Driver to drive?

[Andy]

John Woodgate wrote:

I read in sci.electronics.design that Andy <andy@nodomain.nod> wrote (in
41e1030e$0$6440$8fcfb975@news.wanadoo.fr&gt about 'FM1236 / FM1246 tuner
required power supply quality?', on Sun, 9 Jan 2005:


I am attempting to fix the quality of the video signal coming out of a
similar tuner (it's on a PC TV card). Currently, the brighness of the
picture is fluctuating on the high-brightness areas, in the rythm with
the sound; the tuner is powered from a LM7805-type regulator (which I
have already added to the card; intially there was none, and the
interference on the picture was terrible).

I suspect the power supply quality.


The sound is FM, unless you also have baseband audio stuff with
significant current draw fed from the same regulator, so it shouldn't
cause amplitude modulation of the video. I doubt that the power supply
is at fault.

There are baseband audio outputs from the module, but it looks like
indeed these "audio rhythm" fluctuations are not due to a problem with
the power supply. I have now inserted a ground loop breaking device in
the aerial input path, and these fluctuations are no longer there...

But there are sometimes luminosity artefacts such as luminosity
alteration of a uniform background, around a contrasted object placed on
that background, in the horizontal direction. These could still be due
to an unsufficient power supply regulation (the supply current of the IF
section of the module is 150mA max, that of the TV/FM tuner section -
120mA max).

 

Yes, actually. I probably watch about 3 hours of TV per week, so I
don't find it to be a good value for me. DirecTV is not an option in
this building in any case. Cable is $50. I'd rather save my money for
other things.

 

[Al]

In article <crp7vf$jp7$1@theodyn.ncf.ca>,
et472@FreeNet.Carleton.CA (Michael Black) wrote:

http://www.cnn.com/2005/TECH/01/03/cnn25.top25.innovations

Definition:

innovation ) n.
1. The act of introducing something new.
2. Something newly introduced.

invent tr.v.
1. To produce or contrive (something previously unknown) by the use of
ingenuity or imagination.
2. To make up; fabricate.


So, it could have been "invented" prior to 1980.

Sorta kills some of the arguments -vs- time since invented.
The concept of sending light through conduits has been around for
centuries, but actually doing something useful with it has not.


And eliminating medical avances is sorta bogus.

Al

 

[mc]

"markzoom" <markzoom@digiverse.net> wrote in message
news:7172c4fd.0501090729.17d84f6e@posting.google.com...

Hi folks,
On the back of most equipment requiring an AC adaptor and the adapters
themselves there is usually a symbol, plus the voltage and the
amperage. So:

Does the symbol, a solid line with a dotted line over it, denote an
unregulated or a regulated supply?

It denotes DC but doesn't indicate anything about regulation.

 

[John Popelish]

Ken Smith wrote:

In article <41E0A684.57A4EB10@rica.net>,
John Popelish <jpopelish@rica.net> wrote:
[...]
This is a strange sort of step up supply, what with the full wave
doubler using both swings from the transformer, but the primary driven
only one way.

I've used this same basic design for the output several times. It isn't
all that strange. As far as PWM regulation goes, it is a flyback design.
The doubler means that the output has N*Vin added to it.

As I said, it can be regulated as long as the N*Vin is considerable
less than the desired voltage, so that adjusting the flyback voltage
component is enough.

Normally, in a flyback design, the primary has a current ramp in it. When
you add the doubler to the output, this changes. The doubler causes a
larger current to flow just as the transistor switches on. This added
current tails away as time passes and the output side capacitor gets
charged. This decreasing current tends to cancel the slope of the
normally increasing current seen in the primary.

The OP isn't using current mode control so this doesn't mess up his
current sensing.

The flatter current wave form has a lower RMS to average ratio so the
losses in the pass transistor can be less with this circuit that would be
the case for just a flybacker.

Agreed.

--
John Popelish

 

[Ken Smith]

In article <10u1e2im3h9hc00@corp.supernews.com>,
Scott Miller <scott@3xf.com> wrote:
[...]

Hadn't thought about that, but it makes sense. Is this going to be
temperature-sensitive?

Yes, a bit. At higher temperatures, the recovery time usually gets a bit
longer and the corners in the curve get a bit rounder.

sort of diodes are available at this voltage that'd perform better, or does
it really matter? The diodes are currently 1N4007s.

1N4007 is about the worst one on the market. You want a diode that is
"fast recovery" or "high speed"

Also, D2 has some capacitance. This adds another bit of charge that will
be sucked out of C6 at the edge of the waveform.

The spec sheet puts it at 15 pf. I'm currently using 22,000 pf capacitors
for C5, C6, and C9.

Remember it is the ESR of the capacitors not their capacitance that
matters most to what the diode capacitance is doing. The storage effect
has most of the longer term effect. The capacitance increases the
sharpness of the output edges that happen when the transformer's voltage
swings up and down.

The timing on the transformer was determined experimentally. I tweaked the
frequency until I got the peak output voltage, and reduced the duty cycle to
the lowest level that'd keep C9 charged. Is there a better way to go about
determining these settings?

Yes, there are better ways. If you are regulating the voltage by means
of a servo loop that controls the duty cycle, you don't need to adjust the
frequency for the highest voltage. I'd be inclined to adjust for the
lowest supply current to maximize the battery life.

Yeah, that's exactly what I'm trying now. I think I've got a problem with
the software switching of the PWM module, though. I need to set it to
buffered mode or it does strange things.

I can offer but little help there. I don't use PICs. The basic thing to
check is what happens to the current cycle's pulse width if it ends just
as you are updating the registers.

Seems like the better designs ground the cathode of the GM tube and detect
the pulses on the high side. That means making C11 a HV cap, and
redesigning the amplifier.

I don't know that this matters in your case. The gain of the tube is very
voltage dependant. You are only counting pulse not measuring how big they
are so a slight gain shift shouldn't matter. I think you can safely leave
the detection on the cathode end.

--
--
kensmith@rahul.net forging knowledge

 

[Fred Bloggs]

Scott Miller wrote:

Here's the schematic, minus the regulation experiments. The LCD has been
reconfigured to free up PTB3/ADC3 for feedback input. The configuration I'm
testing at the moment has the MOVs driving a 2N3904 connected to PTB3. The
idea is to use that to detect when the voltage is at the required level.
That input is checked 3200 times per second and the PWM output is switched
on or off. Right now, the behavior could best be characterized as 'freaking
out'.

Didn't we tell you how to dump that asinine MOV crap in a previous
thread you started about this p.o.s.? -PLONK

 

[Rich MacDonald]

m II <C@In.The.Hat> wrote in news:qB6Ed.84204$KO5.65531@clgrps13:

It's an atrocity that will go down in history as an act worse that the
Nazi invasion of Poland.

Thanks for the opportunity to use Godwin's law and call you an SFB at the
same time.

 

[Ken Smith]

In article <41E0A684.57A4EB10@rica.net>,
John Popelish <jpopelish@rica.net> wrote:
[...]

This is a strange sort of step up supply, what with the full wave
doubler using both swings from the transformer, but the primary driven
only one way.

I've used this same basic design for the output several times. It isn't
all that strange. As far as PWM regulation goes, it is a flyback design.
The doubler means that the output has N*Vin added to it.

Normally, in a flyback design, the primary has a current ramp in it. When
you add the doubler to the output, this changes. The doubler causes a
larger current to flow just as the transistor switches on. This added
current tails away as time passes and the output side capacitor gets
charged. This decreasing current tends to cancel the slope of the
normally increasing current seen in the primary.

The OP isn't using current mode control so this doesn't mess up his
current sensing.

The flatter current wave form has a lower RMS to average ratio so the
losses in the pass transistor can be less with this circuit that would be
the case for just a flybacker.

--
--
kensmith@rahul.net forging knowledge

 

[Ken Smith]

In article <10u1evk8rrr2ee8@corp.supernews.com>,
Scott Miller <scott@3xf.com> wrote:
[...]

Anyway, like I said, we learned about driving transformers with AC.. I don't
know exactly what the secondary output is supposed to look like when the
primary is driven only one way with a square wave.

You can make the circuit in LTSpice and study the effects of various
modifications without smoking real parts.


The transformer is two inductors with a coupling K between them.

--
--
kensmith@rahul.net forging knowledge

 

[Ken Smith]

In article <41e0ec67.1713177929@news.planet.nl>,
Nico Coesel <nico@puntnl.niks> wrote:
[...]

Try to simulate it. Some of the shareware sites still carry a trial
version of Microsim called Winspice. It will only allow a limited
number of components, still more than enough to simulate these sort of
circuits.

www.linear.com has a spice that is free, unlimited, easy to use, nearly
bug free, and much faster than most of the others. Look for "switcher CAD
III". Although Linear started out with this just intended to help in the
design of switchers, the software is a complete general purpose spice.

It has some "hacks" in it that makes it able to handle switching circuits
more quickly than normal spices. This is doubly true if you use their
feature of imbedding the resistance and capacitance right into inductors
rather than adding parts to the model to handle them.

--
--
kensmith@rahul.net forging knowledge

 

[ScottL]

I think that as long as you aren't specifying a purpose and you
understate the max specs you aren't needing UL. You only have to worry
about getting in trouble if someone uses it in such a way that they
cause personal or propery damage. Just remember the rule when
designing for consumer use:
"Make it idiot proof, and they will come out with a better idiot"

In other words, make sure you can afford the liability insurance.
-ScottL

 

[ZZZPK]

m II <ohmworkLEOPARD@spots.ca> wrote:

: It seems to be held in by gravity at this time, with a tube slipped inot the
: mast. I don't imagine it will rotate as easily as it should. The slip rings
: still have to be installed also. The blades may be in need of a protective
: coating to protect the wood from falling apart.
:
: It should be interesting.


shades of a ''scraphead challenge'' here.

wheres the ''chaos crew'' when you need them ?

 

[John Larkin]

On Sat, 08 Jan 2005 22:45:38 GMT, Richard the Dreaded Liberal
<eatmyshorts@doubleclick.net> wrote:

You're right. A dreaded liberal would never say such a thing. I just can't
bring myself to call myself a neocon, which are the people who would enjoy
that sort of hate.

The semi-official definition of "neo-conservative" is "a liberal who
has been mugged by reality." That's sort of an engineering approach to
social well-being.

John

 

[keith]

On Sun, 09 Jan 2005 11:07:34 -0800, John Larkin wrote:

On Sat, 08 Jan 2005 22:45:38 GMT, Richard the Dreaded Liberal
eatmyshorts@doubleclick.net> wrote:



You're right. A dreaded liberal would never say such a thing. I just can't
bring myself to call myself a neocon, which are the people who would enjoy
that sort of hate.


The semi-official definition of "neo-conservative" is "a liberal who
has been mugged by reality." That's sort of an engineering approach to
social well-being.

True, but the way the left uses the term it's closer to "damned Jew".

--
Keith

 

[Rene Tschaggelar]

Mark Jones wrote:

John Woodgate wrote:

I read in sci.electronics.design that markzoom <markzoom@digiverse.net
wrote (in <7172c4fd.0501090729.17d84f6e@posting.google.com&gt about
'Quick power supply question', on Sun, 9 Jan 2005:

Does the symbol, a solid line with a dotted line over it, denote an
unregulated or a regulated supply?

Officially, it just means 'DC'. People seem to think they can allocate
new meanings to these IEC 60417 symbols and everyone will be informed of
the changed meanings by telepathy.

Does it mean "DC" or "DC and pulsating DC?"

It seems like the solid line denotes filtered DC and the dotted line
denotes rectified (and unfiltered) DC. (I may be wrong...)

DC is DC and not pulses, sorry. I'd expect some AC components,
perhaps 100Hz wise and definitely switcher noise. Both perhaps in the
sub volt region.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[keith]

On Sun, 09 Jan 2005 16:55:57 +0000, Al wrote:

In article <crp6e602u9o@drn.newsguy.com>,
Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

John Larkin wrote...

Winfield Hill wrote:

http://www.cnn.com/2005/TECH/01/03/cnn25.top25.innovations

CNN's list of the top 25 innovations of the last 25 years.

2. Cell phone
3. Personal computers
4. Fiber optics
5. E-mail
6. Commercialized GPS
7. Portable computers
8. Memory storage discs
9. Consumer level digital camera
10. Radio frequency ID tags
11. MEMS
12. DNA fingerprinting
13. Air bags
14. ATM
15. Advanced batteries
16. Hybrid car
17. OLEDs
18. Display panels
19. HDTV
20. Space shuttle
21. Nanotechnology
22. Flash memory
23. Voice mail
24. Modern hearing aids
25. Short Range, High Frequency Radio

The number one innovation will be announced on Sunday, January 16,
at 8 p.m. ET. What do you think it is?

Probably CNN.

I don't see the Internet, or the web, WWW server + internet + browser.

Uhh, why, except for 12), 13), and 16), is it all electronic?

AFAIAC, #13 and #16 are primarily electronic. Without the electronics
controls developed in the past few years neither would work.

--
Keith

Where
would successful human organ transplantation fit into this?

I believe the rules said "non-medical". The first successful heart
transplant was in '67, so this wouldn't make the 25 year cut anyway.

http://www.historychannel.com/speeches/archive/speech_15.html

--
Keith


> Al

 

[John Larkin]

On Sun, 09 Jan 2005 06:13:30 GMT, Ben Bradley
<ben_nospam_bradley@mindspring.com> wrote:

"Yet without the tiny silicon chip that sensed the impending
collision, the airbag would not have deployed in time.

""The device that causes an airbag to inflate in a crash is a nanotech
device," said David Kirkpatrick, senior editor at Fortune Magazine."

Doncha just love science journalists? As if accelerometers didn't
exist before the MEMS versions were invented.


John

 

[John Woodgate]

I read in sci.electronics.design that Jim Thompson
<thegreatone@example.com> wrote (in <g713u09dv39gdta926aup2ahl66m8t4qft@
4ax.com&gt about 'I was suddenly struck with a thought (POLITICAL)', on
Sun, 9 Jan 2005:

(This location is a true rock pile... remains of an ancient volcano...
actually, studying the terrain, I suspect I'm living in the mouth...
surround on about 300° is conical, remainder looks like the side blew
out ;-)

HOW ancient?
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[m II]

Bob Yates wrote:

The USA has a long history of unprovoked attacks, look at WWII when they
attacked Germany, using an attack by Japan as the excuse. Or, the
destruction of the CSA, just to expand their tax base.

The northern factories wanted cheap cotton. The northern politicians were no
different than today's crop of corrupt bribe takers.

Slavery and human rights had nothing to do with the Civil War. What Sherman
did on the way to the coast was a war crime of the same status as the
Baghdad bombardment. Atlanta was another..







mike