Effects of vibration on capacitors

D

David Harper

Guest
Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Thanks in advance!
Dave
 
dave.harper@gmail.com (David Harper) wrote in
news:364fd697.0411120525.25f3d961@posting.google.com:

Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Caps and resisters should not be affected by vibration. They are
Click to expand...
monolythic (solid) devices. OK, "should not be affected..." up to a point.
If you get vibration that causes g forces great enough to cause mechanical
breakdown of the physical packaging, *then* the values will change. Other
components, however, will be affected because they are either mechanical in
function (crystals), or are such that the shape can be easily changed
(coils, etc.). I suppose if the components were surface mounted on a
circuit board that was flexible enough, and the vibrations caused the
components to bend or otherwise change shape *then* caps and resistors
could change value.


--
Sooner dot boomer at gbronline dot com
 
On 12 Nov 2004 05:25:54 -0800, David Harper wrote:

Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Thanks in advance!
Dave
Click to expand...
Depends on the capacitor. "Condenser" microphones convert vibration into a
proportional voltage intentionally.


Bob
 
"David Harper" <dave.harper@gmail.com> wrote in message
news:364fd697.0411120525.25f3d961@posting.google.com...
Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?
Click to expand...
Some ceramic capacitors exhibit a piezo-electric effect. Try putting a
'scope across one and tapping it (the capacitor, not the 'scope).

Leon
 
David Harper wrote:
Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Thanks in advance!
Dave
Click to expand...
I've already told you about the bad actors. But even those usually
only cause problems in high impedance circuits (integrators, filters,
coupling etc.) Used as power supply bypass, there are usually several
in parallel and in parallel with a low impedance supply, so their
small microphonic currents get absorbed across other loads. There is
little chance that all the caps across the line would experience
exactly the same vibration, in phase, and add. Your big problems in
high vibration environments will be lack of physical ruggedness,
resonance with the vibration, and lead breakage.

--
John Popelish
 
David Harper wrote:
Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?
Click to expand...
Capacitors don't regulate voltage. Do a Google search on "voltage
regulators." Also. most capacitors will fail because vibration
breaks them or the board they are on long before their electrical
characteristics will change. (We are talking about a lot more
vibration than you will find in a model rocket).
 
Dan Major <nospam@this.address> wrote in message news:<Xns959F5E9C79132soonerboomergbronlin@68.12.19.6>...
dave.harper@gmail.com (David Harper) wrote in
news:364fd697.0411120525.25f3d961@posting.google.com:

Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Caps and resisters should not be affected by vibration. They are
monolythic (solid) devices. OK, "should not be affected..." up to a point.
If you get vibration that causes g forces great enough to cause mechanical
breakdown of the physical packaging, *then* the values will change. Other
components, however, will be affected because they are either mechanical in
function (crystals), or are such that the shape can be easily changed
(coils, etc.). I suppose if the components were surface mounted on a
circuit board that was flexible enough, and the vibrations caused the
components to bend or otherwise change shape *then* caps and resistors
could change value.
Click to expand...
Yes, they are solid state devices that "assume" the distance between
charge holders will remain constant. With vibration, if you have a
few microns displacement between charges, that could result in a small
voltage deviation, correct? The question I'm concerned with is "how
much"?

Thanks,
Dave
 
(David Harper) wrote:

[snip]

The question I'm concerned with is "how
much"?
Click to expand...
If you put a ceramic cap across the end of a guitar lead, turn the amp up loud
and shout at the cap you can hear yourself in the speaker.

So your answer is, in the case of ceramics "very much"

Gibbo
 
David Harper wrote:

Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?
Click to expand...
Well, actually capacitors don't *regulate voltage* in the first place.

The capacitance can vary with vibration - which can have implications
depending on the circuit the capacitor is placed in. It won't have any
effect of significance for power supply decoupling - if that's what you
mean.

The least affected caps are probably plastic film types.



Graham
 
dave.harper@gmail.com (David Harper) wrote in message news:<364fd697.0411120525.25f3d961@posting.google.com>...
Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?

Thanks in advance!
Dave
Click to expand...
In coupling high gain amplifier stages beware of microphonics using
the wrong capacitor type.
 
Other thoughts on this for David, and perhaps this is a better newsgroup
than the model rocktery group because of the folks involved here.

Assume the caps *do* change value with vibration. How will this affect
the signal out? Are the caps affected power supply bypass caps? Are
they part of the direct signal path (or part of a feedback loop)? How
much will the value change change the voltage across them? What
frequency will the vibration be, will the caps actually be sensitive at
this frequency, and will the output signal actually be affected by
changes at this frequency.

OK - a bunch of questions, let's see of we can muddle through some of
them.

If these are bypass caps on the power supply, and vibration *does* affect
them, is there some way you can "gang" capacitors so that the vibration
effects caused by one cap are cancelled out by a successive cap? That
is, if you have a cap causing a high frequency "noise", can another cap
act as a low-pass filter?

If the cap is in the direct signal path, or in a feedback loop, let's
look at the circuit for a second. What are the parameters of the circuit
you're using? Does the anticipated vibration fall within the bandpass of
the circuit? In other words, would the changes induced by the caps even
be seen at the output? If they will be, what is the ratio of the noise
(or distortion) to the value of the signal? Are the changes microvolts?
millivolts? You mention that you're designing/using an accellorometer in
the circuit.

How sensitive is the accellerometer? If there are vibrations strong
enough to affect the caps, what will be the effect on the accel? If the
g's on the caps are strong enough to affect their values, is the force
still within the range of the accel? Are the frequencies of the
vibrations within the frequency range of the accel?

What about the rest of the circuit? Is this an analog or digital
circuit? Some digital devices are vibration sensitive (or microphonic)
as well. If you're going from the accel into a D/A converter, how do you
deal with digitization error or anti-aliasing at the A/D converter? How
sensitive (what is the voltage per bit) of the D/A converter? If the
noise level is small enough, A) it might not be significant, or B) might
actually contribute to the accuracy of the D/A conversion. Don Lancaster
has written about the need to deliberatly encorporate noise into a signal
before digitization (Don, if you read this, jump in here...).

There are several ways to go about getting answers. One way is to get
ahold of engineers at the company that makes the components. A lot of
times these guys will be more than willing to talk to you, and are
especially interested in novel applications. The second way is the good
old emperical method - just try it and see whay happens. It's not
terribly hard to come up with a vibration source (sander, motor, etc).
Strap your circuit board onto it and see what happens. As a control, you
can run some leads and mount the accel by its self onto the vibration
source and have the circuit board at rest.

This is definitly not a stupid question. It shows you're thinking about
the possibilities of what could happen.

--
Sooner dot boomer at gbronline dot com
 
In coupling high gain amplifier stages beware of microphonics using
the wrong capacitor type.
Hi K ceramics are piezoelectric due to barium titanate? doping.
Click to expand...
Hi the with a pulse and they can be heard to click.
By reciprocality they are excellent high freq microphones.
Hence use low k , electrolytic or plastic film for low noise.

--
ddwyer
 
"ddwyer" <dd@ddwyer.demon.co.uk> wrote in message
news:5KVeKiAKnnlBFwBM@ddwyer.demon.co.uk...
In coupling high gain amplifier stages beware of microphonics using
the wrong capacitor type.
Hi K ceramics are piezoelectric due to barium titanate? doping.
Hi the with a pulse and they can be heard to click.
By reciprocality they are excellent high freq microphones.
Hence use low k , electrolytic or plastic film for low noise.
Click to expand...
The only porovblem then becomes how to tell a hi K from a Low K. Like,
they con't come labeled as to that factor.

I suppose you could put them into a high gain amp circuit and plink on
them and see if they put out something. But then that's too easy, isn't
it.



--
ddwyer
Click to expand...
 
....that everyone who replied to this question actually GAVE AN ANSWER!!!!! WHAT??!! No
politics, backstabbing or threats of prison sex?!

Huh, PHIL??!! :)>
 
"Gene Costanza" <levelthree@nyc.rr.com> wrote in message
news:2vnj42F2o38f0U1@uni-berlin.de...
...that everyone who replied to this question actually GAVE AN
ANSWER!!!!! WHAT??!! No politics, backstabbing or threats
of prison sex?!

Huh, PHIL??!! :)
Click to expand...
Replied to what question? You began a new thread, there is no question.
 
Gene Costanza wrote:
WHAT??!! No politics, backstabbing or threats of prison sex?!
Click to expand...
I think I have solved that problem for good. Here is what I did:

For one month I killfiled ever poster who posted anything off-topic.
Interesting result: 50% of the participants here post *only* about
electronics, but the other 50% are the authors of 90% of the posts.

Next I started unkillfiling any poster who posted anything about
electronics. Another interesting result: roughly 10% of the
participants here *never* post about electronics, but they are
the authors of nearly half the posts.

I then started killfiling threads and keywords, thus taking
care of the off-topic output of the posters who post on-topic
and off-topic (I am now killing this thread as being off-topic)
and killfiled a couple of known flamers just to make sure that
any insults they sling at me are blocked. Eventually they will
grow tired of shouting into an empty hall. Or not - what I see
on my screen is the same either way.

The result of my efforts is that I only see the electronics
posts, and it takes less than a minute per day to tweak my
filters to catch any stray off-topic threads/keywords.
 
Dan Major wrote:
Other thoughts on this for David, and perhaps this is a better newsgroup
than the model rocktery group because of the folks involved here.

Assume the caps *do* change value with vibration. How will this affect
the signal out? Are the caps affected power supply bypass caps? Are
they part of the direct signal path (or part of a feedback loop)? How
much will the value change change the voltage across them? What
frequency will the vibration be, will the caps actually be sensitive at
this frequency, and will the output signal actually be affected by
changes at this frequency.

OK - a bunch of questions, let's see of we can muddle through some of
them.

If these are bypass caps on the power supply, and vibration *does* affect
them, is there some way you can "gang" capacitors so that the vibration
effects caused by one cap are cancelled out by a successive cap? That
is, if you have a cap causing a high frequency "noise", can another cap
act as a low-pass filter?

If the cap is in the direct signal path, or in a feedback loop, let's
look at the circuit for a second. What are the parameters of the circuit
you're using? Does the anticipated vibration fall within the bandpass of
the circuit? In other words, would the changes induced by the caps even
be seen at the output? If they will be, what is the ratio of the noise
(or distortion) to the value of the signal? Are the changes microvolts?
millivolts? You mention that you're designing/using an accellorometer in
the circuit.

How sensitive is the accellerometer? If there are vibrations strong
enough to affect the caps, what will be the effect on the accel? If the
g's on the caps are strong enough to affect their values, is the force
still within the range of the accel? Are the frequencies of the
vibrations within the frequency range of the accel?

What about the rest of the circuit? Is this an analog or digital
circuit? Some digital devices are vibration sensitive (or microphonic)
as well. If you're going from the accel into a D/A converter, how do you
deal with digitization error or anti-aliasing at the A/D converter? How
sensitive (what is the voltage per bit) of the D/A converter? If the
noise level is small enough, A) it might not be significant, or B) might
actually contribute to the accuracy of the D/A conversion. Don Lancaster
has written about the need to deliberatly encorporate noise into a signal
before digitization (Don, if you read this, jump in here...).

There are several ways to go about getting answers. One way is to get
ahold of engineers at the company that makes the components. A lot of
times these guys will be more than willing to talk to you, and are
especially interested in novel applications. The second way is the good
old emperical method - just try it and see whay happens. It's not
terribly hard to come up with a vibration source (sander, motor, etc).
Strap your circuit board onto it and see what happens. As a control, you
can run some leads and mount the accel by its self onto the vibration
source and have the circuit board at rest.

This is definitly not a stupid question. It shows you're thinking about
the possibilities of what could happen.
Click to expand...
Fuck. I wrote a lengthy post, and my internet connection chose precisely
that moment to shit itself. Luckily thunderbird flipped its lid too, and
voila - instant missing post.

Summary:
caps: i = dQ/dt = C*dV/dt + V*dC/dt

magnetics: V = dPhi/dt = L*dI/dt + I*dL/dt

the RHS terms are the microphonics. Add in the piezo stuff from high-K
ceramic dielectrics.

Every EE student learns this in 1st year physics, and we promptly drop
the RHS terms because "everyone knows dC/dt = dL/dt = 0"

"everyone" is wrong.

Cheers
Terry
 
"Steven P. McNicoll" <roncachamp@earthlink.net> wrote in message
news:_Iwld.10290$_J2.3763@newsread2.news.atl.earthlink.net...
"Gene Costanza" <levelthree@nyc.rr.com> wrote in message
news:2vnj42F2o38f0U1@uni-berlin.de...

...that everyone who replied to this question actually GAVE AN
ANSWER!!!!! WHAT??!! No politics, backstabbing or threats
of prison sex?!

Huh, PHIL??!! :)


Replied to what question? You began a new thread, there is no question.


Just what you'd expect from a Democrat!
Click to expand...
 
"Terry Given" <my_name@ieee.org> wrote in message
news:6KCld.1489$9A.66267@news.xtra.co.nz...
Tim Wescott wrote:
Dan Major wrote:

dave.harper@gmail.com (David Harper) wrote in
news:364fd697.0411120525.25f3d961@posting.google.com:


Does anyone know how severely vibration can affect a capacitor's
ability to regulate voltage? (i.e. how much the voltage can
deviate
as a function of vibration) What types of caps are better at
regulating voltage under high vibration?


Caps and resisters should not be affected by vibration. They are
monolythic (solid) devices. OK, "should not be affected..." up to
a
point. If you get vibration that causes g forces great enough to
cause mechanical breakdown of the physical packaging, *then* the
values will change. Other components, however, will be affected
because they are either mechanical in function (crystals), or are
such
that the shape can be easily changed (coils, etc.). I suppose if
the
components were surface mounted on a circuit board that was
flexible
enough, and the vibrations caused the components to bend or
otherwise
change shape *then* caps and resistors could change value.

High-dielectric constant ceramics certainly pick up vibration long
before anything breaks, and no matter how much you scold them they
do
not stop.


Yet another reason to avoid the poxy things. Z5U, Y5V = shite.
Click to expand...
Avoid, how? I come across a lot of caps tha aren't marked as such, all
they have is '104' marked on them, ferinstance. How do I know if
they're "shite"? And then there's the problem of how to avoid them, if
a replacment has other serious disadvantages, such as being much bigger?

That's why I want to know more aout the different grades of caps, and
what those designations mean. That way, I can make more intelligent
decisions on whether or not they're suitable for a certain application,
and not just make an uninformed generalization and claim they're all
"shite".


Cheers
Terry
Click to expand...
 
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