Driver to drive?

[Michael A. Terrell]

Dennis wrote:

On 1/02/2013 2:30 AM, Michael A. Terrell wrote:

Spehro Pefhany wrote:

On Thu, 31 Jan 2013 16:53:54 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"Paul Hovnanian P.E."

TO-92 package

markings:

"650"
"B24"

** Two legs or three?


... Phil


Three legs good, two legs better.


Have you ever sat on a two legged stool?


If my stools had legs I'd be off to the doctor very quickly.

You'd have to walk. You'd never be able to sit in your car. ;-)

 

[Fred Abse]

On Thu, 31 Jan 2013 22:57:33 -0800, josephkk wrote:

On Thu, 31 Jan 2013 13:33:44 -0800, Fred Abse
excretatauris@invalid.invalid> wrote:

On Wed, 30 Jan 2013 22:09:46 +0000, Adrian Tuddenham wrote:

Fred Abse <excretatauris@invalid.invalid> wrote:

On Wed, 30 Jan 2013 21:23:18 +0000, Adrian Tuddenham wrote:

Fred Abse <excretatauris@invalid.invalid> wrote:

On Mon, 28 Jan 2013 23:30:07 +0000, Adrian Tuddenham wrote:

The signal level at that point is nominally 0dBu.

For the benefit of us non-audio guys, what are dBu referred to?

0dBu is the voltage which would be called "0dBm" if it were
terminated in 600 ohms i.e. 0.775v rms (...because dBm can only
refer to power into 600 ohms).

The dBm I use are relative 1mW in 50 ohms.

I presume you are working with RF. Is there an RF equivalent of dBu,
based on voltage without reference to impedance?

Not as far as I know.

dBmV (ref 1 millivolt) are occasionally used, as are dBKTB.

50 ohm signal sources of whatever frequency are usually calibrated
terminated, whether or not they offer voltage, dBm, or both. Some ancient
signal generators were calibrated "EMF into 50 (sometimes 75) ohms",
which was downright confusing.

A useful thing to remember is that thermal noise power in a 1Hz
bandwidth, at 290K, is -174dBm, irrespective of impedance.

Actually dB and for that matter bels is about power and power ratios,
always irrespective of impedance.

?-)

It's really just a logarithmic way of expressing a ratio.

As are nepers.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Joseph Gwinn]

In article <kjpOs.7608$Sq4.1466@newsfe14.iad>,
Clifford Heath <cjh@no.spam.please.net> wrote:

On 01/30/13 06:57, Jon Elson wrote:
On 26/01/2013 23:08, Jon wrote:
The two female vocalists in the band ABBA have synchronized vibratos,
I can't imagine anybody could sync their vibrato as
a vocal technique

Having been (at one time) a passably good violinist (my sister is still
a world-class player) I don't find it at all unlikely. The vibrato is
primarily driven by beta-rhythms, which though not under direct conscious
control, can be and are finely controlled parametrically. I never tried
to synchronize my vibrato with another violinist (who was also trying)
but I have no doubt whatever that even I could have learnt it. All the
more so professionals and for vocalists, for whom this control is even
more central to their skills.

Yes. Humans do lots of things faster than they can think, and that are
not under obvious control, and yet they are.

For a non-musical example, consider hitting a golf ball with a club.
The head is moving almost 100 mph at impact with the ball, are too fast
to really see clearly or to react to deviations. Yet one must keep
one's eyes on the ball while swinging the club.

As for vibrato, this is a gesture of the throat, and there is no reason
it cannot be synchronized, with sufficient practice. Just as dancers
synchronize their movements.

And ABBA performed live, and it wasn't dull. Sounded just like ABBA. I
saw them on Swedish TV back in the day, when I was visiting friends in
Stockholm in 1973 or 1974.

Joe Gwinn

 

[Bert Hickman]

David Lesher wrote:

Someone has tried to tell me that the free-air distance needed
to prevent arcing varies inversely with frequency; i.e. a 10 KV
RMS 60Hz conductor will need less spacing than a 10 KV RMS 25Hz
one.

I'm no power distribution engineer, but I can't recall anything
close to that. I asked my MIT-grad friend as well, but outside
of the obvious end case [0 Hz, where peak=RMS] we both came up
blank.

Obviously, OAT, %RH, etc alter the result, but frequency?

Hi David,

Unlike DC or 50/60 Hz AC, gap breakdown voltage for low frequency high
voltage at LF and VLF frequencies may be only slightly higher than
corona onset voltage. An RF corona is hot, and the surrounding heated
air becomes less dense, reducing breakdown voltage in the remaining gap.
Streamers develop and quickly grow to bridge the gap. Under appropriate
conditions, a pulsed source of a couple hundred thousand volts will jump
a distance of 5-6 feet (i.e., as in medium sized Tesla Coils).

An excellent paper covering low frequency RF breakdown can be found in
the massive study, "VLF/LF High-Voltage Design and Testing", Technical
Report 1904, Sept 2003 on the DTIC site:

http://www.dtic.mil/dtic/tr/fulltext/u2/a526052.pdf

Bert
--
Bert Hickman
Stoneridge Engineering
http://www.capturedlightning.com
***********************************************************************
World's source for "Captured Lightning" Lichtenberg Figure sculptures,
magnetically "shrunken" coins, and scarce/out of print technical books
***********************************************************************

 

[Phil Allison]

"Uncle Steve"

( snip appalling load of drivel )

Comments and constructive criticism is welcome.

** You are making a fundamental error.

NFB loops ( in audio amplifiers) compare only the INPUT and OUTPUT signals -
so the output *replicates* the input signal at a greater magnitude.

This cannot and does not correct for non-linearities or other flaws in the
load.



.... Phil

 

[Uncle Steve]

On Sat, Feb 02, 2013 at 02:30:16PM +1100, Phil Allison wrote:

"Uncle Steve"

( snip appalling load of drivel )

Comments and constructive criticism is welcome.

** You are making a fundamental error.

NFB loops ( in audio amplifiers) compare only the INPUT and OUTPUT signals -
so the output *replicates* the input signal at a greater magnitude.

You must know that inductive loads are different from resistive loads.
How do you account for that difference?

This cannot and does not correct for non-linearities or other flaws in the
load.

All I am suggesting is that speaker efficiency is a player in NFB amp
systems. Totally hypothetical, but you've not said anything that
would invaldiate the hypothesis.


Regards,

Uncle Steve

--
More than a century has passed since science laid down sound
propositions as to the origins of the universe, but how many have
mastered them or possess the really scientific spirit of criticism? A
few thousands at the outside, who are lost in the midst of hundreds of
millions still steeped in prejudices and superstitions worthy of
savages, who are consequently ever ready to serve as puppets for
religious impostors. -- Peter Kropotkin

 

[Phil Allison]

"Uncle Steve"

Phil Allison wrote:

"Uncle Steve"

( snip appalling load of drivel )

Comments and constructive criticism is welcome.

** You are making a fundamental error.

NFB loops ( in audio amplifiers) compare only the INPUT and OUTPUT
signals -
so the output *replicates* the input signal at a greater magnitude.

You must know that inductive loads are different from resistive loads.
How do you account for that difference?

This cannot and does not correct for non-linearities or other flaws in
the
load.

All I am suggesting is that speaker efficiency is a player in NFB amp
systems. Totally hypothetical, but you've not said anything that
would invaldiate the hypothesis.

** You are clearly a demented half wit.

Fuck off.



..... Phil

 

[josephkk]

On Fri, 1 Feb 2013 23:32:23 +0200, "E" <invalid@invalid.invalid> wrote:

"josephkk" <joseph_barrett@sbcglobal.net> kirjoitti
viestissä:j8nmg899ef19tqslk608ibf5ovvfgt6hk3@4ax.com...



Some Sites/pages to consider:

http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/t8/05-t8-lamp-life.asp

http://www.lrc.rpi.edu/programs/futures/LF-LampLife/

http://en.wikipedia.org/wiki/Electric_light

http://www.lithonia.com/micro_webs/electronicballast/source.pdf

http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/hwcfl/HWCFL-life.asp

It seems that fluorescent life varies a bit over the range of 10,000 -
20,000 hours, LEDs range from 50,000 - 100,000 hours. I thus challenge
your only 2.5 times the life.

Depending on usage LEDs can deliver more lumens per watt, near equivalent
CRI, dimmability (something fluorescent does not handle well at all) and
some other useful trade offs. For some applications LEDs rock, for others
there are plenty of lamp technologies.

Induction lighting in particular is still giving all other technologies
fits in several applications.

Fluorescent lifetime varies very much with use pattern and ignition method.
I have read that in the US they use these rapid/instant start systems that
reduce lamp lifetime somewhat. Around here we use glow starters nearly
allways if using ballast. I think most here haven't even heard of those
rapid
start things
Also if you look at two first links you find that typical lamp lifetime is
given
with many on/off cycles. In typical business use lamps are on for long time
(if not 24/7) so startup wear is not that much concern. If you look at graph
in second link you can find that under these conditions it is reasonable to
expect about 30k life for a tube.
And 2.5 times 30k hours is 75k hours. Of course if there is much on/off
cycles lifetime drops and that 10k figure might be realistic for home use
with instant on starter.

Modern fluorescent lamp with electronic ballast and good reflector give
system efficacy of about 90 lm/W (tube only is approx 110 lm/W) so
they are about equally good as good led lamps. Also modern control
gear is not that bad at dimming.

Yes, certainly there are many places where leds are very good choice.
It just irritates me when green weenies are pushing led lighting as saving
the world wonder thing. Every magazine and newspaper is nowadays
full "leds save 60% energy" articles with no hint as to where on earth
they are pulling those numbers from. And then city engineers have
hard time telling politicians why changing every lamp in city to leds
ain't that great idea.

Nice trim.

The 60% number is averaged over all other technologies without frequency
of use weighting. Thus incandescent bend the figure a lot.

?-)

 

[Bruce Varley]

"Uncle Steve" <stevet810@gmail.com> wrote in message
news:4d4f9fba73d6b43-04af3@gmail.com...

In thinking about this subject, it has occurred to me that a NFB amp
will perform better if the speakers it drives are more expensive than
another, all things being equal.

Talk to your hifi supplier, he'll give you an objective assessment.

Even ambient noise in the listening
environment might affect the negative feedback circuitry.

FGS

 

[geoff]

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:QqYOs.129704$kp4.121677@newsfe09.iad...

geoff wrote:

"SoothSayer" <SaySooth@TheMonastery.org> wrote in message
news:rbimg81f27f5imqkpgdu2sqak7a1398j4d@4ax.com...

matches what a proper, restricted head would deliver.

They would always be red with me. My showers are 125 degrees.


Steam bath ?

geoff
No all of us are on the Metric system..

Jamie

Um, duh ...... ?!!!!

geoff

 

[David Lesher]

Bert Hickman <bert-hickman@comcast.net> writes:

Unlike DC or 50/60 Hz AC, gap breakdown voltage for low frequency high
voltage at LF and VLF frequencies may be only slightly higher than
corona onset voltage.

....

An excellent paper covering low frequency RF breakdown can be found in
the massive study, "VLF/LF High-Voltage Design and Testing", Technical
Report 1904, Sept 2003 on the DTIC site:

http://www.dtic.mil/dtic/tr/fulltext/u2/a526052.pdf

Thanks. Reading now, but I should have been more explicit...I'm
talking DC-100Hz, not RF.

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

On Sun, 27 Jan 2013 14:05:08 -0800, MrTallyman
<MrTallyman@BananaCountersRUs.org> wrote:

The right move for the entire industry would be to place the DC source
conversion IN THE LAMP and make the "light bulbs" just the LEDs and
current limit elements and attachment socket stub.

A better approach for the industry would to standardize some
constant_currents_ (DC) such as 20/50/100/350/1000 mA so that any
light panel from any manufacturer rated for a specific constant
current could be plugged into a series string, just like christmas
tree lights.

In a system driven by a constant current, each load would have the
same current, but the voltage could be different, depending of the
power levels needed. This is very similar as the Pxxnn series tubes
used in old European TVs, in which the filaments were in series across
the 220 Vac mains (with some inrush current limiting).

For larger LED panels it would be mechanically feasible to use
multiple constant current generators with separate strings with two or
more of those standard currents through the sockets. The panels would
only have pins for the required current and the socket would short
circuit the unused current lines, maintaining loop continuity. Some
open/short circuit detection at each constant current source could
take out unused current loops.

 

On Fri, 01 Feb 2013 10:02:22 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Fri, 01 Feb 2013 10:39:08 +0800) it happened Dennis
none@null.net.au> wrote in <i5edndP9R5Ytt5bMnZ2dnUVZ_vmdnZ2d@westnet.com.au>:

Saw this advert - shower head with LEDs to illuminate the water stream,
coulour indicates temperature.

http://www.coolproductsusa.com/shop/led-shower-head-with-temperature-sensor/?fb_action_ids=3921615035746&fb_action_types=og.like
s&fb_source=hovercard&fb_aggregation_id=246965925417366


Supposedly without batteries or external power.

"No batteries and external power supply needed.
The color change tells you the water temperature.
Bright LED light.
Approved by CE & RoHS certificates.
Electricity is generated by hydraulic mechanism."


I wonder what mecahnism they use to generate the power & if it really is
as bright as the marketing pictures depict!


No doubt they will make a few dollars out of it!

Probably some rotating turbine generator
Water pressure can do that, pity water is expensive here,
else it could replace my power company...

Somebody I sent this link to said that this product requires
30 PSI of water pressure to work. Anybody know if that is
true or not ?

boB

 

[Gib Bogle]

On 2/02/2013 3:14 p.m., Uncle Steve wrote:

a NFB amp will perform better if the speakers it drives are more expensive than
another

This common misperception makes the hifi scam business profitable.

 

On Sun, 27 Jan 2013 10:28:43 +0100, Fabio_78 <a@b.it> wrote:

There are many design examples that lack a large
electro cap on the input. AFAIK this is done mainly for
high power factor, but as a side effect the large high
voltage electro disappears. The single stage High PF flyback
is simple to do for low power requirements, and moves the
cap from rectified mains to led output side.
For higher power one could use the usual PFC+flyback
(or PFC+resonant) and use high voltage film capacitors
as storage.
Check appnotes for ST L6561/2, powerint linkswich-PH,
if I remeber correctly also fairchild and ON should have
appnotes on the subject.

Wouldn't replacing the output voltage feedback divider at pin 1 with a
high side load (LED string) and 100 ohm to ground and feeding the
voltage across the resistor to the pin 1 (feedback) produce a 20 mA
constant current source ? This should be able to drive a string of 100
LEDs.

Thus only one switching transistor and one inductor would be needed
for both PFC as well as constant current regulation.

Of course, with such highly integrated chips, this might cause havoc
e.g. in startup functions.

 

[Fabio_78]

Wouldn't replacing the output voltage feedback divider at pin 1 with a
high side load (LED string) and 100 ohm to ground and feeding the
voltage across the resistor to the pin 1 (feedback) produce a 20 mA
constant current source ? This should be able to drive a string of 100
LEDs.

Hello, in my answer I was thinking to isolated designs
with lowish forward voltage led strings, here the
pfc would run around 400V, isolating the leds from
the dissipator will kill the thermal resistance.

If I understand you are thinking to use a pfc booster
to drive the leds directly with a current feedback.
I think that can be done but the output current will
follow input voltage, at least the driver is designed
to work this way, and it's needed to have a reasonable
power factor of the system.

So I think you need a storage capacitor to lessen the
flickering of the leds. This problem is similar to single
stage pfc-flyback, you have only one degree of freedom,
and you need a compromise between current ripple in
the leds (that generates flickering but also reduces
somewhat the luminous efficacy) and filter capacitance.
About the particular implementation in the L6561/2, i'm not
that experienced with feedback loops analysis, as
I understand these pfc devices have a slow contol loop
for output voltage regulation (slow enough to average the
voltage over multiple line cycles) and fast "emergency"
limiter for line transients. The first probably can be
used for average current control in led string.

This approach could be useful with some recent high
voltage led arrays, that promise high efficacy at
reasonable cost.

By the way, reading you answer on another message
of this topic, you made very good points about
the figures reported by datasheets about efficacy,
current and temperature of the leds. The manufacurers
tend to write the best numbers for efficacy, but
usually these are obtaind for best bins, low currents
and impossible junction temperatures, unless you
live in polar regions
Fortunately some manufacturers are starting to specify
efficacy at 85°C Tj.

Ciao!

--
Muvideo altrove
Fabio Eboli nella vita reale...

 

[MrTallyman]

On Sat, 2 Feb 2013 14:30:16 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Uncle Steve"

( snip appalling load of drivel )

Comments and constructive criticism is welcome.

** You are making a fundamental error.

NFB loops ( in audio amplifiers) compare only the INPUT and OUTPUT signals -
so the output *replicates* the input signal at a greater magnitude.

This cannot and does not correct for non-linearities or other flaws in the
load.



... Phil

Yep, and any such corrections would take place AFTER the distortion
event already occurred as well. That would make it worse, IMO.
This whole concept is a fucking joke.
It is like a Doctor attacking the symptom instead of the root problem.

Or a asshole who covers his mouth *after* or *as* he sneezes.

 

[Peter]

SoothSayer <SaySooth@TheMonastery.org> wrote:

On Fri, 01 Feb 2013 13:58:56 +0800, Dennis <none@null.net.au> wrote:

On 1/02/2013 12:45 PM, John Larkin wrote:
On Fri, 01 Feb 2013 10:39:08 +0800, Dennis <none@null.net.au> wrote:

Saw this advert - shower head with LEDs to illuminate the water stream,
coulour indicates temperature.

Supposedly without batteries or external power.

"No batteries and external power supply needed.
The color change tells you the water temperature.
Bright LED light.
Approved by CE & RoHS certificates.
Electricity is generated by hydraulic mechanism."


I wonder what mecahnism they use to generate the power & if it really is
as bright as the marketing pictures depict!


No doubt they will make a few dollars out of it!




You could in theory have a shower head that delivered 50 watts or so of
electrical power from the pressure drop.




Yeah you could but how would you do it in a consumer product flogged for
$10.

Found a video here, doesn't look as bright as in the advert:
http://www.youtube.com/watch?v=gG1ZDpPA5l4


In an apartment, where the water is free, one could use such a device
to generate some of their electrical need. Wasting much free water, of
course. But folks do that all the time these days.

Now you are talking shit. Errrr I mean sewage.
;-)
Miles of pipe under most cities. Don't forget storm water. I still don't
get why we build houses now with a roof then effectively install another
roof (solar panels) on top to be efficient.
I guess the problem is there must be a dollar in it.

The above mentioned product (I am unable to follow the link at the moment
thank you Telstra) I assume is designed to be replaceable over serviceable.
I am also guessing at the mentioned price they plan to flood the market.

Businesses are in business to make money.

--

 

[mi]

EVO8VIII <ravi2neha@gmail.com> writes:

I am working on very low current (10uA) design using LHI 878. Perkin Elmer app not e recommends 47K load resistor on source pin, which make my current goal very difficult. I've come across few designs where people have used over 1M on source pin to achieve this amount current. Does any one know if is okay use over 1M value? what could be side affect?

muRata IRA-E712 at least works perfect with a 2 uA. We're using both S and D resistors
in the circuit with gate tied to ground. I don't remember the exact numbers, but I think
our R is a lot less than 1M, as the current is controlled by the biasing.

-- Mikko OH2HVJ

 

On Sat, 02 Feb 2013 11:46:26 +0100, Fabio_78 <a@b.it> wrote:

By the way, reading you answer on another message
of this topic, you made very good points about
the figures reported by datasheets about efficacy,
current and temperature of the leds. The manufacurers
tend to write the best numbers for efficacy, but
usually these are obtaind for best bins, low currents
and impossible junction temperatures, unless you
live in polar regions
Fortunately some manufacturers are starting to specify
efficacy at 85°C Tj.

Some serious manufacturers these days specify significant parameters
at reasonable values, e.g. usable junction temperatures and at current
levels that might be usable at above 50000 hours.

In the old days, while some manufacturers did have fine charts for
various parameters vs. junction temperature or vs. forward current,
but some parameters specified at Imax and others at Tj=25 C, you
needed quite a few iterations on a spreadsheet to get the forward
voltage, power dissipation and junction temperature calculations to
stabilize , in order to get a stable operating point for the
optical parameters.