chip swelling up and getting fried

[keith]

On Fri, 24 Sep 2004 21:21:21 -0700, Watson A.Name - "Watt Sun, the Dark
Remover" wrote:

Yeah, it's sad.
In the past 20 years, ost of the knowledgeable staff in my area RS
stores have
either been transferred, fired, or have gotten frustrated and quit!

You left out one other alternative: They got a better job - especially
pay-wise.

My son hired a RadioShaft assistant manager away because he was tired of
*having* to sell cell phone service in an area that had no coverage. A
large part of his compensation was in useless cell phone contracts.

--
Keith

 

[Don Kelly]

"tsp" <tspjor@yahoo.com> wrote in message
news:8efbd3ef.0409232206.79cc2e2e@posting.google.com...

Can somebody tell me why the lumped element model breaks down when
actual circuit impedances are very low, or when the length of the wire
approaches the wavelength of the circuit's operating frequency?
---------

Lumped model circuit theory is a quasi-static approximation of field theory.
It works well when distances are considerably less than a quarter
wavelength. However, where it is valid -it is a lot easier than going to
more complex approaches. Below is a <list>(?) in order of complexity
Consider a 1 ft length of wire:
DC and low frequency-lumped model is a resistor.
Higher frequency- Inductance effects are measurable -lumped model OK
higher yet- both L and C lumped model works
Higher- Transmission line models as R, L and C must be considered
distributed- otherwise errors crop up
(example 100mile length of unloaded power transmission line will have about
a 5% higher voltage at the receiving end than at the sending end-lumped
model doesn't show this). However a lumped T or pi model can be used for a
specific line and is correct at the ends but not in the middle(10V at each
end of a 1/4 wavelength line and the mid-line voltage will be about 14V).
Higher yet and it is necessary to consider the line as a wave guide.
Beyond that -now you are not using lines- you are using antennae and
radiating .

As for the lumped model not being valid for low impedances- not true. The
breakdown may be that the model is not including all the factors which can
be ignored at higher impedance levels. For example-at Z=R=0.01 ohms an
ignored contact or meter resistance of 0.1 ohms can make measurements
meaningless. If R=100 ohms, the effect is negligible.

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

 

[Ed Price]

"Bob Ward" <bobward@email.com> wrote in message
news:vo99l05cluekidbs03k7j9okbu1j8qn0c9@4ax.com...

On Fri, 24 Sep 2004 17:49:09 GMT, Don Bruder <dakidd@sonic.net> wrote:


Radio Shack:
You've got questions, we've got blank stares.

Despite being something of a cliche, it's dead-on accurate in the huge
majority of RS stores.


Since you are making this statement as some sort of authoritative
comment, are we to assume that you have personally visiterd over 3500
stores (more than half would be a bare majority - we'll give you the
benefit of the doubt) in doing the research that leads you to this
conclusion?

Name them.

Radio Shack used to be (maybe 30 years ago) an intriguing place to browse
and buy project parts. But for whatever reason, the selection and quality of
discrete components has plummeted to the joke level. It was bad 10 years
ago, and it's even worse now.

My proof? Well, I can go into any store in the San Diego region, and get the
same level of cheap parts. From what I hear on Usenet, this is typical
everywhere else. You could refute my experience, if you could cite a Radio
Shack that sells RG-214 coax, type N coax fittings, or switches that have
tin-plated terminals and a good "feel."

Sure, I still go to Radio Shack. Last week I found myself hovering over the
parts trays, looking for female BNC chassis connectors (none found), two
fuseholders (that bright finish on the terminals sure is hard to get solder
to flow onto it), a pair of SPST bat-handle switches (they had one) and a
metal project box (only carry plastic boxes). While I was searching for
parts dumped back into the wrong bins (hope springs eternal), I was
approached by two different sales droids with their canned welcome / help
speech (and both didn't know what a BNC connector was).

I found myself standing there, wondering why I wanted to build anything with
the crappy quality parts they had. I found myself hoping that the other
sales droids would ignore me, as I don't think I could have tolerated
explaining what a BNC connector looks like a third time. Imagine that you
went into a NAPA store looking for flexible fuel line, and all they had was
8 different fluorescent colors of plastic aquarium hose. Or imagine that
they only had 10mm bolts in 2cm lengths, no other length, and they only had
three of those. And no Grade 8 bolts at all. And no stainless either.

Radio Shack's marketing must really understand their market, because I have
never seen any of the local stores go out of business. Clearly, they can
make enough money selling cell phones, cordless phones, stereos, alarms,
smoke detectors and batteries. The square footage of the stores devoted to
component sales seems to shrink every so often, till now there's just a
couple of metal tray bins and a short wall of plastic bagged stuff.

I don't attack the RS people. I just try to avoid them, because interaction
with their store personnel is painfully embarrassing. I wouldn't expect the
NAPA guys to know what a BNC is, so why should I expect the RS people to
know either? Sure, there's that "radio" in the name, and "shack" harkens
back to the built-it-yourself ham radio days, but you don't seriously expect
to find royalty at Burger King, do you?

Times change, salmon die after the upstream swim. Good parts are still
available on the Web (Mouser, Digikey, Newark, Allied). Acquire Zen.
Ultimately, WGASA?

Ed
wb6wsn

 

[H. Dziardziel]

On Sun, 26 Sep 2004 03:01:48 GMT, Ross Herbert
<rherber1SPAMEX@bigpond.net.au> wrote:

snip

Did you use a digital multimeter?

I have encountered some strange an incomprehensible readings when
taking resistance measurements on highly reactive components such as
transformers when measuring with my Gossen Metrawatt MetraHit 25S
digital meter (a not too cheap instrument), and when this occurs I
always revert back to my trusty old moving coil analogue meter (AVO
model 7) and usually the correct expected measurement is obtained.

Ross H

Hello, yes you've reminded me of that same experience. It's
caused by the DMM sampling (frequency) and back EMF. Sometimes
just shorting out a winding kills the back EMF so a reading can
be made.

 

[Al]

In article <I7x5d.75009$9Y5.72118@fed1read02>,
"Ed Price" <edprice@cox.net> wrote:

"Bob Ward" <bobward@email.com> wrote in message
news:vo99l05cluekidbs03k7j9okbu1j8qn0c9@4ax.com...
On Fri, 24 Sep 2004 17:49:09 GMT, Don Bruder <dakidd@sonic.net> wrote:


Radio Shack:
You've got questions, we've got blank stares.

Despite being something of a cliche, it's dead-on accurate in the huge
majority of RS stores.


Since you are making this statement as some sort of authoritative
comment, are we to assume that you have personally visiterd over 3500
stores (more than half would be a bare majority - we'll give you the
benefit of the doubt) in doing the research that leads you to this
conclusion?

Name them.



Radio Shack used to be (maybe 30 years ago) an intriguing place to browse
and buy project parts. But for whatever reason, the selection and quality of
discrete components has plummeted to the joke level. It was bad 10 years
ago, and it's even worse now.

My proof? Well, I can go into any store in the San Diego region, and get the
same level of cheap parts. From what I hear on Usenet, this is typical
everywhere else. You could refute my experience, if you could cite a Radio
Shack that sells RG-214 coax, type N coax fittings, or switches that have
tin-plated terminals and a good "feel."

Sure, I still go to Radio Shack. Last week I found myself hovering over the
parts trays, looking for female BNC chassis connectors (none found), two
fuseholders (that bright finish on the terminals sure is hard to get solder
to flow onto it), a pair of SPST bat-handle switches (they had one) and a
metal project box (only carry plastic boxes). While I was searching for
parts dumped back into the wrong bins (hope springs eternal), I was
approached by two different sales droids with their canned welcome / help
speech (and both didn't know what a BNC connector was).

I found myself standing there, wondering why I wanted to build anything with
the crappy quality parts they had. I found myself hoping that the other
sales droids would ignore me, as I don't think I could have tolerated
explaining what a BNC connector looks like a third time. Imagine that you
went into a NAPA store looking for flexible fuel line, and all they had was
8 different fluorescent colors of plastic aquarium hose. Or imagine that
they only had 10mm bolts in 2cm lengths, no other length, and they only had
three of those. And no Grade 8 bolts at all. And no stainless either.

Radio Shack's marketing must really understand their market, because I have
never seen any of the local stores go out of business. Clearly, they can
make enough money selling cell phones, cordless phones, stereos, alarms,
smoke detectors and batteries. The square footage of the stores devoted to
component sales seems to shrink every so often, till now there's just a
couple of metal tray bins and a short wall of plastic bagged stuff.

I don't attack the RS people. I just try to avoid them, because interaction
with their store personnel is painfully embarrassing. I wouldn't expect the
NAPA guys to know what a BNC is, so why should I expect the RS people to
know either? Sure, there's that "radio" in the name, and "shack" harkens
back to the built-it-yourself ham radio days, but you don't seriously expect
to find royalty at Burger King, do you?

Times change, salmon die after the upstream swim. Good parts are still
available on the Web (Mouser, Digikey, Newark, Allied). Acquire Zen.
Ultimately, WGASA?

Ed
wb6wsn

Let's face it. Few people do electronic hobbies anymore. When I was a
kid in the 50s, I built my own transistor radio before anyone else had
one. You could actually build something which was not available
commercially. Often if it was available, what you built could be
superior. This is hardly the case anymore. And it's not just
electronics. When was the last time to saw a kit for a stick built model
airplane with tissue paper fabric. Why bother building when you can buy
something for less than 50 bucks on the internet and it flies out of the
box?

Radio Shack is surviving by selling what most people want to buy,
pre-built electronic toys. And the realy trouble started when a woman
took over as CEO. At least the stock holders are somewhat happy.

I needed a couple of -12VDC 3-terminal regulators recently. The only way
to get them is by mail order. I lucked out when my son found some at the
MIT Flea Market. I won't be surprised is soon DIP parts will no longer
be available anywhere. And how are hobbiests able to deal with SMDs.

Al

 

[Rich Webb]

On Sun, 26 Sep 2004 03:48:08 -0700, "Ed Price" <edprice@cox.net> wrote:

Radio Shack used to be (maybe 30 years ago) an intriguing place to browse
and buy project parts. But for whatever reason, the selection and quality of
discrete components has plummeted to the joke level. It was bad 10 years
ago, and it's even worse now.

My proof? Well, I can go into any store in the San Diego region, and get the
same level of cheap parts. From what I hear on Usenet, this is typical
everywhere else. You could refute my experience, if you could cite a Radio
Shack that sells RG-214 coax, type N coax fittings, or switches that have
tin-plated terminals and a good "feel."

I don't have a citation/link (it's been several weeks since I read it)
but a recent industry rag had an article commenting that Radio Shack
might be returning at least partway to its roots. They apparently had a
"D'Oh!" moment and realized that there's no possible way to compete with
the warehouse retailers for the big ticket items. A typical RS has less
total shelf space than in just the notebook PC aisle at CompUSA.

On the other hand, a customer driving to CompUSA (or fill-in-the-blank)
probably passes at least a couple RS stores en route. So they're looking
to capture the "I need a ..." market for smaller items and piece parts.

I wish them luck. It is, perhaps, a sign of uber-geek sophistication to
dump on Radio Shack. But, even in the days of on-line ordering and
overnight delivery, it's pretty handy to be able to walk a couple of
blocks to the local RS and pick up a spool of wire-wrap wire.

--
Rich Webb Norfolk, VA

 

[Ken Smith]

In article <18ebe27.0409040719.1b6e8401@posting.google.com>,
Watson A.Name <veryfree123@hotmail.com> wrote:
[...]

Maybe if I get a chance I'll take a pic and post it to ABSE. I'm just
wondering if anyone has worked with something like this, and if it
will make a decent generator.

It sounds like the motor a friend of mine used in a wind powered battery
charger. He built a wind mill that doesn't get anything like 3600 RPM on
the motor, but does make more than 24V in weak winds. I designed and
build a charger/regulator for it so his battery pack could be kept topped
up.

It works quite well. In his location it is either sunny or windy or both
but never neither. As a result a combined wind, solar system keeps the
battery charged.


--
--
kensmith@rahul.net forging knowledge

 

[Watson A.Name - \"Watt Su]

"Ken Smith" <kensmith@green.rahul.net> wrote in message
news:cj6qe4$4ho$2@blue.rahul.net...

In article <18ebe27.0409040719.1b6e8401@posting.google.com>,
Watson A.Name <veryfree123@hotmail.com> wrote:
[...]
Maybe if I get a chance I'll take a pic and post it to ABSE. I'm
just
wondering if anyone has worked with something like this, and if it
will make a decent generator.

It sounds like the motor a friend of mine used in a wind powered
battery
charger. He built a wind mill that doesn't get anything like 3600 RPM
on
the motor, but does make more than 24V in weak winds. I designed and
build a charger/regulator for it so his battery pack could be kept
topped
up.

It works quite well. In his location it is either sunny or windy or
both
but never neither. As a result a combined wind, solar system keeps
the
battery charged.

Well, at least half the day it's not sunny - it'c called night.

As for wind, it's likely that at night there are periods of no wind.
See, when you think about it, if what you said was true, then there
would be no need for the battery. :-0

With no field winding, I'm not sure how easy it is to regulate the
charging. I'd just disconnect it from the battery and switch a load on
the output.

--
kensmith@rahul.net forging knowledge

 

[Bob Ward]

On Sun, 26 Sep 2004 15:15:32 GMT, Al <no.spam@wanted.com> wrote:

Let's face it. Few people do electronic hobbies anymore. When I was a
kid in the 50s, I built my own transistor radio before anyone else had
one. You could actually build something which was not available
commercially. Often if it was available, what you built could be
superior. This is hardly the case anymore. And it's not just
electronics. When was the last time to saw a kit for a stick built model
airplane with tissue paper fabric. Why bother building when you can buy
something for less than 50 bucks on the internet and it flies out of the
box?

That would be when I stopped into the Hobby Lobby store in Chino Hills
last week - they still have a full selection of advanced level kits
for RC hobbyists.

Why bother building a high performance aircraft when you can buy RTF
junk on the Internet? You tell me.

 

[Sylvia Else]

Ken wrote:

Hi,

I would like to know what is a magnetic field. I mean what is it composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

A magnetic field is part of a theory we use to describe the interaction
between charged particles, which are themselves just part of the theory.

At the end of the day, science only ever describes. It never explains
things except in terms of other descriptions. By asking what a magnetic
field is out in the real world, you're asking for something that is
beyond the scope of measurement, and therefore unknowable even in principle.

Sylvia.

 

[Tim Auton]

Al <no.spam@wanted.com> wrote:
[snip]

Let's face it. Few people do electronic hobbies anymore. When I was a
kid in the 50s, I built my own transistor radio before anyone else had
one.

Was it better (cheaper, smaller, sounded better...) than a
commercially available non-transistor radio?

You could actually build something which was not available
commercially.

You still can. Things have moved on, so we build different things
these days. The components are much better though. I built a PVR
(digital video recorder). I didn't make the motherboard, or the CPU,
or the RAM and I didn't write most of the code (I did write some
though, and I spent a whole lot of time making the damn thing work) -
but I bet you didn't make your own transistors or capacitors or invent
much of the circuit topology for your radio either. I also build
boards for my robots - not from discrete components, but from micro
controllers, integrated H-bridge drivers, packaged power regulators
and the like. Why not make it all from discretes? Same reason you
didn't make your own transistors.

Often if it was available, what you built could be
superior. This is hardly the case anymore. And it's not just
electronics. When was the last time to saw a kit for a stick built model
airplane with tissue paper fabric.

All the time! Go to an R/C hobby shop, the place is full of 'em. Go to
a place they fly gliders, the sky is full of 'em.

Why bother building when you can buy
something for less than 50 bucks on the internet and it flies out of the
box?

Perhaps because the cheap planes suck?


Tim
--
Guns Don't Kill People, Rappers Do.

 

[Brian]

Try quantum physics.


"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:41575f88$0$23895$afc38c87@news.optusnet.com.au...


Ken wrote:

Hi,

I would like to know what is a magnetic field. I mean what is it composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

A magnetic field is part of a theory we use to describe the interaction
between charged particles, which are themselves just part of the theory.

At the end of the day, science only ever describes. It never explains
things except in terms of other descriptions. By asking what a magnetic
field is out in the real world, you're asking for something that is
beyond the scope of measurement, and therefore unknowable even in principle.

Sylvia.

 

[Ryan Wheeler]

Ken wrote:

Hi,

I would like to know what is a magnetic field. I mean what is it
composed of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

look at this one http://www.who.int/peh-emf/en/

search word in google is: emf

 

[Don Kelly]

"Ken" <lera@sympatico.ca> wrote in message
news:yLH5d.2351$MD5.146609@news20.bellglobal.com...

Hi,

I would like to know what is a magnetic field. I mean what is it composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

thank you

ken

A field is a region of influence- hence a magnetic field is a region of

magnetic influence- i.e. there are effects due to the magnetism. Beyond that
one gets into "what is magnetism"
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

 

[TimPerry]

Kevin Kilzer wrote:

On Sun, 26 Sep 2004 18:53:21 -0400, "Ken" <lera@sympatico.ca> wrote:


I would like to know what is a magnetic field. I mean what is it
composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.

i was pretty sure that the magnetic field was the horizontal plane where
alnico, samarium cobalt, and neodymium magnets were stored prior to
instillation in speakers and microphones.

but after some consideration i decided it must be a nickname for 3M stadium.


perhaps its just a wild gauss chase but i wouldn't get too fluxed up over
it.

 

[Repeating Rifle]

in article RAM5d.5110$5H2.4507@news01.roc.ny, John at John@john.com wrote on
9/26/04 9:23 PM:

This is all a bit over my head, but presumably the first observer (the one
who doesn't see the magnetic field because it doesn't exist for him) sees
something else; whatever the second observer sees as a magnetic field
manifests itself somehow for the first observer? Don't conservation laws
say that elements might vary, but the total sum must be the same?
Probably not...

Whatever one observer sees is what another observer sees when transformed ty
the appropriate Lorentz transformation.

Bill

 

[Checkmate]

On Mon, 27 Sep 2004 13:13:03 +1000, Sylvia Else put forth the notion
that...

Kevin Kilzer wrote:

On Sun, 26 Sep 2004 18:53:21 -0400, "Ken" <lera@sympatico.ca> wrote:


I would like to know what is a magnetic field. I mean what is it composed
of.
I searched google , asked people around me , no one seems to know.
Obviously everyone knows where how, but not what.
I thought it was electrons, but that cant be.


Basically, both electric and magnetic fields store electromagnetic
enegy. Electric fields can be created by something as simple as a
battery, and magnetic fields come from magnets or from electrical
coils while a current flows. Why magnets make magnetic fields is a
question for quantum physics.

With respect to Sylvia, James Clerk Maxwell expressed a relationship
between electric and magnetic fields in the mid 1800's. Maxwell's
contribution was to show that a magnetic field is created as an
electric field changes, and an electric field is created as a magnetic
field changes. The result is that if I switch an electric field off
and on, I get a magnetic field that swells and collapses with each
on-off transistion.

If I flip the swith fast enough at some frequency, I will find that
the magnetic field comes and goes with the same frequency. But, since
a changing magnetic field will create its own electric field, the
effect moves out to this new field, which makes another magnetic
field, and so on, and that is radio.

Kevin


I'm not disagreeing with Kevin, but there is a simple thought experiment
that shows how careful one must be about taking a theory, such as that
of James Clerk Maxwell, and attempting to use it as anything more than a
description.

Take two electrons, separated in space, stationary relative to some
observer. There's an electric field, obviously, but no magnetic field.
Now take another observer moving perpendicularly to the line joining the
electrons. This observe sees the electrons in motion. Electrons in
motion are an electric current, and an electric current produces a
magnetic field, so for that observer there is a magnetic field present.

So one observer finds a magnetic field present where another observer
finds none. The notion that a magnetic field has a concrete existence is
clearly problematic. This paradox doesn't appear in the theory itself,
because it simply tells you what will happen (or more exactly, what your
measurements will show). It doesn't say anything about what is "really"
there.

Sylvia.

I think Heisenberg first developed that theory, but I'm not certain.

--
Checkmate

 

[E. Rosten]

Repeating Rifle wrote:

What is a tensor you my ask. Rather than giving a circular argument I
will
present *stress* as an example. Inside a stressed medium there will be a
combination of tensile and shear stresses. This combination is an
entity by
itself, in which tensile and shear stresses cannot be separated out.

Shear stress can always be seperated out: you can represent any
combination of shear and tensile stress as pure tensile stress (google
for Mohr's Circle).

The Mohr's Circle operation is just a graphical way of diagonalizing the
stress matrix (well, it only works in 2D where the tensor is of rank 2).


-Ed

--
(You can't go wrong with psycho-rats.) (er258)(@)(eng.cam)(.ac.uk)

/d{def}def/f{/Times findfont s scalefont setfont}d/s{10}d/r{roll}d f 5/m
{moveto}d -1 r 230 350 m 0 1 179{1 index show 88 rotate 4 mul 0 rmoveto}
for /s 15 d f pop 240 420 m 0 1 3 { 4 2 1 r sub -1 r show } for showpage

 

[E. Rosten]

Bob Ward wrote:

The only hope RS (or any other retailer) has, is its customer base.
With condescending assholes in the field, it can only get worse.
I'll tell you: Every time I walk into a RS store, I express my feelings,
and they are not ALL good. For instance: They are carrying less and less in
the way of discreet electronics components, like IC's, connectors, small
accessories, and even resistors and capacitors. I tell them that. But I do
it constructively. Will it get better? Probably not. It's largely driven by
the market trend.



Is there a discreet way to point out the difference between "discrete"
and "discreet"?

I want discreet components. You know, ones that do the job quietly
without making a fuss or goddiping or any of that stuff. Resistors
should be seen and not heard. Incedentelly that is why I prefer
resistors to, say, capacitors. At worst a resiztor makes a small fizzing
sound (but that is rare). My capacitors on the other hand often make
loud bangs. That is about as indiscreet as it gets.

-Ed



--
(You can't go wrong with psycho-rats.) (er258)(@)(eng.cam)(.ac.uk)

/d{def}def/f{/Times findfont s scalefont setfont}d/s{10}d/r{roll}d f 5/m
{moveto}d -1 r 230 350 m 0 1 179{1 index show 88 rotate 4 mul 0 rmoveto}
for /s 15 d f pop 240 420 m 0 1 3 { 4 2 1 r sub -1 r show } for showpage

 

[CWatters]

"Ken" <lera@sympatico.ca> wrote in message
news:yLH5d.2351$MD5.146609@news20.bellglobal.com...

Hi,

I would like to know what is a magnetic field. I mean what is it composed
of.

It isn't really composed of anything. It's a region in which a magnetic
force can be detected. Ever seen a police car on the motorway? Everyone
within 100 yards drives exactly at the speed limit. the police call this a
bubble or zone of legality. The zone isn't composed of anythig but you can
"feel the force".