the
launch end moves almost instantly by comparison. Not too much range,
but it makes a coarse-fine strategy possible.
A third thing is the utility of notch filters in PZT control loops. You
can get a 10x improvement in the loop bandwidth that way, by notching
out the huge resonant peak.
I did that on my atomic & magnetic force microscopes in 1988-9. Sped
the instrument up by a lot. The cantilever tip was driven by a PZT
bimorph, which had a first bending mode with a Q of about 30 at ~200 kHz
iirc. To avoid oscillation without a notch, you have to roll off the
loop gain by 30 dB at that frequency, making the loop schloooowww.
Notching it out let me run the loop up to about f_bend/3 with good
performance.
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
K
Klaus Kragelund
Guest
Class E efficiency and simplicity vs Class D?
J
Jan Panteltje
Guest
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
<winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:
What is a 'charge based' piezo drive?
I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.
<winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:
What is a 'charge based' piezo drive?
I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.
C
Chris
Guest
On Sun, 14 Jul 2019 10:37:47 -0700, Winfield Hill wrote:
Is that some sort of threat?
Is that some sort of threat?
J
Jamie M
Guest
On 2019-07-14 10:37 a.m., Winfield Hill wrote:
Hi,
Can you put in some type of feedback, ie measurement
of capacitance to correlate to the strain and position?
I don't know if any other piezo drives have direct
feedback built in, but it may give more accurate
positioning compared to other ways of measuring the
extremely small position changes.
cheers,
Jamie
Hi,
Can you put in some type of feedback, ie measurement
of capacitance to correlate to the strain and position?
I don't know if any other piezo drives have direct
feedback built in, but it may give more accurate
positioning compared to other ways of measuring the
extremely small position changes.
cheers,
Jamie
M
Martin Riddle
Guest
On 14 Jul 2019 11:41:27 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:
Do you have a section on Piezo Transformers?
Cheers
wrote:
Do you have a section on Piezo Transformers?
Cheers
S
Sjouke Burry
Guest
On 14.07.19 19:37, Winfield Hill wrote:
Survived very much longer then estimated before launch.
The first lab car on mars had 4 piezo drives in its wheels.
Survived very much longer then estimated before launch.
W
Winfield Hill
Guest
Martin Riddle wrote...
Good idea. Sorry, no.
--
Thanks,
- Win
Good idea. Sorry, no.
--
Thanks,
- Win
A
amdx
Guest
On 7/14/2019 1:13 PM, Jan Panteltje wrote:
When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek
When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek
C
Clifford Heath
Guest
On 15/7/19 3:37 am, Winfield Hill wrote:
It's hard to say anything about that section before you show it to us
all flippancy aside...
I had an issue using piezo wafers as a sensor, because rectification in
the sensor pulse stretcher caused strange charge accumulation effects.
That would not have occurred if I knew I should be treating them as a
charge source (rather than current or voltage source). I think that
might be a relevant comment to make.
Clifford Heath.
It's hard to say anything about that section before you show it to us
all flippancy aside...
I had an issue using piezo wafers as a sensor, because rectification in
the sensor pulse stretcher caused strange charge accumulation effects.
That would not have occurred if I knew I should be treating them as a
charge source (rather than current or voltage source). I think that
might be a relevant comment to make.
Clifford Heath.
J
Jamie M
Guest
On 2019-07-14 12:15 p.m., Jamie M wrote:
Well I was curious (having used voltage drive piezo nano-positioning
stages in the past and noticing position drift) so I guess you are
doing this:
https://journals.sagepub.com/doi/abs/10.1177/1045389X17733330
"These actuators are normally driven by voltage amplifiers; however, the
relationship of the applied voltage on the actuator and its position is
nonlinear and complex due to phenomena such as hysteresis. This
adversely influences actuatorâs position control which is the core
component of nanopositioning. However, the electrical charge applied on
a piezoelectric actuator has a significantly less complex relationship
with its position."
cheers,
Jamie
Well I was curious (having used voltage drive piezo nano-positioning
stages in the past and noticing position drift) so I guess you are
doing this:
https://journals.sagepub.com/doi/abs/10.1177/1045389X17733330
"These actuators are normally driven by voltage amplifiers; however, the
relationship of the applied voltage on the actuator and its position is
nonlinear and complex due to phenomena such as hysteresis. This
adversely influences actuatorâs position control which is the core
component of nanopositioning. However, the electrical charge applied on
a piezoelectric actuator has a significantly less complex relationship
with its position."
cheers,
Jamie
J
Jan Panteltje
Guest
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
<nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:
I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.
I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.
What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
<nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:
I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.
I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.
What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
J
Jamie M
Guest
On 2019-07-14 10:37 a.m., Winfield Hill wrote:
Hi,
I just realized "section" is referring to AOE.
That makes more sense than requesting guesses on a
section of a circuit board you designed which is
what I assumed you meant!!
cheers,
Jamie
Hi,
I just realized "section" is referring to AOE.
That makes more sense than requesting guesses on a
section of a circuit board you designed which is
what I assumed you meant!!
cheers,
Jamie
G
George Herold
Guest
On Sunday, July 14, 2019 at 2:20:35 PM UTC-4, Phil Hobbs wrote:
Way back when... (Tim Wescott was still posting here.) I tried putting a
notch in a piezo control loop, (I think on your advice) And didn't have
much luck making it work. How deep a notch do you need?
george H.
Way back when... (Tim Wescott was still posting here.) I tried putting a
notch in a piezo control loop, (I think on your advice) And didn't have
much luck making it work. How deep a notch do you need?
george H.
A
amdx
Guest
On 7/15/2019 1:17 AM, Jan Panteltje wrote:
I don't recall why, but we ran our transducers at anti-resonance, as I
said my boss was in acoustics from the start, did navy soar, several
ultrasonic companies, one time said he took a job just to find out if
the people in the company knew what he knew. He even specified how to
pole his ceramics. (all above me). It seems driving at anti-resonance
might have been something about the beam shape, but I could be wrong, he
held some things secret.
After tuning out the capacitance we were left with about 20 ohms of
resistance to drive. He built the transducers, had a hot plate and
pneumatic press to apply pressure while the epoxy cured under heat. I
recall he used a sheet conductive epoxy 0.004" thick, but always said
the gauze in the sheet reduced the efficiency of his transducers.
We sorted the ceramics to find what he expected to be the best, had a
lot of duds, then when he built the transducer we tested it's
efficiency. If it was not over 80%, he would build another. Don't
remember his cutoff, just know it was over 80%.
I don't recall if you are in the states, if you are, and want to
experiment with a high frequency ceramic I could send you a couple.
My email is good.
You would need to bond it to an aluminum plate, and build the amp to
drive it. I think I have some ceramics to build 660kHz and some 440kHz
transducers. I don't know the numbers, but it has to do with the speed
of sound in the aluminum and the thickness of it and the ceramic and 1/2
waves. I do recall the ceramics we built 660kHz transducers with had a
resonance at about 1.2MHz and after bonding to 1/16" aluminum it dropped
to 660kHz. I don't recall the aluminum thickness for the 440kHz
transducer faceplate.
When the boss quit, he left everything in the building, I knew the
landlord and bought a lot of it cheap just because he was throwing it
out. I wish I gotten there sooner, I missed some stuff I wanted.
I tried to get the boss to write a book before he died, he didn't and
he did pass.
Let me know if you want ceramics.
Mikek
BTW, here's a link to some pictures of how we cooled the transducer
while allowing the solution to avoid contamination from the aluminum
faceplate. Transducer housing is 4" in diameter.
I don't recall why, but we ran our transducers at anti-resonance, as I
said my boss was in acoustics from the start, did navy soar, several
ultrasonic companies, one time said he took a job just to find out if
the people in the company knew what he knew. He even specified how to
pole his ceramics. (all above me). It seems driving at anti-resonance
might have been something about the beam shape, but I could be wrong, he
held some things secret.
After tuning out the capacitance we were left with about 20 ohms of
resistance to drive. He built the transducers, had a hot plate and
pneumatic press to apply pressure while the epoxy cured under heat. I
recall he used a sheet conductive epoxy 0.004" thick, but always said
the gauze in the sheet reduced the efficiency of his transducers.
We sorted the ceramics to find what he expected to be the best, had a
lot of duds, then when he built the transducer we tested it's
efficiency. If it was not over 80%, he would build another. Don't
remember his cutoff, just know it was over 80%.
I don't recall if you are in the states, if you are, and want to
experiment with a high frequency ceramic I could send you a couple.
My email is good.
You would need to bond it to an aluminum plate, and build the amp to
drive it. I think I have some ceramics to build 660kHz and some 440kHz
transducers. I don't know the numbers, but it has to do with the speed
of sound in the aluminum and the thickness of it and the ceramic and 1/2
waves. I do recall the ceramics we built 660kHz transducers with had a
resonance at about 1.2MHz and after bonding to 1/16" aluminum it dropped
to 660kHz. I don't recall the aluminum thickness for the 440kHz
transducer faceplate.
When the boss quit, he left everything in the building, I knew the
landlord and bought a lot of it cheap just because he was throwing it
out. I wish I gotten there sooner, I missed some stuff I wanted.
I tried to get the boss to write a book before he died, he didn't and
he did pass.
Let me know if you want ceramics.
Mikek
BTW, here's a link to some pictures of how we cooled the transducer
while allowing the solution to avoid contamination from the aluminum
faceplate. Transducer housing is 4" in diameter.
P
Phil Hobbs
Guest
On 7/14/19 2:32 PM, Martin Riddle wrote:
You sense the integrated charge and feed back on that. Conceptually
like running the piezo with a very small capacitor in series, and
jacking up the drive voltage.
Of course you have to get the DC from someplace, but that can be a
capacitive gauge or something like that--much slower than the piezo.
The reason that charge control is a good idea is that it reduces the
nonlinearity and hysteresis of the piezo actuator, so you can get better
control over a wider displacement range.
One way of looking at it is that the capacitance goes down as the piezo
material starts to saturate, so an increment of charge dq produces a
larger voltage change dV, helping compensate the nonlinearity.
There's an analogous process that reduces hysteresis, but I'm less clear
on how that works.
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
You sense the integrated charge and feed back on that. Conceptually
like running the piezo with a very small capacitor in series, and
jacking up the drive voltage.
Of course you have to get the DC from someplace, but that can be a
capacitive gauge or something like that--much slower than the piezo.
The reason that charge control is a good idea is that it reduces the
nonlinearity and hysteresis of the piezo actuator, so you can get better
control over a wider displacement range.
One way of looking at it is that the capacitance goes down as the piezo
material starts to saturate, so an increment of charge dq produces a
larger voltage change dV, helping compensate the nonlinearity.
There's an analogous process that reduces hysteresis, but I'm less clear
on how that works.
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
P
Phil Hobbs
Guest
On 7/15/19 10:47 AM, pcdhobbs@gmail.com wrote:
Should have said 1/(several times Q).
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
Should have said 1/(several times Q).
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