The mechanism behind bouncing...

[KILOWATT]

Hi... thanks for your attention.

I just wish to know the precise reason why for example, a digital counter
may count many pulses on it's clock input when the clock is feed via a non
noise-free source like a mechanical switch. It is because when the contacts
makes/breaks, arcing (i've read somewhere that there can be a possibility of
arcing even at low voltage) occurs, 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?
TIA for your reply.


--
Alain(alias:Kilowatt)
Montréal Québec
PS: 1000 excuses for grammatical errors or
omissions, i'm a "pure" french canadian!
(If replying also by e-mail, remove
"no spam" from the adress.)

 

[default]

Hi... thanks for your attention.

I just wish to know the precise reason why for example, a digital counter
may count many pulses on it's clock input when the clock is feed via a non
noise-free source like a mechanical switch. It is because when the contacts
makes/breaks, arcing (i've read somewhere that there can be a possibility of
arcing even at low voltage) occurs, 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?
TIA for your reply.

You got it - on a microscopic level the metal contacts will create
high frequency noise (a good scope may be necessary to see it). Some
reed switches were produced that eliminate the bounce by using
electrodes with a mercury coating in an inert gas capsule.

Ironically, they were also used with mechanical actuators to produce
fast rise time pulses to test semiconductors. Nothing says "on" like
mercury coming together.

Some dry switches deliberately induce a wiping action on the contacts
which prolongs the switch life, but creates more noise.

The clock input of logic circuits is fast enough to count the
transitions.

 

[John Larkin]

Hi... thanks for your attention.

I just wish to know the precise reason why for example, a digital counter
may count many pulses on it's clock input when the clock is feed via a non
noise-free source like a mechanical switch. It is because when the contacts
makes/breaks, arcing (i've read somewhere that there can be a possibility of
arcing even at low voltage) occurs, 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?
TIA for your reply.

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. Mercury-wetted
contacts don't bounce at all.

There's no significant arcing contribution at low voltages.

Incidentally, for both wet and dry contacts, the initial electrical
connection can have sub-nanosecond risetime.

John

 

[Jon Slaughter]

Hi... thanks for your attention.

I just wish to know the precise reason why for example, a digital counter
may count many pulses on it's clock input when the clock is feed via a non
noise-free source like a mechanical switch. It is because when the
contacts
makes/breaks, arcing (i've read somewhere that there can be a possibility
of
arcing even at low voltage) occurs, 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?
TIA for your reply.

The atoms of the two materials are not configured in such a way that there
is complete contact. If they were then the materials would be fused. Since
there are not fused and they slide there is friction involved and this
friction causes the contacts to move farther a part and then closer
together. So the average distance between the constants is changing
significantly campared to when is not moving and they are making good
contact. So now the electric field is changing because of the distances
changing between the contacts. As the contacts move farther away the field
becomes weaker but now we have a capacitive effect. This effect creates a
force between the contacts that attract them. One now has a kinematic force
pulling the contacts away(so it can slide), one of friction that wants to
stop the slide, and one of capacitance that is attractive(I'm sure there are
more too).

Anyways, So there are all these forces that are interacting and the end
result is this oscillation of the contacts moving toward and away from each
other. One always gets "arcing" but thats kinda relative turn. (In some
sense all electronic flow is "arcing".) Generally this term is used when
there is significant macroscopic arcing and this requires much higher
voltages than the microscopic arcing that always happens. (Its just a matter
of degree). This oscillation that happen is called bouncing and the net
effect is to increase and decrease the resistance but with a trend towards
increasing it(which happens very sharply when the contacts finally break
away).

When a switch bounces it does turn on and off instantaneously a few times
then finally settles on off. Nothing is every instanenous in the real
world. The net resistance is dependent on many factors and one of them is
the distance between the contacts. Theres a point where the distance becomes
so great that microscopic forces do not have any significant effect. The
bound that you see on an oscilloscope occurs right at this point where D
becomes more significant and the other forces do not. This point has to do
with how much of the two contacts are actually in contact although it
happens over the whole surface since some points on the contacts are more in
contact than other points. In this case we have an average that approximates
the whole surfeces very well unless the contacts are very distorted.


I guess ultimately the effect I'm talking about is sorta middle ground
between the atomic and the macroscopic. Whats really important here is what
happens when the two contacts are about to completely leave each other and
not what happens before(although it could be significant it is just a
smaller version of the main one). Once you understand this then its not
hard to see that it happens many times before but just on a smaller and
smaller scale. (One could say that bouncing is always happening so its just
a matter of degree).

Anyways, I'm kinda rambling there but maybe it will shed a little light on
your problem.

Jon

 

[Ben Jackson]

Incidentally, for both wet and dry contacts, the initial electrical
connection can have sub-nanosecond risetime.

I knew I shouldn't have paid a premium for these "high speed digital
buttons"!

 

[John Fields]

Incidentally, for both wet and dry contacts, the initial electrical
connection can have sub-nanosecond risetime.

 

[John Larkin]

The atoms of the two materials are not configured in such a way that there
is complete contact. If they were then the materials would be fused. Since
there are not fused and they slide there is friction involved and this
friction causes the contacts to move farther a part and then closer
together. So the average distance between the constants is changing
significantly campared to when is not moving and they are making good
contact. So now the electric field is changing because of the distances
changing between the contacts. As the contacts move farther away the field
becomes weaker but now we have a capacitive effect. This effect creates a
force between the contacts that attract them. One now has a kinematic force
pulling the contacts away(so it can slide), one of friction that wants to
stop the slide, and one of capacitance that is attractive(I'm sure there are
more too).

Sorry, but that's all nonsense. At low voltages and currents, switch
contacts bounce for purely mechanical reasons.

If your field theories were true, the applied voltage would radically
change the bounce waveform. It doesn't. Try it.

Anyways, So there are all these forces that are interacting and the end
result is this oscillation of the contacts moving toward and away from each
other. One always gets "arcing" but thats kinda relative turn. (In some
sense all electronic flow is "arcing".)

Metallic conduction is not "arcing." Arcing is gaseous conduction.
Vacuum tunneling happens too, but the range is just on the order of an
atomic diameter, not important for things like switch contacts.

John

 

[Jon Slaughter]

Sorry, but that's all nonsense. At low voltages and currents, switch
contacts bounce for purely mechanical reasons.

Um, and you seem to think that mechanical bouncing is some real thing. Its
an abstract concept. There is no real think as bouncing. When a ball bounces
you think that the surfaces are idealized. No, they are governed by quantum
mechanics. Believe it or not, doesn't matter ot me.

If your field theories were true, the applied voltage would radically
change the bounce waveform. It doesn't. Try it.

hmm. so the waveforms are exactly the same? They do not scale with voltage?
You seem to think that ohms law doesn't apply here? V = IR or did you not
learn that? What do you really think these waveforms will look like? Do you
think they will be perfect unit step functions? Get into the real physics
of it and stop trying using idealized descriptions of the behavor.

http://www.ece.uci.edu/rfmems/publications/papers/mems/C021-EUMTT99.pdf

http://www.scienceprog.com/dealing-with-switch-bounce-problem/

Do you really think that the effects I'm talking about are going to
radically change the macroscopic scale? The time scale is femto or less and
the forces are fN or less. (although the above analysis are still idealized)

Your logic is like saying a resistor behaves exactly the same no matter what
conditions. Your a bafoon in thinking that everything is some simple
mathematical equation that you learned in cal 101.

You think that a resistor doesn't change its "waveform" with voltage? R =
V/I. What happen when V is very low? what about when V is very high? What
about most of the time? Most of hte time R is the APPOXIMATELY constant.
THATS RIGHT!!! A resistor doesn't change its "waveform"(which is wrong way
to put it as switches and resistors are not waveforms) for a wide range of
voltages. If this what the case then they would be practically useless.

Did you ever take quantum mechanics 101? Hell, even basic physics supplies
an approximately correct answer. Coulomb's law for the contacts state
something like

Sum(k*Qi*Qj/r_ij^2,i=1..N)

(this is better described in a statistical quantum fashion but I don't want
to confuse your little brain)

Do you think that distances in this equation have some special meaning
between when a switch is open and not? Sure there is a point where the
strenght of the field drops off almost to 0 but it is not instantaneous.

The OP asked for the microscopic answer and not something you read out of an
electricians manual.

(BTW, show me some waveforms's from two different switches using the same
voltage and lets see if they are even close. Hell, show me two waveforms
from the same switch using the same voltage and lets see if they are even
close.)

Metallic conduction is not "arcing." Arcing is gaseous conduction.
Vacuum tunneling happens too, but the range is just on the order of an
atomic diameter, not important for things like switch contacts.

So we cannot have an arc in a vacuum without any gas? Hmm, can you prove
this? I think this would go to explaining a lot about vacuum tubes(I guess
they don't "arc" or must contain a gas(a significan't amount to explain the
arcing)).

It may not be significant to you but you are not the genius you think you
are. People like you are satisfied with any explaination that doesn't
confused them people like the KILOWATT want to know the real reason why
things work. You take it on faith(sure, you might look at a few switch
characteristics using an oscilliscope but then you do not care to go
farther) while he wants to know the real reasons. The difference is one of
religon and one of science.

The same factors that cause friction are at work with a mechanical switch.
You can ignore this all you want and thats fine. But don't try to act like
the world is some idealized place that is perfectly described by few simple
mathematical equations. (all equations are wrong to some extent and some are
better than others. Usually the better equations are more complicated).

Your logic is like "A diode is a switch" while mine is "A diode is a device
that can behave like a switch but this is because of the properties of the
material. (then I'd have to talk about doping, holes, drift, junctions,
valence electrons, pauli exclusion principle, etc...). Rarely is any simple
explination the full explination.

If he asked what was switch bounce then your answer is good enough. What he
asked was what was the microscopic reason for switch bounce. Now I didn't
talk about quarks because obviously that level is to low and there is no
need(as far as we know). Even the theory of friction at the atomic level is
not know that well. But this is the best level to explain it because you
get at the heart of the reason. Now my explinations might not be perfect but
just because you think they are wrong doesn't mean they are. I also never
said the effects were significant, but there is a macroscopic effect.

Its fine if you want to act like the world is not made up of atoms and
idealize everything. I have no problem with that. But when someone else
wants to know more then don't try to make them believe what you believe.
Only thing I can think of is that your afraid that if they go and explore
that they might prove you wrong. So you care more about looking right than
being right.

Did you factor in resistance into your switch? Didn't think so. Do you know
that resistance depends on voltage? (doesn't matter how, just that there
exists two different voltages that produce two different values of
resistance). You know that voltage and heat are related? (Even directly.
Not that its significant. Even absolutely zero cannot stop an atom from
moving.)

Anyways...

 

[John Larkin]

Um, and you seem to think that mechanical bouncing is some real thing. Its
an abstract concept. There is no real think as bouncing. When a ball bounces
you think that the surfaces are idealized. No, they are governed by quantum
mechanics. Believe it or not, doesn't matter ot me.


hmm. so the waveforms are exactly the same? They do not scale with voltage?
You seem to think that ohms law doesn't apply here? V = IR or did you not
learn that? What do you really think these waveforms will look like? Do you
think they will be perfect unit step functions? Get into the real physics
of it and stop trying using idealized descriptions of the behavor.

http://www.ece.uci.edu/rfmems/publications/papers/mems/C021-EUMTT99.pdf

That paper describes a simulated mems switch that is electrostatically
operated and *never* makes electrical contact. That's not very
relevant to a conventional mechanical contact that is mechanically
driven and *does* make electrical contact.

Get an oscilloscope, a toggle switch, a power supply, and a resistor.
Set up to observe the bounce waveform. See if changing the applied
voltage changes the nature and timing of the bounce waveform, which is
must if electrostatic forces are significant. Of course the voltage
will change when you change the voltage; I won't argue that point.

This is real physics: try it.

http://www.scienceprog.com/dealing-with-switch-bounce-problem/

That says nothing about the physics. And it's actually easier to
"debounce" a pushbutton: just read it every 50 milliseconds and accept
what you see.

Your logic is like saying a resistor behaves exactly the same no matter what
conditions. Your a bafoon in thinking that everything is some simple
mathematical equation that you learned in cal 101.

No, I'm an engineer who knows how real parts actually behave.

So we cannot have an arc in a vacuum without any gas? Hmm, can you prove
this? I think this would go to explaining a lot about vacuum tubes(I guess
they don't "arc" or must contain a gas(a significan't amount to explain the
arcing)).

Vacuum tubes don't arc in normal operation; thyratrons do. Arcing is
plasma (ionic) conduction. Vacuum tubes operate by electron-only flow.
Metals conduct through movement of conduction-band electrons.

John

 

[John Fields]

The atoms of the two materials are not configured in such a way that there
is complete contact.

---
That's not true.

When the contacts come to rest after the bouncing period is over
they will either be in intimate contact or they will be completely
separated.
---

If they were then the materials would be fused.

---
Which, indeed, they are until the coil is de-energized and the
return spring exerts force on the armature, breaking the microscopic
weld(s) and allowing the contacts to open.
---

Since there are not fused and they slide there is friction involved
and this friction causes the contacts to move farther a part and then
closer together.

---
No. The friction you're talking about is only about the contacts
rubbing against each other when they're making or breaking and is a
second order phenomenon compared to bounce, which occurs when the
contacts alternately make and break when the coil is energized.
Bounce also occurs when the armature is de-energized, but to a
lesser degree, and is caused by the moving contact skipping across
the stationary contact when the coil is de-energized.
---

So the average distance between the constants is changing
significantly campared to when is not moving and they are making good
contact. So now the electric field is changing because of the distances
changing between the contacts. As the contacts move farther away the field
becomes weaker but now we have a capacitive effect. This effect creates a
force between the contacts that attract them. One now has a kinematic force
pulling the contacts away(so it can slide), one of friction that wants to
stop the slide, and one of capacitance that is attractive(I'm sure there are
more too).

---
No. The high-level bouncing behavior is due only to the gross
mechanical characteristics of the contacts and has vanishingly
little to do with the microscopic effects, which are at least six
orders of magnitude smaller than the mechanical effects, I'd guess.

Do you have some hard numbers which would prove otherwise?

 

[John Fields]

On Sat, 03 Feb 2007 21:58:27 GMT, "Jon Slaughter"

....

Anyways...

Why are you being so angrily defensive?

Contact bounce is nothing more than a spring-loaded screen door
bouncing back from the jamb when it's let go early.

 

[Jon Slaughter]

That paper describes a simulated mems switch that is electrostatically
operated and *never* makes electrical contact. That's not very
relevant to a conventional mechanical contact that is mechanically
driven and *does* make electrical contact.

Get an oscilloscope, a toggle switch, a power supply, and a resistor.
Set up to observe the bounce waveform. See if changing the applied
voltage changes the nature and timing of the bounce waveform, which is
must if electrostatic forces are significant. Of course the voltage
will change when you change the voltage; I won't argue that point.

This is real physics: try it.

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.

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.

That says nothing about the physics. And it's actually easier to
"debounce" a pushbutton: just read it every 50 milliseconds and accept
what you see.

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.

No, I'm an engineer who knows how real parts actually behave.

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.

Vacuum tubes don't arc in normal operation; thyratrons do. Arcing is
plasma (ionic) conduction. Vacuum tubes operate by electron-only flow.
Metals conduct through movement of conduction-band electrons.

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

Try reading that and you'll see that they do bring in EM a little but there
equations or not formulated on EM. The reason is simply that the macroscopic
effect can be described in such a simple fashion and this is how they were
found. Those that discovered these "laws" didn't start with the atom but
started with the macroscopic effects and tried to formulate descriptive
mathematics out of it.

 

[Jon Slaughter]

On Sat, 03 Feb 2007 21:58:27 GMT, "Jon Slaughter"

...


Why are you being so angrily defensive?

Contact bounce is nothing more than a spring-loaded screen door
bouncing back from the jamb when it's let go early.

Because you guys always seem to think that your way is the right way. I know
you guys are not stupid but it seems that you take a simple view of the
world and if someone else wants more info then you act like they are stupid.
You think, say, that if you measure the V-I curve on a resistor and see that
it looks like a perfectly straight line then it must be.

You neglect all the other factors involved. This is fine if you don't care
about them but if someone else does then you tell them what you have
observed and that is what they should believe.

To me, its like your trying to tell someone the world is flat. Now because
it you believe it you don't doubt that it is. It must be. It sounds as if
you think you know everything. And while you guys may not be wrong in most
cases in some way or another, usually you have an idealized or even a narrow
minded view of things. If you never experienced it then it must not be
possible.

Usually when someone asks something one doens't get a response like "In my
experiences I have no had this happen" but instead "It can't happen". Now
the problem with the second is that history should have taught you that
nothing is impossible but if you really believe it then you should have good
reasons. So just state them. "It can't happen and heres why...". Better
yet, "I don't think it can happen and heres my reasoning...". The first
sounds like an arrogant fool while the second one sounds like a rational
human being. Ofcourse maybe you can convince most people with the
"authority" loic but its wrong and should specially not be used in a
scientific place.

If you disagree with something then just explain why. Don't act like you
know everything about everything because you could be wrong(not saying
you/they do this all the time but it happens to much in this NG).

I could be wrong on many things I say. I'm not perfect and I do not know
everthing. But I try to rationalize everything with proof. Sometimes my
logic is faulty and sometimes I use bad evidence. I will admit when I'm
wrong if there is good counter logic involved(and not the authoritative
logic). Maybe you guys were kings in another life and are used to having
everyone do what you say no questions asked?

Actually any reasonable person who has a desire for knowledge would love for
everything they say to be questioned because it gives them a chance to
understand explain to others and reinforce there own understanding(or change
them if necessary) there view. Many times when I have "argued" with others
I have come up with a better understanding of my own point of view.
Sometimes I have also realized that my original logic was quite shakey or
even wrong. This has happened to help me be self-analyzing on much a
greater scale than most. Although in the last couple of years I've lost
almost all that ability as I do not hang around with any intelligent people
any more. Maybe thats why I get defensive, I don't know. I guess I just see
this arrogance everywhere and I feel that it does no good for humanity. (Its
getting so bad that eventually everyone will not care what others think and
believe they are kings)

Anyways...

 

[Jon Slaughter]

---
That's not true.

When the contacts come to rest after the bouncing period is over
they will either be in intimate contact or they will be completely
separated.
---


---
Which, indeed, they are until the coil is de-energized and the
return spring exerts force on the armature, breaking the microscopic
weld(s) and allowing the contacts to open.
---

So can you shear a part a solid piece of metal with a spring? Its a matter
of degree. If the contact interface was completely "fused" then thee would
not be any contact interface(assuming the same material is used for both
contacts).

---
No. The friction you're talking about is only about the contacts
rubbing against each other when they're making or breaking and is a
second order phenomenon compared to bounce, which occurs when the
contacts alternately make and break when the coil is energized.
Bounce also occurs when the armature is de-energized, but to a
lesser degree, and is caused by the moving contact skipping across
the stationary contact when the coil is de-energized.
---

The friction is due to electrical forces. There are only 4 known
forces(well, 4 main ones) in the world. Gravitations, Electrical, Strong and
weak. Gravitational is like 10^(-40) smaller than electrical. The strong
and weak work only as a sub-atomic level.

So are you saying there is some other forces involved?

---
No. The high-level bouncing behavior is due only to the gross
mechanical characteristics of the contacts and has vanishingly
little to do with the microscopic effects, which are at least six
orders of magnitude smaller than the mechanical effects, I'd guess.

Sure, but we are not talking about high level. The high level is strictly
due to the averging of the microscopic. See above about the forces.

Do you have some hard numbers which would prove otherwise?

Yes I do. 4 forces, 1 is too weak to be of any use for this problem, the
other 2 are too weak at the distances we are discussing.

Here, I'll even get you a link with some pretty pictures:

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html

How do you explain yourself out of this one? Just cause you have a quarter
doesn't mean the quarter is smallest denomination. (Ok, stupid analogy but
works).

All of reality is based on these 4 forces(at the present understanding of
reality). You can ignore that fact and just look at the infituide of
outcomes that these forces produce but you are then neglecting what really
happens. Its even much more complicated than this but these are adaquate for
the OP's problem. He asked what was happening at this level and these are
the tools one has to use to explain it. You cannot explain something at a
lower level higher level tools(ok, maybe a little but theres no guarantee
that it will work).

 

[John Fields]

Because you guys always seem to think that your way is the right way. I know
you guys are not stupid but it seems that you take a simple view of the
world and if someone else wants more info then you act like they are stupid.
You think, say, that if you measure the V-I curve on a resistor and see that
it looks like a perfectly straight line then it must be.

---
To a first approximation, it is, and for the purposes of this
newsgroup that's good enough most of the time.
---

You neglect all the other factors involved. This is fine if you don't care
about them but if someone else does then you tell them what you have
observed and that is what they should believe.

---
Yes. And rightfully so. In the absence of a specific request for
the microscopic, the macroscopic explanation will generally suffice.
If it doesn't, then the onus is on the querant to ask for more
detail. You seem to think that everyone wants to know the minutiae
of "why", and that's just not the case. In this instance the OP
asked for an explanation of why a noisy switch causes a counter to
count falsely, and the answer is: "Because the switch contacts make
and break many times before they settle down, causing multiple
transitions at the counter's clock input."

This can be shown to be true by using a mercury-wetted reed relay or
switch in place of a conventional switch. Doing that will result in
precisely one count made for each make-break cycle of the switch.

That suggests, to me, that the reasons you cited for the miscounts
(the electric field attracting or repelling the contacts, for one)
are flawed, since the very mobility of the mercury film would
certainly cause it to be more affected by that field than a big mass
on the end of a spring would be.
---

To me, its like your trying to tell someone the world is flat.

---
It is, in places, so why shouldn't I tell them that if the micro
view is necessary?

You seem to be saying that when it's convenient for you to use the
macro view you will, but that no one else is allowed to.
---

Now because it you believe it you don't doubt that it is.
It must be. It sounds as if you think you know everything.
And while you guys may not be wrong in most cases in some
way or another, usually you have an idealized or even a narrow
minded view of things. If you never experienced it then
it must not be possible.

---
Don't you think that lumping us all together as "you guys" is taking
a narrow-minded view of things? That is, you're doing exactly what
you say it's wrong for us to do.
---

Usually when someone asks something one doens't get a response like "In my
experiences I have no had this happen" but instead "It can't happen". Now
the problem with the second is that history should have taught you that
nothing is impossible

---
Can you uncook an egg?
---

but if you really believe it then you should have good reasons.
So just state them. "It can't happen and heres why...". Better
yet, "I don't think it can happen and heres my reasoning...". The first
sounds like an arrogant fool while the second one sounds like a rational
human being. Ofcourse maybe you can convince most people with the
"authority" loic but its wrong and should specially not be used in a
scientific place.

---
Sounds to me like you're getting a little authoritarian there.

In the first place, If I want to make an all-encompassing statement
and not back it up with proof, that's my business. I'm certainly
not bound by _your_ rules, and if you have a problem with the
statement, then the burden of proving it false is on you.
---

If you disagree with something then just explain why.
---
Exactly.
---

Don't act like you know everything about everything because
you could be wrong(not saying you/they do this all the time
but it happens to much in this NG).

---
Well, the very act of disagreeing with someone is saying: "I think
you're wrong" or just plain old: "You're wrong", which means that
you think you know more about it than they do, so if you disagree
with the way people post in this newsgroup that means that you know
better than they do about how they should post. Don't you agree?
---

I could be wrong on many things I say. I'm not perfect and I do not know
everthing. But I try to rationalize everything with proof. Sometimes my
logic is faulty and sometimes I use bad evidence. I will admit when I'm
wrong if there is good counter logic involved(and not the authoritative
logic).

---
"If there is good counterlogic involved" means that you get to be
the judge of what is and what isn't good counterlogic, so you get to
be in the favorable position of deciding whether you're right or
wrong by deciding whether your opponent's logic is good or not
regardless of whether your opinion is right or wrong. Handy, no?
---

Maybe you guys were kings in another life and are used to having
everyone do what you say no questions asked?
---
Maybe.
---

Actually any reasonable person who has a desire for knowledge would love for
everything they say to be questioned because it gives them a chance to
understand explain to others and reinforce there own understanding(or change
them if necessary) there view.

---
Not true. I wouldn't love being questioned in a hostile manner by a
person who is frustrated by his inability to understand the answer
to the question and is trying to prove me wrong because of his
inability to admit to being wrong.

 

[John Fields]

So can you shear a part a solid piece of metal with a spring?

---
Of course. Have you ever seen how a set of contacts is made?

Usually one contact is flat and the other rounded (or they're both
rounded) so that when they're in contact with each other only a
very small area of metal is involved in making the contact.

That way, when the contacts bounce and microscopic welds are made
between the contacts, the spring will have the strength to break the
welds and open the contacts.
---

If the contact interface was completely "fused" then thee would
not be any contact interface(assuming the same material is used for both
contacts).

---
It doesn't make any difference if the metals are dissimilar or not,
at the weld there is no "interface".
---

The friction is due to electrical forces.
---
http://en.wikipedia.org/wiki/Friction
---

There are only 4 known
forces(well, 4 main ones) in the world. Gravitations, Electrical, Strong and
weak. Gravitational is like 10^(-40) smaller than electrical. The strong
and weak work only as a sub-atomic level.

So are you saying there is some other forces involved?

---
Nope, but I'm talking at the macro level where when two materials
are pressed together more and more tightly it becomes more and more
difficult to slide them past each other.
---

Sure, but we are not talking about high level.

---
I am, because that's all that's needed to describe contact bounce in
response to the OP's question.
---

The high level is strictly
due to the averging of the microscopic.

---
Yes, but so what?

What the OP wanted to know about was what caused the false count and
I can assure you that the electrostatic attraction or repulsion of
the contacts has nothing to do with it. It's merely the contacts
making and breaking repeatedly until they settle down, and that's
caused by a movable mass on the end of a spring bouncing against a
fixed mass.
---

 

[Jon Slaughter]

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)

---
Yes. And rightfully so. In the absence of a specific request for
the microscopic, the macroscopic explanation will generally suffice.
If it doesn't, then the onus is on the querant to ask for more
detail. You seem to think that everyone wants to know the minutiae
of "why", and that's just not the case. In this instance the OP
asked for an explanation of why a noisy switch causes a counter to
count falsely, and the answer is: "Because the switch contacts make
and break many times before they settle down, causing multiple
transitions at the counter's clock input."

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. (wether it is relvant to engineers
is irrelevant to me. He ased a question and I would answer it in his context
the best I can. 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. )

This can be shown to be true by using a mercury-wetted reed relay or
switch in place of a conventional switch. Doing that will result in
precisely one count made for each make-break cycle of the switch.

That suggests, to me, that the reasons you cited for the miscounts
(the electric field attracting or repelling the contacts, for one)
are flawed, since the very mobility of the mercury film would
certainly cause it to be more affected by that field than a big mass
on the end of a spring would be.

Because when you *tell* someone they might think that that is the answer and
only answer. 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. 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.

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. I believe that it is a
fact(ofcourse its more of belief) that "god" does not exist. I do not state
this as a fact when talking to other people though and I accept there
opinions as long as they do not try and make it a fact for me. When they
try and make me except there facts they better prove it to me and not just
try and force feed it to me. 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. 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. Why? Because facts are not a
popularity context. Majority does not rule logic or facts. So many people
believe this(Specially religious people) that its disgusting. Some people
think that if they can get enough people ot believe what they beieve then it
will make it true. I don't think you guys believe that but many times you
act that way. Else you wouldn't get mad when someone disgree's with you or
asks you to explain yourself.

You seem to be saying that when it's convenient for you to use the
macro view you will, but that no one else is allowed to.

no, for all I know I could be completely wrong. I do have to think I know
something though as then I would be quite useless. I don't know everything
and I'm not even close. I could also be wrong in everything I say. I have a
minor in physics and have taken quantum mechanics, I have a degree in math
and have taken over 200+ credic hours. Does this mean anything? Maybe...
maybe not. I have forgot a great deal of what I have learned and could have
easily gotten things confused. But sure, there are somethings I believe
very strongly about just like you do. BUT I rarely see you guys give any
evidence to support your claims. I will happily give my evidence and
reasoning if it is asked for in a way that isn't belittling. Ultimately I
want to learn and share knowledge and not get into childish games. Sure it
happens and sometimes maybe its my fault but that is not the goal for me. I
do not come to this newsgroup and offer help when I can feed my ego. I come
here to learn and thats pretty much it. Who knows what I can learn by
helping someone else out. Maybe it will lead to things that I can't imagine
now.


Sure. What else am I suppose to do. Well, maybe I am. But I do have
experience with you, Larkin, and several others that do the same sorta
things so its not such a bad approximation. Ultimately we will run into
issues like this because thats life and its full of contraditions. Its not
a narrow-minded view as it is simply being lazy I cannot possibly talk about
all of you guys seperately and describe all the reasons I have come to my
conclusions(would be a waste of time to do so). Similarly as you make the
macroscopic approximations to make things easy I have to make things easy.
If you asked "Why do you feel this way about me" then either I would tell
you the reasons(and if they are not proof enough for you then you could ask
me and then I would try to find the proof. Maybe I would learn that it was
my fault and a made a mistake or misinterpreted something. Who knows) or I
would tell you I don't have time to waste on it(cause unfortunately theres
only so much one human being can do).

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.

Do you know that just because you have no proof of the existance of
something does not mean is is false? We know by the incompleteness theorem
that there are things that are even unprovable. We know also that we can
prove somethings about something but not find any specific examples. (We
might be able to prove that there exists something but actually never be
able find it.)

Quantum mechanics also tells us that time can be reversed(and must be) so
maybe one can find a way to uncook and egg. This is assuming QM is true and
we do not know htat 100% but it looks like it. 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.

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

In the first place, If I want to make an all-encompassing statement
and not back it up with proof, that's my business. I'm certainly
not bound by _your_ rules, and if you have a problem with the
statement, then the burden of proving it false is on you.

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. We can learn a lot from history and while
history is not always right it does help a lot. I cannot make you do
anything but only offer evidence that its probably not a good idea to think
like that. The evidence simply might be wrong or wrong to you(some stuff is
just relative and we can't escape it).

---


---
Well, the very act of disagreeing with someone is saying: "I think
you're wrong" or just plain old: "You're wrong", which means that
you think you know more about it than they do, so if you disagree
with the way people post in this newsgroup that means that you know
better than they do about how they should post. Don't you agree?

No, not necessarily. I do see your point but if I say someone is wrong its
more "I think your wrong, please explain why." 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!!". 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. Atleast thats what I
do. 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.)

---
"If there is good counterlogic involved" means that you get to be
the judge of what is and what isn't good counterlogic, so you get to
be in the favorable position of deciding whether you're right or
wrong by deciding whether your opponent's logic is good or not
regardless of whether your opinion is right or wrong. Handy, no?

But this isn't a chess game. We are not trying to play king of the
mountain. We are hear to learn, no?

---
Not true. I wouldn't love being questioned in a hostile manner by a
person who is frustrated by his inability to understand the answer
to the question and is trying to prove me wrong because of his
inability to admit to being wrong.

I agree. But I do believe that I rarely question people in a hostile
way(saying "Prove it" is not hostile). I only get that way when someone does
or has tried to force feed me there garbage and I have found out from much
more reliable sources that they were wrong.(maybe the sources were wrong but
I have to believe someone).

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.


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. 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.
Sometimes I let my ego take control and all that. Again, I'm only human. I
think the main goal, whatever the problems is ultimate to learn(sometimes I
wonder why I think this way as it can be quite frustrating ;/). Anything
that gets in the way is a distraction.

I suppose. The problem is that there is no king without someone to clean the
toilets.

Jon

 

[Jon Slaughter]

I'd like to see that.

---
Of course. Have you ever seen how a set of contacts is made?

Usually one contact is flat and the other rounded (or they're both
rounded) so that when they're in contact with each other only a
very small area of metal is involved in making the contact.

That way, when the contacts bounce and microscopic welds are made
between the contacts, the spring will have the strength to break the
welds and open the contacts.

Yes, but this is explained in a microscopic way.

Sure it does. Sheesh. Do you remember in physics when doing experiements
with friction? You would slide different materials along a flat surface and
measure there coefficient of friction? Did you ever remember reading about
the case when the two materials were the same? (if they were perfectly
clean then they could stick together much easier than different materials).

This is due to the crystal structure of metals. You don't have this if the
metals are different.

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).

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.

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.

---
Yes, but so what?

What the OP wanted to know about was what caused the false count and
I can assure you that the electrostatic attraction or repulsion of
the contacts has nothing to do with it. It's merely the contacts
making and breaking repeatedly until they settle down, and that's
caused by a movable mass on the end of a spring bouncing against a
fixed mass.

Yes, that is true. BUT he asked why in terms of the micrscopic. He did not
asked why in terms of the macroscopic level. I already pointed out the
quote.

Ok, you don't have to believe me...

Ok John. All I can say is that we'll have to disagree. I believe you are
wrong here. (in the above statement).

My only logic evidence I can give you is that:

Physics as described 4 fundamental forces. These forces as the only forces
that exist. All other forces are some combination of these. This is physics
talking and not me.

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


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.

 

[ehsjr]

Jon Slaughter wrote:

Your a bafoon

You calling Larkin a "bafoon" ?

Congratulations! You have just won the
"Most Ridiculous Comment of The Year" award.

Ed

 

[KILOWATT]

Thanks to all for the informative replies. Sorry that my op generated some
arguing but anyway, i've learned from it. ;-)