Driver to drive?

[Uncle Monster]

On Monday, February 19, 2018 at 9:56:57 AM UTC-6, John Larkin wrote:

There have been articles lately about the new Apple Spaceship campus,
about people walking into the glass walls and doors.

We had a grubby bathroom refurbed at the cabin. The bathroom is small
and the new shower doors are clear glass, right next to the toilet.
First time I peeded in the middle of the night, I whacked my head on
the glass. It is very dark up here at night.

https://www.dropbox.com/s/k35nbdquxrywse6/P2190701.JPG?raw=1

There is a light/vent thing in the shower, so I was thinking it would
be cool if the light were on dim all the time.

https://www.dropbox.com/s/po8e9iku1a2zxt0/P2190702.JPG?raw=1

So I need an LED spotlight that runs at low current; most do. Maybe
the one already there would.

So I need to put an impedance across the switch for this light. It
could be a resistor, a cap, or a series RC. But it has to be small to
jam inside the switch box, and it can't get very hot.

A resistor could conduct 10 mA and dissipate a watt, which might work.
Or I could use one of those high-voltage XY-type film caps. If the cap
ever shorted, it wouldn't be a big deal... the light would just go on.

ps- It's 10F up here in Sunny California.
--
John Larkin Highland Technology, Inc trk

Have you thought of putting decals on the glass such as those put on windows to keep birds from flying into them? Some hawk decals would look pretty cool on the glass shower doors. ^_^

[8~{} Uncle Mensa Monster

 

On Wednesday, February 21, 2018 at 2:43:12 PM UTC+11, k...@notreal.com wrote:

On Tue, 20 Feb 2018 22:38:29 -0500, bitrex
bitrex@de.lete.earthlink.net> wrote:

On 02/20/2018 10:19 PM, krw@notreal.com wrote:
On Tue, 20 Feb 2018 21:40:31 -0500, bitrex
bitrex@de.lete.earthlink.net> wrote:

On 02/20/2018 08:43 PM, Paul Hovnanian P.E. wrote:
Jim Thompson wrote:

https://www.nbcbayarea.com/news/local/Diseased-Streets-472430013.html

If they are smart, they won't wake up the hobos before running the steam
cleaner down the sidewalk.


The news story claims "Over 100!" discarded IV needles found in the
areas they surveyed but you can easily click through all the "red"
streets in the map and see that the tally tops out at barely 50. And
there are big clumps of 7 or 10 needles in some locations.

Whew! That's *SO* much better. Nice place to live, then.

Doesn't seem that much better or worse than most cities of several
million people. They found some trash on the street O M G

Yeah, HIV is nothing more than a common cold, too.

I wonder how krw thought that he'd found that implication in what has been posted. He's certainly not going to tell us.

Pay one or two bums a couple bucks to dump their spent needles in a
couple locations and hey presto you've got yourself a story. Extremely
photogenic bags of needles spilled out and lying all over the place in
the middle of the street waiting for a journalist to happen by are
extremely _suspect_ they do that with gas masks at Pripyat near
Chernobyl for the tourists

Why bother paying them when they do it for you? Every day.


"Just Say No" was a fine anti-drug policy in the sense that it wasn't at
all incorrect, even when primarily directed at the crack epidemic among
the black population at the time, but with the opioid epidemic it seems
white Americans have trouble taking their own advice

Sure, change the subject when you're losing.

Krw thinks that anybody who argues with him is losing - whereas nobody bothers arguing with him at all and he just posts his posturings as if they were arguments. It isn't as if he can post an actual response to anything anybody else says. His brain doesn't seem to have absorbed any new information for some decades now, or if it has his output doesn't suggest that he has processed any of it.

--
Bill Sloman, Sydney

 

[Robert Baer]

krw@notreal.com wrote:

On Mon, 19 Feb 2018 22:22:43 -0800, Robert Baer
robertbaer@localnet.com> wrote:

Piotr Wyderski wrote:
Hello,

I need a moderate amount of non-volatile memory (for FPGA
configuration purposes and the like), but can't tolerate
configuration errors due to charge leaks, cosmic radiation
or just the malfunction of the chip. I thought that something
like RAID5 imposed on memory chips/SD cards would be fine.
It would be extremely simple in an FPGA, but it creates
a chicken and egg problem: how can you read the controller's
configuration from flash if the flash itself might be corrupt.

It could also be done easily in hardware, but would require
parallel-output chips, which are not particularly trendy nowadays
and the SPI decoding circuitry would be insanely complex with
simple gates.

I presume I am not the first person to have such a need, so
what would you recommend me? It has to be autonomous only
for (early) reads, the write mode part can materialize later
within the FPGA. Any ideas?

Best regards, Piotr

Punched paper tape or cards?

I'll take plastic.

MMMmmm with embedded chip..

 

[Steve Wilson]

John Larkin <jjlarkin@highlandtechnology.com> wrote:

On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <no@spam.com> wrote:
Amps are amps. The load step demonstrates the ringing, and the fix for
the ringing.

Your simulation shows considerably different ringing between current
rise and fall. So the currents matter.

Sure, the output transistor emitter has a very different impedance
from 30 to 200 mA. So the pole from that impedance into the ceramic
caps is different for the two currents.

You need to model the actual currents you are using. I suspect the idle
current may be much lower, and the actual charge current may be higher.

I'd be happier to see the results with a pulsed 100ns 12 Amp load.

I did it for you. The compensation cap is critical and very different from
your result. See below.

You may need to use a switched resistive load to provide some damping.
This may have a significant effect on the ringing.

Note the load transient response in Figs 3 and 4 of the TI datasheet
show a considerably different response than your model.

They probably use caps with a lot of ESR. And the models differ too.

You need to model the ESR.

Say the caps need to hold 0.1V drop for 100ns. The required capacitance
is

i = c dv/dt
i dt = c dv
c = i * dt / dv
= 12 * 1e-7 / 0.1
= 12 uf

You can now calculate the max ESR for 0.1V drop:

R = E / I
= 0.1 / 12
= 8.33 milliohms

A bunch of parallel caps should do. But you need to specify the ESR in
your model.

Version 4
SHEET 1 1184 680
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SYMBOL LT317A 192 128 R0
SYMATTR InstName U1
SYMBOL cap 496 160 R0
SYMATTR InstName C1
SYMATTR Value 20uf
SYMBOL current 624 160 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName I1
SYMATTR Value PULSE(30m 200m 1m 1u 1u 4m)
SYMBOL cap 176 288 R0
SYMATTR InstName C2
SYMATTR Value 20n
SYMBOL res 176 352 R0
SYMATTR InstName R3
SYMATTR Value 20m
SYMBOL res 496 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 1u
TEXT 72 -16 Left 2 !.tran 10m
TEXT 80 -40 Left 2 ;'LT317A Demo With Capacitive Load

 

[Phil Allison]

tabb...@gmail.com wrote:

------------------------

I'm looking at putting together something similar to a Class AB/B audio
amp, but it will be driven outside its linear range into saturation
a lot of the time.

** So are guitar amps, some have little NFB and some have lots.

That's all well & good but for one thing: wrapping nfb round saturating
outputs doesn't work too well as it takes time for output devices to
unsaturate, and the nfb effectively overreacts, adding distortion.

** Getting the basics right - global NFB acting on its own does not pull an output stage out of saturation. Fact it does the direct opposite by fixing the closed loop gain. Long as the instantaneous input signal level, times gain, exceeds the DC supply, output devices are gonna be hammered.

Keeping distortion low matters here. What tips would you recommend to
keep unwanted distortion minimised?

** So NT wants output device saturation but don't want much waveform distortion ? While keeping all nature of his project secret?

NT can go fuck himself.



..... Phil

 

[Phil Allison]

whit3rd wrote:

-----------------

On the old florescent tubes, such as the common 4ft shop lights, the
filament only came on during starting. I thought that was also true for
CFLs, but I could be wrong.

It varied; some ballast/starter systems turned the filament
down, but not off. And CFLs usually have a bit of radioactive gas for a
starter (not much, and the half-life is a decade or so), so don't need
heater power.

** Wot bollocks.

CFLs all have heaters party covered with with a coating like that used on the cathodes of vacuum tubes. These must heat and emit electrons for the tube to start.

Magnetic ballast fluoros typically use a glow discharge starter to generate a back emf pulse from the ballast coil to "kick start" the discharge in the mercury vapour. They also have filaments with cathode type coatings.



..... Phil

 

[Jasen Betts]

On 2018-02-21, bitrex <bitrex@de.lete.earthlink.net> wrote:

That's called "waterfall design" and has been passe in the software
world for I'd guess 30 years or so. It's brittle, inflexible, too
"top-down", there is no one "architect" or small group of architects who
have a complete God's-eye picture of every single "state" or function or
branch of code in a 100 million-line codebase.

So far as I can tell they have calling something "waterfall",
re-lableling the same beans, stirring the pot and calling something
else that's essentially the same with the latest buzzword for over
30 years.

Processor design is a different animal it takes years and years to bring
a new architecture from concept to finalized design, the software world
is working under much tighter deadlines and customers _expect_ major
changes to be possible for most of the development cycle.

The customers don't know what is a major change and what isn't.

--
This email has not been checked by half-arsed antivirus software

 

[John Larkin]

On Wed, 21 Feb 2018 04:51:28 GMT, Steve Wilson <no@spam.com> wrote:

John Larkin <jjlarkin@highlandtechnology.com> wrote:

On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <no@spam.com> wrote:
Amps are amps. The load step demonstrates the ringing, and the fix for
the ringing.

Your simulation shows considerably different ringing between current
rise and fall. So the currents matter.

Sure, the output transistor emitter has a very different impedance
from 30 to 200 mA. So the pole from that impedance into the ceramic
caps is different for the two currents.

You need to model the actual currents you are using. I suspect the idle
current may be much lower, and the actual charge current may be higher.

I'd be happier to see the results with a pulsed 100ns 12 Amp load.

I did it for you. The compensation cap is critical and very different from
your result. See below.

That seems to be my sim; same currents, no ESR in the output cap, just
not as pretty. Any engineering doc should have a title, author, and
date.

I tried adding 20 mohms ESR to the output caps in my sim. Nothing
changed; it rings badly without the added compensation, and doesn't
ring with the RC, or just the C, from ADJ to ground.

Pulsing at 10 amps for 100 ns, the results are about the same: lots of
ringing, fixed by adding the same comps.

The compensation parts help.

You may need to use a switched resistive load to provide some damping.
This may have a significant effect on the ringing.

Note the load transient response in Figs 3 and 4 of the TI datasheet
show a considerably different response than your model.

They probably use caps with a lot of ESR. And the models differ too.

You need to model the ESR.

You sure like to tell me what I need to do. But I don't report to you.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Tue, 20 Feb 2018 20:06:44 -0800 (PST), Uncle Monster
<unclemon@gmail.com> wrote:

On Monday, February 19, 2018 at 9:56:57 AM UTC-6, John Larkin wrote:
There have been articles lately about the new Apple Spaceship campus,
about people walking into the glass walls and doors.

We had a grubby bathroom refurbed at the cabin. The bathroom is small
and the new shower doors are clear glass, right next to the toilet.
First time I peeded in the middle of the night, I whacked my head on
the glass. It is very dark up here at night.

https://www.dropbox.com/s/k35nbdquxrywse6/P2190701.JPG?raw=1

There is a light/vent thing in the shower, so I was thinking it would
be cool if the light were on dim all the time.

https://www.dropbox.com/s/po8e9iku1a2zxt0/P2190702.JPG?raw=1

So I need an LED spotlight that runs at low current; most do. Maybe
the one already there would.

So I need to put an impedance across the switch for this light. It
could be a resistor, a cap, or a series RC. But it has to be small to
jam inside the switch box, and it can't get very hot.

A resistor could conduct 10 mA and dissipate a watt, which might work.
Or I could use one of those high-voltage XY-type film caps. If the cap
ever shorted, it wouldn't be a big deal... the light would just go on.

ps- It's 10F up here in Sunny California.
--
John Larkin Highland Technology, Inc trk



Have you thought of putting decals on the glass such as those put on windows to keep birds from flying into them? Some hawk decals would look pretty cool on the glass shower doors. ^_^

[8~{} Uncle Mensa Monster

They would have to be glow-in-the-dark decals, strontium aluminate to
hold up all night.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

On Tue, 20 Feb 2018 14:50:53 -0800 (PST), Phil Allison
<pallison49@gmail.com> wrote:

olds...@tubes.com wrote:

-------------------------


On the old florescent tubes, such as the common 4ft shop lights, the
filament only came on during starting.


** The filaments are hot all the time.

Take a look at an old or dead fluoro tube and see what the ends look like.

At least in 220-240 Vac countries, the heater is on only during the
start sequence. The starter connects the two heaters in series with
the inductance (ballast). When the starter opens, the current is cut
and the inductive kickback strikes the tube.

Once lit, the electrons hit the anode (and ions hit the cathode),
heating them up to such a temperature that allows sufficient cathode
emission, so no need for any filament current any more.

Of course, the role of anode and cathode is reversed during next mains
half-cycle.

 

[Phil Allison]

upsid...@downunder.com wrote:

----------------------------

On the old florescent tubes, such as the common 4ft shop lights, the
filament only came on during starting.


** The filaments are hot all the time.

Take a look at an old or dead fluoro tube and see what the ends look like.


At least in 220-240 Vac countries, the heater is on only during the
start sequence.

** The context for my remark has been snipped - see if you can find it.

It had to do with "filaments" in CFLs running hot and heating the electronics in the same enclosure, given hundreds or thousands of hours.

Seeing as both ends appear exposed inside the same small enclosure - guess what ??

The starter connects the two heaters in series with
the inductance (ballast). When the starter opens, the current is cut
and the inductive kickback strikes the tube.

** A fluoro ballast is a multi Henry inductor sized to drop the supply voltage just enough to supply the correct running current for the particular tube or combination. It is also designed NOT to saturate when full AC voltage is applied, limiting current to a safe value for the filaments during the pulse start sequence. Typically it's about double the running current.

Once lit, the electrons hit the anode (and ions hit the cathode),
heating them up to such a temperature that allows sufficient cathode
emission, so no need for any filament current any more.

** Fraid filaments and cathodes are one and the same. The tube's running current passes through the filaments constantly HEATING them.

The tungsten coil has a mixture of oxides applied so it acts as a good cathode.



..... Phil

 

On Tuesday, February 20, 2018 at 10:01:46 PM UTC-5, tabb...@gmail.com wrote:

I'm looking at putting together something similar to a Class AB/B audio amp, but it will be driven outside its linear range into saturation a lot of the time. That's all well & good but for one thing: wrapping nfb round saturating outputs doesn't work too well as it takes time for output devices to unsaturate, and the nfb effectively overreacts, adding distortion. Keeping distortion low matters here. What tips would you recommend to keep unwanted distortion minimised?


thanks, NT

I believe the effect you described is worse when there is more saturation, usually. Just some mild output clipping does not upset it so badly, so maybe you should consider pre-clipping the input signal. If the maximum output is fairly constant, and gain gain is of course with the negative feedback, seems like at the right point in the circuit something as simple as a couple of diodes might do the trick. I wouldn't tske that to the bank, but I'm sure you know how to clip a waveform at any given level.

If you do it just right you shouldn't lose any output level. The output still clips, but is not driven to umpteen times what it can reproduce.

Worth a try ?

 

>"** So NT wants output device saturation but don't want much waveform distortion ? While keeping all nature of his project secret? "

Well it does pique the curiosity a bit, and evoke an invective from you.

Translation : Things are the same as always.

Just what might be the mystery application ? Is there a prize for figuring it out maybe ?

 

[Tauno Voipio]

On 21.2.18 05:01, tabbypurr@gmail.com wrote:

I'm looking at putting together something similar to a Class AB/B audio amp, but it will be driven outside its linear range into saturation a lot of the time. That's all well & good but for one thing: wrapping nfb round saturating outputs doesn't work too well as it takes time for output devices to unsaturate, and the nfb effectively overreacts, adding distortion. Keeping distortion low matters here. What tips would you recommend to keep unwanted distortion minimised?


thanks, NT

If it's going to be a guitar amp, forget distortion, it's
a part of the steel-wire music ...

It seems that you have re-invented the transient intermodulation
distortion (TIM). Google for articles of prof. Matti Otala about
the TIM.

--

-TV

 

[Martin Brown]

On 19/02/2018 19:22, Carl Ijames wrote:

In the good old days there were incandescent bulbs and fluorescent fixtures
with magnetic ballasts, and both seemed to have "graceful" failure modes in
the vast majority of cases. By graceful, I mean a simple transition to an
open circuit with no damage to the fixture or anything else close by. We
regularly left an incandescent lamp or two on for a week or more when we
traveled, to make it look like someone was home. Over the last twenty years
I've almost completely switched to CFL bulbs, and of the six or seven that
have gone dark (not counting the ones I broke knocking a lamp over trying to
reach the alarm clock ) four of them died by emitting flames and smoke
and one by emitting just smoke (I was right next to that one so got it off
within seconds, or maybe it would have progressed to flames too?).

I have never had a CFL actually catch fire. Emit the magic smoke and/or
blow a fuse yes, but nothing more than that. Kitchen spotlamps used to
be the worst for plunging the house into darkness when they blew. Since
swapping to almost entirely LED based they are much more reliable. YMMV

So, is there any kind of bulb you would leave on with no one home? Am I
just unlucky or is this the new normal?

My nobody home lights of choice are now Wemo based LED devices and
internet controllable with default timings set to come on at dusk and
early morning matching normal use patterns in the house. Wemo may no
longer be the best choice of such lamps but I was an early adopter.

The only slightly annoying thing is that you can't set "dusk" as a start
time and a fixed clock stop time. This time of year you have to adjust
them every couple of weeks or it stands out a bit.

--
Regards,
Martin Brown

 

[gregz]

"Carl Ijames" <carl.ijames@NOverizon.net> wrote:

In the good old days there were incandescent bulbs and fluorescent fixtures
with magnetic ballasts, and both seemed to have "graceful" failure modes in
the vast majority of cases. By graceful, I mean a simple transition to an
open circuit with no damage to the fixture or anything else close by. We
regularly left an incandescent lamp or two on for a week or more when we
traveled, to make it look like someone was home. Over the last twenty years
I've almost completely switched to CFL bulbs, and of the six or seven that
have gone dark (not counting the ones I broke knocking a lamp over trying to
reach the alarm clock ) four of them died by emitting flames and smoke
and one by emitting just smoke (I was right next to that one so got it off
within seconds, or maybe it would have progressed to flames too?). First
time was about 15 years ago, when I was sitting at my computer and heard a
noise behind me and saw flames about 6-8 inches tall rising from the top of
a lampshade. A year later another bulb did the same thing. The most recent
one was last month. Only two or three CFL bulbs have failed by just going
dark while lit or not turning on. I'm all for saving energy but I will not
ever leave a CFL turned on when I leave the house for more than a couple of
minutes, even just to go work in the yard. I rarely experience power
flickers or failure and have never lost an appliance or surge suppressed
power strip (knock on wood ). I've recently replaced a couple of CFLs
with LED bulbs and so far am happy with them output-wise but I have no idea
what excitement their eventual failure will bring.

So, is there any kind of bulb you would leave on with no one home? Am I
just unlucky or is this the new normal?

After over 20 years of using CFLs never had a fire. I usually replace if it
goes dim. I have some I leave on all the time. I am more cautious with
lampshades now. I have run them continuously outside, either plastic
encased, or a glass bulb type cover that got very hot in the sun. I prefer
an enclosure. I have some upside own in ceramic holders. I'm gradually
switching to LED, but trying to stay cautious with type of fixtures.

Greg

 

[Steve Wilson]

John Larkin <jjlarkin@highlandtechnology.com> wrote:

On Wed, 21 Feb 2018 04:51:28 GMT, Steve Wilson <no@spam.com> wrote:

John Larkin <jjlarkin@highlandtechnology.com> wrote:

On Wed, 21 Feb 2018 01:54:05 GMT, Steve Wilson <no@spam.com> wrote:
Amps are amps. The load step demonstrates the ringing, and the fix
for the ringing.

Your simulation shows considerably different ringing between current
rise and fall. So the currents matter.

Sure, the output transistor emitter has a very different impedance
from 30 to 200 mA. So the pole from that impedance into the ceramic
caps is different for the two currents.

You need to model the actual currents you are using. I suspect the
idle current may be much lower, and the actual charge current may be
higher.

I'd be happier to see the results with a pulsed 100ns 12 Amp load.

I did it for you. The compensation cap is critical and very different
from your result. See below.

That seems to be my sim; same currents, no ESR in the output cap, just
not as pretty. Any engineering doc should have a title, author, and
date.

Sorry, I picked the wrong file. You can see the original by changing the
current, pulse width and cap values as listed below.

This is a newsgroup discussion. The title is shown at the top of the
schematic. The date is the date of the post and is shown in the header. If
I put my name on the document, you will get pissed.

I tried adding 20 mohms ESR to the output caps in my sim. Nothing
changed; it rings badly without the added compensation, and doesn't
ring with the RC, or just the C, from ADJ to ground.

Pulsing at 10 amps for 100 ns, the results are about the same: lots of
ringing, fixed by adding the same comps.

The compensation parts help.

You may need to use a switched resistive load to provide some
damping. This may have a significant effect on the ringing.

Note the load transient response in Figs 3 and 4 of the TI datasheet
show a considerably different response than your model.

They probably use caps with a lot of ESR. And the models differ too.

You need to model the ESR.

You sure like to tell me what I need to do. But I don't report to you.

Sensitive? Not at all. Try the generic "you".

I increased the output cap from 12 uF to 20uF to match your value, amd
changed the pulse width from 100ns to 160ns to maintain the same dv.

The compensation cap was very difficult to optimize. You either get
underdamped with overshoot or overdamped with overshoot. But I ended up
with the same value as you - 20nF. So the response is sensitive to pulse
width, compensation cap and output cap values. Relatively small changes
have a big effect on the response.

The compensation cap ESR seems to have no effect. The output cap ESR has a
very significant effect on the shape of the response.

(I checked the title - this is the correct file. I need to always do that
in the future.)

Version 4
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WIRE 512 160 512 128
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TEXT 72 -16 Left 2 !.tran 0 200u 0 50n
TEXT 80 -40 Left 2 ;'LT317A 12A Load Transient Response

 

[Tim Williams]

"Ivan Shmakov" <ivan@siamics.net> wrote in message
news:87d10zdpzj.fsf@violet.siamics.net...

The former. Can you please point me to the relevant reading on
the latter? I've found some links with a Web search, but they
seem to be describe microwave filters, and our frequencies are
much lower. (Yet.)

There used to be an excellent Java applet, modeling coupled resonators (in
the abstract -- doesn't matter how you couple them, just that you get the
f_o and k_{m,n}'s correct), but it died back when Java went away. Not aware
of a port or replacement of it, unfortunately.

This is a more basic two resonator example:
https://www.jrmagnetics.com/rf/doubtune/doubccl_c.php

You see them a lot at microwave, of course, but also for cellular and
commercial radio filters (especially diplexing, where high Q and tight
frequency edges are needed). I have a rather large one in my junk bin which
seems to be a VHF TV channel, with half a dozen coils inside (helical
resonators). Must be very sharp; I haven't bothered to measure it yet.

They're not too common at lower frequencies, where, heck, active filters may
even be easier -- but it works out the same way.

The basics for analysis are this: all f_o's are the same, and k ~= 1/Q ~=
f_BW / f_o. The k's are symmetrical from end to end (k_{1,2} = k_{N-1,N})
and the variations of each pair (around the [geometric] mean 1/Q value) are
determined by the filter prototype (Butterworth, etc.). To introduce
zeroes, couple non-adjacent pairs (e.g., 1,3 and etc.). Which pairs are
chosen, determines which side (above or below) and number of zeroes.

The input and output coupling are also abstract; typically a tapped coil is
used.

The Jackson case above uses capacitor dividers for input and output
coupling, and a small capacitance to couple between the top of the two
resonators. This detunes the tanks downward a bit, which makes the
calculation a bit crappy (all the better that they've written a calculator
to do it for you!).

Magnetic coupling (inductors in proximity: shared flux) does not cause
detuning, which is handy. In practice, there is some capacitance from
proximity as well, which still detunes them, but not nearly as much.

The Q of individual components, of course, you want much higher than the
filter Q.

The ladder configuration, by the way, is a special case of this; there, the
series-parallel transformation is used on half the resonators, so that
instead of parallel-resonant tanks linked "somehow", the current through the
series branches is exactly the current linking parallel branches. The
coupling factor is the ratio of each LC's impedance from the mean impedance
(which for a RS = RL double terminated case, is just that resistance), the
parallel tanks being Q times lower impedance and the series tanks being Q
times higher.

Which is why the ladder configuration is preferred for large bandwidths (Q <
3, say) -- you can't really get a coupling factor that large with coupled
resonators. Conversely, it's difficult to avoid parasitics (capacitance
across a series inductor's terminals, and from its body to nearby ground or
free space; and series inductance of parallel capacitors), so coupled
resonator designs are preferred at high Q.

In the former case, you can't reasonably measure pairs of components
together, except for bandpass/stop.

The latter is indeed our case. But we of course can tune
the individual LC circuits before installing them on board.
(Takes considerable time, but doable given the small-ish
number of filters we have to make.)

(Not to mention that we actually have small gaps in the PCB
tracks, as well as test points, so we can tune the circuits
on the board before connecting them all into a filter proper.
Also helps to account for the effect of the case, etc.)

Ah, so there we are -- you should indeed be able to test each pair, and them
coming out wrong is a bit troubling.

Coupled resonators should always measure on f_c, when they are
coupled magnetically, on taps, or resistively.

If they are coupled with small capacitors or large inductors,
it's detuned of course.

?

Explained above

Aren't S-parameters "analogous" to (as in: interchangeable with)
complex impedance?

Yes, or easily converted anyway (there is a relation between all the various
port formats).

Unfortunately, it doesn't seem possible to fit a complex value,
or more than one set of scalar (float) values at a time in
general, with Gnuplot, and the latter offers the most
sophisticated L-M implementation I have an experience with.

I haven't touched it, so I don't know. :^)

Would it help to set a fitness function (say, |distance| on the complex
plane) and regress a given curve to match the data?

That's what I do a lot of the time, say when creating a model of an existing
component. Example:
https://www.seventransistorlabs.com/Images/Filter_MI1206L391R-10_Model.png

Matches pretty closely with the datasheet value for MI1206L391R-10 (well, at
zero bias). Set up the parameters, then run regression and hope it finds a
good local minima.

Some stock Coilcraft models show inductance rising with frequency,
which is unreasonable /and/ nonphysical. (Those are harder to
adapt...)

Any specific explanation as to why is that nonphysical?

A two-pin component is a one-port: current in one pin goes right out the
other. There is only one such pair of pins, so it's a one-port.

For it to be real-valued and passive (not a generator), the impedance and
phase angle must obey the Kramers-Kronig relations.

For a passive two (or more) port, a more general rule of course applies.

The test board we're measuring the S-parameters with has the
test coil, two SMA connectors, and the tracks to connect them
all. (It has a rather large "ground," however; we can try with
another board, which doesn't, I suppose.) Any suggestion on how
we can improve it?

Dunno. Picture?

Proof is in the pudding; build the complete filter, see if it matches the
design prototype, and how far off f_c is; then work backwards to determine
how far off your component values were? Any means of measuring their
values, near f_c, should do well enough. I guess you have a VNA, so you're
way more than well enough equipped to do this!

The trouble with powdered iron cores is, A_L isn't very well defined,
especially on lower permeability parts, and with few turns, where the
winding geometry is critical. This is a bit of a protip: if you need to
tune one by less than a turn's worth. (Much more info on Micrometals's
website, they have good appnotes.)

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/

 

[Phil Allison]

jurb...@gmail.com wrote:

-----------------------------

"** So NT wants output device saturation but don't want much
waveform distortion ? While keeping all nature of his project secret? "



Just what might be the mystery application ? Is there a prize for
figuring it out maybe ?

** If you guessed it - he would deny it.

A though bubble looking for a clever idea for him to plagiarise.




..... Phil

 

[TTman]

On 21/02/2018 00:57, mpm wrote:

On Tuesday, February 20, 2018 at 5:44:32 PM UTC-5, TTman wrote:

Fit a nice big pair of 100W Cibie rally lights. It will be like driving
in daylight

...and it will also be like driving in a ditch after I run you off the road!

I consider it extremely rude, unsafe (and possibly illegal) to use high-beams, especially super-bright aftermarket bulbs, that blind other drivers. The use of these bulbs seems to be gaining popularity with the younger crowd (which arguably, doesn't really know how to drive in the first place.) Unless you define driving as Fast-&-Furious video game.

Of course, the opposite is also very annoying and unsafe:
Drivers who either don't turn their lights on at all, or run around with no brake lights. (Don't get me started on that -- ever since LED's.. more and more folks with brake lights out. Or so it seems!)

Certainly not illegal in the UK and anyway, the OP said he drives on
rural roads. They also have to operate on main beam only and go out on
dipped beam. No problem for other drivers.....

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