interesting inductor

On Sun, 18 Aug 2019 07:30:36 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sat, 17 Aug 2019 21:17:26 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
j7khle9q5rsj7ld0iblliphov3o2a83pj2@4ax.com>:

On Sat, 17 Aug 2019 22:31:26 -0500, "Tim Williams"
tiwill@seventransistorlabs.com> wrote:

jlarkin@highlandsniptechnology.com> wrote in message
news:eek:ddhlehu5jglvajkkt65p5pg55k1qpkdg7@4ax.com...
Ferrites store similar energy by volume.

When gapped, yes.


Millijoules, not microjoules.

You snipped your "few microjoules" claim. We'll just forget you ever
said that.

A mu_eff about 1000 times higher than the powdered iron core is both very
likely for the choke, and fully accounts for the 1000 times lower energy
rating.

Capacitors go as epsilon E^2 / 2, but high-k dielectrics have considerably
lower Emax so store about the same energy (give or take how much you want to
saturate them in the process).

Inductors go as B^2 / (2 mu), so a mu=10k core stores fuck-all energy at
saturation.

Tim

The estimate of a few mA to saturate this core corresponds to ballpark
10 nJ storage capacity.

John,
Tim may have a good point,
long ago I dissasembled (bought a load for 1 dollar or so on ebay)
one of those coils,
http://panteltje.com/pub/mains_filter_coils_disssasembled_IMG_0149.JPG
core is very tiny.
Only one half shown here other is missing.

I guess the two small ferrite U pieces form a toroidal loop, which
would give pretty good coupling between the coils. I would prefer less
coupling in a line filter, to block both differential and common-mode
spikes.

Not much ferrite there, and lots of wire. Probably saturates easily
with DC load current.

Regarding saturation and stored energy, when I was thermal testing the
Schaffner I connected it to a bench supply, 2 volts and current
limiting at 3 amps. When I disconnected, I got a nice little spark,
from stored energy in the inductor.

I've never calibrated sparks. How many nanojoules does it take to make
a visible spark? I used to make CD ignitions for motorcycles, and I
recall that 50 mJ was a fat, noisy spark.
 
On a sunny day (Sun, 18 Aug 2019 09:31:18 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<gfuiletsr6bf1kaqih9u3pqnkheiu52rng@4ax.com>:

On Sun, 18 Aug 2019 07:30:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sat, 17 Aug 2019 21:17:26 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
j7khle9q5rsj7ld0iblliphov3o2a83pj2@4ax.com>:

On Sat, 17 Aug 2019 22:31:26 -0500, "Tim Williams"
tiwill@seventransistorlabs.com> wrote:

jlarkin@highlandsniptechnology.com> wrote in message
news:eek:ddhlehu5jglvajkkt65p5pg55k1qpkdg7@4ax.com...
Ferrites store similar energy by volume.

When gapped, yes.


Millijoules, not microjoules.

You snipped your "few microjoules" claim. We'll just forget you ever
said that.

A mu_eff about 1000 times higher than the powdered iron core is both very
likely for the choke, and fully accounts for the 1000 times lower energy
rating.

Capacitors go as epsilon E^2 / 2, but high-k dielectrics have considerably
lower Emax so store about the same energy (give or take how much you want to
saturate them in the process).

Inductors go as B^2 / (2 mu), so a mu=10k core stores fuck-all energy at
saturation.

Tim

The estimate of a few mA to saturate this core corresponds to ballpark
10 nJ storage capacity.

John,
Tim may have a good point,
long ago I dissasembled (bought a load for 1 dollar or so on ebay)
one of those coils,
http://panteltje.com/pub/mains_filter_coils_disssasembled_IMG_0149.JPG
core is very tiny.
Only one half shown here other is missing.

I guess the two small ferrite U pieces form a toroidal loop, which
would give pretty good coupling between the coils. I would prefer less
coupling in a line filter, to block both differential and common-mode
spikes.

Not much ferrite there, and lots of wire. Probably saturates easily
with DC load current.

Regarding saturation and stored energy, when I was thermal testing the
Schaffner I connected it to a bench supply, 2 volts and current
limiting at 3 amps. When I disconnected, I got a nice little spark,
from stored energy in the inductor.

I've never calibrated sparks. How many nanojoules does it take to make
a visible spark? I used to make CD ignitions for motorcycles, and I
recall that 50 mJ was a fat, noisy spark.

I have no numbers on Joules,
but been zapped plenty of times by 16 kV and 25 kV TV sets.

What makes a lot of noise is my 400 kV (bogus more like 40 kV) ebay
Tesla coil:
https://www.ebay.com/itm/141077605344
Have not found a practical use for it yet.
 
On Sunday, 18 August 2019 18:31:30 UTC+2, jla...@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 07:30:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sat, 17 Aug 2019 21:17:26 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
j7khle9q5rsj7ld0iblliphov3o2a83pj2@4ax.com>:

On Sat, 17 Aug 2019 22:31:26 -0500, "Tim Williams"
tiwill@seventransistorlabs.com> wrote:

jlarkin@highlandsniptechnology.com> wrote in message
news:eek:ddhlehu5jglvajkkt65p5pg55k1qpkdg7@4ax.com...
Ferrites store similar energy by volume.

When gapped, yes.


Millijoules, not microjoules.

You snipped your "few microjoules" claim. We'll just forget you ever
said that.

A mu_eff about 1000 times higher than the powdered iron core is both very
likely for the choke, and fully accounts for the 1000 times lower energy
rating.

Capacitors go as epsilon E^2 / 2, but high-k dielectrics have considerably
lower Emax so store about the same energy (give or take how much you want to
saturate them in the process).

Inductors go as B^2 / (2 mu), so a mu=10k core stores fuck-all energy at
saturation.

Tim

The estimate of a few mA to saturate this core corresponds to ballpark
10 nJ storage capacity.

John,
Tim may have a good point,
long ago I dissasembled (bought a load for 1 dollar or so on ebay)
one of those coils,
http://panteltje.com/pub/mains_filter_coils_disssasembled_IMG_0149.JPG
core is very tiny.
Only one half shown here other is missing.

I guess the two small ferrite U pieces form a toroidal loop, which
would give pretty good coupling between the coils. I would prefer less
coupling in a line filter, to block both differential and common-mode
spikes.

That really depends on what you are doing

For motor drives, you need as much CM inductance as possible, since the DC link cap will take the DM noise. Granted, yes, a very little DM inductance can also be beneficial, for cost optimization

For other equipment, that has no real parasitic path to the surroundings, you need all the DM inductance you can get

Cheers

Klaus
 
On Sun, 18 Aug 2019 10:26:55 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Sunday, 18 August 2019 18:31:30 UTC+2, jla...@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 07:30:36 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Sat, 17 Aug 2019 21:17:26 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
j7khle9q5rsj7ld0iblliphov3o2a83pj2@4ax.com>:

On Sat, 17 Aug 2019 22:31:26 -0500, "Tim Williams"
tiwill@seventransistorlabs.com> wrote:

jlarkin@highlandsniptechnology.com> wrote in message
news:eek:ddhlehu5jglvajkkt65p5pg55k1qpkdg7@4ax.com...
Ferrites store similar energy by volume.

When gapped, yes.


Millijoules, not microjoules.

You snipped your "few microjoules" claim. We'll just forget you ever
said that.

A mu_eff about 1000 times higher than the powdered iron core is both very
likely for the choke, and fully accounts for the 1000 times lower energy
rating.

Capacitors go as epsilon E^2 / 2, but high-k dielectrics have considerably
lower Emax so store about the same energy (give or take how much you want to
saturate them in the process).

Inductors go as B^2 / (2 mu), so a mu=10k core stores fuck-all energy at
saturation.

Tim

The estimate of a few mA to saturate this core corresponds to ballpark
10 nJ storage capacity.

John,
Tim may have a good point,
long ago I dissasembled (bought a load for 1 dollar or so on ebay)
one of those coils,
http://panteltje.com/pub/mains_filter_coils_disssasembled_IMG_0149.JPG
core is very tiny.
Only one half shown here other is missing.

I guess the two small ferrite U pieces form a toroidal loop, which
would give pretty good coupling between the coils. I would prefer less
coupling in a line filter, to block both differential and common-mode
spikes.


That really depends on what you are doing

For motor drives, you need as much CM inductance as possible, since the DC link cap will take the DM noise. Granted, yes, a very little DM inductance can also be beneficial, for cost optimization

For other equipment, that has no real parasitic path to the surroundings, you need all the DM inductance you can get

Cheers

Klaus

That Schaffner cm inductor only has about 17 uH of leakage inductance.
K > 0.999.

If it indeed saturates at a few mA of diff DC, an imperfect load, like
an imperfectly timed triac for example, will make enough DC to
saturate it.
 
On Sunday, 18 August 2019 17:53:53 UTC+1, Jan Panteltje wrote:

What makes a lot of noise is my 400 kV (bogus more like 40 kV) ebay
Tesla coil:
https://www.ebay.com/itm/141077605344
Have not found a practical use for it yet.

Violet ray. Good at killing surface bugs & for vacuum work.


NT
 
<jlarkin@highlandsniptechnology.com> wrote in message
news:gfuiletsr6bf1kaqih9u3pqnkheiu52rng@4ax.com...
Regarding saturation and stored energy, when I was thermal testing the
Schaffner I connected it to a bench supply, 2 volts and current
limiting at 3 amps. When I disconnected, I got a nice little spark,
from stored energy in the inductor.

I've never calibrated sparks. How many nanojoules does it take to make
a visible spark? I used to make CD ignitions for motorcycles, and I
recall that 50 mJ was a fat, noisy spark.

You were seeing the energy from the huge capacitors they put on the output
of the supply.

Just tried it with my supply, a single winding of a much larger CMC makes no
additional spark compared to just shorting the leads (Lstray < 0.5uH). It
also sparks on contact, not release. (The spark is rather more noticeable
as I used a rather large adjustable switching supply, totaling something
like 6mF on the output.)

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
 
On 8/17/19 12:31 PM, jlarkin@highlandsniptechnology.com wrote:
https://www.digikey.com/products/en?keywords=RN%20242-6-02-1M8

That is technically a commmon-mode choke - which makes it cheap - but
is probably useful for a real-inductor need that we have now.

It's spec'd at 1.8 mH per winding, but my AADE meter says about 2.5. I
should measure it some other ways to be sure.

(K seems to be over 0.99, so it would be a good common-mode filter but
not good for diff mode noise.)

I want an inductive DAC, namely a series of steps of inductance made
from inductors and relays. One of these could get me 2.5 uH, or 10 uH
with the windings in series. Two of the same part gives 0, 2.5, 5, 10,
and 20 mH, plus the oddball 12.5.

With 3 amps DC on both windings in series, it didn't get detectably
warm.

What I need to do, or actually delegate, is to measure L better, and
then L vs current. Need to hack up some rigs to do that.

Nice small PCB footprint. I can envision using this as a real
transformer, in power applications.

It would be cool if you could use one set of windings for the taps on
the DAC, and the other to push a DC current thru biasing them so they're
on the cusp of saturation, and use some kind of feedback to detect the
DAC linearity and feed back the right currents to each to dynamically
adjust their inductances, so you get a nice inductive DAC out of maybe
just a couple values instead of having to parallel/series together the
appropriate ones for the exact value for each tap
 
On Sun, 18 Aug 2019 15:39:45 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

jlarkin@highlandsniptechnology.com> wrote in message
news:gfuiletsr6bf1kaqih9u3pqnkheiu52rng@4ax.com...
Regarding saturation and stored energy, when I was thermal testing the
Schaffner I connected it to a bench supply, 2 volts and current
limiting at 3 amps. When I disconnected, I got a nice little spark,
from stored energy in the inductor.

I've never calibrated sparks. How many nanojoules does it take to make
a visible spark? I used to make CD ignitions for motorcycles, and I
recall that 50 mJ was a fat, noisy spark.


You were seeing the energy from the huge capacitors they put on the output
of the supply.

The spark was when I disconnected the inductor. It was clearly an
inductive kick from energy stored in the L. Disconnecting a dead short
from that 2 volt supply would not make a spark. Its output caps would
start from zero volts and begin to recharge towards 2 volts.

One term in use when an inductor is disconnected is "break flash."

Wild guess, 1 mJ would make a visible spark, but 1 uJ wouldn't.




Just tried it with my supply, a single winding of a much larger CMC makes no
additional spark compared to just shorting the leads (Lstray < 0.5uH). It
also sparks on contact, not release. (The spark is rather more noticeable
as I used a rather large adjustable switching supply, totaling something
like 6mF on the output.)

Tim
 
On 8/18/19 6:09 PM, bitrex wrote:

We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.
 
On 8/18/19 5:48 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 17:30:08 -0400, bitrex <user@example.net> wrote:

On 8/17/19 12:31 PM, jlarkin@highlandsniptechnology.com wrote:

https://www.digikey.com/products/en?keywords=RN%20242-6-02-1M8

That is technically a commmon-mode choke - which makes it cheap - but
is probably useful for a real-inductor need that we have now.

It's spec'd at 1.8 mH per winding, but my AADE meter says about 2.5. I
should measure it some other ways to be sure.

(K seems to be over 0.99, so it would be a good common-mode filter but
not good for diff mode noise.)

I want an inductive DAC, namely a series of steps of inductance made
from inductors and relays. One of these could get me 2.5 uH, or 10 uH
with the windings in series. Two of the same part gives 0, 2.5, 5, 10,
and 20 mH, plus the oddball 12.5.

With 3 amps DC on both windings in series, it didn't get detectably
warm.

What I need to do, or actually delegate, is to measure L better, and
then L vs current. Need to hack up some rigs to do that.

Nice small PCB footprint. I can envision using this as a real
transformer, in power applications.


It would be cool if you could use one set of windings for the taps on
the DAC, and the other to push a DC current thru biasing them so they're
on the cusp of saturation, and use some kind of feedback to detect the
DAC linearity and feed back the right currents to each to dynamically
adjust their inductances, so you get a nice inductive DAC out of maybe
just a couple values instead of having to parallel/series together the
appropriate ones for the exact value for each tap

This is a large-signal (very large signal!) application. Some PM
alternator regulators work by shorting the generator, which PM
alternators tolerate because they have a lot of inductance.

We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

I think I'll buy a few alternators and spin them up, just to get in
the ballpark.

I found a paper a while back that was a mathematical model of how much
current an average small car (of the time) with an I4 or something draws
at cranking, it doesn't look like this problem was even approached in
an academic way via maths/computational numerical methods until the late
1970s.

Put battery and alternator in car. If it starts reliably, great. If not
get somewhat bigger battery and alternator. Repeat until satisfied.
 
On Sun, 18 Aug 2019 17:30:08 -0400, bitrex <user@example.net> wrote:

On 8/17/19 12:31 PM, jlarkin@highlandsniptechnology.com wrote:

https://www.digikey.com/products/en?keywords=RN%20242-6-02-1M8

That is technically a commmon-mode choke - which makes it cheap - but
is probably useful for a real-inductor need that we have now.

It's spec'd at 1.8 mH per winding, but my AADE meter says about 2.5. I
should measure it some other ways to be sure.

(K seems to be over 0.99, so it would be a good common-mode filter but
not good for diff mode noise.)

I want an inductive DAC, namely a series of steps of inductance made
from inductors and relays. One of these could get me 2.5 uH, or 10 uH
with the windings in series. Two of the same part gives 0, 2.5, 5, 10,
and 20 mH, plus the oddball 12.5.

With 3 amps DC on both windings in series, it didn't get detectably
warm.

What I need to do, or actually delegate, is to measure L better, and
then L vs current. Need to hack up some rigs to do that.

Nice small PCB footprint. I can envision using this as a real
transformer, in power applications.


It would be cool if you could use one set of windings for the taps on
the DAC, and the other to push a DC current thru biasing them so they're
on the cusp of saturation, and use some kind of feedback to detect the
DAC linearity and feed back the right currents to each to dynamically
adjust their inductances, so you get a nice inductive DAC out of maybe
just a couple values instead of having to parallel/series together the
appropriate ones for the exact value for each tap

This is a large-signal (very large signal!) application. Some PM
alternator regulators work by shorting the generator, which PM
alternators tolerate because they have a lot of inductance.

We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I think I'll buy a few alternators and spin them up, just to get in
the ballpark.
 
On Sun, 18 Aug 2019 18:12:31 -0400, bitrex <user@example.net> wrote:

On 8/18/19 6:09 PM, bitrex wrote:


We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a
real inductor and trim its effective value. That works with resistors
and caps, too.
 
On 8/18/19 7:46 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 18:12:31 -0400, bitrex <user@example.net> wrote:

On 8/18/19 6:09 PM, bitrex wrote:


We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a
real inductor and trim its effective value. That works with resistors
and caps, too.

That was actually patented until 2015 lol

<https://patents.google.com/patent/US5652537A/en>
 
On Sun, 18 Aug 2019 20:02:14 -0400, bitrex <user@example.net> wrote:

On 8/18/19 7:46 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 18:12:31 -0400, bitrex <user@example.net> wrote:

On 8/18/19 6:09 PM, bitrex wrote:


We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a
real inductor and trim its effective value. That works with resistors
and caps, too.

That was actually patented until 2015 lol

https://patents.google.com/patent/US5652537A/en

It wouldn't surprise me if people were doing that in the 1930's.
 
On 8/18/19 8:27 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 20:02:14 -0400, bitrex <user@example.net> wrote:

On 8/18/19 7:46 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 18:12:31 -0400, bitrex <user@example.net> wrote:

On 8/18/19 6:09 PM, bitrex wrote:


We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a
real inductor and trim its effective value. That works with resistors
and caps, too.

That was actually patented until 2015 lol

https://patents.google.com/patent/US5652537A/en

It wouldn't surprise me if people were doing that in the 1930's.

Bootstrapping impedance or getting patents for obvious things approved?
Both, I guess.

I recall I saw a patent from olden times (when the vacuum tubes in
schematics looked like Egyptian hieroglyphics and the resistor symbols
were drawn with all right-angles) where they ran the heater current thru
a second winding on the power supply filter choke somehow to bootstrap
its effective value, that was probably worth a patent in 1932.
 
On Monday, August 19, 2019 at 8:09:51 AM UTC+10, bitrex wrote:
On 8/18/19 5:48 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 17:30:08 -0400, bitrex <user@example.net> wrote:

On 8/17/19 12:31 PM, jlarkin@highlandsniptechnology.com wrote:

<snip>

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Another approach is to generate a 90 degree phase shifted version of the current in the inductor and use a Wien bridge type feedback circuit to add that to the current coming out of the inductor (or subtract from it).

This creates an additional positive or negative synthetic inductance, and lets you tune the frequency as finely as you can tweak the gain.

I've got a bunch of simulations doing that around 17kHz (100,000 radians per second, which keeps the arithmetic simple).

I dumped it when my collaborator in the UK pointed out that hysteresis in even a heavily gapped ferrite core inductor was going to introduce harmonics 95dB below the fundamental.

<snip>

--
Bill Sloman, Sydney
 
On a sunny day (Sun, 18 Aug 2019 12:52:03 -0700 (PDT)) it happened
tabbypurr@gmail.com wrote in
<9d9073d4-1beb-40ca-b7ab-1045cad9a623@googlegroups.com>:

On Sunday, 18 August 2019 17:53:53 UTC+1, Jan Panteltje wrote:

What makes a lot of noise is my 400 kV (bogus more like 40 kV) ebay
Tesla coil:
https://www.ebay.com/itm/141077605344
Have not found a practical use for it yet.

Violet ray. Good at killing surface bugs & for vacuum work.


NT

Yes, that would work, ozone,,
I use an EPROM erase tube for that:
http://panteltje.com/pub/UV_EPROM_erase_tube_IMG_7110.JPG

I noticed somebody on TV using it to purify water,
this sort of product:
https://www.sciencedirect.com/science/article/pii/S147789391500174X
 
<jlarkin@highlandsniptechnology.com> wrote in message
news:s3rjle1kenjnjgu8vvjkc5sv05unjphkmk@4ax.com...
It wouldn't surprise me if people were doing that in the 1930's.

There's zillions of adjustment methods documented in the famous RDH4, this
probably included.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
 
On Sun, 18 Aug 2019 21:49:18 -0400, bitrex <user@example.net> wrote:

On 8/18/19 8:27 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 20:02:14 -0400, bitrex <user@example.net> wrote:

On 8/18/19 7:46 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 18 Aug 2019 18:12:31 -0400, bitrex <user@example.net> wrote:

On 8/18/19 6:09 PM, bitrex wrote:


We may get away with using a single, maybe 1 mH, inductor and doing
DSP inductor simulation behind that. There's remarkably little data
around on actual alternator impedances, or details on how the
regulators actually work.

It's annoying that there are a goodly number of papers and thesies
around about alternators, full of equations and matrices and all that
fancy math, with no actual numbers. That's typical of most scientific
papers, lots of theory but no useful numbers.

I found a use for a gyrator! I am working on a thing for a client that
has a tuned circuit in a feedback network with an inductor to ground. to
meet the requirement it has to be tuned very precisely and I could
continue grunging math but I think I'm just going to make it a two op
amp "inductance simulator", make one of the relevant resistors a pot and
say "turn this knob until it works the way you like."

Well within a couple uH should be fine.

You can also use a variable gain < 1, to bootstrap the low end of a
real inductor and trim its effective value. That works with resistors
and caps, too.

That was actually patented until 2015 lol

https://patents.google.com/patent/US5652537A/en

It wouldn't surprise me if people were doing that in the 1930's.



Bootstrapping impedance or getting patents for obvious things approved?
Both, I guess.

I recall I saw a patent from olden times (when the vacuum tubes in
schematics looked like Egyptian hieroglyphics and the resistor symbols
were drawn with all right-angles) where they ran the heater current thru
a second winding on the power supply filter choke somehow to bootstrap
its effective value, that was probably worth a patent in 1932.

Bootstrapping can also turn a resistor into an inductor or a capacitor
or a resistor bigger or smaller than its usual value.

"Dynamic" speakers had electromagnets, instead of permanant magnets,
and the field current was reused for filament power, or the field coil
was also a power supply choke.

I have a bunch of radio engineering books, starting in 1922.

Good grief, that's almost 100 years.
 
On Monday, 19 August 2019 04:38:01 UTC+1, Jan Panteltje wrote:
On a sunny day (Sun, 18 Aug 2019 12:52:03 -0700 (PDT)) it happened
tabbypurr wrote in
9d9073d4-1beb-40ca-b7ab-1045cad9a623@googlegroups.com>:
On Sunday, 18 August 2019 17:53:53 UTC+1, Jan Panteltje wrote:

What makes a lot of noise is my 400 kV (bogus more like 40 kV) ebay
Tesla coil:
https://www.ebay.com/itm/141077605344
Have not found a practical use for it yet.

Violet ray. Good at killing surface bugs & for vacuum work.


NT

Yes, that would work, ozone,,
I use an EPROM erase tube for that:
http://panteltje.com/pub/UV_EPROM_erase_tube_IMG_7110.JPG

I noticed somebody on TV using it to purify water,
this sort of product:
https://www.sciencedirect.com/science/article/pii/S147789391500174X

VRs are good for most skin issues.
Water can be sterilised just by putting it in a plastic bottle in the sun.


NT
 

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