magnetic field

[Rich Grise]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:EpxEsXAiHbMAFwJ6@jmwa.demon.co.uk...

I read in sci.electronics.design that John Larkin <jjlarkin@highlandSNIP
On Mon, 16 Feb 2004 23:33:25 +0000, John Woodgate
I read in sci.electronics.design that John Larkin <jjlarkin@highSNIPland
Yes, he *might* be, if everything went the wrong way. Suppose something
he did unintentionally provoked a war with China. That would be pretty
dangerous. But he *probably* won't be.

Well, that's just chaos theory. I could drop a banana peel on a
sidewalk somewhere and wind up destroying France.

Hey, that's a GOOD idea! (;-)

Not by intent, of course.

Yes, we call it 'chaos theory' now, but history records many instances
where good intentions caused very bad consequences. Shakespeare wrote
about it in 'King Lear'.

"Really, I'm not out to destroy Microsoft. That will just be a
completely unintentional side effect."
- Linus Torvalds, 2003

Cheers!
Rich

 

[Mark]

"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote in message
news:FKaZb.518$72.179350528@news.telia.no...

"Mjolinor" <mjolinor@hotmail.com> skrev i melding
news:Gp8Zb.77$m47.7@newsfe1-win...
"Anvil" <rbf@spacebbs.com> wrote in message
news:e0d9014a.0402191117.73b23d72@posting.google.com...
Bernt-Johan Bergshaven:

Thank you for this link, I'll download it and hook it up.
But there is one problem..

I dont own a orignal gps module, so I have no traffic to analyze. I want
to
build
my own module and hook it up with the I2C bus in the R-DAS.
So if someone out there with a R-DAS and a gps module could
capture some traffic and try to localize wich adresses and what coding is
used
between the components, I would be really happy.

Well, now I'm REALLY confused. You want to build your own GPS Engine?!?

I'm thinking that you don't understand exactly what a GPS engine is... it is
a combination of very complex time keeping doo-dads, a microprocessor,
extremely complex algorithms, internal (or optionally external) antenna's,
etc, etc.

In addition... there are US government (and some International) regulations
on 'blanking' that MUST be observed if you don't wanna find your butt on a
base in Cuba... that is, if the GPS module is going above a certain altitude
AND a velocity faster than 'X' then the GPS unit

Trust me... you want to purchase your GPS engine... I like the Garmin
variety.

As far as I know, the information coming from the GPS (no matter what module
you decide to use) is straight serial... there is no 'address'. I know this
is true for Garmin... I know this is true for *ALL* NEMA compliant GPS
receivers.

If you want to CONVERT the information that the GPS unit spits out into the
IC2 bus protocol, then the addressing would be assigned during YOUR
conversion. I'd recommend a PIC for this operation.

Since you want to build your own GPS module, I would suggest that;
1. You choose which GPS engine you will use.
2. Study the NEMA protocols.
3. Examine the flavour of the GPS engine NEMA protocols that you've chosen.
4. Study the IC2 bus architecture
5. Study (a suitable) Microcontroller language (RICS \ PIC recommended).
6. Pick a programming language and study it. (In your case, BASIC).
7. Learn to live without friends or social life.
8. Learn to like alcohol... yes... the dry Martini is your friend.

 

[Bernt-Johan Bergshaven]

"Mark" <mburggra1@earthlink.net> skrev i melding
news:cAWZb.3313$yZ1.3270@newsread2.news.pas.earthlink.net...

"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote in message
news:FKaZb.518$72.179350528@news.telia.no...
"Mjolinor" <mjolinor@hotmail.com> skrev i melding
news:Gp8Zb.77$m47.7@newsfe1-win...
"Anvil" <rbf@spacebbs.com> wrote in message
news:e0d9014a.0402191117.73b23d72@posting.google.com...
Bernt-Johan Bergshaven:

Thank you for this link, I'll download it and hook it up.
But there is one problem..

I dont own a orignal gps module, so I have no traffic to analyze. I want
to
build
my own module and hook it up with the I2C bus in the R-DAS.
So if someone out there with a R-DAS and a gps module could
capture some traffic and try to localize wich adresses and what coding
is
used
between the components, I would be really happy.

Well, now I'm REALLY confused. You want to build your own GPS Engine?!?

I'm thinking that you don't understand exactly what a GPS engine is... it
is
a combination of very complex time keeping doo-dads, a microprocessor,
extremely complex algorithms, internal (or optionally external) antenna's,
etc, etc.

In addition... there are US government (and some International)
regulations
on 'blanking' that MUST be observed if you don't wanna find your butt on a
base in Cuba... that is, if the GPS module is going above a certain
altitude
AND a velocity faster than 'X' then the GPS unit

Trust me... you want to purchase your GPS engine... I like the Garmin
variety.

As far as I know, the information coming from the GPS (no matter what
module
you decide to use) is straight serial... there is no 'address'. I know
this
is true for Garmin... I know this is true for *ALL* NEMA compliant GPS
receivers.

If you want to CONVERT the information that the GPS unit spits out into
the
IC2 bus protocol, then the addressing would be assigned during YOUR
conversion. I'd recommend a PIC for this operation.

Since you want to build your own GPS module, I would suggest that;
1. You choose which GPS engine you will use.
2. Study the NEMA protocols.
3. Examine the flavour of the GPS engine NEMA protocols that you've
chosen.
4. Study the IC2 bus architecture
5. Study (a suitable) Microcontroller language (RICS \ PIC recommended).
6. Pick a programming language and study it. (In your case, BASIC).
7. Learn to live without friends or social life.
8. Learn to like alcohol... yes... the dry Martini is your friend.

Okey, sorry If I have been unclear in certain points, and let me clear it
out.

I have a GPS ( Magellan Colortrack), I want to use the circuit board,
and antenna and all the other things needed to have this gps working.
This I want to put inside a rocket, and hook it up with the data collector
( R-DAS ). So far okey?
If you check the R-DAS homepage ( http://home.iae.nl/users/aed/rdas/ ),
you will find that they sell a gps module ready for connection with the
R-das.
It's a ordinary gps in most ways, and on this module or board if you like,
you'll also find
a Atmel AVR uC. This uC does the magical things; stripping the data from the
gps ( NMEA ),
so that we get only what we need. It also converts the stripped binary
stream to fit onto an I2C bus.

What I relly need to know, is how the NMEA data looks after it has been
stripped, and in which format,
or protocol if you like it sends the data. So when I use my own GPS and my
own Atmel AVR, I can copy
this behaviour and make the R-DAS believe that my homemade GPS-MODULE (not
gps reciver), is infact the original.
I also need to know what adress the R-das motherboard is, so i know where to
send the data on the I2C bus, and I need to
know if there are some interrupts in this picture....

At least, but not less, the answers to your 1.2.3.4.5.6.7.8. points of wisom


1. I have a gps, ( Magellan Colortrack )
2. I know the NMEA protocol, at least good enough to find what I'm looking
for
3. I know exactly what kind of NMEA strings my GPS sends, and I can read
them with rs232
4. I need some more studying here, but I think I got enough info to
understand the basics.
5. I know some ASM, and some C. ( Got educated people who can help me here )
6. In my case BASIC,...? I dont want to use BASIC, I use C and ASM. And on
the reciever side I use C++.
7. I actually live in a student house, so thats kinda complicated. And if
everyone with an electronics projects should learn to live without friends,
than we all would be pretty asosial types.
8. No not dry martini, my favourite is a cold MACK BEER from Tromso Norway


Thanks for your post, and I hope that things are more clear now
It was funny to write this so, no hard feelings

Regards
Bernt-Johan Bergshaven

 

[Stephen Woolhead]

"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote

Okey, sorry If I have been unclear in certain points, and let me clear it
out.

I have a GPS ( Magellan Colortrack), I want to use the circuit board,
and antenna and all the other things needed to have this gps working.
This I want to put inside a rocket, and hook it up with the data collector
( R-DAS ). So far okey?

It seems the easyist way to do this is not to use the I2C bus for your data,
but to hook into the serial stream being sent to the transmitter and rewite
it using the values from your GPS.

RDAS --- FILTER -- TRANSMITTER
|
YOUR GPS

There are several posts on the R-DAS mailing list on Topica which mention
this. It is a better route as the tramsmitter serial protocol has been
published by AED on the above list.

Stephen.

 

[Bernt-Johan Bergshaven]

"Stephen Woolhead" <stephen@grosvenortechnology.com> skrev i melding
news:bjn_b.9114173$Of.1499450@news.easynews.com...

"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote

Okey, sorry If I have been unclear in certain points, and let me clear
it
out.

I have a GPS ( Magellan Colortrack), I want to use the circuit board,
and antenna and all the other things needed to have this gps working.
This I want to put inside a rocket, and hook it up with the data
collector
( R-DAS ). So far okey?

It seems the easyist way to do this is not to use the I2C bus for your
data,
but to hook into the serial stream being sent to the transmitter and
rewite
it using the values from your GPS.

RDAS --- FILTER -- TRANSMITTER
|
YOUR GPS

There are several posts on the R-DAS mailing list on Topica which mention
this. It is a better route as the tramsmitter serial protocol has been
published by AED on the above list.

Stephen.

Yes, i read some information regarding the serial bus between the R-DAS and
the transmitter,
and this may be the right way to go
Thanks for all your help.

But still: If there are anyone out there with a RDAS and an origial gps
module,
it would be great if you used an I2C sniffer and collected the information
sent
between theese to components. So that projects in the future can be built
with I2C support.

Thanks again.
Regards
Bernt-Johan Bergshaven

 

[Tom MacIntyre]

On Mon, 23 Feb 2004 21:21:15 GMT, "Roger Gt" <not@here.net> wrote:

"Tim Williams" wrote
: "John Fields" wrote

: > >Remember, we did beat the US once already.
: > ---
: > At what, hockey?
:
: Probably refers to 1812. Or perhaps even earlier than that.

No, it was a rebellion in Canada, the losers fled to the US.
1838 - 1840
Read about it at:

http://www.globalsecurity.org/military/ops/patriots.htm

We got even when all the Draft Dodgers fled to Canada!

Didn't Canadians burn the original White House down?

Tom

 

[Tom MacIntyre]

On 23 Feb 2004 14:23:01 -0800, jeffm_@email.com (JeffM) wrote:

Mexico is a great country, rich in resources and great people,
but with one of the most corrupt governments in the world.
Since Mexico is already pretty much a US welfare state
we should just seize the place. I doubt that more than
a handful of people would even attempt resistance.
Jim Thompson

Let's annex Canada while we're at it. All their best people are here anyway.
**Ducking before Speff, Boris, Black, et al start throwing things@my.head.**

We apparently lost a lot of our best in the early 60's (late 50's?)
when the Diefenbaker government scuttled the Avro Arrow project.
Probably one of the worst political moves in the history of Canada.

Tom

 

[Mark]

"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote in message
news:mS1_b.595$72.179263488@news.telia.no...

"Mark" <mburggra1@earthlink.net> skrev i melding
news:cAWZb.3313$yZ1.3270@newsread2.news.pas.earthlink.net...
"Bernt-Johan Bergshaven" <bernt@netbase.no> wrote in message
news:FKaZb.518$72.179350528@news.telia.no...
"Mjolinor" <mjolinor@hotmail.com> skrev i melding
news:Gp8Zb.77$m47.7@newsfe1-win...
"Anvil" <rbf@spacebbs.com> wrote in message
news:e0d9014a.0402191117.73b23d72@posting.google.com...
Bernt-Johan Bergshaven:

Okey, sorry If I have been unclear in certain points, and let me clear it
out.

I have a GPS ( Magellan Colortrack), I want to use the circuit board,
and antenna and all the other things needed to have this gps working.
This I want to put inside a rocket, and hook it up with the data collector
( R-DAS ). So far okey?

Okay... Got it!

If you check the R-DAS homepage ( http://home.iae.nl/users/aed/rdas/ ),
you will find that they sell a gps module ready for connection with the
R-das.
It's a ordinary gps in most ways, and on this module or board if you like,
you'll also find
a Atmel AVR uC. This uC does the magical things; stripping the data from
the
gps ( NMEA ),
so that we get only what we need. It also converts the stripped binary
stream to fit onto an I2C bus.

True... the fog is beginning to lift... I'm beginning to understand...

What I relly need to know, is how the NMEA data looks after it has been
stripped, and in which format,
or protocol if you like it sends the data. So when I use my own GPS and my
own Atmel AVR, I can copy
this behaviour and make the R-DAS believe that my homemade GPS-MODULE (not
gps reciver), is infact the original.

NOW I understand! Actually, that would be very interesting information to
know!

I don't have the RDAS GPS module....

But, tell you what... I've got the RDAS with the optional magnetometer and
2-axis accelerameter board... I know it's not the GPS, but I'm sure we can
glean a little information about the bus by using BreakOut or some other
such tool we've got laying around the shop.

I also need to know what adress the R-das motherboard is, so i know where
to
send the data on the I2C bus, and I need to
know if there are some interrupts in this picture....

Understood...

At least, but not less, the answers to your 1.2.3.4.5.6.7.8. points of
wisom


1. I have a gps, ( Magellan Colortrack )
2. I know the NMEA protocol, at least good enough to find what I'm looking
for
3. I know exactly what kind of NMEA strings my GPS sends, and I can read
them with rs232
4. I need some more studying here, but I think I got enough info to
understand the basics.
5. I know some ASM, and some C. ( Got educated people who can help me
here )
6. In my case BASIC,...? I dont want to use BASIC, I use C and ASM. And on
the reciever side I use C++.
7. I actually live in a student house, so thats kinda complicated. And if
everyone with an electronics projects should learn to live without
friends,
than we all would be pretty asosial types.
8. No not dry martini, my favourite is a cold MACK BEER from Tromso Norway

Heh, heh... great post. Not sure how much I can add to the pool of
knowledge, but I could probably snap a picture of the addressing scheme. If
memory serves, it's a simple 'first board', 'second board' type of thing.

Thanks for your post, and I hope that things are more clear now

Yes, very clear... thank you!
BTW, I'll also query RDAS and see if they can impart a bit of wisdom.

It was funny to write this so, no hard feelings

No, no... no hard feelings at all... in fact, in re-reading your post... I'm
not really sure why I didn't understand you the first time.

Best.

Mark

 

[Sodah]

Just to add an interesting footnote... Late evening/night (e.g. the present
moment) the 'flicker' diminishes _dramatically_. My guess is that this is
due to it being "off peak" hours for electricity demand (i.e. less energy
going through --and therefore, being emitted by-- the powerlines).


"DaveW" <none@zero.org> wrote in message
news:hmQ0c.160011$uV3.707652@attbi_s51...

An LCD is about the only workable solution.

--
DaveW

Thought so. But I love my CRT monitor! So... before I decide to
throw-in-the-towel and "downgrade" to an LCD (just my personal
preference/opinion), I'm going to put just a little more time into looking
for some way to "magnetically shield" my monitor (i.e. the space it is in).
To anyone out there technically versed in such stuff (i.e. "magnetic
shielding"), I'd eagerly welcome any useful information/insight/etc. you
might be able to share towards this.

Thanks,

Sodah

"Sodah" <sodah6@home.com> wrote in message
news:X4N0c.661124$X%5.80923@pd7tw2no...
Hi!
I just moved into my sisters place, which is adjacent to some
high-tension
power-lines. Set up my computer yesterday, and immediately observed a
fine
but pervasive 'flicker' on my (CRT) monitor (similar to what my sister
has
been experiencing with her own two [CRT] computer monitors for years).
This
is quite annoying, not to mention rapidly productive of eyestrain and
fatigue. Based on my own monitor's past performance, coupled with my
sister's consistent experience with her own monitors, it seems obvious
to
me
that this 'flicker' is due entirely to electromagnetic-interference from
the
power lines. What I would like to know, if anybody out there can tell
me,
is: (1) Might there be any conceivable action I could take to better
shield
my monitor from such electromagnetic interference (e.g. a commercial
add-on
product, or home-made metallic shroud, etc...)? ; (2) Please correct me
if
I am not right in my guess that (failing the above) replacing my CRT
monitor
with an LCD monitor should avoid the problem (i.e. since the latter does
not
utilize an electromagnetically-hypersensitive electron beam).

Thanks in advance for any helpful advice, experience, links to info,
etc...

Sodah

 

[Charles Perry]

"Sodah" <sodah6@home.com> wrote in message
news:goX0c.646438$JQ1.309669@pd7tw1no...

Just to add an interesting footnote... Late evening/night (e.g. the
present
moment) the 'flicker' diminishes _dramatically_. My guess is that this is
due to it being "off peak" hours for electricity demand (i.e. less energy
going through --and therefore, being emitted by-- the powerlines).
Do a search on Google for mu metal . It works. It is VERY expensive

(around $300 for a monitor). You can probably do some good by changing the
location of the monitor. You would be surprised at what a few feet can do.
The strength of the field drops by the distance squared, so a small change
in the distance from the source can make a huge difference in the strength
of the field.

Also, assuming you are in a 60hz power location, change the scan rate of the
monitor (if possible). This often helps.

Charles Perry P.E.

 

[Jerry G.]

Did you try to increase the scan rate to about 80 Hz or something like this?

Are you located right under the power lines, or within a few hundred feet?

If the flicker is from the magnetic field of the power lines, you are
correct in assuming that the flicker will vary at particular times of the
day. This is correct in assuming that this has to do with the peak loading.

Your monitor CRT is shielded by a u-metal ( mew-metal ) shied according to
the international safety standards. This is to meet specific requirements.
Any type of magnetic field that can pass through in any direction would be
considered excessively strong, or the shield in your monitor is not adequate
according to established standards.

If you want to add shielding, the required type of metal is very expensive,
and the design of the shield set-up would be complex. To shield out the
lower frequencies, such as the 50 and 60 Hz from AC power sources is more
complicated than to shield out high frequencies such as X-Ray and microwave.

My suggestion is that if you are living in a condition where the field is so
strong to cause a monitor to flicker, you should strongly consider moving!
These fields are known to be dangerous over time. The power companies are in
denial about this, because there are not many long term studies, and many
that have been done were not openly published.


I would think your problem may be more serious than just a monitor
condition, if this is the case. I even have thoughts about the electrical
wiring in my home, even though it is of the average, and the fields from it
are very small. But, they are present, or I would not be able to have power
in my home.

Effect Of Electro Magnetic Fields (ELF) on humans, World Health Organization
http://www.who.int/peh-emf/about/WhatisEMF/en/index1.html

Power Line, Electro Magnetic Field (ELF), health concerns
http://www.niehs.nih.gov/emfrapid/extrmurabs/marino.html

I very strongly suggest you go to this site, and read the links!
http://www.business.com/directory/human_resources/workplace_health_and_safety/environmental_issues/electric_and_magnetic_fields_emf/

Search criteria (sample)
http://www.google.com/search?q=long+term+effect+magnetic+fields+health&btnG=Google+Search

ISO definitions
http://www.narda-sts.de/en/hilfe/schlagwortregister.htm



--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Sodah" <sodah6@home.com> wrote in message
news:goX0c.646438$JQ1.309669@pd7tw1no...
Just to add an interesting footnote... Late evening/night (e.g. the present
moment) the 'flicker' diminishes _dramatically_. My guess is that this is
due to it being "off peak" hours for electricity demand (i.e. less energy
going through --and therefore, being emitted by-- the powerlines).


"DaveW" <none@zero.org> wrote in message
news:hmQ0c.160011$uV3.707652@attbi_s51...

An LCD is about the only workable solution.

--
DaveW

Thought so. But I love my CRT monitor! So... before I decide to
throw-in-the-towel and "downgrade" to an LCD (just my personal
preference/opinion), I'm going to put just a little more time into looking
for some way to "magnetically shield" my monitor (i.e. the space it is in).
To anyone out there technically versed in such stuff (i.e. "magnetic
shielding"), I'd eagerly welcome any useful information/insight/etc. you
might be able to share towards this.

Thanks,

Sodah

"Sodah" <sodah6@home.com> wrote in message
news:X4N0c.661124$X%5.80923@pd7tw2no...
Hi!
I just moved into my sisters place, which is adjacent to some
high-tension
power-lines. Set up my computer yesterday, and immediately observed a
fine
but pervasive 'flicker' on my (CRT) monitor (similar to what my sister
has
been experiencing with her own two [CRT] computer monitors for years).
This
is quite annoying, not to mention rapidly productive of eyestrain and
fatigue. Based on my own monitor's past performance, coupled with my
sister's consistent experience with her own monitors, it seems obvious
to
me
that this 'flicker' is due entirely to electromagnetic-interference from
the
power lines. What I would like to know, if anybody out there can tell
me,
is: (1) Might there be any conceivable action I could take to better
shield
my monitor from such electromagnetic interference (e.g. a commercial
add-on
product, or home-made metallic shroud, etc...)? ; (2) Please correct me
if
I am not right in my guess that (failing the above) replacing my CRT
monitor
with an LCD monitor should avoid the problem (i.e. since the latter does
not
utilize an electromagnetically-hypersensitive electron beam).

Thanks in advance for any helpful advice, experience, links to info,
etc...

Sodah

 

[Bob Myers]

"Jerry G." <jerryg50@hotmail.com> wrote in message
news:c226o8$6i9$1@news.eusc.inter.net...

Did you try to increase the scan rate to about 80 Hz or something like
this?

Actually, assuming that the problem IS magnetic interference, this
is exactly the wrong advice. Minimizing the visible effects of such
interference requires setting the refresh rate as close as possible
to the local power frequency or an integer multiple of that.

Your monitor CRT is shielded by a u-metal ( mew-metal ) shied according
to
the international safety standards. This is to meet specific
requirements.
Any type of magnetic field that can pass through in any direction would be
considered excessively strong, or the shield in your monitor is not
adequate
according to established standards.

Nope. International standards do not cover magnetic
SUSCEPTIBILITY on the part of CRT monitors, only their
magnetic emissions. Those are generally NOT addressed through
internal shielding, and it is actually somewhat rare for a mainstream
CRT monitor these days to contain much, if any, "mu-metal" or
other magnetic shielding material. (There MAY be a bit within the
CRT itself, but even that is becoming less common.)

If you want to add shielding, the required type of metal is very
expensive,
and the design of the shield set-up would be complex. To shield out the
lower frequencies, such as the 50 and 60 Hz from AC power sources is more
complicated than to shield out high frequencies such as X-Ray and
microwave.

Mostly because in the former case, we ARE talking about a straight
magnetic field and not EM. Very different beasts.

My suggestion is that if you are living in a condition where the field is
so
strong to cause a monitor to flicker, you should strongly consider moving!
These fields are known to be dangerous over time. The power companies are
in
denial about this, because there are not many long term studies, and many
that have been done were not openly published.

It doesn't take much in the way of magnetic field strength to cause
visible problems on the monitor - in fact, the fields involved are generally
on roughly the same order of magnitude as the Earth's own field (and
you're not overly worried about THAT, I hope..) The problem is
that the power-line fields are AC, which causes the image on the screen to
move rapidly back and forth, and thus be visually objectionable. (The
Earth's own field also moves the image, but since it's a static displacement
you don't notice this as a problem.) In any event, the possible health
concerns over low-frequency magnetic fields have, IMHO, been
grossly overstated.


Bob M.

 

88 Hz works great, I've used it. Still some distortion, but not too
bad, right in a load center.

At 60 Hz you get the slow flag wave. DUH

On Tue, 02 Mar 2004 20:07:59 GMT, "Bob Myers"
<nospamplease@address.invalid> wrote:

"Jerry G." <jerryg50@hotmail.com> wrote in message
news:c226o8$6i9$1@news.eusc.inter.net...
Did you try to increase the scan rate to about 80 Hz or something like
this?

Actually, assuming that the problem IS magnetic interference, this
is exactly the wrong advice. Minimizing the visible effects of such
interference requires setting the refresh rate as close as possible
to the local power frequency or an integer multiple of that.

 

[Floyd L. Davidson]

dummy@home.com wrote:

88 Hz works great, I've used it. Still some distortion, but not too
bad, right in a load center.

At 60 Hz you get the slow flag wave. DUH

At 88 Hz you get a 28 Hz wave, which is faster than the human
eye can follow. However, that means your eye doesn't see each
change, and instead you see a wide, fuzzy vertical line rather
than a wavy vertical line.

The loss of definition may bother you as much or perhaps even
more than the wavy lines did!

"Bob Myers" <nospamplease@address.invalid> wrote:
"Jerry G." <jerryg50@hotmail.com> wrote:

Did you try to increase the scan rate to about 80 Hz or something like
this?

Actually, assuming that the problem IS magnetic interference, this
is exactly the wrong advice. Minimizing the visible effects of such
interference requires setting the refresh rate as close as possible
to the local power frequency or an integer multiple of that.

That is essentially true, but doesn't help. The requirement is not
"as close as possible", but rather "closer than is possible"! You
have to *lock* the vertical rate to the power line frequency. That
is because both the power line and the monitor will change enough
over a day's time to cause a very slow wave unless the monitor tracks
the power. (The power lines have very good long term stability,
but that is an average, not an instantaneous accuracy.)

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com

 

[Sodah]

Also, assuming you are in a 60hz power location, change the scan rate of
the
monitor (if possible). This often helps.

Very true!! In fact I'm keeping my refresh rate at 60 hz (during "peak
hours", that is) as it does make quite a difference ... The image stops
shaking around (which, btw, further confirms the, "it's the powerlines",
explanation...). (Other available refresh rates don't do the trick.)
Unfortunately, 60 mhz itself inherently appears as 'strobe-like' (rather
than appearing to my eye as 'continuous and uninterrupted'), thus similarly
productive of eyestrain/fatigue/etc ... thus not a long term solution.


Thanx,
Sodah



"Charles Perry" <pipesandtobacco@hotmail.com> wrote in message
news:c21itc$1fksb1$1@ID-103962.news.uni-berlin.de...

"Sodah" <sodah6@home.com> wrote in message
news:goX0c.646438$JQ1.309669@pd7tw1no...
Just to add an interesting footnote... Late evening/night (e.g. the
present
moment) the 'flicker' diminishes _dramatically_. My guess is that this
is
due to it being "off peak" hours for electricity demand (i.e. less
energy
going through --and therefore, being emitted by-- the powerlines).
Do a search on Google for mu metal . It works. It is VERY expensive
(around $300 for a monitor). You can probably do some good by changing
the
location of the monitor. You would be surprised at what a few feet can
do.
The strength of the field drops by the distance squared, so a small change
in the distance from the source can make a huge difference in the strength
of the field.

Also, assuming you are in a 60hz power location, change the scan rate of
the
monitor (if possible). This often helps.

Charles Perry P.E.

 

[Charles Perry]

"Sodah" <sodah6@home.com> wrote in message
news:2Ld1c.671740$X%5.68074@pd7tw2no...

Also, assuming you are in a 60hz power location, change the scan rate of
the
monitor (if possible). This often helps.


Very true!! In fact I'm keeping my refresh rate at 60 hz (during "peak
hours", that is) as it does make quite a difference ... The image stops
shaking around (which, btw, further confirms the, "it's the powerlines",
explanation...). (Other available refresh rates don't do the trick.)
Unfortunately, 60 mhz itself inherently appears as 'strobe-like' (rather
than appearing to my eye as 'continuous and uninterrupted'), thus
similarly
productive of eyestrain/fatigue/etc ... thus not a long term solution.


Thanx,
Sodah

By the way, don't assume that those big power lines you see outside are the

cause. They often aren't. This type of interference is caused by magnetic
fields, which are caused by current. The strength of the field decreases by
the square of the distance. Those big lines often have no more current than
the low voltage ones attached to your home and they are much farther away.
It is very likely that the conductors causing the problem are low voltage
(600v or less). It could be the service conductor to the house (or
apartement building). It could also be a transformer. It could be wiring
in the wall.

Charles Perry P.E.

 

[Sodah]

"Charles Perry" <pipesandtobacco@hotmail.com> wrote in message
news:c23upg$1oofd4$1@ID-103962.news.uni-berlin.de...

By the way, don't assume that those big power lines you see outside are
the
cause. They often aren't. This type of interference is caused by
magnetic
fields, which are caused by current. The strength of the field decreases
by
the square of the distance. Those big lines often have no more current
than
the low voltage ones attached to your home and they are much farther away.
It is very likely that the conductors causing the problem are low voltage
(600v or less). It could be the service conductor to the house (or
apartement building). It could also be a transformer. It could be wiring
in the wall.

Well, I'll just add that the builder of the house had to ground all of the
window frames (which are aluminum, of course) when this house was
constructed. The other day when the cable guy came to install my internet
connection, he was mystified and daunted when he saw all the cabling
seemingly "coming out of everywhere". I had to explain to him that it was
not television (or other coaxial) cable...

Sodah

 

[Charles Perry]

"Sodah" <sodah6@home.com> wrote in message
news:iag1c.673376$X%5.202631@pd7tw2no...

"Charles Perry" <pipesandtobacco@hotmail.com> wrote in message
news:c23upg$1oofd4$1@ID-103962.news.uni-berlin.de...
[...]
By the way, don't assume that those big power lines you see outside are
the
cause. They often aren't. This type of interference is caused by
magnetic
fields, which are caused by current. The strength of the field
decreases
by
the square of the distance. Those big lines often have no more current
than
the low voltage ones attached to your home and they are much farther
away.
It is very likely that the conductors causing the problem are low
voltage
(600v or less). It could be the service conductor to the house (or
apartement building). It could also be a transformer. It could be
wiring
in the wall.


Well, I'll just add that the builder of the house had to ground all of
the
window frames (which are aluminum, of course) when this house was
constructed. The other day when the cable guy came to install my internet
connection, he was mystified and daunted when he saw all the cabling
seemingly "coming out of everywhere". I had to explain to him that it was
not television (or other coaxial) cable...

Sodah

Why did he have to ground them? Who told him he had to ground them? What

was grounding them going to fix?

Charles Perry P.E.

 

[Hactar]

In article <c245vc$1p9ob0$1@ID-103962.news.uni-berlin.de>,
Charles Perry <pipesandtobacco@hotmail.com> wrote:

"Sodah" <sodah6@home.com> wrote in message
news:iag1c.673376$X%5.202631@pd7tw2no...

"Charles Perry" <pipesandtobacco@hotmail.com> wrote in message
news:c23upg$1oofd4$1@ID-103962.news.uni-berlin.de...

By the way, don't assume that those big power lines you see outside are
the cause. They often aren't. This type of interference is caused by
magnetic fields, which are caused by current.

Well, I'll just add that the builder of the house had to ground all of
the window frames (which are aluminum, of course) when this house was
constructed.

Why did he have to ground them?

High electric field produces a voltage differential across a distance toward
the conductor (0 V at ground, $HIGH V at wire). In some cases, unattached
fluorescent tubes will illuminate.

Who told him he had to ground them?

Probably the codes, or the power company.

What was grounding them going to fix?

Buildup of charge, or maybe a humming noise.

--
-eben ebQenW1@EtaRmpTabYayU.rIr.OcoPm home.tampabay.rr.com/hactar

Q: What kind of modem did Jimi Hendrix use?
A: A purple Hayes.

 

[Charles Perry]

"Hactar" <ebenONE@tampabay.ARE-ARE.com.unmunge> wrote in message
news:c24lqg$4tr$1@pc.tampabay.rr.com...

In article <c245vc$1p9ob0$1@ID-103962.news.uni-berlin.de>,
Charles Perry <pipesandtobacco@hotmail.com> wrote:

"Sodah" <sodah6@home.com> wrote in message
news:iag1c.673376$X%5.202631@pd7tw2no...

"Charles Perry" <pipesandtobacco@hotmail.com> wrote in message
news:c23upg$1oofd4$1@ID-103962.news.uni-berlin.de...

By the way, don't assume that those big power lines you see outside
are
the cause. They often aren't. This type of interference is caused
by
magnetic fields, which are caused by current.

Well, I'll just add that the builder of the house had to ground all
of
the window frames (which are aluminum, of course) when this house was
constructed.

Why did he have to ground them?

High electric field produces a voltage differential across a distance
toward
the conductor (0 V at ground, $HIGH V at wire). In some cases, unattached
fluorescent tubes will illuminate.

Who told him he had to ground them?

Probably the codes, or the power company.

Actually unlikely.

What was grounding them going to fix?

Buildup of charge, or maybe a humming noise.

Exactly, none of which have anything to do with the flickering monitor!
Electric fields cause the voltage problem, magnetic fields cause the monitor
problem. Like I said in a previous post, just because you have a high
voltage line does NOT mean you will have a high B field outside of the right
of way. The origonal poster gave the "E field protection" answer as
justification that the line was causing his problem.

Charles Perry P.E.