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The mechanism behind bouncing...

J

John Fields

Jan 1, 1970
0
Except when it doesn't suffice. Sometimes its a naive view in that some
people when told that will believe it to be a fact when its not. Just like
ohms law is not a fact. Its a law that breaks down under certain conditions.
When people are just learning about these things they tend to be reluctant
to question. So I think it does everyone better if instead of trying to
state things as fact they are stated in the right context. (the context of
the right level of approximation for the job)

---
That's right. And telling a newbie more than he needs to know at
that moment is a disservice to him. There's a reason why college
level material isn't presented to kindergarten students, you know.
---
But the OP did ask for such and explination and I tried my best.

"or if it's because of the very rough
surface (microscopically-speaking) of the switch contacts, were the metal
molecules grinds (and possibly flexes) together, during switch activation?
"

since he brings in this microscopic level I can only assume he wants a
corresponding answer in the microscopic.

---
I disagree. What he was asking about was the physical mechanism
which is responsible for bounce, not what was ultimately responsible
for the physical mechanism.
---
(wether it is relvant to engineers is irrelevant to me.

---
It seems to me that all that's relevant to you is you.
---
He ased a question and I would answer it in his context
the best I can.

---
No, you answered it in what you _thought_ was his context.
To be sure you would have had to post and ask him before replying.
---
Its not my job to question his reasons why he wants to know
this as I assume he has a better understand of his motivations than me. )

---
Without having asked him, specifically, what he wanted to know, your
post may have been nothing but gibberish to him.
---
Because when you *tell* someone they might think that that is the answer and
only answer.

---
You're telling me that, and if that's supposed to be fact, then
according to you I should take what you claim to be fact with a
grain of salt, no?

Don't be absurd.
Telling someone the world is flat in places is perfectly legitimate.
---
Then this propagates arrogance. Those people then grow up tell
someone else the "fact" and everyone thinks its a fact. Then comes along
some guy that questions it and he's jumped on by everyone else.

---
Some guy like you, who knows for sure that someone who was asking
about contact bounce wanted, really, to delve into QM, huh?
---
Its sorta
like how some laws are. Someone creates a law for a specific reason and
then many years down the line the reasons are forgotten and the law is
enforced even though its original reason for existing makes it invalid. But
it is enforced because people cannot think for themselfs(most people). They
don't question authority because they are afraid. To many people think facts
are a popularity contest. Life just doesn't work that way.

---
Then there are people who question everything; not because they're
searching for the truth, but because they're desperately seeking to
be noticed...
---
Again, the issues I tend to have with you guys is that you seem to think
that what you think are facts must be facts for everyone else. This is not
the cause and I think you guys are smart enough to really understand that
but its just easier to act like everyone has the same set of facts. But the
point is that just because you believe something as fact doesn't mean you
should state it as fact to someone else.

---
Is that a fact?
---
This, to me, is exactly what you guys try and
do. You force feed people your "facts" when in reality they are not facts at
all(usually). Actually nothing is fact so we shouldn't force feed anything
to anyone else.

---
But you're trying to force-feed me the "fact" that nothing is fact.
Are you so logically immature that you can't see that hypocrisy?
---
We present the evidence and let the other person decide. If
they come to a different conclusion then so be it. Its not our job to get
everyone else to believe what we believe.

---
Not true. You want me to believe that what you told the OP was
right and what I told him was wrong, and you also want the OP to
believe your version of what you think he asked for.
---
So true, I might be guilty of it and sometimes I am guilty of the exact same
things you guys do. I have no problems admitting it. Its not right but
sometimes it a necessary evil.

---
What a pompous ass you are!

You sit there, playing God, saying that we're all so bad but that on
occasion even the GREAT YOU succumbs to the evils we do.

**** you.
---
So sure, I don't know how to
uncook an egg. But I don't know how to do a lot of things but that should
not stop me from trying to learn.
[/QUOTE]

Maybe. That is not my goal as I'm just trying to express my point of view.[/QUOTE]

---
OK, but more than just trying to express it, it sounds like you're
saying your view is the "right" view and everyone else's is wrong
unless you agree with it.
---
Sure. I cannot change that. I hope that you understand that it is not as
productive, atleast I hope you would reason to that because I believe the
alternative is much better.

---
The alternative you're proposing is falling into step with you, and
while that might be better for you, it certainly wouldn't be better
for me.
---
We can learn a lot from history and while
history is not always right it does help a lot.

---
LOL, "History is not always right?"

Don't you mean "The way history is presented is not always right?"
---
I cannot make you do
anything but only offer evidence that its probably not a good idea to think
like that.

---
Evidence? Surely you mean 'opinion.'

And surely because it's contrary to the way you'd have me think? I
don't live my life based upon whether what you think I do is right
or wrong, I live it to please myself and do what I think is right.
---
The evidence simply might be wrong or wrong to you(some stuff is
just relative and we can't escape it).

---
Everything is relative, and that's absolutely true.
---
No, not necessarily. I do see your point but if I say someone is wrong its
more "I think your wrong, please explain why."

---
That makes no sense, since it puts the onus on whoever you say is
wrong to explain why you think they're wrong.

That's _your_ job, not theirs.

But, while we're at it, let's explore why you can't do something as
simple as avoiding spelling and grammar faux pas while pretending to
grander vistas.

You do know your writing is full of avoidable mistakes, no?
---
Its not as polite to just say
"Your wrong" and I try not to say it like that. What I really mean is
"EXPLAIN WHY!!".

---
Then you should say something which reflects what you mean instead
of expecting your readers to read your mind.
---
Why do I say it like I do? Because if I say "Your wrong"
then most people that actually understand why they think they are right are
going to present the evidence if they want to explain.

---
Why would they want to? So far you've not proven that your way is
the better way, all you've done is ask for partners in suicide.
---
Atleast thats what I do.

---
Uh Huh...
---
I also know that if people get angry when they are told they are wrong
then it probably means that they don't really know why they believe what
they do. (else why get angry. If a 2 yr old kid comes up to you and says
"Your stupid. The earth is flat!" do you get mad and punch the kid in the
face? I would hope not.)

---
You're trying to cast yourself as the innocent 2 year old kid
asking innocent questions while also trying to cast yourself as a
sage.

You're neither.
---
But this isn't a chess game.

---
Right. It's a different kind of game
---
We are not trying to play king of the mountain.

---
We aren't?
---
We are hear to learn, no?

---
And to teach, and to troll, and to do anything else we want to.
---
Several of the problems I have had with "you guys" is that I have asked a
question about something and I was told something that may or may not have
been true. I have had contradicting sources and so I ask you to explain your
reasoning and evidence and instead I get jumped on. When that happens I do
not like it at all because now that means I will not learn anything about it
except by going somewhere else. It also seems to point that either someone
doesn't want to share there knowledge(they only want to dictate) or they
don't have the knowledge(so they pretend). In either cause it means I will
not learn anything from them any farther.

---
It could also mean that you've got an attitude and you're so firmly
entrenched in your way of thinking and you have such a high opinion
of yourself that you really don't want to hear any contradictions
from mere mortals like us and would fight to the death to keep from
having to believe that we proved you were wrong.
---
I think I'd be more of the chopped liver than you guys. I think you guys are
normal, probably pretty intelligent people but have lived in a hostil
enviroment that makes you a little to rough for me.

---
Then stop whining and either go away or plonk whoever offends you,
or learn to take your lumps. This is USENET, and if you're that
thin-skinned it may not be the place for you.
---
I'm like a shark and I
can smell a drop ego a mile away. Sometimes I do over react and sometimes I
do let my own ego take control. This is not my goal. I'm only human just
like you guys. But what I do know is that when things become childish that
nothing important will probably come out of it. I understand that you want
to be treated with respect and that you have worked hard to learn the things
you have but you have to understand that I'm not the type of person that
takes anyone elses logic or knowledge on faith(even if its at my own
perile). I do this because I like to learn for my self. Just don't take it
the wrong way. If I sound like a kid sometimes its because maybe I am.
 
J

John Fields

Jan 1, 1970
0
Yes, but this is explained in a microscopic way.

---
And you object to that, why?
---
Sure it does.

---
No, it doesn't. If the metals are welded together, then there is no
interface. Even the dissimilar metals will only have a small region
where one diffused into the other and an alloy was formed.
---
This is due to the crystal structure of metals. You don't have this if the
metals are different.

---
Bullshit. There will be no interface if the molten metals are
capable of dissolving into each other.
---
Not sure wha tyour getting at:

It is not, however, a fundamental force, as it originates from the
electromagnetic forces and exchange force between atoms.

The key is originates. It means that it can be "explained" in terms of the
fundamental forces(which there are only 4 so essentially everything can be
explained in terms of that).

---
You were claiming that it was a fundamental force. It is not.
---

Yes, but how can you even talk about that? You act like the macroscopic
level is something totally different some the microscopic. The macroscopic
is just a manifestation of the microscopic. If you want to talk in those
terms then thats fine. But then we are talking about different things.
Although since the macroscopic is derived from the large scale microscopic
my ideas should, if correct, explain the macroscopic in a much more detailed
way.

---
Why do you persist in the idiocy of preaching to the choir?

What the OP was asking about was what caused a counter to miscount
when clocked by a noisy set of contacts, and all you keep doing is
parroting your four-force crap, which is totally irrelevant from the
POV of having the OP understand why contact bounce causes miscounts.

It's as if he'd asked how much charge would flow in a circuit
comprising a resistance of one ohm being driven by a one volt source
and your parroting endlessly that all that matters is electrons
repel each other.
---
Well, here we have to disagree. Since the OP talked about the microscopic
effect of "friction"(and by the wiki page is the EM and interatomic forces)
then I assumed he ment at the microscopic level.

---
Well, there's microscopic and then there's microscopic.
My belief is that he was talking microscopic at the level of minute
hills and valleys on a metal surface, and metal masses physically
colliding with and repelling each other, which would be consistent
with the generation of the high-level electrical signals required to
clock the counter.

Your bringing up the four fundamental forces and applying them to
the problem incorrectly not only didn't answer the OP's question,
they added considerable confusion to the "discussion".
---
From here one doesn't even have to do any estimation. If there are only 4
forces in the physical world then any macroscopic forces must be derived
from these 4. Friction is not a fundamental force. It is based on the
interactions of a huge number of atoms and the 4 forces. Mechanical
"bounce" is not due to some macroscopic force(although we can use an average
to get it) but only due to the 4 forces. I don't see how you can conclude
anything else. I am not saying that we cannot talk about some derived force
because its almost necessary. What I am saying, now atleast, is that
everything in the physical world is due to these 4 forces(assuming they are
the correct). Any force that you claim is "fundamental" better be one of
these 4 forces and if its not then you better prove it(atleast make enough
of a convincing argument so that it is accepted as a new fundamental force).

If you want to talk about friction or bounce or whatever and ignore the fact
that they exist only because of these 4 forces then you are doing yourself a
disservice. You might get along just fine with beliving that but your no
different than those who thought the world was flat or that the thunder god
was angry at them.

---
You're either grasping at straws or your reading comprehension is
very poor, or both.

I never stated that the four fundamental forces don't exist or that
they're not responsible for our universe being the way it is; what I
stated was that in order to give the OP an answer which was relevant
to his question there was no need to muddy the water by bringing up
the four forces.

As a matter of fact, your claim that an electric field around the
contacts was attracting/repelling them and causing the bounce was
100% off the mark.
 
D

default

Jan 1, 1970
0
Bouncing means bouncing. When contacts collide, they, well, bounce,
like a ball hitting the floor. Multiple contacts are made and unmade
until it settles down. This is quite visible on an oscilloscope.
Small, low mass contacts have a higher mechanical resonant frequency
so tend to have higher bounce rates and settle faster.

Bouncing on a scope looks like hash from what I've seen. Actual
bouncing should look more like an increasing frequency square wave.
First bounce greatest and longest distance to close, with subsequent
bounces occurring with smaller periods.

Toggle switches have contacts that wipe as they make contact, relays
(quality ones) use over travel of the armature to wipe/slide the
contacts together.

Switches seem designed to minimize actual bounce. Can you imagine how
long the contacts on something like a high power contactor would last
if they were designed to bounce? The mass of the contacts is often
decoupled from the actuating plunger with a set of springs so the
plunger can drive a 1/2" or so past the point where the contacts touch
one another.

Control relays do something similar. Cheaper relays or low power
ones, allow the reed the contacts are mounted on to flex so the iron
can travel past where it makes electrical contact. - makes all the
contacts self aligning, wipes oxide off and compensates for wear -
but eliminates bounce.
 
J

John Larkin

Jan 1, 1970
0
Electrostatic forces? No one said anything about electrostatic forces. That
is kinda irrelevant too as electrostatic forces are forces generated by
charges not in motion. When charges in motion one has electodynmaics which
is a completely different phenomena(which is not decribed in parameterized
way on time because it would not explain the magenetic fields created.


For pete's sake, read the first paragraph you wrote in your post just
above.
What your thinking is that these minute forces some how change in a way on
voltage that is not linear. This is true but only in a certain range of
voltages. Just like a resistor is "linear" but actually this is not true at
all. its an apporoximation that in no way explains the true mechanisms of
resistance. If you could see the true "waveform" then every one would be
different even for the same resistor. Its more like a stochastic brownian
process and you see its statistical average. I doubt a 1GHZ scope could even
capture those subtle effects.

My original point to you was that even though these interatomic forces are
"random" doesn't mean the macroscopic behavor is random or even close. Just
like gravity of the earth is extremly complicated and due to an extremly
large number of small forces we can still describe it by g at the surface
and it is quite accruate. In some sense the large number of "random"(not
truely random but best described by random processes) events have a simple
non-random macroscopic effect. One even can have an effect that is simply V
= IR. The microscopic behavor is extremly complex and somewhat random but
its pretty much perfectly described by that equation.

You are babbling. Get a toggle switch or a relay, a power supply, a
resistor, and an oscilloscope and actually learn something.
Yes, I was only showing it because of the waveform which I believe is the
tyep of waveform that you think real switches actually exhibit.


Like I keep saying, try it.
Really? Do you know that all materials are made up of atoms and atoms are
quite random(Stochasic is a better term). That is, trying to describe the
motion of any one atom/electron is impossible(not even because its hard but
becaues of the uncertainty principle) but all the atoms of a material taken
together exhibit a property that is independent of any single atom. If this
were not the case we could not have any simple laws describing those
macroscopic properties(cause they would change so easily and we could never
do any experiments with them).

What your trying to do is talk about engineering when teh OP wanted to know
about the physics. Engineer's could care less about what causes the
properties but only care about the dollar.


Ok, then maybe I'm not using some technical definition of arcing. If arcing
must involve a plasma to be called arcing then thats fine. I was wrong. I
normally just think of arcing as electronic flow. I could say that any time
an electronic flows through a material it is arcing from one atom to the
next. In some sense this still works with your definition since the
conductor could be though of a plasma but ofcourse this is wrong by the
defefinition of plasma. Ofcourse when electricity arcs in air we don't
normally think of it as creating a temporary plasma(that only lasts for
probably a ms at most) but we still say it arcs? Or do you just call this a
electron flow.

When the electrons flow in a flow the tube they do flow without ionization
because there is no gas in the tube to interfer with the flow. Put a gas in
the tube and you get ionization and if there is enough then a plasma. While
not technically correct, to me this seems to say that arcing is more matter
of degree than just a simple black and white definition.

I think here that arcing and electric flow are very similar and overlap.
Ionization usually happens(if not always) when there is electric flow.
Metalic conduction is just electric flow because the metal atoms are so
easily ionized while in ionizing a gas tends to be a lot harder(more work
for the electrons to flow until it is already ionized).

Anyways, doesn't matter so much as thats not what the OP asked about.

The main point I'm trying to make to you is that your ideal view of how
things work is not how they work. Maxwell's equations do not govern true
electronic flow. It assumes that the current density is continuous and this
is far from the case. It works because on such a macroscopic scale one does
see what looks to be a continuous medium. If you only ask about what
happens on that scale then the equations are valid(Similar to Newton's law
and the speed of light). But to describe what happens at the microscopic
level you have to use quantum mechanics. If you want to know how total
macroscopic effect of a contact switch then Maxwell's equations along with
classical dynamics work just fine. If you want to know what really happens
you'll have to bring in QED and QM. Its just that simple. Classical physics
was not formulated at the level of QM and it was only important for
macroscopic purposes(Not that this didn't stop them from hypothesizing at
the atomic level). QM is formulated on the atomic level(and some of it at
the sub-atomic). It has proven that when its laws are taken in a statistical
sense on the macroscopic level they reduce to the classical formulations.

http://en.wikipedia.org/wiki/Friction

Oscillatory behavior is described by a differential equation of the
2nd or higher order, and friction is just one of the terms. In plain
English, if you want a bounce you need a spring. Friction doesn't
cause bouncing, it *dampens* bouncing. Non-springy swiches, like tact
and membranes, do bounce because of grotty, sliding contacts, and the
bounce pattern more random, less oscillatory than that of a toggle
switch or a relay.

Contact bounce is easily observed optically, and acoustically, and
matches electrical bounce almost exactly. Try it.

John
 
M

me

Jan 1, 1970
0
snip
Oscillatory behavior is described by a differential equation of the
2nd or higher order, and friction is just one of the terms. In plain
English, if you want a bounce you need a spring. Friction doesn't
cause bouncing, it *dampens* bouncing. Non-springy swiches, like tact
and membranes, do bounce because of grotty, sliding contacts, and the
bounce pattern more random, less oscillatory than that of a toggle
switch or a relay.

Contact bounce is easily observed optically, and acoustically, and
matches electrical bounce almost exactly. Try it.

John

give up. Ignorance is fixable, stupid is not...
 
R

Rich Grise

Jan 1, 1970
0
Um, and you seem to think that mechanical bouncing is some real thing. Its
an abstract concept.

Well, you clearly have your head in the clouds. Contact bounce is what
happens when the contacts bounce. And physical stuff bounces when it
slams into other physical stuff. In a switch or relay you probably
want to move the contacts fairly quickly, and since we only have real
materials to work with, when contact "C" hits contact "A", it phycically,
mechanically, measurably, bounces, just like a tennis ball.

Try hitting an anvil with a hammer some time and see if you can make it
_NOT_ bounce! :)

Good Luck!
Rich
 
R

Rich Grise

Jan 1, 1970
0
Because you guys always seem to think that your way is the right way.

Only because that's what the observations tell us.

Cheers!
Rich
 
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