Maker Pro
Maker Pro

Capacitor Question

P

Pooh Bear

Jan 1, 1970
0
If you observed 7805s going unstable, then you didn't have enough
output cap.

Funny then that every data sheet or app note I've ever seen for a 78 series regulator
*explicitly* states that no output cap is required for stability.

The advantage of an output cap here is enhanced transient response.

I just noticed you're from an educational institution ! No damn surprise there. Time you
got out of your ivory tower and had to deal with the *real world*.

Some of the most fuckwittedly idiotic things I've heard in my entire life have come out
of the mouths of so-called 'pro-fess-ors' !

Graham
 
G

Guest

Jan 1, 1970
0
: [email protected] wrote:

: < snip elegant discourse of no practical value >

: Also note that every batch of ICs may perform slightly differently. Making something
: that works on the bench doesn't guarantee every product using that design will behave
: identically.

Therein lies your problem. You don't see the value of
understanding what you work with. You simply follow "rules of thumb," or
"ground rules," and make no effort to understand what is going on around
you. The fact that your "ground rules" work for your specific
application does nothing to demonstrate how knowledgeable you are.
In this specific example, your filtering of the input signal to the
regulator does not guarantee that the regulator will remain stable.
Give me enough time and I will find a scenario that breaks it.

Since you want to bring numbers of successful designs into this,
out of the HUNDREDS OF MILLIONS of the ICs with my regulators on them, I
am not aware of a single RMA relating to those regulators. Does that, in
and of itself, mean that I am correct here? No, but at least I can
present my ideas elegantly (in your own words) and describe the workings
of the circuits involved without (initially) resorting to name calling.
What I was describing wasn't a "clever trick," but a simple mathematical
truth about a simple analog circuit. Your assertion that understanding
what is happening around you is of no value is just plain sad.

And you call me blind? My participation in this thread is over.
I have better things to do than argue with you over simple details about
simple circuits. Perhaps, one day, you will see the value of
understanding the circuits that you work with, but I'm certainly not
going to be able to convince you of that over the internet.

Best of Luck,

Joe
 
P

Pooh Bear

Jan 1, 1970
0
: [email protected] wrote:

: < snip elegant discourse of no practical value >

: Also note that every batch of ICs may perform slightly differently. Making something
: that works on the bench doesn't guarantee every product using that design will behave
: identically.

Therein lies your problem.

I don't have a problem. I solved the problem that happened before I came along and fixed
it.

You don't see the value of
understanding what you work with.

I understand perfectly thank you. I use rather more theoretical analysis than most
engineers I know. I don't use that as a substitute for practical experience though. I
combine the two.

You simply follow "rules of thumb," or
"ground rules," and make no effort to understand what is going on around
you.

You haven't a clue. I was writing circuit models using Mathcad back in 1989.

The fact that your "ground rules" work for your specific
application does nothing to demonstrate how knowledgeable you are.

I don't care about demonstrating that. Engineering is about making stuff that *works* - not
arguing to the board of directors when the line is backed up that ' it shouldn't have
happened ' according to some hare-brained theory.

In this specific example, your filtering of the input signal to the
regulator does not guarantee that the regulator will remain stable.
Give me enough time and I will find a scenario that breaks it.

You just said that the input *doesn't* need local decoupling !

Since you want to bring numbers of successful designs into this,
out of the HUNDREDS OF MILLIONS of the ICs with my regulators on them, I
am not aware of a single RMA relating to those regulators. Does that, in
and of itself, mean that I am correct here? No, but at least I can
present my ideas elegantly (in your own words) and describe the workings
of the circuits involved without (initially) resorting to name calling.
What I was describing wasn't a "clever trick," but a simple mathematical
truth about a simple analog circuit. Your assertion that understanding
what is happening around you is of no value is just plain sad.

Your university directory lists you as a student.

Where are these hundreds of millions of ICs ? They obviously aren't 78XXs.

And you call me blind? My participation in this thread is over.
I have better things to do than argue with you over simple details about
simple circuits. Perhaps, one day, you will see the value of
understanding the circuits that you work with, but I'm certainly not
going to be able to convince you of that over the internet.

Maybe one day you'll understand the value of making stuff that has to work in the real
world rather than in academia.

Graham
 
G

Guest

Jan 1, 1970
0
: [email protected] wrote:

: I just noticed you're from an educational institution ! No damn surprise there. Time you
: got out of your ivory tower and had to deal with the *real world*.

: Some of the most fuckwittedly idiotic things I've heard in my entire life have come out
: of the mouths of so-called 'pro-fess-ors' !

: Graham

Last, short comment: I am not a professor, but, do attend a
University, as you so cleverly deduced from my .utexas.edu email address
(boy, that must've been tough!) I earned my engineering degrees a long
time ago, however, from a different university.

Since you like spending time checking me out, point your browser
to www.uspto.gov, instead. The patents that you're likely to find
aren't all mine (by some coincidence, there's someone else with a
similar name that has a lot more patents than I do.)

Why did my comments bother you so much that you actually spent
time "investigating" me? I could care less about you, although I DO see
why you hide behind an alias (there ARE sickos like you out there that go
around looking people's personal information up over a disagreement over
voltage regulators!)

Successful innovation requires a thorough knowledge and
understanding of what you are working with. Perhaps, unlike you, I'm not
in this to slap circuits together using "ground rules" that someone else
told you. I'm not denying that that's how a lot of engineering is done,
but engineering needs thinkers like me, as well as followers like you.
Perhaps I'm wrong and you are a world-class innovator, but your attitude
doesn't show that.

Granted, this thread began about how to choose capacitors for a
7805, (hardly a problem requiring innovation,) but in my experience, your
method of desinging by "rules of thumb" has gotten people around me in
more trouble than my method of thoroughly understanding what I am working
with has gotten me.

Joe
 
C

Chris

Jan 1, 1970
0
John said:
Is the sensor (a potentiometer that varies with gear position) powered
by your 5 volt regulator, or by a connection directly to the battery
(or through a dropping resistor to the battery)?

Is your regulated 5 volts varying with engine speed, or only the
battery voltage?

Hi, John (and all). I believe the signal voltage output from the
transmission varies proportionately to the battery voltage, which may
change with motor RPM. In that case, it might be easier for the OP to
use an external reference voltage which is a voltage divider of the
battery voltage, rather than using the on-board reference voltage on
the PIC. Or, if the OP wants to go back to the comparator model, he
could just use a voltage divider from the power supply as the reference
to be divided down by the resistor divider string.

Chris
 
P

Pooh Bear

Jan 1, 1970
0
Chris said:
Hi, John (and all). I believe the signal voltage output from the
transmission varies proportionately to the battery voltage, which may
change with motor RPM.

Oh Lord !

Battery voltages don't mysteriously vary with motor rpm !

Battery voltage varies with state of charge and applied load/charge current. A
small battery driven from a motor driven generator will indeed vary its voltage
according to the charge current ( which may vary with speed ) but not in any
direct useful relationship.
In that case, it might be easier for the OP to
use an external reference voltage

It seems he was already using a 7805 regulator to drive his sensor.

If it was indeed a potentiometer sensor ( as guessed by some posters but never
mentioned by the OP ) the varying output in any given gear is likely due to
'uncertainty' on the input shaft of the pot since a gear selection doesn't
provide a precise mechanical input.

Graham
 
J

John Popelish

Jan 1, 1970
0
Chris said:
Hi, John (and all). I believe the signal voltage output from the
transmission varies proportionately to the battery voltage, which may
change with motor RPM. In that case, it might be easier for the OP to
use an external reference voltage which is a voltage divider of the
battery voltage, rather than using the on-board reference voltage on
the PIC. Or, if the OP wants to go back to the comparator model, he
could just use a voltage divider from the power supply as the reference
to be divided down by the resistor divider string.

I agree.
 
J

John Popelish

Jan 1, 1970
0
Pooh said:
Chris wrote:




Oh Lord !

Battery voltages don't mysteriously vary with motor rpm !

There is little mystery about it. On many motorcycles, the alternator
regulation is very poor, with thew alternator not keeping up at low
engine RPM, and overcharging the battery at full RPM. Many don't even
have a regulator, but just rely on a fair match between alternator
current capability and motorcycle electrical system load.
Battery voltage varies with state of charge and applied load/charge current. A
small battery driven from a motor driven generator will indeed vary its voltage
according to the charge current ( which may vary with speed ) but not in any
direct useful relationship.




It seems he was already using a 7805 regulator to drive his sensor.

No. He said the sensor is already connected to the electrical system,
and he is just tapping into the output signal. It is a pot that
senses gear shifter position and is probably part of a voltage divider
across the electrical supply.
 
P

Pooh Bear

Jan 1, 1970
0
John said:
There is little mystery about it. On many motorcycles, the alternator
regulation is very poor, with thew alternator not keeping up at low
engine RPM, and overcharging the battery at full RPM. Many don't even
have a regulator, but just rely on a fair match between alternator
current capability and motorcycle electrical system load.

I fully appreciate the above which you have explained excellently.

It seems however that certain ppl are mistakenly associating a change in battery
voltage with a direct relationship to motor rpm - which there *isn't*.

No. He said the sensor is already connected to the electrical system,
and he is just tapping into the output signal.

So where did the 7805 ever come into the equation ? I got the impression that the
sensor's input was 5V.
It is a pot that
senses gear shifter position

I guessed that much, from your posts as much as anything. The 'uncertainty' about the
output voltage would clearly seem to be a result of the mechnical input not being
precise.
and is probably part of a voltage divider
across the electrical supply.

Once again I thought it was driven from 5V. Why mention a 7805 otherwise ? Of course
the OP seemed to be terminally incapable of describing his setup accurately.

Graham
 
J

John Popelish

Jan 1, 1970
0
Pooh said:
John Popelish wrote:

I fully appreciate the above which you have explained excellently.

It seems however that certain ppl are mistakenly associating a change in battery
voltage with a direct relationship to motor rpm - which there *isn't*.

The O.P. has stated that his electrical system voltage rises as engine
RPM rises. I take him at his word, on this. This does not imply
proportionality, only variation in a particular direction.
You are being a bit too literal.

(snip)
So where did the 7805 ever come into the equation ? I got the impression that the
sensor's input was 5V.

The O.P copied a commercial circuit that has a microprocessor powered
from a 5 volt regulator, and so, has an A/D converter that uses the 5
volt regulated voltage as its A/D reference voltage. It is the
mismatch between the pot supply and the A/D supply that is causing
trouble, in my opinion.
I guessed that much, from your posts as much as anything. The 'uncertainty' about the
output voltage would clearly seem to be a result of the mechnical input not being
precise.

There will certainly be some of that, but it doesn't explain the wrong
gear position indicator flashing when the engine is revved up.
Once again I thought it was driven from 5V. Why mention a 7805 otherwise ? Of course
the OP seemed to be terminally incapable of describing his setup accurately.

That may be a big part of his problem. He really doesn't understand
the workings of the key pieces of his puzzle (the pot and the way it
is powered, and the A/D converter and how it is powered and
referenced). Rather than give him a complete course, we have sort of
been hanging around, discussing various details, waiting for the
various lights to come on in his mind, so he will either figure some
of it out, or ask useful questions. There are no answers so useless
as the answers to unasked questions. We have to be patient and wait
for the questions to be asked, if we are to have any hope that the
answers will not be misunderstood, or worse, ignored. We have lots of
understanding and answers that the O.P. may not be ready to hear, yet.

He just wants to get this thing finished and working, so he can ride.
I am interested in his electronics education, and know that
frustration and desire are good motivators for learning. If we had
redesigned his circuit immediately on his first post, so he could have
built a perfectly working unit, without understanding anything, he
would be doing something else, now, instead of building up all this
new understanding. So far, we have bumped into voltage dividers, A/D
converters, microprocessor programming, regulators and the electrical
systems on motorcycles. How much better is that than just having a
shift indicator that merely works, perfectly? I am willing to bet
that his new knowledge will change his life for the better more than
the shift indicator, eventually will.

Why are you taking part in this discussion? That is not sarcasm, but
a sincere question.
 
P

Pooh Bear

Jan 1, 1970
0
John said:
The O.P. has stated that his electrical system voltage rises as engine
RPM rises. I take him at his word, on this. This does not imply
proportionality, only variation in a particular direction.
You are being a bit too literal.

I take your point. In effect I'm being 'terribly precise' because I note that those without
a formal science background are prone to 'jumping to conclusions'. But I'll bet there's a
*lag* involved in that relationship too

(snip)

The O.P copied a commercial circuit that has a microprocessor powered
from a 5 volt regulator, and so, has an A/D converter that uses the 5
volt regulated voltage as its A/D reference voltage. It is the
mismatch between the pot supply and the A/D supply that is causing
trouble, in my opinion.

I saw a link to a motorbike site that had some comparators driving leds. Is that the one
you mean ?

There will certainly be some of that, but it doesn't explain the wrong
gear position indicator flashing when the engine is revved up.

Without looking in greater detail at the comparator arrangement I'd hesitate to comment.

That may be a big part of his problem. He really doesn't understand
the workings of the key pieces of his puzzle (the pot and the way it
is powered, and the A/D converter and how it is powered and
referenced). Rather than give him a complete course, we have sort of
been hanging around, discussing various details, waiting for the
various lights to come on in his mind, so he will either figure some
of it out, or ask useful questions. There are no answers so useless
as the answers to unasked questions. We have to be patient and wait
for the questions to be asked, if we are to have any hope that the
answers will not be misunderstood, or worse, ignored. We have lots of
understanding and answers that the O.P. may not be ready to hear, yet.

He just wants to get this thing finished and working, so he can ride.
I am interested in his electronics education, and know that
frustration and desire are good motivators for learning. If we had
redesigned his circuit immediately on his first post, so he could have
built a perfectly working unit, without understanding anything, he
would be doing something else, now, instead of building up all this
new understanding. So far, we have bumped into voltage dividers, A/D
converters, microprocessor programming, regulators and the electrical
systems on motorcycles. How much better is that than just having a
shift indicator that merely works, perfectly? I am willing to bet
that his new knowledge will change his life for the better more than
the shift indicator, eventually will.

I admire your tenacity.

I've done this with the likes of Boki too and got a result. The thing is - Boki will
actually respond sensibly when you ask a direct question. The OP here simply seems to go
off at a tangent when asked for detail.

Seems to me like a classic case of the '**** you' attitude. If you can't spoon-feed me the
answer then screw you. The way 'education' seems to be going.
Why are you taking part in this discussion? That is not sarcasm, but
a sincere question.

You'll note that I gave a detailed answer to the OP's original question, having had to make
an assumption that he knew what 'smoothing' was about when he mentioned it. Since the
original post was a complete blind alley and I had simply wasted my time I was curious to
see why the OP then chose to respond with such bile to someone making an effort to provide
some knowledge.

I'll bet that his guy is an utter waster frankly. His attitude ( and arrogant ignorance of
technology ) speaks volumes.

Graham
 
J

John Popelish

Jan 1, 1970
0
Pooh said:
John Popelish wrote:


I take your point. In effect I'm being 'terribly precise' because I note that those without
a formal science background are prone to 'jumping to conclusions'. But I'll bet there's a
*lag* involved in that relationship too

Doesn't that depend on the internal resistance of his battery? It may
be a tiny thing (and he kick starts the bike).
I saw a link to a motorbike site that had some comparators driving leds. Is that the one
you mean ?

This is the microprocessor design he is trying to copy:
http://www.sportdevices.com/gearindicator/schematics.htm

He has also built a multi comparator version, so we may be talking
about two different circuits.
Without looking in greater detail at the comparator arrangement I'd hesitate to comment. (snip)

I admire your tenacity.

I've done this with the likes of Boki too and got a result. The thing is - Boki will
actually respond sensibly when you ask a direct question. The OP here simply seems to go
off at a tangent when asked for detail.

He may be having too many conversations with too many people at the
same time, and getting them confused.
Seems to me like a classic case of the '**** you' attitude. If you can't spoon-feed me the
answer then screw you. The way 'education' seems to be going.

I haven't gotten that impression, but we probably see people differently.
You'll note that I gave a detailed answer to the OP's original question, having had to make
an assumption that he knew what 'smoothing' was about when he mentioned it. Since the
original post was a complete blind alley and I had simply wasted my time I was curious to
see why the OP then chose to respond with such bile to someone making an effort to provide
some knowledge.

Evidently, he didn't see in your response, what you intended it to
contain. Communication from this distance has problems.
I'll bet that his guy is an utter waster frankly. His attitude ( and arrogant ignorance of
technology ) speaks volumes.

He cannot waste anything he doesn't have.
 
P

Pooh Bear

Jan 1, 1970
0
John said:
Doesn't that depend on the internal resistance of his battery? It may
be a tiny thing (and he kick starts the bike).

Internal resistance certainly plays a part.

Strange thing is - he talked about a *car* originally. I know my car's battery voltage sticks
nicely at 13.8V ( typical on-charge voltage ) after a few minutes drive.

This is the microprocessor design he is trying to copy:
http://www.sportdevices.com/gearindicator/schematics.htm

Ok. Hadn't seen that one before. Sadly doesn't show the 'gear sensor' itself.

He has also built a multi comparator version, so we may be talking
about two different circuits.

It seems so. I have indeed seen the comparator version.

I suspect the underlying problem is the same though.

I also suspect he went to a new circuit to 'fix the problem' not realising that underlying cause.


He may be having too many conversations with too many people at the
same time, and getting them confused.

I haven't gotten that impression, but we probably see people differently.

Maybe so. I reckon I'm right though. I get the distinct impression that this is one 'cocky' guy
who's happy to accept he knows little but plans to 'blag it' anyway.

I certainly wouldn't want anyone like that on any team of mine. Likely to have a net negative
influence.

Evidently, he didn't see in your response, what you intended it to
contain.

Given that he didn't apparently understand what his own question asked I guess so !

Communication from this distance has problems.


He cannot waste anything he doesn't have.

I use the term in the vernacular sense. As in 'a waste of space'.

Graham
 
J

John Popelish

Jan 1, 1970
0
Pooh Bear wrote:
(snip)
Maybe so. I reckon I'm right though. I get the distinct impression that this is one 'cocky' guy
who's happy to accept he knows little but plans to 'blag it' anyway.

Think back. Was there a period in your life (a long time ago, I'll
grant) that this description might have applied to you?
 
P

Pooh Bear

Jan 1, 1970
0
John said:
Pooh Bear wrote:
(snip)


Think back. Was there a period in your life (a long time ago, I'll
grant) that this description might have applied to you?

No.

I might have seemed cocky to some but I *never* needed to 'blag it'. Strange as it may seem to
today's kids I actually enjoyed learning and delighted in educating myself about technology.

I *still* enjoy learning too.

I've always felt confident about my work because it's backed up by a strong knowledge of the
fundamentals.

Graham
 
J

John Popelish

Jan 1, 1970
0
Pooh said:
John Popelish wrote:




No.

Perhaps I have guess wrong on the meaning of "to blag". It sounded
like something I might have done in my youth.
I might have seemed cocky to some but I *never* needed to 'blag it'. Strange as it may seem to
today's kids I actually enjoyed learning and delighted in educating myself about technology.

I *still* enjoy learning too.

But we are talking about teaching.
I've always felt confident about my work because it's backed up by a strong knowledge of the
fundamentals.

And you are able to be humble about it, too. ;-)
 
J

John Popelish

Jan 1, 1970
0
Bob said:
"He distinctly said 'to blave.' And, as we all know, "to blave" means "to
bluff." So you're probably playing cards, and he cheated --"

- Miracle Max, "The Princess Bride"

True Love, he said "True Love", Max.

-Valerie, "The Princess Bride"

Happy Valentines day.
 
B

Bob Myers

Jan 1, 1970
0
Perhaps I have guess wrong on the meaning of "to blag". It sounded
like something I might have done in my youth.

"He distinctly said 'to blave.' And, as we all know, "to blave" means "to
bluff." So you're probably playing cards, and he cheated --"

- Miracle Max, "The Princess Bride"


Bob M.
 
H

Hangglider

Jan 1, 1970
0
Wow. That took a long time to read all the way though this post. I am
a novice at electronics and I'm excited just to get a circuit to work
the way I want it to. I posted a while back about a blown sub woofer
and was delighted by the quick replies and helpful advice I received
from this group and I was actually able to fix the problem! (damn if
that didn't make me feel like a million bucks!)

Please fellas, keep in mind that this google group is titled
"sci.electronics.basics" (I emphasize BASICS). I appreciate that you
guys are experts in the field but please don't scare away the folks who
truly just want to get a little help as they get started with their
projects and questions. Maybe their is another Google group out their
for "philosophical" discussions about electronics theory, but this is
just for us "simple folk".

Please cool off boys.

Thanks,
Joe
 
J

John Popelish

Jan 1, 1970
0
Hangglider said:
Wow. That took a long time to read all the way though this post. I am
a novice at electronics and I'm excited just to get a circuit to work
the way I want it to. I posted a while back about a blown sub woofer
and was delighted by the quick replies and helpful advice I received
from this group and I was actually able to fix the problem! (damn if
that didn't make me feel like a million bucks!)

Please fellas, keep in mind that this google group is titled
"sci.electronics.basics" (I emphasize BASICS). I appreciate that you
guys are experts in the field but please don't scare away the folks who
truly just want to get a little help as they get started with their
projects and questions. Maybe their is another Google group out their
for "philosophical" discussions about electronics theory, but this is
just for us "simple folk".

Please cool off boys.

Thanks,
Joe

Each person who posts here does it for their own reasons. Some of the
side trips get pretty useless, but some of them lead to pay dirt.
 
Top