Chip with simple program for Toy

[Cliff]

On Thu, 24 Nov 2005 02:27:36 GMT, "Gary H. Lucas"
<gary.lucas@verizon.net> wrote:

"Bill Roberto" <upnrunning@earthlink.net> wrote in message
news:Ba7hf.1357$A23.374@newsread2.news.pas.earthlink.net...
I had to make a communication cable for a customer today. I went to Orvac's
and asked for 100' feet of 4 wire shielded cable. The salesman said he went
to a 3 day wire seminar from Beldon Cable. They claim that twisted wire
will work as good or better than shielded cable. I asked why and he said
that any noise picked up by one wire gets cancelled out by being wrapped
around the other wires. I figured that would probably be true for any
electromagnetic noise but what about RF noise? He didn't know, so I bought
the shielded because I don't want to experiment on a customer. Has anyone
used twisted wire cable for communications?

Bill,
Good call. I believe you would have been very unhappy with just twisted
pair. Twisted pair has replaced shielded wire in many applications, that
were designed for twisted pair. Yes the cancellation does occur because
both wires tend to pass through fields equally. However the circuitry must
be designed for balanced signals to take advantage of that. I've done some
installation work with large twisted pair cables for Ethernet. The thing I
find interesting is that in a 25 pair cable each pair has the twist at a
different rate! One pair will twist say 2 times per inch while the one
along side twists at 1-1/12 times per inch. This is supposed to reduce the
crosstalk between pairs.

You are of course aware that the shield gets grounded at only one end. This
may be somewhat difficult to determine unless you use an ohm meter to find
out what is connected on the computer end and what is connected at the
machine end. Since most ELECTRONICS engineers seem to have a difficult time
grasping the concepts of good SIGNAL shielding in a POWER (machine)
environment, this is nearly universally done wrong.

Gary H. Lucas

 

[skeptic]

I'd say it depends on the application - frequency, impedance and
allowable attenuation.

I personally know of an example of a strip mine that wanted video
cameras at each of their gates, all viewable from a central guard
shack. The gates were about a mile apart and coax had too much loss so
they used twisted pairs for the video. I saw the video at the guard
shack and it was flawless.

Unfortunately I know very little of the characterists of twisted pairs
at higher frequencies so I wouldn't risk it. However at audio and
video frequencies I'd give it a try.


Cliff wrote:

"Bill Roberto" <upnrunning@earthlink.net> wrote in message
news:Ba7hf.1357$A23.374@newsread2.news.pas.earthlink.net...
I had to make a communication cable for a customer today. I went to
Orvac's and asked for 100' feet of 4 wire shielded cable. The salesman
said he went to a 3 day wire seminar from Beldon Cable. They claim that
twisted wire will work as good or better than shielded cable. I asked
why and he said that any noise picked up by one wire gets cancelled out
by being wrapped around the other wires. I figured that would probably
be true for any electromagnetic noise but what about RF noise? He didn't
know, so I bought the shielded because I don't want to experiment on a
customer. Has anyone used twisted wire cable for communications?

On Wed, 23 Nov 2005 18:43:47 -0600, "shu" <washu@hiwaay.net> wrote:

Absolutely not

Oh, Goodie <G>.

Unshielded Twisted Pairs cancel noise out, only because each line recieves
equal amount of noise, and Hence at the *Balanced* line RECEIVERS there is
noise cancellation

Delta V = ~0 at about any place on the twisted pairs as a result
of EM noise from the environment, assuming that it's wavelength
is at right angles to the lines and it's wavelengths far larger than
the pair conductor to conductor distance (excluding speed of
light changes<G>.)

the actual noise cancellation occurs AT the receivers,

How did it get there?

and ONLY if they are
balanced on each end... like computer network cables.

??

If your communication cable setup is not balanced at each end, then the
magical noise cancellation disappears, and in fact you'll get quite a bit of
noise.

You could add a rectifier and get free energy, right? Just from
the thermal background noise ...
--
Cliff

 

[shu]

"skeptic" <jgreimer@yahoo.com> wrote in message
news:1132890964.341034.113490@z14g2000cwz.googlegroups.com...

I'd say it depends on the application - frequency, impedance and
allowable attenuation.

I personally know of an example of a strip mine that wanted video
cameras at each of their gates, all viewable from a central guard
shack. The gates were about a mile apart and coax had too much loss so
they used twisted pairs for the video. I saw the video at the guard
shack and it was flawless.

Unfortunately I know very little of the characterists of twisted pairs
at higher frequencies so I wouldn't risk it. However at audio and
video frequencies I'd give it a try.

Twisted pairs eliminate noise because the amplifier/reciever on both ends
have matching impendence.. that is to say both ends of the cable are
balanced
in audio and video applications it's very rare that both ends will be
balanced, a twisted pair is generally bad choice for wiring audio and video.
In computer networks they work very well because the network cards/devices
all have the exact same impendence, and the noise is canceled out. If the
impendence is NOT the same, then the twisted pair does nothing to sheild
away noise.


a normal coax cable consists of an inner conductor, a dielectric, and an
outer conductor, and a jacket.. these are also known as "transmission"
cables, if you dont' use the right coax cable (ie matching impendence) you
can have a lot of loss... ie 50ohm coax on a 75 ohm system, or 75 ohm coax
on a 50 ohm system
if you had a lot of loss, you probably could have just as well used a normal
Shielded cable and not get the loss.. a shielded cable consists of an
innerconductor, an insulator, and an EM sheild

if your twisted pair video system worked really well, then it was because
both ends were balanced (quite possible) , or you dont' have a lot of EM
noise around,


**********
shu

 

[skeptic]

Twisted pairs eliminate noise because the amplifier/reciever on both ends
have matching impendence.. that is to say both ends of the cable are
balanced
in audio and video applications it's very rare that both ends will be
balanced, a twisted pair is generally bad choice for wiring audio and video.
In computer networks they work very well because the network cards/devices
all have the exact same impendence, and the noise is canceled out. If the
impendence is NOT the same, then the twisted pair does nothing to sheild
away noise.

Yes, twisted pairs do work because they are balanced but it is not true
that it is rare that both ends of audio and video lines have the same
impedance. With audio the standard impedance is 600 ohms and with
video it is 75 ohms.

Secondly the principle effect of a mismatched line is not a lot of
loss, but reflections. Reflections on a video line would be seen as
multiple images. I did not see multiple images on the strip mine
monitors I described which means they correctly matched the twisted
pair to 75 ohms.

Thirdly, I'm not claiming that there was a lot of electrical noise
around the strip mine and that is one of the reasons it was a good
choice. I did say that the use of twisted pair depends on the
application and a high level of EMI would be a vote against using it.

if your twisted pair video system worked really well, then it was because
both ends were balanced (quite possible) , or you dont' have a lot of EM
noise around,

I think you've answered yourself quite well.

 

[shu]

"skeptic" <jgreimer@yahoo.com> wrote in message
news:1132923755.198911.29710@z14g2000cwz.googlegroups.com...

Twisted pairs eliminate noise because the amplifier/reciever on both
ends
have matching impendence.. that is to say both ends of the cable are
balanced
in audio and video applications it's very rare that both ends will be
balanced, a twisted pair is generally bad choice for wiring audio and
video.
In computer networks they work very well because the network
cards/devices
all have the exact same impendence, and the noise is canceled out. If
the
impendence is NOT the same, then the twisted pair does nothing to sheild
away noise.

Yes, twisted pairs do work because they are balanced but it is not true
that it is rare that both ends of audio and video lines have the same
impedance. With audio the standard impedance is 600 ohms and with
video it is 75 ohms.

actually there are two Main standards for Coax "low loss" 50 Ohm. and 75 Ohm
on a coax the audio can travel down the same line, and have the same
impendance, ie 50 or 75
audio and video impedances themselves are fairly wide and varied
I've seen 75 Ohm 22 Ohm and 50 Ohm video
audio is worse with impedence rarely matching on even the same system
ie.. 18 Ohm's in .. 50 Ohms out. i've not seen any 600 Ohm systems.




while there may be a "Standard" audio impedance

Secondly the principle effect of a mismatched line is not a lot of
loss, but reflections. Reflections on a video line would be seen as
multiple images. I did not see multiple images on the strip mine
monitors I described which means they correctly matched the twisted
pair to 75 ohms.

if it's not done right, you'll get a lot of loss.

Thirdly, I'm not claiming that there was a lot of electrical noise
around the strip mine and that is one of the reasons it was a good
choice. I did say that the use of twisted pair depends on the
application and a high level of EMI would be a vote against using it.

well ok, but you could have just as well used a shielded (non transmission)
cable rather then a twisted pair, and gotten the same result

if your twisted pair video system worked really well, then it was
because
both ends were balanced (quite possible) , or you dont' have a lot of
EM
noise around,

I think you've answered yourself quite well.

*****
shu

 

[Jasen Betts]

["Followup-To:" header set to sci.electronics.basics.]
On 2005-11-25, shu <washu@hiwaay.net> wrote:

if your twisted pair video system worked really well, then it was because
both ends were balanced (quite possible) , or you dont' have a lot of EM
noise around,

Cat 5E (network cable) is cheap, special video baluns are available
off the shelf for putting composite video through it.

with 4 pairs, one can carry video, one audio, one audio back the other way,
and one power for the camera etc...

Tone, or DC, signalling on the audio return, can be used to
operate a latch or boom gate etc...


Bye.
Jasen

 

[St. John Smythe]

Omicron wrote:

So much jargon is so vague and
general, that it is not meant for the unexperienced.

Yes...perhaps you should take a lesson from that.

--
St. John
All theoretical chemistry is really physics;
and all theoretical chemists know it.
-Richard P. Feynman

 

[Gary]

Fred Abse wrote:

<snip>

If you mean by "DC resistance", the impedance you would see at the input
of an infinitely long line, it's not bullshit, it's perfectly true, even
if the line is made of zero-resistance conductors. You'll just see the
line's characteristic impedance.

*Please* , read my post on calculation of characteristic impedance. I
am not talking about Infinite length transmission lines. I am talking
about the calculation of impedance.
Fer krissake, keep the discussion in context.
What do I give a shit about infinitely long lines. I don't use 'em.
Valid only if you want to discuss voltage and current distribution.
That's not where this started.



--
Regards,
Gary

I know not with what weapons World War III will be fought,
but World War IV will be fought with sticks and stones.

Albert Einstein

 

[Gary]

Fred Abse wrote:

<snip>

If you mean by "DC resistance", the impedance you would see at the input
of an infinitely long line, it's not bullshit, it's perfectly true, even
if the line is made of zero-resistance conductors. You'll just see the
line's characteristic impedance.

You can simulate the same "infinite length transmission line" by
terminating a transmission line into a *purely* resistive load whose
resistance is exactly the same as the characteristic impedance of the
transmission line.

That's the purpose of overall system matching. Maximum transfer of
energy from generator to load. The load may be either a piece of
equipment, a dummy load or an antenna. In either case we attempt to
remove all reactive components and make them appear truly resistive. So
what???

That doesn't change the characteristic impedance of the transmission one
"tic". The object of the exercise here was to show that a 75 Ohm line
mated to a 50 Ohm line does not produce an "insertion" loss but instead
results in a "reflection" loss due to mismatch.

I have no idea how the infinite line blurb got in here at all. True
though it may be, it's of no consequence other than to show voltage and
current distribution and that was not part of the original problem.


--
Regards,
Gary

I know not with what weapons World War III will be fought,
but World War IV will be fought with sticks and stones.

Albert Einstein

 

[John Fields]

On Sun, 27 Nov 2005 19:29:03 -0330, Gary <g.h@sympatico.ca> wrote:

Fred Abse wrote:

snip

If you mean by "DC resistance", the impedance you would see at the input
of an infinitely long line, it's not bullshit, it's perfectly true, even
if the line is made of zero-resistance conductors. You'll just see the
line's characteristic impedance.

*Please* , read my post on calculation of characteristic impedance. I
am not talking about Infinite length transmission lines. I am talking
about the calculation of impedance.
Fer krissake, keep the discussion in context.
What do I give a shit about infinitely long lines. I don't use 'em.
Valid only if you want to discuss voltage and current distribution.
That's not where this started.

---
Regardless, if you want to talk about the charachteristic impedance
of a peculiar transmission line, you _have_ to start with an
infinitely long unterminated line.

If you want to talk about something shorter, then you need to
terminate the line with a resistance equal to the generator's
resistance.

Can you understand why that's so?


--
John Fields
Professional Circuit Designer

 

[David]

On 27 Nov 2005 17:29:03 -0800, Winfield Hill
<Winfield_member@newsguy.com> wrote:

Since the electrons travel on the surface and multi-strand wire
has more surface area it should be better <G

Only if the strands are insulated from one another.

More twaddle. The skin effect doesn't care.

 

[Paul Hovnanian P.E.]

Jasen Betts wrote:

["Followup-To:" header set to sci.electronics.basics.]
On 2005-11-26, Paul Hovnanian P.E. <Paul@Hovnanian.com> wrote:

Twisting wires helps reduce noise induced from ambient H fields. If you
have a high ambient E field, you can still get common mode noise coupled
to a bare twisted pair. Particularly on a high impedance circuit. This
becomes a problem at low signal levels, where a CMRR sufficient to
reject the noise may be impractical. Low signal level circuits are where
one finds high impedances as well. In this case, carefully designed
shielding can help.

transformers typically have very a high CMRR. this may be whay they are used
in network cards.

Yes. But some circuits must be DC coupled.

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
Your mouse has moved. Windows must be restarted for
the change to take effect. Reboot now? [OK]

 

[David]

On Mon, 28 Nov 2005 21:33:41 +0000, Fred Abse
<excretatauris@cerebrumconfus.it> wrote:

On Mon, 28 Nov 2005 02:24:50 +0000, David wrote:

On 27 Nov 2005 17:29:03 -0800, Winfield Hill
Winfield_member@newsguy.com> wrote:

Since the electrons travel on the surface and multi-strand wire
has more surface area it should be better <G

Only if the strands are insulated from one another.

More twaddle. The skin effect doesn't care.

I suggest you read a standard textbook, such as Horowitz & Hill's "The Art
Of Electronics"


FX: Removes tongue from cheek

 

[David]

On Mon, 28 Nov 2005 21:33:41 +0000, Fred Abse
<excretatauris@cerebrumconfus.it> wrote:

On Mon, 28 Nov 2005 02:24:50 +0000, David wrote:

On 27 Nov 2005 17:29:03 -0800, Winfield Hill
Winfield_member@newsguy.com> wrote:

Since the electrons travel on the surface and multi-strand wire
has more surface area it should be better <G

Only if the strands are insulated from one another.

More twaddle. The skin effect doesn't care.

I suggest you read a standard textbook, such as Horowitz & Hill's "The Art
Of Electronics"


FX: Removes tongue from cheek
Can't I just take your word for it? Books are so yesterday.

 

[ah]

Peter Hucker wrote:

On Mon, 28 Nov 2005 19:57:34 -0000, Mr Pounder <Mr <Pounder@rationalthought.com>> wrote:


"Peter Hucker" <no@spam.com> wrote in message
newsp.s0w904e8wabk2w@blue.mshome.net...
On Sun, 27 Nov 2005 18:59:37 -0000, Mr Pounder <Mr
Pounder@rationalthought.com>> wrote:


"Peter Hucker" <no@spam.com> wrote in message
newsp.s0wvepw0wabk2w@blue.mshome.net...
On Sun, 27 Nov 2005 17:46:12 -0000, Mr Pounder <Mr
Pounder@rationalthought.com>> wrote:

Off for a nosy.
I wish that I the time that you have.

I entered the group to ask a question about LED brightness, and
accidentally started a nuclear war.

"Accidentally"?

I mentioned that someone was being unsafe using an unfused (!) extension
cord, at which point an American said they are all like that over there,
which I said was insane, etc.

Somehow I think the American must be wrong.
Ok, they are on 110 volts I believe, but even so!

It's true. There are no fuses in plugs over there.

Yup. Totally unnecessary . . . there's already a fuse on both ends (panel and
appliance).
--
ah

 

[Tim Shoppa]

billcalley wrote:

Hi all,

I cannot seem to find any strong explanations for "residual AM",
"residual PM", and "residual FM" in any of my electronic's books or
Online. What are the causes and symptoms of these particular effects?
Any help is most appreciated!

"residual AM" is the unwanted amplitude modulation when you
frequency-modulate an oscillator. This can be because your FM is tuning
outside the bandpass of some element or simply because of
gain-bandwidth product for very wide deviations. You eliminate it by
running the signal through limiter stages.

"residual FM" is the unwanted frequency shift caused as you attempt to
do amplitude modulation. Cause is usually too much coupling of the
modulation into voltage-variable-reactances in the tank. The solution
is usually to add more buffering and isolation between the oscillator
stage and the modulator stage.

"residual PM" is an unwanted phase shift as you amplitude-modulate a
stage or as the input level to a discriminator changes. Solution is
usually better limiting/isolation/bypassing/power supply regulation
(this is often not too different than residual FM).

The above definitions of residual AM and FM are pretty much as
described in old radio texts. Unwanted PM most often occurs in a
comparator stage (boundary between analog and digital).

Tim.

 

[Puckdropper]

David <rickets@knac.com> wrote in
news:2n5no1dg5ms2d5p7mv4dr27kn01otka2bv@4ax.com:

Can't I just take your word for it? Books are so yesterday.

Yeah... We can really believe everything we read on USENET. (Sarcasm)

Puckdropper
--
www.uncreativelabs.net

Old computers are getting to be a lost art. Here at Uncreative Labs, we
still enjoy using the old computers. Sometimes we want to see how far a
particular system can go, other times we use a stock system to remind
ourselves of what we once had.

To email me directly, send a message to puckdropper (at) fastmail.fm

 

[Jasen Betts]

On 2005-11-27, Fred Abse <excretatauris@cerebrumconfus.it> wrote:

On Sun, 27 Nov 2005 17:14:25 -0330, Gary wrote:

David wrote:

snip

Characteristic impedance and DC resistance are the same if the line is
infinitely long and unterminated.


Bullshit.

If you mean by "DC resistance", the impedance you would see at the input
of an infinitely long line, it's not bullshit, it's perfectly true, even
if the line is made of zero-resistance conductors. You'll just see the
line's characteristic impedance.

what about lines made of copper and plastic?

ISTM that a few hundered kilometers if RG59 is going to measure more
than 75 ohms even with far end is shorted.

There's no way an infinite length will have a lower resistance.

Bye.
Jasen

 

[Cliff]

On Mon, 28 Nov 2005 14:51:55 -0600, John Fields
<jfields@austininstruments.com> wrote:

On Mon, 28 Nov 2005 13:32:27 -0500, Cliff <Clhuprich@aol.com
wrote:

On Mon, 28 Nov 2005 00:56:50 GMT, David <rickets@knac.com
wrote:

Characteristic impedance is purely a function of the
capacitance and inductance distributed along the line's length, and
would exist even if the dielectric were perfect (infinite parallel
resistance) and the wires superconducting (zero series resistance).
Velocity factor is a fractional value relating a transmission line's
propagation speed to the speed of light in a vacuum. Values range
between 0.66 and 0.80 for typical two-wire lines and coaxial cables.
For any cable type, it is equal to the reciprocal (1/x) of the
square
root of the relative permittivity of the cable's insulation.''

How odd then that the speed of propagation in conductors
varies.

Not at all. Since resistivity varies between conductors because of
the materials of which they're composed and inductance varies
because of their diameters, why would one _not_ expect c to vary?

You think that resistivity controls the speed of light?

I think I heard that a good vacuum has a lot of resistance
but a fairly high speed of light.
The speed of light goes down as things become more
conductive?
--
Cliff

 

[Joel Kolstad]

"Jasen Betts" <jasen@free.net.nospam.nz> wrote in message
news:23fb.438c3242.b9698@clunker.homenet...

2 > a solitary bare wire is an antenna, not a transmission line

In general I'd agree, although strictly speaking you can take something like
coax, flare out the shield into a horn, and just keep the inner conducting
going until you reverse the process on the other end. This ends up being sort
of an inside-out waveguide; I've read that it's been used successfully for
things like communications in mines or caves where it's cheaper and easier to
deploy (lighter) than traditional coax.