magnetic field

[Scott Seidman]

"John E. Hadstate" <jh113355@hotmail.com> wrote in news:a9k2h.18885
$Fd7.1319@bignews6.bellsouth.net:

To instantiate or process a digital
state, it must be encoded into a voltage/current analog.

True, but only well enough to differentiate a low from a high, and you can
also build in error correction.

--
Scott
Reverse name to reply

 

[Homer J Simpson]

"CCE" <cenglish@snapsinc.com> wrote in message
news:1162490145.877448.8540@b28g2000cwb.googlegroups.com...

I'm looking for some advice on a motor application. To keep it
simple, I'll use the following description. I have a 20 lb weight
that I want to raise and lower according to a time schedule. When the
process starts, there is an initial delay and then the motor will pick
up the weight say 12 inches. Next there is another delay and the motor
will lower the weight back to its original position. This may repeat
several times with the weight being picked up different heights each
time.

How many different heights?


--
++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Required crap appended to avoid restrictions imposed by brain +
+ damaged idiots.
+
+ Server Response: '441 Posting Failed (Rejected by POST filter)', +
+ Port: 119, Secure(SSL): No, Server Error: 441,
+
+ Error Number: 0x800CCCA9
+
++++++++++++++++++++++++++++++++++++++++++++++++++++

 

[CCE]

Homer J Simpson wrote:

How many different heights?

Two or three. The cycle time would be less than one minute. This is not
an application that would run continuously either.

 

CWatters wrote:

Despite being registered with telephone preference services we still get a
lot of silent and marketing calls. I'm looking for a box of tricke of some
software to help...

What I'd like to do is silently divert all "caller ID witheld" calls to a
recorded message that says something like.. "This person does not accept
marketing calls. If you are calling about something else please enter your
phone number and I will connect you". At which point it will ring our phone
in the normal manner and forward the number entered as a caller ID.

Is there such a box of tricks?

http://www.ainslie.org.uk/callerid/tel_soft.htm
looks like a list of devices and services that might do what you want
and some are even relatively inexpensive.

Now if I could just find a way to get the Sharp UX1100 fax machine
to hang up on any incoming call EXCEPT from a single number.
It will allow blocking up to 5 phone numbers but doesn't seem to
allow blocking from all but a list of numbers. (I haven't got caller
id
on that phone line but I could pay for that if really necessary)

 

[Jerry Avins]

Richard Owlett wrote:

Jerry Avins wrote:

Richard Owlett wrote:

Jerry Avins wrote:

[snip much]

As far as I know,

digital circuits exist only as abstractions and on schematics. I
would be delighted to learn of exceptions.


electo-mechanical relays

'nuff said


Better say more. Make before break, or break before make? We're
looking at transitions here. Even with SPST, contacts bounce

Jerry


The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"

ain't no other option!

Arcing contacts? Zero risetime?

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

 

[Richard Owlett]

Ron N. wrote:

Richard Owlett wrote:

The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"


Said by somebody who's never put a VOM across a batch
of old rusted relays (scavenged from dead pinball machine
parts found in a outdoor scrap heap I think).

Your abstraction does work a bit better with new ones.


IMHO. YMMV.

BULL!
irregardless of "contact resistance" they are *either* open/closed

 

[Ron N.]

Richard Owlett wrote:

Richard Owlett wrote:

The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"

irregardless of "contact resistance" they are *either* open/closed

So what resistance value, and for what duration, would you
call closed?

Do you think that all "open" relays have zero resistance?


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

 

[Jerry Avins]

Richard Owlett wrote:

Ron N. wrote:

Richard Owlett wrote:

The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"


Said by somebody who's never put a VOM across a batch
of old rusted relays (scavenged from dead pinball machine
parts found in a outdoor scrap heap I think).

Your abstraction does work a bit better with new ones.


IMHO. YMMV.

BULL!
irregardless of "contact resistance" they are *either* open/closed

You could say the same about a door, but degree matters, especially to
the obese.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

 

[Ron N.]

Floyd L. Davidson wrote:

You are denying that the standardized definitions are correct,
and that is an absurd stance to take,

I disagree. Many standardized definitions are committee
compromises, and have sometimes what comes out of a
committee has little to do with what real people try to mean
or understand when using those words (especially if a
committee has gotten politicized or influenced by marketing
agendas).

(in general. not expressing an opinion on digital/analog).
IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

 

[Richard Owlett]

Ron N. wrote:

Jerry Avins wrote:

Richard Owlett wrote:


The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"

ain't no other option!

Arcing contacts? Zero risetime?


I can't remember where, but I seem to recall some
ultra high-speed photography of the formation of an
arc. It didn't look like it was happening instantly.

Or does Richard count that first electron at "closed"?

OK let's not tooooo far to the extreme .

So a relay is "analogue" in sense that on closure its resistance may
change "gradually" from 10^10 ohms thru 10^8 ohms to 10^-3 ohms.

And I've worked with "analog" systems capable of noticing individual
electrons as they came. Had an interesting argument with bull-headed
chemistry post doc that some of his instrumentation requirements were
silly as they implied capability of measuring tenths of electrons per
second -- can anyone say "gain bandwidth product". I "lost" as I was
ONLY a technician he was a *PHD*

 

[Richard Owlett]

Bob Myers wrote:

"Jerry Avins" <jya@ieee.org> wrote in message
news:qYKdnZM7_tTLm9TYnZ2dnUVZ_oednZ2d@rcn.net...

It seems to me important to agree on criteria for deciding whether a
particular circuit or signal is digital or analog


Circuits and signals themselves are neither digital nor
analog, even though we unfortunately do tend to classify
them as such.

I've seen a 7400 series inverter used as an 'op amp'
Don't recall why it was done, suspect was just to prove it could be ;/

 

[John E. Hadstate]

"Bob Myers" <nospamplease@address.invalid> wrote in message
news:yMf2h.1888$ax1.595@news.cpqcorp.net...

"Jerry Avins" <jya@ieee.org> wrote in message
news:qYKdnZM7_tTLm9TYnZ2dnUVZ_oednZ2d@rcn.net...

It seems to me important to agree on criteria for
deciding whether a particular circuit or signal is
digital or analog

This is a general prerequisite for any kind of
communication, digital or analog ;-)

Circuits and signals themselves are neither digital nor
analog, even though we unfortunately do tend to classify
them as such.

That is demonstrably incorrect. All circuits that have a
physical instantiation are analog, as are the signals that
they process.

[snip fairly lucid description of analog encoding]

Similarly, in a "digital" information encoding or
transmission
system, various states of the transmitted signal
correspond
to numeric values - or more generally, symbols - and must
be interpreted accordingly. Again, the name says it all -
we're not sending something that directly represents
another
thing, but instead are sending symbols or "digits."

In and of itself, a digital state has no representation in
the physical world. To instantiate or process a digital
state, it must be encoded into a voltage/current analog.
People have been known to group binary states into a
multi-state logic and represent the combined states with a
single value of voltage/current analog. If you group enough
binary states together the analog of the digital value
becomes indistinguishable from continuous.

 

[Richard Owlett]

Floyd L. Davidson wrote:

Richard Owlett <rowlett@atlascomm.net> wrote:

Bob Myers wrote:

Circuits and signals themselves are neither digital nor
analog, even though we unfortunately do tend to classify
them as such.

I've seen a 7400 series inverter used as an 'op amp'
Don't recall why it was done, suspect was just to prove it could be ;/


Of course to make it work as an analog circuit... components had
to be added. Which means that was *not* the same "circuit"
which functions as a digital circuit, even if it used the same
IC.

Circuits may or may not be analog or digital, though *clearly*
some are one or the other. Signals *are* one or the other, by
definition.

COMPONENTS ;? :?
2 resistors ;/
Basically we agree :>

 

[Jerry Avins]

Steve Underwood wrote:

Jerry Avins wrote:
Richard Owlett wrote:
Bob Myers wrote:

"Jerry Avins" <jya@ieee.org> wrote in message
news:qYKdnZM7_tTLm9TYnZ2dnUVZ_oednZ2d@rcn.net...

It seems to me important to agree on criteria for deciding whether
a particular circuit or signal is digital or analog


Circuits and signals themselves are neither digital nor
analog, even though we unfortunately do tend to classify
them as such.


I've seen a 7400 series inverter used as an 'op amp'
Don't recall why it was done, suspect was just to prove it could be ;/

Lousy choice. The symmetric CD40xx, on the other hand, was well enough
suited to be used in at least onecommercial product.

Sure. You may think of a one-shot as a digital device, but it takes a
fair amount of analog savvy to build one whose pulse width is
independent of duty cycle.

If there was a choice you'd use a proper op-amp. You only use these
gates because they are leftovers in a multi-gate package. 74xx devices
were used quite often in semi-analogue roles.

I recall one audio device that used an entire hex inverter chip as a
stereo headset amplifier.

I find it an interesting paradox that in the old days nobody sold single
gate devices. Now simple logic has been reduced to the role of glue, a
number of suppliers make tiny one gate devices.

I may have a few one-gate RTL packages (six lead, round).

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

 

[jasen]

On 2006-11-03, Homer J Simpson <nobody@nowhere.com> wrote:

"jasen" <jasen@free.net.nz> wrote in message
news:eic51k$1c5j$1@news.ndhu.edu.tw...

Is there such a box of tricks?

sounds like asterisk@home

http://www.trixbox.org/ ??

that's one implementation.
asterisk is free open source.

http://asteriskathome.sourceforge.net/

AIUI it'll do VoIP, but also handle PSTN voice calls, fax and answering
machine functions...

--

Bye.
Jasen

 

[Frithiof Andreas Jensen]

"CCE" <cenglish@snapsinc.com> wrote in message
news:1162490145.877448.8540@b28g2000cwb.googlegroups.com...

I'm looking for some advice on a motor application. To keep it
simple, I'll use the following description. I have a 20 lb weight
that I want to raise and lower according to a time schedule. When the
process starts, there is an initial delay and then the motor will pick
up the weight say 12 inches. Next there is another delay and the motor
will lower the weight back to its original position. This may repeat
several times with the weight being picked up different heights each
time.

I want to use a PLC to control the system. The speed of the application
is relatively slow. Let's say it takes 1 second to raise or lower
the weight 12 inches. Since I need to hold the weight for a few
seconds, I'm thinking I need a stepper motor. 20 lbs is pretty heavy
for a stepper motor so I'll need a high torque motor. I'll also
need a controller for the stepper motor. The way I see it, the PLC will
need to send pulses to the controller to raise and lower the weight. It
is an open loop system, so I don't need feedback.

Questions:
1. Should I consider some other type of motor and if so, what kind?
2. Any recommendations on high torque, low cost steppers and stepper
controllers?
3. What kind of power requirements will this application have? AC, DC
etc.
4. I'm trying to keep the whole system down to a minimal size, any
suggestions?
5. I'm trying to keep the cost of the whole system down, but I
don't want to have to build my on controller. Any suggestions?

Thanks in advance for your feedback.

Maybe this will do you?

http://www.linak.com/Products/?id3=1 -> "LA-29"

A.F.A.I.K. these products all use a normal motor driving a lead screw with a
Reed-switch counting spindle revolutions.

They are used in furniture - like my ergonomic desk here - for raising beds
under fat blokes, opening windows e.t.c. so there is some volume to push prices
down!

 

[Frithiof Andreas Jensen]

"Frithiof Andreas Jensen" <frithiof.jensen@die_spammer_die.ericsson.com> wrote
in message news:eif5vm$6hb$1@news.al.sw.ericsson.se...

Maybe this will do you?

http://www.linak.com/Products/?id3=1 -> "LA-29"

A.F.A.I.K. these products all use a normal motor driving a lead screw with a
Reed-switch counting spindle revolutions.

They are used in furniture - like my ergonomic desk here - for raising beds
under fat blokes, opening windows e.t.c. so there is some volume to push
prices
down!

PS:
There are industrial versions too off the main site: http://www.linak.com/

 

[CCE]

Frithiof Andreas Jensen wrote:

"Frithiof Andreas Jensen" <frithiof.jensen@die_spammer_die.ericsson.com> wrote
in message news:eif5vm$6hb$1@news.al.sw.ericsson.se...

Maybe this will do you?

http://www.linak.com/Products/?id3=1 -> "LA-29"

A.F.A.I.K. these products all use a normal motor driving a lead screw with a
Reed-switch counting spindle revolutions.

They are used in furniture - like my ergonomic desk here - for raising beds
under fat blokes, opening windows e.t.c. so there is some volume to push
prices
down!

PS:
There are industrial versions too off the main site: http://www.linak.com/

Thanks for the suggestion. I'm using a linear actuator now, but it is
too slow and has limited stroke.

 

[Ray Andraka]

Jerry Avins wrote:

Sure. You may think of a one-shot as a digital device, but it takes a
fair amount of analog savvy to build one whose pulse width is
independent of duty cycle.

As a digital guy, I sure don't consider one-shots digital. By
one-shots, I am referring to those devices that use the physical
characteristics of components (typically capacitance and resistance) to
set a time delay.

The distinction I use in my book (which sadly will probably never be
finished because of the time involved writing it) is that an analog
circuit depends on the physical properties of the components of the
circuit as an integral part of the processing. A digital circuit
processes the signal through a logical or numerical manipulation of the
signal so that the circuit itself is only incidental to the processing.

Clearly, with that definition, one-shots such as the 74123 belong to the
class of analog circuits regardless of whether they were offered as a
component within a digital logic family. The only thing digital about
these parts is the logic family compatible I/O and the simple logic
controls built in to allow the one shot to be operated by and output to
the logic family.

Another circuit that used to be commonly used with digital logic that is
really an analog part is the delay line.

 

[Jerry Avins]

Ray Andraka wrote:

Jerry Avins wrote:


Sure. You may think of a one-shot as a digital device, but it takes a
fair amount of analog savvy to build one whose pulse width is
independent of duty cycle.


As a digital guy, I sure don't consider one-shots digital. By
one-shots, I am referring to those devices that use the physical
characteristics of components (typically capacitance and resistance) to
set a time delay.

The distinction I use in my book (which sadly will probably never be
finished because of the time involved writing it) is that an analog
circuit depends on the physical properties of the components of the
circuit as an integral part of the processing. A digital circuit
processes the signal through a logical or numerical manipulation of the
signal so that the circuit itself is only incidental to the processing.

Clearly, with that definition, one-shots such as the 74123 belong to the
class of analog circuits regardless of whether they were offered as a
component within a digital logic family. The only thing digital about
these parts is the logic family compatible I/O and the simple logic
controls built in to allow the one shot to be operated by and output to
the logic family.

Another circuit that used to be commonly used with digital logic that is
really an analog part is the delay line.

I'd say that a one-shot is digital in intent and analog in execution. I
believe that's true of any physical digital component, just more clearly
evident with circuits that intentionally use Rs and Cs for timing. All
circuits incorporate Rs and Cs, whether intentionally or not. Memory
buses are "digital" too, but modern clock speeds dictate that they be
designed like the broadband transmission lines they really are.

Very few dichotomies are entirely clear. For most, it is possible to
assign most items to one class or the other although the matter is
ambiguous for some near the division. The analog-digital dichotomy puts
the fuzzy dividing line over near one edge. We may use current,
pressure, voltage, fluid flow and other analogs to represent ones and
zeros, but they are all analogs nonetheless. Those ones and zeros exist
in pure form only in out minds. Even marks on paper are analogs of a
sort. We move the division to match a particular purpose. Assuming that
it is fixed hobbles our thoughts.

I began this thread to isolate this discussion from the rancor
developing in another one. I'm pleased to note that it seems to have
succeeded.

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ