magnetic field

[Ross Herbert]

Allan Adler wrote:

Herbert Ross writes:

This how to do it.
http://www.computronics.com.au/kinsten/

It is a nice site. I'd like it better if it also included information
on environmentally responsible ways to dispose of the used chemicals
and maybe also sold stuff to facilitate doing so.

Allan Adler
ara@zurich.ai.mit.edu

Hi Allan,

Yes, I have to agree with you that sellers of potentaially hazardous
chemicals should also act responsibly by giving information about
disposal of waste products.

I did some digging and found the MSDS for the 2 most common etchants;
Ferric Chloride http://www.deltrex.com.au/products/s080.htm
Ammonium Persulphate
http://www.progen.com.au/zone_files/Life_Sciences_MSDS/ammonium_persulphate_ud007-02.pdf

Recycling of Ferric Chloride etchant can be done but is really only
economical in large quantities as indicated by this item
http://emeso.lanl.gov/Stories/FeCl.htm

This paper http://www.rsc.org/pdf/jem/1999/A9808158.PDF indicates
several techniques for re-utilisinf Ferric Chloride but again, none of
these methods would be available to the hobby or small pcb manufacturer.

This University of Wisconsin page recommends that up to 5lbs of Ammonium
Persulphate is safe to dispose of via the sewer
http://www.uwm.edu/Dept/EHSRM/HAZMAT/SOPoxidizer.html

I suppose that all of this really highlights the fact that in most cases
hobby pcb manufacturers are almost forced to dispose of our waste
etchant down the sewer. I dare say that eventually it will come back to
bite us on the bum.

Ross Herbert

 

[H. Dziardziel]

On 15 Aug 2003 23:26:33 -0700, HoldenCaulfield@att.net (Bill
Bowden) wrote:

snip

Yes, that explains it. I'm pretty sure the core was saturating.
I added about 30% more windings (40 more turns, 200 total) and
the unloaded primary current dropped from 3 amps to below 1 amp.

But the thing still gets fairly warm with no load, so I think
I'll send it back to where it was found.

-Bill

The core material, construction and size would probably need
nearly triple the turns and that would give a very inefficient
nearly useless transformer. Small welder is a use without primary
rewinding.

 

[Ed Ellers]

"Orange" <cheap@chips.co.uk> wrote:

"Ed, what's the difference between 'closed caption' and page 888?."

Closed captioning uses a very slow data transmission system designed for the
purpose.

 

[Stephen Neal]

On 17/8/03 12:58 am, in article
oyz%a.35267$2x.3502@rwcrnsc52.ops.asp.att.net, "Ed Ellers"
<edellers@mis.net> wrote:

"Orange" <cheap@chips.co.uk> wrote:

"Ed, what's the difference between 'closed caption' and page 888?."

Closed captioning uses a very slow data transmission system designed for the
purpose.

Yep - Closed Captioning survives on poor VHS recordings - and for this
reason has also been deployed in the UK for pre-recorded VHS video releases.
It was (and may still be) possible to purchase a closed caption decoder in
the UK for this purpose (though I don't think any TVs come with the
circuitry required, or at least enabled)

Steve

 

[R. Steve Walz]

Neil Jackson wrote:

I have an AIRPAX 4SH-12A46S stepper motor
label markings are as follows

AIRPAX
North American Phillips Controls Corp.
Cheshire, Conn

VOLTS - 12
OHMS/COIL 28
DEG/STEP 1.8
4SH-12A46S

I have six leads
red
blue
yellow
white
brown
black

How do I determine what my connections should be?
I've spend nearly the last four hours trying to find info on this motor.

TIA
Neil Jackson
-------------------

Listen kid!:
You don't need a diagram!!

There are two coils, and each one has a wire on on each end, and a
center-tap wire in the middle of each coil.

All you do is use an ohmmmeter on the leads to find which three are
on which coil, and the one wire for each that is half the ohms to the
other two end wires is the centertap, of course.

Then you take the two centertaps of both coils and tie them together,
and connect them to your positive supply, +12V, and then you can
ground (connect to the supply ground or minus) only one of the two
at a time for each coil. When you ground only one of these end wires of
each in what is called "quadrature order", it will rotate, and if
you don't like the direction just swap the end wires of JUST ON of
the two coils.

Quadrature order is THIS for the grounding the end wires labeled
like this: A - centertap - B , and C - centertap - D , and it goes:

Grounding order for quadrature.
A and C,
A and D,
B and D,
B and C,
repeat over and over.

Or the reverse to reverse directions.

Here's an animation of it.

http://www.armory.com/~rstevew/Public/Motors/Steppers/DougWJones/typesf/2anim.html
(all one line)

Or:

http://www.cs.uiowa.edu/~jones/step/typesf/2anim.html
-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

 

[The Technical Manager]

Ed Ellers wrote:

Doug Smith, W9WI wrote.

"I don't know as a fact that any TVs were ever built that had both teletext
and caption decoders but there's no reason it couldn't be done."

Some TVs sold in Europe are PAL and NTSC switchable. They have Teletext
decoders and could possibly have closed caption decoders as well. I don't know
whether Teletext can be accessed when the TV is switched to NTSC mode.

ITT Semiconductor offered just such a chip to TV makers in time for the 1993
line-21 mandate.

What was its number ?

 

[Martin Angove]

In message <BB65AE0B.DE16%stephen.neal@as-directed.com>,
Stephen Neal <stephen.neal@as-directed.com> wrote:

On 17/8/03 12:58 am, in article
oyz%a.35267$2x.3502@rwcrnsc52.ops.asp.att.net, "Ed Ellers"
edellers@mis.net> wrote:

"Orange" <cheap@chips.co.uk> wrote:

"Ed, what's the difference between 'closed caption' and page 888?."

Closed captioning uses a very slow data transmission system designed for the
purpose.


Yep - Closed Captioning survives on poor VHS recordings - and for this
reason has also been deployed in the UK for pre-recorded VHS video releases.
It was (and may still be) possible to purchase a closed caption decoder in
the UK for this purpose (though I don't think any TVs come with the
circuitry required, or at least enabled)

This is an extremely interesting concept - that some domestic tellies
may have CC decoding circuitry which just "isn't enabled". I know a
*huge* population which would worship anyone who could work out which
chassis had the circuitry and how it could be enabled - Britain's deafies.

Closed caption decoders *are* still available but considering how
trivial the technology must be they can be phenominally expensive. Video
recorders designed to record (teletext) subtitles are also now rare (no
manufacturer lists a current model). The latest "Omnidirectory" (the
"Bible" on these matters) lists just two devices. The Telemole TAD150
decodes teletext subtitles from broadcasts, producing a composite output
which can then be recorded - i.e. with "in vision" subtitles. It also
decodes CC encoded tapes. It costs a staggering 229ukp.

The other device is the VR20 from Sarabec Ltd. This only does CC and you
fit it between the VCR and telly. It is a more reasoable 45ukp.

Now, if the decoding circuitry was already in the telly, that'd save a
bit of money and also (presumably) increase picture quality.

I presume the same "feature available but not enabled" thing won't apply
to VCRs, but with the increasing number of S-VHS machines available at
reasonable prices that's less of an issue, though I have to say that my
attempts at recovering teletext from an S-VHS recording on my ageing JVC
HR-S7500 were rather hit-and-miss.

Looking forward to any further investigations on this matter

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Don't fight technology, live with it: http://www.livtech.co.uk/
.... As far as we know, our computer has never had an undetected error.

 

[Watson A.Name - 'Watt Sun]

In article <3F431D96.369D4AD3@imec.be>, friedtj@imec.be mentioned...

How to create a data link of 115.2KBits/sec over 50-100Km (line of sight)
with total power consumption of less than 5W?
Is there any commercial unit for these type of an application?

modulated laser + photodiode at the focal point of a telescope ?
(I think there is an article about such an experiment in the ARRL
Handbook IIRC).

Hmmm actually the colimation will have to be excellent, because at 100
km
and a 4 mrad divergence of a laser diode (as the ones I've used
previously)
the laser would illuminate a 400 m-diameter area. I don't know what the
divergence
of a HeNe laser is (still less than 5 W, but takes more space).

I think the major problem would be atmospheric disturbances such as
heat waves, making the link extremely unreliable, in fact nearly
unusable. Also, at those distances, you will have to have the two
sites at a higher elevation, because of the curvature of the earth.

You might check out the RONJA which uses LEDs to make a link over a
half km. The original Loo Pipe version was for 115.2 kbps.

Jean-Michel

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[onestone]

If it's definitely line of sight then the distance is achievable with
off the shelf gear. I used a Johnson data radio at about 2.5W max in
amining fleet management application. despite not being line of sight we
had reasonably good communications between 2 sites over 100km apart.
Unintentional, it was actually interference for us. With line of sight
you should do much better.

I would avoid 2.4GHz. Every little change in the weather will cause you
problems. 458MHz band is available off the shelf. Although the data
rates are typically quite low, we used 38.4 and 19.2kbaud, you can get
up to 115.2. Another option would be microwave. try www.shfmicro.com.
There are links there to some sites that have been experimenting with
long distance comms using very low power microwave systems and dish
antennas.

Al

Joel Kolstad wrote:

Pang Fu <pangfu@hotmail.com> wrote:

How to create a data link of 115.2KBits/sec over 50-100Km (line of sight)
with total power consumption of less than 5W?


Well, let's see here...

The Friis Transmission formula is:

Pr=Pt+Gr+Gt-32.4-20log(D)-20log(f)

Pr: Received power in dB
Pt: Transmitted power in dB
Gr: Receiving antenna gain
Gt: Transmitting antenna gain
D: Distance you wish to go, in kilometers
f: Frequency of operation, in MHz
(the '32.4' constant takes care of the various constants in the 'non-dB'
version of the formula and for D and f not being in meters and Hz; the last
three terms together represent free space attenuation)

So... the first thing you have to do is to decide how good of a receiver you
can build. For a digital system, this is specified as something like,
'requires a signal power of so-many dB to produce a bit error rate of
something.' (It's not a question or whether or not you'll have bit
errors -- you will! -- it's just a question of how many!) But we'll just
solve for Pr and let you worry about the receiver...

Therefore... 5W=7dB... and let's use 2.4GHz, since you can find some pretty
inexpensive high-gain antennas (microwave dishes) at such frequencies; 24dB
is a typical high-gain dish spec. We'll use your worst case distance of
100km...

Pr = 7+24+24-32.4-20log(100)-20log(2400) = -85dB = -55dBm

(Notice that due to the log functions 50km vs. 100km doesn't make much of a
difference -- 6dB, to be precise. Also notice that the guy to getting a
reasonable number above was the use of the high gain antennas.)

-55dBm is a very 'workable' amount of power; I'd wager that some experienced
RF folks could readily build a receiver that had a bit error rate <1e-6 with
that much power, some forward error correction, and a careful choice of
modulation. (Cell phones often deal with quantities more along the lines
of -90dBm with 'reasonable' bit error rates.) The next step would be to
look at what the signal to noise ratio is at the antenna (effectively noise
is just thermal noise at 2.4GHz), so that one can decide how 'low noise' the
front end of the RF circuitry needs to be.


Is there any commercial unit for these type of an application?


Probably, but I suspect it's not cheap! Microwave links like this are quite
common, but since they're being sold to, e.g., the telcos, the price of the
radios and antennas is often small compared to that of towers, buildings,
labor, etc.

---Joel Kolstad

 

[Shawn]

Where can you find the I2C spec?

A E wrote:

Andreas Trenkwalder wrote:


Hi!

I'm working on an autonomous mobile robot using a atmel mega128 mcu. This
device has 2 usarts but i have 3 serial devices i want connect to. So my
question is has anyone an idea or a shematic on how to multiplex the usart
lines to connect two devices to one usart?

tnx,
Andreas


On a PIC, I used its own comparators as a crude multiplexer, but it needs a few
more PIC pins to do this, but few external parts are needed.
How fast do you want to go? And do you need three full duplex ports? And what,
exactly, do you mean by serial devices? A device like a PC or RS-232 type
peripheral?
Because I2C is a serial interface that you can use to connect many devices to
one serial port.

 

[Jeremy D. Grotte]

Yeah but will e-bay hold out that long for the $$$?
JDG

"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:63aakv01cqler6ai9rj3l9dtmhnmthsum9@4ax.com...

On Thu, 21 Aug 2003 19:10:16 GMT, fun-ding@intro-tech.nohyphens.com
wrote:

SEEKING WORTHY TECHNOLOGY PROJECTS

To competent startups, we offer a unique combination
of business development support with NO PAYMENT until
the project achieves funding or other success.

There are no advance fees whatsoever, nothing tricky
in the wording, and or secrets to discover. This means
what you thought it meant when you first scanned it.

Available services include: establishing coherence
and agreements among founders, incorporation, market
research,financial modeling, business planning, patent
filings, and funding. We absorb costs of incorporation,
patent filings, outside services, etc. Our objective is
to generate equity investment, negotiate licensing, or
otherwise make your project "successful" - a term that
Introtech and clients carefully define in writing before
work begins.

If this is interesting, and you have confidence in your
project, visit http://www.introtech.com and examine the
process carefully. New applications will be accepted
after the end of August.



Hey, I have just the project for you: faster-than-light transmission
lines!

John

 

[Sir Charles W. Shults III]

You absolutely must use filter capacitors, and you really should use a full
wave bridge rectifier. Since you have no input filter capacitor, but you DO
have an output capacitor, about half the time your regulator chip is powered IN
REVERSE!!! This is because the charge on the output capacitor is greater than
the incoming voltage most of the time- only during the peaks does the input
voltage exceed the voltage on the output capacitor.
Rebuild your circuit, use a full wave bridge rectifier and an input filter
capacitor. You would also do well to put a large inductor (like a noise filter
choke for automotive audio systems) inline with the input, since the raw output
of a little alternator like that can easily create transients in the 200 volt
range.
Incandescent bulbs don't really care, but semiconductors do.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[yeahright]

Thanks for the advice. A couple of questions though: I'm trying to keep
the parts count low, the board small, and I was worried that a cap being
exposed to large voltage transients might not work for long. What kind
of capacity and working voltage should I be looking for on the filter
cap: 100uF-1000uF - 200V 400V? If I am using a 1N4001 for half wave
rectification before the regulator, how is the regulator being put into
reverse? Given it's super choppy DC, but the voltage regulator and LED's
shouldn't care. Neither side of the regulator circuit has an
electrolytic cap, just some external ceramics for proper triggering as
suggested by the datasheet. The 5V output is going directly to the
LED's with some current limiting resistors. What would a full wave
bridge offer over half wave rectification for such a primitive task? I
could see if I wanted to run a CD player or something, but for lights
running at just shy of 200mA, I'm not so sure.. All the LED's still
work, so I'm guessing the voltage didn't kill it, but a dead short did..
maybe it was just a flaw in how I made the proto-board or the regulator
shorted internally?..

-Richard


Sir Charles W. Shults III wrote:

You absolutely must use filter capacitors, and you really should use a full
wave bridge rectifier. Since you have no input filter capacitor, but you DO
have an output capacitor, about half the time your regulator chip is powered IN
REVERSE!!! This is because the charge on the output capacitor is greater than
the incoming voltage most of the time- only during the peaks does the input
voltage exceed the voltage on the output capacitor.
Rebuild your circuit, use a full wave bridge rectifier and an input filter
capacitor. You would also do well to put a large inductor (like a noise filter
choke for automotive audio systems) inline with the input, since the raw output
of a little alternator like that can easily create transients in the 200 volt
range.
Incandescent bulbs don't really care, but semiconductors do.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

 

[N. Thornton]

fun-ding@intro-tech.nohyphens.com wrote in message news:<681626ca0d8611fcd42c890a60fa35d5@news.teranews.com>...

To competent startups, we offer a unique combination
of business development support with NO PAYMENT until
the project achieves funding or other success.

The business that gives you all this for free! Ahem, sure.

There are no advance fees whatsoever, nothing tricky
in the wording, and or secrets to discover. This means
what you thought it meant when you first scanned it.

Are you saying it is a scam then?


Regards, NT

 

In sci.electronics.misc Harry Conover <hhc314@yahoo.com> wrote:

"Pang Fu" <pangfu@hotmail.com> wrote in message news:<3f3cf991_1@news.iprimus.com.au>...
How to create a data link of 115.2KBits/sec over 50-100Km (line of sight)
with total power consumption of less than 5W?
Is there any commercial unit for these type of an application?

At ranges of 50-100 Km, a microwave link is probabably the most
practical solution. Still, you are very unlikely to do this with a
total power consumption of less than 5W.

5W per end sounds doable, with big dishes the TPO could be measured
in terms of a few 10s of mW, and at 10Ghz or so a dish a meter or so in
diameter has a stupid amount of gain. 10Ghz (or thereabouts) is
also good, because very quiet recever front ends are available cheaply
off the shelf in any town in europe.....

What I want to know is where is he going to find a 100Km line of sight
path? The curvature of the earth gets in the way long before then for
most paths.

Regards, Dan.
--
** The email address *IS* valid, do NOT remove the spamblock
And on the evening of the first day the lord said...........
..... LX 1, GO!; and there was light.

 

[Fred Abse]

On Thu, 21 Aug 2003 20:10:16 +0100, fun-ding wrote:

establishing coherence and agreements among founders

WTF does that mean?

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Richard Crowley]

"Fred Abse" <excretatauris@cerebrumconfus.it> wrote in message
newsan.2003.08.22.20.32.56.713523.1014@cerebrumconfus.it...

On Thu, 21 Aug 2003 20:10:16 +0100, fun-ding wrote:

establishing coherence and agreements among founders

WTF does that mean?

If you have to ask, don't worry about it.

 

[Spehro Pefhany]

On Sat, 23 Aug 2003 18:52:14 +0100, the renowned Fred Abse
<excretatauris@cerebrumconfus.it> wrote:

On Thu, 21 Aug 2003 20:10:16 +0100, fun-ding wrote:

establishing coherence and agreements among founders

WTF does that mean?

Nobody likes incoherent and disagreeable founders.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Keith R. Williams]

In article <rpcgkvsfsqnctnrnhguru887s0br65htp0@4ax.com>,
speff@interlog.com says...

On Sat, 23 Aug 2003 18:52:14 +0100, the renowned Fred Abse
excretatauris@cerebrumconfus.it> wrote:

On Thu, 21 Aug 2003 20:10:16 +0100, fun-ding wrote:

establishing coherence and agreements among founders

WTF does that mean?

Nobody likes incoherent and disagreeable founders.

Please, anyone who has read Dilbert knows exactly what this
means! The PHBs *own* the subordinates, for whom they sign the
checks.

"You will cohere and agree, or I won't sign the check."

....basically the "Golden Rule". ;-)/2

--
Keith

 

[the Wiz]

"ham" <mhz_2@hotmail.com> wrote:

Wanted: manuals for the following test equipment.
TestLab signal generator/counter SG-4162AD &
frequency counter 50mhz counter/DVM mod 174.
Please mail details.
Thanks Shaun

Try here:


Manual Merchant
Telephone
520-742-2028
FAX
520-742-2029
Postal address
PO Box 68058
Tucson AZ 85737-8058
Electronic mail
General Information: info@manualmerchant.com




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