Crystal Controlled Oscillator...

[Anthony William Sloman]

On Wednesday, January 5, 2022 at 5:15:37 PM UTC+11, Artist wrote:

The driven waveform must be sinusoidal. Purity is not critical. It can
be somewhat ragged.

A way to detect phase I am considering is to use comparators to convert
sinewave to square wave, and then detect phase difference in the similar
way the CD4046 does. The logic would have to be more complex than just
an exclusive OR gate though, because the XOR adjusts phase to 90 degrees.

As Clifford Heath has pointed out, there are a variety of ways of detecting phase.

The classical approach is to use a four quadrant multiplier to gerenate the product of the sine wave being looked at and the your reference sinewave.

Trigometry lets you see that the product waveform has a DC content the corresponds to the phase difference between the two sine waves. You do have to filter out the alternating components.

A switching detector effectively multiplies the sine wave you are looking by a square wave of the same frequency. It doesn\'t give quite the same result, but it close enough for most applications.

Turning both sine waves into square waves before you multiply them together is even cruder, but can be good enough.

> I have trouble finding a successor to the EOL XR-2206. Suggestions would be appreciated. If I do not find one I may have to try self excitation.

Since we haven\'t got a clue what kind of voltage, current and frequency you have to deal with , we can\'t really give you any useful advice.
There are a lot of sine wave oscillators around. Some of them can be tuned to run over a range of frequencies.

I have suggested using a \"modfied sine wave\" to drive your transducer - it\'s just a three level approximation to a sine wave. It\'s virtue is that it doesn\'t have any third harmonic content, but it does have the higher odd harmonics you\'d get from a square wave drive. if less of the fifth and a bit less of the seventh.

--
Bill Sloman, Sydney

 

[Phil Hobbs]

Artist wrote:

The driven waveform must be sinusoidal. Purity is not critical. It can
be somewhat ragged.

A way to detect phase I am considering is to use comparators to convert
sinewave to square wave, and then detect phase difference in the similar
way the CD4046 does. The logic would have to be more complex than just
an exclusive OR gate though, because the XOR adjusts phase to 90 degrees.

I have trouble finding a successor to the EOL XR-2206. Suggestions would
be appreciated. If I do not find one I may have to try self excitation.

A filtered square wave, or (for fun) a 74HC4017 and some weighted
resistors. We had a thread on that awhile back--2011, it was. The OP
was George Herold. (George? You still out there, man?)

<https://groups.google.com/g/sci.electronics.design/c/sZWMknd6yjw/m/8HdJPZFUriAJ>

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

 

[Jeroen Belleman]

Artist wrote:
The driven waveform must be sinusoidal. Purity is not critical. It
can be somewhat ragged.

A way to detect phase I am considering is to use comparators to
convert sinewave to square wave, and then detect phase difference
in the similar way the CD4046 does. The logic would have to be more
complex than just an exclusive OR gate though, because the XOR
adjusts phase to 90 degrees.
[...]

Why does that matter?

Jeroen Belleman

 

[Artist]

On 1/5/22 1:01 AM, Anthony William Sloman wrote:

On Wednesday, January 5, 2022 at 5:15:37 PM UTC+11, Artist wrote:
The driven waveform must be sinusoidal. Purity is not critical. It can
be somewhat ragged.

A way to detect phase I am considering is to use comparators to convert
sinewave to square wave, and then detect phase difference in the similar
way the CD4046 does. The logic would have to be more complex than just
an exclusive OR gate though, because the XOR adjusts phase to 90 degrees.

As Clifford Heath has pointed out, there are a variety of ways of detecting phase.

The classical approach is to use a four quadrant multiplier to gerenate the product of the sine wave being looked at and the your reference sinewave.

Trigometry lets you see that the product waveform has a DC content the corresponds to the phase difference between the two sine waves. You do have to filter out the alternating components.

A switching detector effectively multiplies the sine wave you are looking by a square wave of the same frequency. It doesn\'t give quite the same result, but it close enough for most applications.

Turning both sine waves into square waves before you multiply them together is even cruder, but can be good enough.

I have trouble finding a successor to the EOL XR-2206. Suggestions would be appreciated. If I do not find one I may have to try self excitation.

Since we haven\'t got a clue what kind of voltage, current and frequency you have to deal with , we can\'t really give you any useful advice.
There are a lot of sine wave oscillators around. Some of them can be tuned to run over a range of frequencies.

I have suggested using a \"modfied sine wave\" to drive your transducer - it\'s just a three level approximation to a sine wave. It\'s virtue is that it doesn\'t have any third harmonic content, but it does have the higher odd harmonics you\'d get from a square wave drive. if less of the fifth and a bit less of the seventh.

The max frequency should be no lower than 80kHz, and at least 70kHz. For
part count reasons I am hoping not to have to filter out that higher
harmonics of a square wave to get a sine wave. The VCO output will be
amplified by an OPA552, which is known by prior experience to be
sufficient to drive the piezoelectric element. Since the VCO will not
drive the piezoelectric element directly its voltage, and current,
output limits are not important.

--
To email me directly remove sj. from my email address\'s domain name.
This is a spam jammer.

 

[Artist]

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

--
To email me directly remove sj. from my email address\'s domain name.
This is a spam jammer.

 

[Jan Panteltje]

On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
<sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc

 

[Phil Hobbs]

Jan Panteltje wrote:

On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc

Won\'t work. The mechanical resonance dominates the response.

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

 

[Piglet]

On 06/01/2022 16:27, Artist wrote:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You can use the VCO in a CD4046 at (say) 8x or 16x the desired frequency
into a weighted resistor \"DAC\" using a shift register or ring counter (I
think Phil H suggested a CD4017 as one possibility).

The resulting multi-stepped near sine is very easy to filter if needed.

You could use either of the CD4046 phase comparators to servo the VCO
frequency to resonance on the piezo current vs voltage, as others
already suggested.

With each passing day your project looks to be getting easier and easier!

piglet

 

[server]

On Thu, 6 Jan 2022 12:33:48 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Jan Panteltje wrote:
On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc



Won\'t work. The mechanical resonance dominates the response.

Cheers

Phil Hobbs

Seems to me that the op should characterize the device before
speculating about things to drive it.



--

I yam what I yam - Popeye

 

[Jan Panteltje]

On a sunny day (Thu, 6 Jan 2022 12:33:48 -0500) it happened Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote in
<3dcd26aa-0a7c-269d-5597-b39ce9bc3239@electrooptical.net>:

Jan Panteltje wrote:
On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc



Won\'t work. The mechanical resonance dominates the response.

He said he uses an opamp amplifier AFTER the sine wave generator
This LC oscillator circuit has been working for 50 years or more

 

[Phil Hobbs]

Jan Panteltje wrote:

On a sunny day (Thu, 6 Jan 2022 12:33:48 -0500) it happened Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote in
3dcd26aa-0a7c-269d-5597-b39ce9bc3239@electrooptical.net>:

Jan Panteltje wrote:
On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc



Won\'t work. The mechanical resonance dominates the response.

He said he uses an opamp amplifier AFTER the sine wave generator
This LC oscillator circuit has been working for 50 years or more

Quite right--I read too fast.

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]

On a sunny day (Thu, 6 Jan 2022 14:50:25 -0500) it happened Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote in
<8af24784-0ed7-5329-b3d7-637937920e50@electrooptical.net>:

Jan Panteltje wrote:
On a sunny day (Thu, 6 Jan 2022 12:33:48 -0500) it happened Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote in
3dcd26aa-0a7c-269d-5597-b39ce9bc3239@electrooptical.net>:

Jan Panteltje wrote:
On a sunny day (Thu, 6 Jan 2022 08:27:14 -0800) it happened Artist
sepflanze@sj.gmail.com> wrote in <sr7594$ro5$1@dont-email.me>:

My last post was not clear. Apologies

The VCO I seek preferably produces a sine wave to reduce the part count
required to filter out the higher harmonics of a square wave.

The sine wave need not be clean. There can be some raggedness to it.

It must be capable of frequencies at least within the band between
70kHz, and 80kHs. That\'s 70 kHz or below on the low end., and 80kHz or
above on the high end.

Output voltage level, and current source limits, are not important
because its output will be boosted to what is needed by a following stage.

You will have to be more specific,
but a few thoughts
Those transducrs are normally capacitive, several nF, at leas the big ones I use
Big ones
http://panteltje.com/pub/40_KHz_ultrasonic_transducers_IMG_5133.JPG

But I use small ones too
http://panteltje.com/pub/44kHz_Doppler_radar_Rx_transducer_and_coil_IMG_4097.JPG

the driving method differs!

For a sine wave, drive it with an inductor (you can, once you know C_transdcer and frequency
calculate L.

opamp - L - [transducer]--- ground

Now L sets the resonance.

You will get very high voltage on the transducer for even a low drive that way,
You can reduce Q by adding a series resistor for example.
For a one stage you can take feedback from the transducer to an input
and it will self oscillate (at value set by L).
One way to go about it...

If all you want is a sinewave between 70 kHz and 80 kHz
wind a coil and use this

+12
coil |
|--- d
---------->| JFET
| | |--- s
| { === |
| ( | 1 n |--------0 approx sine out
| ( L |--------|
| ( | |
| === [ ] 470
| | 2 n |
/// /// ///


calculate L, wind it on some core.
Note the C value ratio, could be 10 nF 20 nF etc



Won\'t work. The mechanical resonance dominates the response.

He said he uses an opamp amplifier AFTER the sine wave generator
This LC oscillator circuit has been working for 50 years or more

Quite right--I read too fast.
Cheers

Phil Hobbs

Ok no problem,
As to those small 44 kHz transducers,
some here may remember the remote controls that used ultrasound (before the IR thing took over).
I took one apart and had a good look a the circuit.
It is just a tuned LC with the transducer capacitance part of the LC.
As Phil Alison already pointed out, not much resonance in those transducers, just are big capacitors.
Speakers have also resonance (usually quite low) but are driven over the full audio range or more.

So I digged in my old files
http://panteltje.com/pub/experiment_with_44kHz_doppler_from_philips_remote_control_IXIMG_0758.JPG
on the left that transducer X1 parallel to a tunable coil (measured the inductance of it windings back then)
and an other similar transducer X2 tuned with L1 as receiver into a dual gate MOSFET to make a Doppler radar.
That thing was so sensitive you could detect if you blinked an eye.
Here that original Philips coil and transducer from the remote:
http://www.panteltje.com/pub/44kHz_piezo_transmitter_from_old_acoustic_remote_IMG_4075.GIF
All about tuning out the transducer capacitance.
Cannot seem to find the circuit diagram of the original remote, but what I used as oscillator was pretty much the same parts and circuit.
It makes sense to, in stead of driving a high frequency into the transducer C, use L combined with transducer C to get electrical resonance
as power consumption counts in a TV remote.
There are many projects on the web that drive the transducer from say an opamp directly however.

 

[Jan Panteltje]

PS
did not even have to go back that far, acoustic phase wind speed meter,
note the sine wave LC oscillator:
http://panteltje.com/pub/acoustic_wind_speed_phase_only_test_circuit_diagram_IMG_4890.JPG

test setup. fan makes the wind:
http://www.panteltje.com/pub/acoustic_wind_speed_phase_only_test_setup_IMG_4887.JPG
original Philips coil used bottom right.

Was all published here I am sure

Did many experiments with those transducrs:
http://panteltje.com/pub/44kHz_radar_time_of_flight_test_in_wind_tunnel_IMG_4105.JPG
all use the same simple LC oscillator to drive the piezo at 44 kHz IIRC or there about.

 

[Clifford Heath]

On 7/1/22 7:18 pm, Jan Panteltje wrote:

As to those small 44 kHz transducers,
some here may remember the remote controls that used ultrasound (before the IR thing took over).
I took one apart and had a good look a the circuit.
It is just a tuned LC with the transducer capacitance part of the LC.
...
and an other similar transducer X2 tuned with L1 as receiver into a dual gate MOSFET to make a Doppler radar.
That thing was so sensitive you could detect if you blinked an eye.

Jan, your creativity is always a source of inspiration! I\'d never
thought to change the inductor for a different resonant frequency.


> There are many projects on the web that drive the transducer from say an opamp directly however.

For those who remember Gerry Coe at Devantech, he designed the now
ubiquitous-on-Ebay SRF04 and SRF08 ultrasound ranging devices. These
used two outputs of a MAX232 driver in push-pull to get 20V p-p drive
into these transducers from a 5V supply. His other innovation was using
an exponential RC decay as the reference level for the LM311 comparator,
which increased sensitivity with increasing range.

I had a lot of fun with a stereo version I made, two receivers 5cm each
side of one transmitter module - yielding not only range but also
angular measurement to about 4 degrees. The main issue was the threshold
detector, which could trigger +- one cycle, depending on whether the
return impulse arrived in-phase or out-of-phase with the mechanical
ring-down of the receiver. With the extra compute power that\'s now
available, it would be possible to digitise the signal to model that
ring-down, and detect the return wavefront by divergence from the model.
That wasn\'t possible using an MC68HC11 in 1995.

Clifford Heath.

 

[Artist]

Why not a circuit similar to this self excited one used for the muRata
piezoelectric microblower:

https://www.mouser.com/pdfdocs/MurataMicroblowerDriverInfo.pdf

?

The op amp I would use instead is the OPA552P. It is known this has the
bandwidth, and the output power, to do the job. I would, therefore, not
need the buffering transistors.

To determine a compensation network I recognize I will need to
characterize the piezo electric actuator either with a resistor, and a
function generator, or a network analyzer if we have one. It may be that
it won\'t need one due to there being no buffering transistors.

--
To email me directly remove sj. from my email address\'s domain name.
This is a spam jammer.

 

[Jan Panteltje]

On a sunny day (Sat, 8 Jan 2022 09:39:26 +1100) it happened Clifford Heath
<no.spam@please.net> wrote in
<16c81e1bd248678a$1$4060634$30dd3a6f@news.thecubenet.com>:

On 7/1/22 7:18 pm, Jan Panteltje wrote:
As to those small 44 kHz transducers,
some here may remember the remote controls that used ultrasound (before the IR thing took over).
I took one apart and had a good look a the circuit.
It is just a tuned LC with the transducer capacitance part of the LC.
...
and an other similar transducer X2 tuned with L1 as receiver into a dual gate MOSFET to make a Doppler radar.
That thing was so sensitive you could detect if you blinked an eye.


Jan, your creativity is always a source of inspiration! I\'d never
thought to change the inductor for a different resonant frequency.


There are many projects on the web that drive the transducer from say an opamp directly however.

For those who remember Gerry Coe at Devantech, he designed the now
ubiquitous-on-Ebay SRF04 and SRF08 ultrasound ranging devices. These
used two outputs of a MAX232 driver in push-pull to get 20V p-p drive
into these transducers from a 5V supply.

Right, that MAX232 trick is nice!
In the Philips remote the step up in that oscillator is a factor 42
(something like sqrt(8.9E-3 / 4.9E-6) from the inductance I measured of the coil.
Do not remember what batteries it had, but makes sense to get a good signal from 3 V (2 x AA) or so.

His other innovation was using
an exponential RC decay as the reference level for the LM311 comparator,
which increased sensitivity with increasing range.

I had a lot of fun with a stereo version I made, two receivers 5cm each
side of one transmitter module - yielding not only range but also
angular measurement to about 4 degrees. The main issue was the threshold
detector, which could trigger +- one cycle, depending on whether the
return impulse arrived in-phase or out-of-phase with the mechanical
ring-down of the receiver. With the extra compute power that\'s now
available, it would be possible to digitise the signal to model that
ring-down, and detect the return wavefront by divergence from the model.
That wasn\'t possible using an MC68HC11 in 1995.

Clifford Heath.

I also have some ultrasonic distance meter modules from ebay, something like this:
https://www.ebay.com/itm/322948018241
those have some special chip and a crystal.
Cheap way to get transducers

Now I just received some about 3 GHz? (still have to measure it) doppler motion detectors that work through glass etc.
from a local shop, also for about 2 Euro a piece, on ebay those are even cheaper:
https://www.ebay.com/itm/311911747154
Is using that frequency even legal here?
Plenty of stuff play with!

 

[Anthony William Sloman]

On Saturday, January 8, 2022 at 1:05:05 PM UTC+11, Artist wrote:

Why not a circuit similar to this self excited one used for the muRata
piezoelectric microblower:

https://www.mouser.com/pdfdocs/MurataMicroblowerDriverInfo.pdf

?

The op amp I would use instead is the OPA552P. It is known this has the
bandwidth, and the output power, to do the job. I would, therefore, not
need the buffering transistors.

To determine a compensation network I recognize I will need to
characterize the piezo electric actuator either with a resistor, and a
function generator, or a network analyzer if we have one. It may be that
it won\'t need one due to there being no buffering transistors.

You clearly haven\'t characterised your actuator, and whoever developed the original circuit may not have bothered to.

You need to known the impedance of your actuator as a function of frequency.. You seem to think that it is resonant somewhere around 80KHz but you have suggested that this varies from actuator to actuator.

You need to monitor the amplitude and phase of the current going into the actuator and of the voltage appearing across the actuator . It would be a good idea to keep track of the mechanical movement occurring at the same time - this is the effect you are trying to create.

You are going to need a function generator to generate the drive frequency, and at least a two-channel oscillisocope to keep track of the voltage and current.

A network analyser delivers all of this in one package (if you are lucky).

You should find that amplitude of the mechanical movement will peak at the resonant frequency - which means that it doesn\'t change at all for small excursion in frequency. You should find that the phase of the mechanical movement will change quite rapidly with frequency around the peak, and if you keep track of that you can use it to servo the drive frequency to stay at the peak. With any luck you won\'t have to - the mechanical resonance may well be stable for any given actuator, though this isn\'t guaranteed.

--
Bill Sloman, Sydney

 

[Jan Panteltje]

PS
see
https://github.com/jdesbonnet/RCWL-0516

Now I just received some about 3 GHz? (still have to measure it) doppler motion detectors that work through glass etc.
from a local shop, also for about 2 Euro a piece, on ebay those are even cheaper:
https://www.ebay.com/itm/311911747154
Is using that frequency even legal here?
Plenty of stuff play with!

 

[Jeroen Belleman]

On 2022-01-08 10:53, Jan Panteltje wrote:

PS
see
https://github.com/jdesbonnet/RCWL-0516

Now I just received some about 3 GHz? (still have to measure it) doppler motion detectors that work through glass etc.
from a local shop, also for about 2 Euro a piece, on ebay those are even cheaper:
https://www.ebay.com/itm/311911747154
Is using that frequency even legal here?
Plenty of stuff play with!

Interesting gadget. I suppose Q1 does double duty as oscillator
and mixer. The schematics are of no help to figure out how it
really works. Anyone care to comment? The secret is all in the
PCB layout around Q1, clearly.

Also, it doesn\'t look like this thing could work for years on
a little battery, like some PIR detectors do.

Jeroen Belleman

 

[Clifford Heath]

On 8/1/22 6:23 pm, Jan Panteltje wrote:

I also have some ultrasonic distance meter modules from ebay, something like this:
https://www.ebay.com/itm/322948018241
those have some special chip and a crystal.
Cheap way to get transducers

Pretty sure that\'s a version of one of Gerry\'s designs.

> Now I just received some about 3 GHz? (still have to measure it) doppler motion detectors that work through glass etc.

There\'s a bunch of new 24GHz ones too, things like this are all over
AliExpress: <https://www.aliexpress.com/item/4000057318135.html>

Clifford Heath