Role of ignition condenser in a distributor?
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ignition system?
And what is the role (if any) of a condenser in an electronic
conversion 'kit' in an older 'points' based ignition system?
Note I'm not asking about the capacitor installed off the coil in some
cars for RF reduction - but rather the condensor connected to points
in the distributor.
thanks,
JazzMan
It keeps the points from arcing when they break IIRC, been
a while since I worked on a point style ignition system.
Arcing destroys point contacts pronto.
JazzMan
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Bill
>It keeps the points from arcing when they break IIRC, been
>a while since I worked on a point style ignition system.
>Arcing destroys point contacts pronto.
>
>JazzMan
The arc also dissipates the energy built up in the coil, reducing spark output.
« Paul »
Put condensor ignition into google and you will get over
4500 hits, including this one:
http://www.type2.com/library/electrip/ignwor.htm
pgtr deletethisnsubsatsymbol>bigfoot[ddot]com>
precisely it - a condensor must be 'properly matched' to the
application and prevents sparks from potentially jumping across the
points as contact is broken. (which in turn would lead to pitting and
a dramatic reduction in points life). E.g. it 'absorbs' the volts that
might otherwise 'jump' across the opening points.
Now what about if you converted an existing standard ignition to
electronic ignition. The 'switching' occurs 'electronically' thru some
sort of solid state circuit but would a condensor help the electronics
life or longevity or is it simply no longer necessary at all? I'm
speaking of a generic electronic conversion kit for points - say
magnetic induction triggering.
thanks,
On Wed, 22 Sep 2004 21:49:14 -0500, JazzMan <No_...@airmail.net>
wrote:
Nate Nagel
> Thanks for the response - OK I found it in a text book - that's
> precisely it - a condensor must be 'properly matched' to the
> application and prevents sparks from potentially jumping across the
> points as contact is broken. (which in turn would lead to pitting and
> a dramatic reduction in points life). E.g. it 'absorbs' the volts that
> might otherwise 'jump' across the opening points.
>
> Now what about if you converted an existing standard ignition to
> electronic ignition. The 'switching' occurs 'electronically' thru some
> sort of solid state circuit but would a condensor help the electronics
> life or longevity or is it simply no longer necessary at all? I'm
> speaking of a generic electronic conversion kit for points - say
> magnetic induction triggering.
>
If you eliminate the points (i.e. hall effect sensor or similar) there's
no need for a condensor.
nate
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Tegger®
news:ggb4l0hemg7gblevu...@4ax.com:
Current is flowing through the points as they open. As they open, the
current wants to keep flowing. The current flows from + to -.
If there is no condenser, they will continue arcing over until the distance
is too great (resistance too high) to sustain the arc. This arcing is
damaging to the points.
To minimize arcing, and thus points damage, a condenser is added to the +
side of the points (the power source) in order to provide a low-resistance
path for the current to jump to as resistance increases in the widening gap
between the + and - sides of the points.
The capacitance of the condenser is tailored to the characteristics of the
ignition system, in order to make sure the current jump is timed correctly
to make sure the coil is fed properly.
--
TeGGeRŽ
How to find anything on the Internet:
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SAMMMMM
together they form a 'tank circuit' to make the coil (a transformer)
'ring' which enhances the energy transfer from the magnetic
energy stored in the coil's magnetic circuit to high voltage alternating
current. this is what gives the spark.
when the points close, the current and voltage developed, are stored in
the coil. when the points open, the energy from the magnetic field's
collapse
rattles back and forth between the coil and the condenser, providing the
high voltage
at the secondary of the coil.
sammmm
pgtr bigfoot[ddot]com>" <pgtr(deletethisnsubsatsymbol> wrote in message
news:ggb4l0hemg7gblevu...@4ax.com...
pgtr deletethisnsubsatsymbol>bigfoot[ddot]com>
wrote:
>
>If you eliminate the points (i.e. hall effect sensor or similar) there's
>no need for a condensor.
>
>nate
Thanks Nate, if I look at an HEI setup I see inside what appears to be
a condenser or capacitor - in this case (since the coil is integrated
into the cap) is this actually a capacitor to counter RF noise?
Also is there any real difference between a condenser and capacitor
other than usage or application (and farad rating)? Aren't they both
essentially 'capacitors'?
thanks,
Don Bruder
Regardless of location (in the distributor, on the firewall/fender with
the coil, or somewhere else) they both perform essentially the same
primary task: preventing the contacts of the points from burning up or
welding themselves together in *VERY* short order. Any reduction of RFI
that they may contribute is an accidental (but not at all "un-useful")
side-effect.
--
Don Bruder - dak...@sonic.net - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
Don Bruder
pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> wrote:
> On Thu, 23 Sep 2004 00:15:33 -0400, Nate Nagel <njn...@flycast.net>
> wrote:
> >
> >If you eliminate the points (i.e. hall effect sensor or similar) there's
> >no need for a condensor.
> >
> >nate
>
> Thanks Nate, if I look at an HEI setup I see inside what appears to be
> a condenser or capacitor - in this case (since the coil is integrated
> into the cap) is this actually a capacitor to counter RF noise?
Not Nate, but...
More likely, it's damping the oscillation that goes on when the coil
field collapses. That will have an effect on RFI, but the more important
effect, and the one intended, is to make the coil dump all of its energy
through the spark gap, rather than having a fairly large portion of it
wasted by just "bouncing back and forth" inside the coil.
> Also is there any real difference between a condenser and capacitor
Other than the word used for them most commonly, there is no difference
whatsoever. A capacitor and a condenser are indistinguishable from each
other electrically because they're the same thing. No different than
putting a baked confection made of sugar, butter, eggs, flour, and
chocolate chips on the table and having an American come in and call it
a cookie, and a Brit come in and call it a biscuit. Same item, different
name, just like capacitor/condenser.
Like the Brit coming in and asking for a biscuit in an American bakery,
though, you might get some puzzled looks if you go into a parts store
and ask for a capacitor instead of calling it a condenser. Unless, of
course, you're at Radio Shack, where you'll get a look that's not just
puzzled, but positively bovine in its utter lack of anything resembling
the spark (Errr... no pun intended) of intelligence.
pgtr deletethisnsubsatsymbol>bigfoot[ddot]com>
>Regardless of location (in the distributor, on the firewall/fender with
>the coil, or somewhere else) they both perform essentially the same
>primary task: preventing the contacts of the points from burning up or
>welding themselves together in *VERY* short order. Any reduction of RFI
>that they may contribute is an accidental (but not at all "un-useful")
>side-effect.
Thanks,
On an older pre-HEI GM setup I thought there were 2 caps. One (the
condenser) was inside the distributor as part of the points circuit to
perform the function we've described above.
The 2nd was mounted on the coil off the POS terminal (IIRC) and was
there purely as function of mitigating RFI.
---
Now generically speaking for a typical aftermarket electronic ignition
conversion kit of some sort (say magnetic induction) for a pre HEI GM
- the points AND the points-condenser are eliminated. But as far as I
know the capacitor mounted to the external coil is generally left in
place.
That's why I was thinking they performed different tasks - one to
preserve points and avoid mis-fire and the other to reduce RFI.
pgtr deletethisnsubsatsymbol>bigfoot[ddot]com>
>course, you're at Radio Shack, where you'll get a look that's not just
>puzzled, but positively bovine in its utter lack of anything resembling
>the spark (Errr... no pun intended) of intelligence.
LOL - Too funny!
Daniel J. Stern
> Regardless of location (in the distributor, on the firewall/fender with
> the coil, or somewhere else) they both perform essentially the same
> primary task: preventing the contacts of the points from burning up or
> welding themselves together in *VERY* short order. Any reduction of RFI
> that they may contribute is an accidental (but not at all "un-useful")
> side-effect.
Not sure what "both" you're talking about here, but it's tough to agree
that the one and only primary task is to prevent the points burning up.
That's certainly *a* primary task; but the other primary task of the
condenser is permitting there to be a usably-strong spark in the first
place.
Let's pretend we have a set of points made out of some super-duper alloy
that never burns or melts, so we don't need a condenser to prevent them
burning. We still need a condenser!
We'll start with the points closed and the ignition on. The distributor
shaft rotates, the cam bumps the points open, primary current arcs across
the points (because there's no condenser to absorb the spike). This arc
across the points means no sharp transition from high to low occurs in the
coil primary winding. Therefore, shitty/no induction in secondary winding.
Therefore, shitty/no spark.
DS
Daniel J. Stern
> Like the Brit coming in and asking for a biscuit in an American bakery,
> though, you might get some puzzled looks if you go into a parts store
> and ask for a capacitor instead of calling it a condenser. Unless, of
> course, you're at Radio Shack, where you'll get a look that's not just
> puzzled, but positively bovine in its utter lack of anything resembling
> the spark (Errr... no pun intended) of intelligence.
...with the pierced lips flapping up and down as the bovine counterdroid
says "We have a phat DVD player on sale."
Christopher Green
> the condenser forms a 'ringing' with the inductance of the coil.
> together they form a 'tank circuit' to make the coil (a transformer)
> 'ring' which enhances the energy transfer from the magnetic
> energy stored in the coil's magnetic circuit to high voltage alternating
> current. this is what gives the spark.
> when the points close, the current and voltage developed, are stored in
> the coil. when the points open, the energy from the magnetic field's
> collapse
> rattles back and forth between the coil and the condenser, providing the
> high voltage
> at the secondary of the coil.
> sammmm
I think you're thinking of capacitive discharge ignition systems.
These have a capacitor capable of significant energy storage, and they
operate by switching the capacitor to dump current through the coil.
The capacitor and coil do form a tank of sorts in a CDI system.
The condenser in a Kettering (inductive discharge) ignition system
with mechanical breaker points is merely a snubber. In a Kettering
ignition, the points are susceptible to arcing when they begin to
open. Charge stored in the (small, compared to the coil or to the
capacitor of a CDI system) condenser is fed into the coil to slow the
collapse of the field and thus reduce the voltage that appears across
the points after the points open.
--
Chris Green
Don Bruder
pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> wrote:
> On Thu, 23 Sep 2004 15:55:44 GMT, Don Bruder <dak...@sonic.net> wrote:
> >Regardless of location (in the distributor, on the firewall/fender with
> >the coil, or somewhere else) they both perform essentially the same
> >primary task: preventing the contacts of the points from burning up or
> >welding themselves together in *VERY* short order. Any reduction of RFI
> >that they may contribute is an accidental (but not at all "un-useful")
> >side-effect.
>
> Thanks,
>
> On an older pre-HEI GM setup I thought there were 2 caps. One (the
> condenser) was inside the distributor as part of the points circuit to
> perform the function we've described above.
>
> The 2nd was mounted on the coil off the POS terminal (IIRC) and was
> there purely as function of mitigating RFI.
Not unreasonable. The "first" one (in the cap) was the "anti-charcoal"
device. The second was the "anti-noise" device. Any *LONE*
capacitor/condenser in a kettering-type ignition system is there for the
main purpose of keeping the points intact, and as Dan has said (jogging
my memory) making the opening of the points a "clean break", rather than
just a "decrease in conductivity" - any other benefit it provides is a
fortuitous accident that's secondary to preserving the points/cleaning
up the spark. Any "extra" caps/condensers in the system are probably
there for killing RFI, and have little or no impact on the spark or the
health of the points.
> Now generically speaking for a typical aftermarket electronic ignition
> conversion kit of some sort (say magnetic induction) for a pre HEI GM
> - the points AND the points-condenser are eliminated. But as far as I
> know the capacitor mounted to the external coil is generally left in
> place.
It can be, sure. And it will do no harm. But removing it will likewise
do little, if any, harm beyond increasing the amount of RFI the car
creates. Which, depending on the car, may be a complete non-issue, or an
utter disaster. (Imagine driving a "noisy" car somewhere near a
demolition site as one "ferinstance")
> That's why I was thinking they performed different tasks - one to
> preserve points and avoid mis-fire and the other to reduce RFI.
You *CAN* add on a "specifically to kill RFI" cap, or two, or more, and
in the case of the ones you're mentioning here, that's probably what
you're looking at.
Christopher Green
> pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> muttered darkly in
> news:ggb4l0hemg7gblevu...@4ax.com:
>
> > What is the role of ignition condenser in a traditional 'points' based
> > ignition system?
> >
> > And what is the role (if any) of a condenser in an electronic
> > conversion 'kit' in an older 'points' based ignition system?
> >
> > Note I'm not asking about the capacitor installed off the coil in some
> > cars for RF reduction - but rather the condensor connected to points
> > in the distributor.
>
>
>
> Current is flowing through the points as they open. As they open, the
> current wants to keep flowing. The current flows from + to -.
No. When the points open, the magnetic field in the coil collapses.
This creates a negative voltage much greater than the battery voltage.
This is what causes the arc.
The condenser had been charging, as had the coil, while the points
were closed. When the points open, the coil primary is no longer being
fed, and its field collapses. It is the collapse that induces the
spark voltage in the secondary, but it also produces a high back
voltage in the primary. The condenser opposes the collapse by
discharging into the coil.
> If there is no condenser, they will continue arcing over until the distance
> is too great (resistance too high) to sustain the arc. This arcing is
> damaging to the points.
True. Just that it's the high voltage that is produced by the coil
when the points open that causes the arc.
> To minimize arcing, and thus points damage, a condenser is added to the +
> side of the points (the power source) in order to provide a low-resistance
> path for the current to jump to as resistance increases in the widening gap
> between the + and - sides of the points.
The resistance goes from effectively zero to effectively infinity over
an infinitesimal time, so long as arcing is prevented. If an arc gets
started, it creates a low-resistance path through the points. This not
only damages the points but also diverts energy from spark.
The condenser is not so much a low-resistance path (actually, its DC
resistance is effectively infinite) as a small energy source used as a
kind of snubber.
> The capacitance of the condenser is tailored to the characteristics of the
> ignition system, in order to make sure the current jump is timed correctly
> to make sure the coil is fed properly.
The coil is not fed by the condenser in a Kettering system, except to
snub the discharge when the points open; you may be thinking of a CDI
system. The condenser slows the voltage jump when the points open just
enough to prevent arcing. It is tailored to fit the system, though: if
it were larger and slowed it more, it would impair the spark; if it
were smaller, it would permit arcing.
Systems for switching inductive loads almost always have a snubber of
some kind that performs this same function.
--
Chris Green
Christopher Green
"Condenser" is merely the usual usage for the capacitor that is used
to prevent arcing across the points in a Kettering distributor. It is
an old name that stuck because the Kettering ignition was invented
before the term "capacitor" became current. ("Condenser" is also still
current in audio ("condenser mic") and telco usage.)
--
Chris Green
Tegger®
news:c31fa7b1.04092...@posting.google.com:
> "Tegger®" <teggerati...@changetheobvious.invalid> wrote in
> message news:<Xns956D3D68D37...@207.14.113.17>...
<snip>
>>
>> Current is flowing through the points as they open. As they open, the
>> current wants to keep flowing. The current flows from + to -.
>
> No. When the points open, the magnetic field in the coil collapses.
> This creates a negative voltage much greater than the battery voltage.
> This is what causes the arc.
>
> The condenser had been charging, as had the coil, while the points
> were closed. When the points open, the coil primary is no longer being
> fed, and its field collapses. It is the collapse that induces the
> spark voltage in the secondary, but it also produces a high back
> voltage in the primary. The condenser opposes the collapse by
> discharging into the coil.
>
<snip>
>
> The condenser is not so much a low-resistance path (actually, its DC
> resistance is effectively infinite) as a small energy source used as a
> kind of snubber.
Hmm. If I am to use a physical analogy then, the back voltage from the
collapsed primary speeds south. The condenser's storage heads north at the
same time and the two crash into each other, resulting in zero voltage?
'Scuse me if that sounds dumb, I'm trying to understand this better.
--
TeGGeR®
Dick C
> Thanks for the response - OK I found it in a text book - that's
> precisely it - a condensor must be 'properly matched' to the
> application and prevents sparks from potentially jumping across the
> points as contact is broken. (which in turn would lead to pitting and
> a dramatic reduction in points life). E.g. it 'absorbs' the volts that
> might otherwise 'jump' across the opening points.
>
> Now what about if you converted an existing standard ignition to
> electronic ignition. The 'switching' occurs 'electronically' thru some
> sort of solid state circuit but would a condensor help the electronics
> life or longevity or is it simply no longer necessary at all? I'm
> speaking of a generic electronic conversion kit for points - say
> magnetic induction triggering.
With a conventional points and condensor ignition system you have
quite a bit of voltage going through the points. With an HEI, or
other form of triggering system, you have a small voltage and current
being generated. A condensor at that point would absorb the voltage,
thus preventing the engine from firing. And the electronics will have
their own condensors as needed.
The design and principles are entirely different, except for the
coil.
--
Dick #1349
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
~Benjamin Franklin
Home Page: dickcr.iwarp.com
email: dic...@comcast.net
Christopher Green
<teggerati...@changetheobvious.invalid> wrote:
Close...
The coil is an inductor, so the voltage induced is proportional to the
rate of change of current. Without a condenser, the current through
the primary falls from maximum to zero in almost no time at all. But
there's a charged condenser across the ponts, and it discharges
through the coil when the points open, providing enough current to
limit the induced voltage and prevent arcing.
Sort of like pass blocking in football. You don't need to keep the
rushers out, just slow them down long enough that the QB can get the
pass off.
--
Chris Green
Tegger®
news:58d7l0hmp46lo0ttg...@4ax.com:
<snip>
> The coil is an inductor, so the voltage induced is proportional to the
> rate of change of current. Without a condenser, the current through
> the primary falls from maximum to zero in almost no time at all. But
> there's a charged condenser across the ponts, and it discharges
> through the coil when the points open, providing enough current to
> limit the induced voltage and prevent arcing.
So then if you have a condenser with too much capacitance, would that mean:
1) The field collapse in the coil would be *delayed* for too long,
resulting in a weak secondary voltage, or
2) would it mean the field would collapse *too slowly*?
Are you trying to delay the field collapse only until the points are too
far apart for the arc to form?
Silly question now, but could you not put a diode in the feed from the
points to the coil, and use that to prevent the back-voltage from getting
to the points?
--
TeGGeRŽ
~^Johnny^~
<pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> wrote:
>Thanks for the response - OK I found it in a text book - that's
>precisely it - a condensor must be 'properly matched' to the
>application and prevents sparks from potentially jumping across the
>points as contact is broken. (which in turn would lead to pitting and
>a dramatic reduction in points life). E.g. it 'absorbs' the volts that
>might otherwise 'jump' across the opening points.
>
>Now what about if you converted an existing standard ignition to
>electronic ignition. The 'switching' occurs 'electronically' thru some
>sort of solid state circuit but would a condensor help the electronics
>life or longevity or is it simply no longer necessary at all? I'm
>speaking of a generic electronic conversion kit for points - say
>magnetic induction triggering.
>
>thanks,
Specifically, the magnetic field can't collapse fast enough on its own,
without an external shunt of some sort, due to the inductance of the coil
primary winding. Current can't stop flowing in an inductor immediately after
its external power source is removed. The magnetic field collapses, inducing
counter-emf, aka "inductive kick". The condenser, which is discharged just
before the points open, is charged, and offers a *current sink* for this
counter-emf. It does resonate, and would oscillate, except for the
transferal energy to the spark plug via the secondary winding through
transformer action. In fact, when the spark is spent, there is some
residual oscillation, at the natural resonant frequency of the coil primary
and the condenser. This energy is wasted, and is dissipated as 'I-squared-R'
losses in the coil winding itself, and the connecting wires. Energy is also
wasted at lower RPM's, due to the long dwell time (when the coil is
saturated, current flows according to the CD resistance of the coil's
primary winding). The coil gets hot. This is why tuning is important, and,
in fact, is an art, in racing. The goal in racing is to minimize the losses
at higher RPM's (shorter dwell times).
CDI has similar issues to ordinary Kettering ignition, although losses are
slightly alleviated via rudimentary electronics.
An interesting article:
http://www.hotrod.com/techarticles/17399/
--
-john
wide-open at throttle dot info
~^Johnny^~
>Unless, of
>course, you're at Radio Shack, where you'll get a look that's not just
>puzzled, but positively bovine in its utter lack of anything resembling
>the spark (Errr... no pun intended) of intelligence.
Be nice! A lot of RS stores have gone to Hell in a hand basket, but I resent
the stereotype, nonetheless.
Up until fairly recently (I'm talking 6 or 7 years ago), my local RS stores
had quite knowledgeable staff.
But let me tell you what happened to me about 19 or 20 years ago.
There was a local RS office in downtown ("Old Town") Eureka. It was a few
years prior to the start of the "Urbanization of Eureka" project. God Damn
the city council!
In this event, there was an employment ad run in the local job market, for a
"manager trainee" position. This point is important to note! I did not want
to be a salesman. I like dynamics, not stagnation. Thank you very much!
Well, it turns out that the so-called "manager trainee" position was a hoax:
A come-on. Truth is: ANY employee can be later considered, trained, and
promoted. I didn't realize that then, but I do now.
Let's backtrack.
OK. I applied for the job.
At the interview, we talked turkey. This is where I probably shot myself
down, but I didn't care at the time. I was blinded by intellect. During the
course of the interview, I was alarmed to learn that RS was phasing out the
"smart salesmen", in a quest for volume sales push. The interviewer started
to explain the policy to me. Here is what I heard him say:
"Actually, we are not looking for manager with electronics knowledge. The
less they know about electronics, the better."
I asked, "Why?" (big mistake)
"Well, it's a distraction. We don't want customers calling up our store to
pick our brain. We want to be able to keep sales on an even keel, and
basically just run the store."
I proceeded to tell him, quite frankly, what I thought about that protocol.
I didn't get the job, needless to say. But at least I left an impression.
Yeah, it's sad.
In the past 20 years, ost of the knowledgeable staff in my area RS stores have
either been transferred, fired, or have gotten frustrated and quit!
~^Johnny^~
wrote:
>"Condenser" is merely the usual usage for the capacitor that is used
>to prevent arcing across the points in a Kettering distributor. It is
>an old name that stuck because the Kettering ignition was invented
>before the term "capacitor" became current. ("Condenser" is also still
>current in audio ("condenser mic") and telco usage.)
Thank you for the canned answer. <g>
Bill
<teggerati...@changetheobvious.invalid> wrote:
>Silly question now, but could you not put a diode in the feed from the
>points to the coil, and use that to prevent the back-voltage from getting
>to the points?
A diode has a certain amount of voltage drop. Ones I've dealt with (in non
auto applications) have been in the range of .4V to .7V.
A V drop of .2V is considered the good/bad dividing line for breaker point
resistance.
~^Johnny^~
Some typos manually corrected below.
>Specifically, the magnetic field can't collapse fast enough on its own,
>without an external shunt of some sort, due to the inductance of the coil
>primary winding. Current can't stop flowing in an inductor immediately after
>its external power source is removed. The magnetic field collapses, inducing
>counter-emf, aka "inductive kick". The condenser, which is discharged just
>before the points open, is charged, and offers a *current sink* for this
>counter-emf. It does resonate, and would oscillate, except for the
>transferal [of] energy to the spark plug via the secondary winding through
>transformer action. In fact, when the spark is spent, there is some
>residual oscillation, at the natural resonant frequency of the coil primary
>and the condenser. This energy is wasted, and is dissipated as 'I-squared-R'
>losses in the coil winding itself, and the connecting wires. Energy is also
>wasted at lower RPM's, due to the long dwell time (when the coil is
>saturated, current flows according to the DC resistance of the coil's
~^Johnny^~
wrote:
Interesting read.
As an aside note,
let's see if I can provide just a little more insight:
Technically, the 'ignition coil' is a pulse transformer!
It is specifically designed not to step up gradually varying potentials well.
Even so, this design is not inherently lossy, until the coil saturates.
Pulse transformers are quite efficient, without the DC coponent in the
primary. This is why CDI and other electronic ignition schemes are generally
superior in efficiency to the old Kettering system, as only a pulse is
transmitted to the coil.
~^Johnny^~
<teggerati...@changetheobvious.invalid> wrote:
>Current is flowing through the points as they open. As they open, the
>current wants to keep flowing. The current flows from + to -.
>
>If there is no condenser, they will continue arcing over until the distance
>is too great (resistance too high) to sustain the arc. This arcing is
>damaging to the points.
>
>To minimize arcing, and thus points damage, a condenser is added to the +
>side of the points (the power source) in order to provide a low-resistance
>path for the current to jump to as resistance increases in the widening gap
>between the + and - sides of the points.
It is instructive to note that in electronic ignition, a diode replaces the
condenser, in a sense. It is placed in reverse across the device, usually
from the MOSFET drain or BJT collector to ground, or across the coil itself,
to collapse the field and to prevent destruction of the MOSFET or BJT (reverse
avalanche, or exceeding VCEO or VDSS). Sometimes (incorrectly) referred to
as "snubbing" or "damping", I prefer to call it "kickback steering". <g>
~^Johnny^~
<teggerati...@changetheobvious.invalid> wrote:
>How to find anything on the Internet:
>www.google.com
:-)
Don Bruder
~^Johnny^~ <nos...@gyrogearloose.com> wrote:
> On Thu, 23 Sep 2004 16:39:19 GMT, Don Bruder <dak...@sonic.net> wrote:
>
> >Unless, of
> >course, you're at Radio Shack, where you'll get a look that's not just
> >puzzled, but positively bovine in its utter lack of anything resembling
> >the spark (Errr... no pun intended) of intelligence.
>
>
> Be nice!
Be nice, my ass.
Too damned many people in this world are "being nice" in an effort to
avoid offending the tender sensibilities of some worthless waste of
humanity, when what's needed is a good solid smack upside the head with
a dose of reality.
> A lot of RS stores have gone to Hell in a hand basket, but I resent
> the stereotype, nonetheless.
Resent it all you like. Your resentment means *EXACTLY NOTHING* to me,
as my view is dead-on accurate: If you walk into pretty much any Radio
Shack today, you cannot find anyone with even the amount of electronic
know-how needed to point you at the capacitor rack, let alone give you
any useful information to decide why "This one is the one you want,
rather than that one." You'll find a shitload of salesdroids that'll try
and sell you a cell-phone when what you want is a 33K resistor, but
beyond that, you're walking into an intellectual wasteland.
Most of them wouldn't know a capacitor from a resistor from a pimple on
their ass. Of course, this assumes that the store you walk into even
*HAS* a capacitor rack. It's getting to the point where Radio Shack
should seriously consider renaming itself to "Cell phone and satellite
TV shack" to reflect their true business.
Radio Shack:
You've got questions, we've got blank stares.
Despite being something of a cliche, it's dead-on accurate in the huge
majority of RS stores.
And no, I don't care whose feelings I hurt by saying so. Get over it. If
you don't want to be seen as "the imbecile behind the counter", you've
got two options: Learn something, or get the hell out. But don't expect
any touchy-feely "spare your poor sensitive feelings" bullshit from me.
I call 'em as I see 'em, and if you don't like what I'm seeing, you need
to change what it is I see. At Radio Shack, I see morons. Don't like
that? Then change it - Get yourself at least rudimentary education in
the field you're supposedly working in, so that when I come in with a
question, you've got an actual answer, instead of a blank stare or a
line of bullshit that's so obvious even a blind man couldn't miss seeing
it.
Izzat clear enough for you to understand, "Johnny"?
Jim Thompson
There was an RS "droid" who really cracked me up trying to convince me
that a gold-anodized antenna was required to receive color signals ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Don Bruder
Jim Thompson <thegr...@example.com> wrote:
Lemme guess... The "plain aluminum" version can only get black and white?
And I'd be willing to bet my last nickel that the "gold" version was at
least 10-20 bucks (if not quite a bit more than that) pricier than the
"regular", wasn't it?
Thanks for illustrating my point so nicely, Jim :)
~^Johnny^~
wrote:
>"TeggerŽ" <teggerati...@changetheobvious.invalid> wrote in message news:<Xns956D3D68D37...@207.14.113.17>...
>> pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> muttered darkly in
>> news:ggb4l0hemg7gblevu...@4ax.com:
>>
>> > What is the role of ignition condenser in a traditional 'points' based
>> > ignition system?
>> >
>> > And what is the role (if any) of a condenser in an electronic
>> > conversion 'kit' in an older 'points' based ignition system?
>> >
>> > Note I'm not asking about the capacitor installed off the coil in some
>> > cars for RF reduction - but rather the condensor connected to points
>> > in the distributor.
>>
>>
>>
>> Current is flowing through the points as they open. As they open, the
>> current wants to keep flowing. The current flows from + to -.
>
>No. When the points open, the magnetic field in the coil collapses.
>This creates a negative voltage much greater than the battery voltage.
>This is what causes the arc.
>
>The condenser had been charging, as had the coil, while the points
>were closed.
No! When the points are closed, the condenser is DISCHARGED, as it is
shorted out.
>When the points open, the coil primary is no longer being
>fed, and its field collapses.
That is correct.
>It is the collapse that induces the
>spark voltage in the secondary, but it also produces a high back
>voltage in the primary. The condenser opposes the collapse by
>discharging into the coil.
No!
The condenser *aids* the collapse, by providing a current path for the
counter-emf generated by the cessation of excitation of the coil's primary.
The collapse would be opposed, in part, by the arcing of the points, were
it not for the condenser. Current _cannot_ cease when excitation is removed,
because the field is collapsing; the current has to have somewhere to go!
>Just that it's the high voltage that is produced by the coil
>when the points open that causes the arc.
But the collapsing field induces current in both the primary and secondary.
The rate of collapse determines the induced voltage. Here's the catch:
No current in the primary = no current in the secondary. Due to the turns
ratio, the primary current *must be* on the order of 100 times the secondary
current, but at about a hundredth of the voltage. So, you've got a negative
pulse of several hundred volts at the points, when they open. The air
ionizes, and less than an ampere of current flows, but the arc discharges
the field until the gap is too great for the diminishing potential. This is
worst at middle RPM's, around cruising speed.
>
>> To minimize arcing, and thus points damage, a condenser is added to the +
>> side of the points (the power source) in order to provide a low-resistance
>> path for the current to jump to as resistance increases in the widening gap
>> between the + and - sides of the points.
It is instructive to note that, at the instant the points open, the
condenser appears as a short circuit, because it is *discharged*.
The arcing (however slight) only occurs when the points *close*.
When the points close, you do get a 12 volt arc, but the 350 volt arc on
opening is virtually eliminated.
>
>The resistance goes from effectively zero to effectively infinity over
>an infinitesimal time, so long as arcing is prevented.
But the condenser takes care of this, through a phenomenon called reactance.
Really, I kid you not.
>If an arc gets
>started, it creates a low-resistance path through the points.
True.
>This not
>only damages the points but also diverts energy from spark.
It diverts energy because the spark has resistance!
Think about it...
>
>The condenser is not so much a low-resistance path (actually, its DC
>resistance is effectively infinite) as a small energy source used as a
>kind of snubber.
Wrong. It is an energy *sink*.
It presents a VERY LOW resistance path, as the points open, because it wants
to charge.
>The coil is not fed by the condenser in a Kettering system,
Correct
>except to
>snub the discharge when the points open; you may be thinking of a CDI
>system. The condenser slows the voltage jump when the points open just
>enough to prevent arcing.
I'll buy that.
Ideally, we want zero voltage change, with instantaneous current increase,
across the points. Of course, that can't happen in the real world.
>It is tailored to fit the system, though: if
>it were larger and slowed it more, it would impair the spark; if it
>were smaller, it would permit arcing.
>
>Systems for switching inductive loads almost always have a snubber of
>some kind that performs this same function.
A large capacitance can be detrimental at higher RPM's because the
oscillations would not have enough time to die out. The coil could still have
a substantial yet arbitrary field on point closing (this is bad). Ideally, we
want zero volts, but we settle for 13.8 volts, across the points, when they
close.
The capacitance should be small enough for good ignition in the power band
(several thousand RPM's), but large enough to handle the long dwell times at
curb idle (several hundred RPM's). The capacitance is therefore a compromise,
usually somewhere in the hundreds of nanofarads.
Back in the Kettering era, Racers would "tune" their ignitions, by fudging
the value to suit their driving habits. Dual-point distributors were quite
common, for maximum performance at extreme revs. :-)
~^Johnny^~
On Fri, 24 Sep 2004 11:42:15 -0700, ~^Johnny^~ <nos...@gyrogearloose.com>
wrote:
>Ideally, we
>want zero volts, but we settle for 13.8 volts, across the points, when they
>close.
Maximum. During cranking, or in race cars.
Usually, it is only 9 to 10 volts, *average*.
But note that, even with a resistor, the open circuit voltage across the
points, field collapsed, is still 13.8 volts (engine running) or 12 volts
(engine off).
~^Johnny^~
<teggerati...@changetheobvious.invalid> wrote:
>Christopher Green <cj.g...@att.net> muttered darkly in
>news:58d7l0hmp46lo0ttg...@4ax.com:
>
><snip>
>
>> The coil is an inductor, so the voltage induced is proportional to the
>> rate of change of current. Without a condenser, the current through
>> the primary falls from maximum to zero in almost no time at all. But
>> there's a charged condenser across the ponts, and it discharges
>> through the coil when the points open, providing enough current to
>> limit the induced voltage and prevent arcing.
>
>
>
>So then if you have a condenser with too much capacitance, would that mean:
>1) The field collapse in the coil would be *delayed* for too long,
>resulting in a weak secondary voltage, or
>2) would it mean the field would collapse *too slowly*?
No. The field collapse would be immediate.
The more capacitance, the better for this, but:
But too much capacitance can be too much of a good thing.
Don't forget, you have system (battery) potential across the condenser and
points upon closing. The larger the condenser, the more stored energy in
coulumbs. When the points close, they must handle this energy. And the
points are supposed to minimize arcing, for one thing...
>
>Are you trying to delay the field collapse only until the points are too
>far apart for the arc to form?
No!
Ideally, the collapse should be instantaneous, at the time the points open.
Of course, nothing is ideal in this world. Eerything takes time, due to
losses.
>
>Silly question now, but could you not put a diode in the feed from the
>points to the coil, and use that to prevent the back-voltage from getting
>to the points?
Yes!
It could work even better than a condenser.
But there is a drawback:
The energy dissipation in the diode would be so great,
that it would be impractical. This is due to the (almost) linear
discharge of the coil with a diode. On the other hand, a capacitor
(condenser) has a reverse exponential curve, when charged from a constant
voltage source. But the coil is losing voltage, so the condenser fares even
better! The current pulse is somewhat integrated, at the cost of spark
duration. Performance is sacrificed, but it is still good enough to make an
effective spark at the plug under diverse conditions, so the condenser is
used. It's a trade-off in efficiency. The coil can already take the heat,
so the condenser wins. :-)
~^Johnny^~
>In article <415239...@airmail.net>, See_my_sig@for_info wrote:
>
>>It keeps the points from arcing when they break IIRC, been
>>a while since I worked on a point style ignition system.
>>Arcing destroys point contacts pronto.
>>
>>JazzMan
>
>The arc also dissipates the energy built up in the coil, reducing spark output.
Correct.
We want the spark inside the cylinder, not inside the distributor! <g>
~^Johnny^~
--
~^Johnny^~
Easy fix. Reduce the value of the ignition resistor. :-)
~^Johnny^~
wrote:
Jim, I always read and enjoy your posts in s.e.d., and I always will.
There is no doubt in my mind that Radio Shack is starting to suck.
I have made light of this several times.
Nevertheless, Mr. Bruder has taken it upon himself to personally attack me,
and flame me. That wouldn't be so bad, in and of itself. I can handle a
good flaming, believe me.
But Mr. Bruder has gone beyond that, with his general condescending attitude.
I have filtered his posts, and I will continue to filter him, until he loses
his nasty little disposition.
The only hope RS (or any other retailer) has, is its customer base.
With condescending assholes in the field, it can only get worse.
I'll tell you: Every time I walk into a RS store, I express my feelings,
and they are not ALL good. For instance: They are carrying less and less in
the way of discreet electronics components, like IC's, connectors, small
accessories, and even resistors and capacitors. I tell them that. But I do
it constructively. Will it get better? Probably not. It's largely driven by
the market trend.
But still, I have little empathy for railers like Don Bruder. He needs to
take a chill pill! I find it in my best of interest to simply filter him.
YMMV.
Don Bruder
~^Johnny^~ <nos...@gyrogearloose.com> wrote:
> =plonk!=
Awwww... Guess I hurt his poor widdle feelings...
--
Don Bruder
~^Johnny^~ <nos...@gyrogearloose.com> wrote:
How, when and where? Since you so conveniently included the full text of
my post, it was an easy matter to re-read, and I can see nothing that
looks even a little like an attack. A definite dose of "too bad if you
don't like it", but nothing like an attack. If you refer to the use of
"you" in the final paragraph, and assume that I'm trying to say you're a
Radio Shack drone, my apologies for poor wording. I should have made it
more obvious that my statement was intended as a "generic" you - As in
"you, the offended counter-droid at Radio Shack", rather than a specific
"You, John, the guy I'm typing at." Aside from that, I'll stand by every
word I said, and make no apology whatsoever for saying it, regardless of
who might be offended.
> and flame me. That wouldn't be so bad, in and of itself. I can handle a
> good flaming, believe me.
When did I flame you? Where? How? <puzzled look> You trying to say that
stating an opinion and the facts that it's based on is now considered
flaming??? I guess I shouldn't be surprised, since it's coming from
someone who has already expressed indignation over someone saying he
thinks the droids at Radio Shack are a bunch of morons.
> But Mr. Bruder has gone beyond that, with his general condescending attitude.
Condescending attitude? Hardly. More like righteous disgust at the
ruining of what was once a good company.
> I have filtered his posts, and I will continue to filter him, until he loses
> his nasty little disposition.
Keep your filter handy, then, since my attitude isn't likely to change.
Meanwhile, a sop for you:
Oh, woe! I've been killfiled by John! My life is over! The rejection and
hurt is intolerable! I can't go on like this! Somebody pass me the
hemlock!
Feel better now?
> The only hope RS (or any other retailer) has, is its customer base.
True enough. And unless/until they change, they've lost me as part of
it. I can spend my money other places, and actually get something
resembling service in the process. No problem at all there.
> With condescending assholes in the field, it can only get worse.
> I'll tell you: Every time I walk into a RS store, I express my feelings,
> and they are not ALL good. For instance: They are carrying less and less in
> the way of discreet electronics components, like IC's, connectors, small
> accessories, and even resistors and capacitors. I tell them that. But I do
> it constructively. Will it get better? Probably not. It's largely driven by
> the market trend.
>
> But still, I have little empathy for railers like Don Bruder. He needs to
> take a chill pill! I find it in my best of interest to simply filter him.
A chill pill? Heh... Apparently you ain't seen me get rolling on
something I'm TRULY passionate about then, John.
Have a nice time sticking your head in the sand.
~^Johnny^~
wrote:
>Not sure what "both" you're talking about here, but it's tough to agree
>that the one and only primary task is to prevent the points burning up.
>That's certainly *a* primary task; but the other primary task of the
>condenser is permitting there to be a usably-strong spark in the first
>place.
Agreed.
Bill
<dak...@sonic.net> wrote:
>Don Bruder - dak...@sonic.net - New Email policy in effect as of Feb. 21, 2004.
>Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
>subject unless it comes from a "whitelisted" (pre-approved by me) address.
>See <http://www.sonic.net/~dakidd/main/contact.html> for full details.
PLONK
Daniel J. Stern
> ~^Johnny^~ <nos...@gyrogearloose.com> wrote:
>
> > =plonk!=
>
> Awwww... Guess I hurt his poor widdle feelings...
Well, yeah, but he's got this *great* gold-plated DVD player dust cover,
which you need if you're going to watch DVDs put out by Disney in the
widescreen format, and it's available for only $39.99. It's also eligible
for the Radio Shack Protection Plan for only an additional $13.49. How
many would you like today? Three dozen? Four dozen? Let's start by giving
me your home address and telephone number...
Daniel J. Stern
> There is no doubt in my mind that Radio Shack is starting to suck.
Umm..."starting"?
They *started* a little over a decade ago. They've pretty much finished
the job.
> For instance: They are carrying less and less in the way of discreet
> electronics components
Right, they mostly carry the loud and impolite kind, nowtimes.
> But still, I have little empathy for railers like Don Bruder.
You think DB is a "railer"? Shug, you ain't seen *nothin'* yet!
DS
RV
<pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> wrote:
>What is the role of ignition condenser in a traditional 'points' based
>ignition system?
>
It is there because points cant switch fast enough.
When the points open and the field inside the coil collapses it must
do so rapidly.
At slow engine speeds they dont open quick enough.
In fact so slow that they are still not open enough to stop the "back
emf" returning from the coil as the field collapses from leaping
across the points.
If you increased the ramp on the lobe to make them snap open faster
the points would start bouncing at revs.
So, the condensor deals with each cycle of Back EMF from the coil
ringing or oscillating.
This ensures the lines of flux in the coil are rapid as the field
collapses into the secondary, the condensor is able to follow that
oscillation or ringing.
Charging and discharging as fast as the coil rings, if its working
right.
If the condensor did not have to follow the coild ringing and it was
just to stop the back emf leaping acorss the point we could use a
diode like you might use one to snub the back emf off a starter
solenoid to stop it welding the ignition switch contacts.
After the end of the spark duration the coil continues to ring but the
spark has ended and changes the resistance the induced voltage sees so
the ringing or oscillation slows down a lot and finally decays
completely.
You can see this on a tune scope, from the points closing to charge up
the coil during dwell period, then the points open and the secondary
spark is created at the spark plug, during the spark time period on
the scope you will see a small tight rapid oscilations, at the end of
the spark time line you will see the inductive voltage remaning when
the spark time ceases, (secondary output drops below voltage required
to jump plug gap) and then you will see the remaining oscilations but
much slower as there is no spark occuring.
After which the points close again, there you wil note a small slow
oscilation which is the condensor discharging via the points to earth.
On a tune scope of you see a lack of trailing oscilation it is either
a bad condensor or bad coil resistance.
Any changes to the capacitor or resistance will effect the timing and
slope of the oscilations.
Thus any changes in the coil resistance will effect the coil
oscilation and as will a change in the condensor value.
So, the two must be matched correctly so that the condensor will
charge and discharge over the coil resistance in time with the coil
ringing.
If the condensor value is out a bit there will be a bias to one
polarity of the ringing, this can be seen as a pit and lump on the
points.
Depeding on the pitting being on the positive side of the points of
the negative side of the points tells you if the condensor is too high
in micro farad rating or too small.
If you see ponts that are like this you might want to throw it a
condensor and test the coil resitance.
If you note no pit or spike on them but they are just burnt that
indicates excess current across them.
If the load is not excess and the impedance of the coild, lepads and
plug gaps is right, and the condensor matched to the coil resitances
right, the points can last and run the engine until the rubbing block
wears down and they dont open anymore.
If any of the above are not right the points will go bad in one of the
few ways Ive outlined above.
>And what is the role (if any) of a condenser in an electronic
>conversion 'kit' in an older 'points' based ignition system?
It has no purpose
The elctronic igniton resolves the points not opening fast enough, the
electronics switches rapidly at starting and high revs.
It also is not victim to the points closed time or dwell period
(resolved by fitting twin points in old race applications), the elec
ignition can give maximum dwell time for all engine speeds.
The coil oscilations are still present but may be too fast to see on
the tune scope, in some cases there will only be oscilations toward
one polarity.
Youll note when the points close there is no condensor discharging
oscilation there.
>
>Note I'm not asking about the capacitor installed off the coil in some
>cars for RF reduction - but rather the condensor connected to points
>in the distributor.
The RF condensor or capacitor is simply a line filter.
They are easy to tell appart from the condensor that goes with the
points, any RF capacitor is fitted to the 12v side of things,
including the ignition coil, the spark condensor is fitted to the
negative points side of the coil.
If you have electronic ignition added you can leave the RF condensor
on the coil +, the coild still oscilates even if there are no points
anymore..
Bob Ward
>
>Radio Shack:
>You've got questions, we've got blank stares.
>
>Despite being something of a cliche, it's dead-on accurate in the huge
>majority of RS stores.
Since you are making this statement as some sort of authoritative
comment, are we to assume that you have personally visiterd over 3500
stores (more than half would be a bare majority - we'll give you the
benefit of the doubt) in doing the research that leads you to this
conclusion?
Name them.
Bob Ward
<nos...@gyrogearloose.com> wrote:
>
>The only hope RS (or any other retailer) has, is its customer base.
>With condescending assholes in the field, it can only get worse.
>I'll tell you: Every time I walk into a RS store, I express my feelings,
>and they are not ALL good. For instance: They are carrying less and less in
>the way of discreet electronics components, like IC's, connectors, small
>accessories, and even resistors and capacitors. I tell them that. But I do
>it constructively. Will it get better? Probably not. It's largely driven by
>the market trend.
Is there a discreet way to point out the difference between "discrete"
and "discreet"?
I guess not.
Nate Nagel
Have you ever visited a RS store where the counter help actually knows
anything about anything other than the CD players out front? I think I
may have, once, but I'm not sure. Most of the time I can find what I'm
looking for (or determine they don't have it) faster than any employee.
I suspect the "parts" section of RS is much like the little bins of
metric fasteners in the "big box" hardware stores - they're stocked
once, when the store opens, and never looked at again.
nate
--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel
Watson A.Name - "Watt Sun, the Dark Remover"
"~^Johnny^~" <nos...@gyrogearloose.com> wrote in message
news:0sc8l0dopocvkubu3...@4ax.com...
> On Thu, 23 Sep 2004 16:39:19 GMT, Don Bruder <dak...@sonic.net> wrote:
>
> >Unless, of
> >course, you're at Radio Shack, where you'll get a look that's not
just
> >puzzled, but positively bovine in its utter lack of anything
resembling
> >the spark (Errr... no pun intended) of intelligence.
>
>
I resent
> the stereotype, nonetheless.
>
stores
> had quite knowledgeable staff.
>
> But let me tell you what happened to me about 19 or 20 years ago.
>
> There was a local RS office in downtown ("Old Town") Eureka. It was a
few
> years prior to the start of the "Urbanization of Eureka" project. God
Damn
> the city council!
>
> In this event, there was an employment ad run in the local job
market, for a
> "manager trainee" position. This point is important to note! I did
not want
> to be a salesman. I like dynamics, not stagnation. Thank you very
much!
>
> Well, it turns out that the so-called "manager trainee" position was
a hoax:
> A come-on. Truth is: ANY employee can be later considered, trained,
and
> promoted. I didn't realize that then, but I do now.
>
> Let's backtrack.
>
> OK. I applied for the job.
>
> At the interview, we talked turkey. This is where I probably shot
myself
> down, but I didn't care at the time. I was blinded by intellect.
During the
> course of the interview, I was alarmed to learn that RS was phasing
out the
> "smart salesmen", in a quest for volume sales push. The interviewer
started
> to explain the policy to me. Here is what I heard him say:
>
> "Actually, we are not looking for manager with electronics knowledge.
The
> less they know about electronics, the better."
>
> I asked, "Why?" (big mistake)
>
> "Well, it's a distraction. We don't want customers calling up our
store to
> pick our brain. We want to be able to keep sales on an even keel,
and
> basically just run the store."
>
> I proceeded to tell him, quite frankly, what I thought about that
protocol.
> I didn't get the job, needless to say. But at least I left an
impression.
>
>
> Yeah, it's sad.
> In the past 20 years, ost of the knowledgeable staff in my area RS
stores have
> either been transferred, fired, or have gotten frustrated and quit!
You left out one other alternative: They got a better job - especially
pay-wise.
Watson A.Name - "Watt Sun, the Dark Remover"
"Don Bruder" <dak...@sonic.net> wrote in message
news:p6Z4d.14971$54.2...@typhoon.sonic.net...
[snip]
> Radio Shack:
> You've got questions, we've got blank stares.
>
> Despite being something of a cliche, it's dead-on accurate in the huge
> majority of RS stores.
Why just RS? Include McD and BK in there too.
> I call 'em as I see 'em, and if you don't like what I'm seeing, you
need
> to change what it is I see. At Radio Shack, I see morons. Don't like
In the education biz, they're called intellectually challenged, among
other things..
> that? Then change it - Get yourself at least rudimentary education in
> the field you're supposedly working in, so that when I come in with a
> question, you've got an actual answer, instead of a blank stare or a
> line of bullshit that's so obvious even a blind man couldn't miss
seeing
> it.
>
> Izzat clear enough for you to understand, "Johnny"?
Oh, bruder - er, brother!
Daniel J. Stern
> > You've got questions, we've got blank stares. Despite being something
> > of a cliche, it's dead-on accurate in the huge majority of RS stores.
> Why just RS? Include McD and BK in there too.
The critical key difference is that Shit Shack *used* to be useful.
McDeath and Booger King have *always* sold crapola.
keith
Remover" wrote:
>
>> Yeah, it's sad.
>> In the past 20 years, ost of the knowledgeable staff in my area RS
> stores have
>> either been transferred, fired, or have gotten frustrated and quit!
>
> You left out one other alternative: They got a better job - especially
> pay-wise.
My son hired a RadioShaft assistant manager away because he was tired of
*having* to sell cell phone service in an area that had no coverage. A
large part of his compensation was in useless cell phone contracts.
--
Keith
Ed Price
> In article <3eq5l0d3f8io9p8gh...@4ax.com>,
> pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> wrote:
>
>> wrote:
>> >
>> >If you eliminate the points (i.e. hall effect sensor or similar) there's
>> >no need for a condensor.
>> >
>> >nate
>>
>> Thanks Nate, if I look at an HEI setup I see inside what appears to be
>> a condenser or capacitor - in this case (since the coil is integrated
>> into the cap) is this actually a capacitor to counter RF noise?
>
> Not Nate, but...
> More likely, it's damping the oscillation that goes on when the coil
> field collapses. That will have an effect on RFI, but the more important
> effect, and the one intended, is to make the coil dump all of its energy
> through the spark gap, rather than having a fairly large portion of it
> wasted by just "bouncing back and forth" inside the coil.
>
>> Also is there any real difference between a condenser and capacitor
>
> Other than the word used for them most commonly, there is no difference
> whatsoever. A capacitor and a condenser are indistinguishable from each
> other electrically because they're the same thing.
Early attempts to describe the concept of storing electrical charge on the
plates of a capacitor tried to help the student by visualizing the charge as
little drops of water that "condensed" on the plate surface. Not a bad
attempt, except that charge on a conductor has nothing at all to do with the
physical process of condensation, and hobbles your ability to understand how
electrical charge really moves. Still, the name "condenser" stuck,
especially in areas of technology that were not electrical or electronic
intensive.
Other name confusion is the coil, which is really a transformer. And points
are simply a cam-actuated single-pole, single-throw, normally-closed switch.
Points have no "points", they actually use a convex dome shape. And plugs
are actually an arc-discharge gap. And coil springs are more correctly
called helix springs. And your radiator doesn't radiate hardly at all, it
moves heat by convection.
And everyone knows that the Check Engine light isn't connected to anything
except a random timer.
Ed
Ed Price
"Bob Ward" <bob...@email.com> wrote in message
news:vo99l05cluekidbs0...@4ax.com...
Radio Shack used to be (maybe 30 years ago) an intriguing place to browse
and buy project parts. But for whatever reason, the selection and quality of
discrete components has plummeted to the joke level. It was bad 10 years
ago, and it's even worse now.
My proof? Well, I can go into any store in the San Diego region, and get the
same level of cheap parts. From what I hear on Usenet, this is typical
everywhere else. You could refute my experience, if you could cite a Radio
Shack that sells RG-214 coax, type N coax fittings, or switches that have
tin-plated terminals and a good "feel."
Sure, I still go to Radio Shack. Last week I found myself hovering over the
parts trays, looking for female BNC chassis connectors (none found), two
fuseholders (that bright finish on the terminals sure is hard to get solder
to flow onto it), a pair of SPST bat-handle switches (they had one) and a
metal project box (only carry plastic boxes). While I was searching for
parts dumped back into the wrong bins (hope springs eternal), I was
approached by two different sales droids with their canned welcome / help
speech (and both didn't know what a BNC connector was).
I found myself standing there, wondering why I wanted to build anything with
the crappy quality parts they had. I found myself hoping that the other
sales droids would ignore me, as I don't think I could have tolerated
explaining what a BNC connector looks like a third time. Imagine that you
went into a NAPA store looking for flexible fuel line, and all they had was
8 different fluorescent colors of plastic aquarium hose. Or imagine that
they only had 10mm bolts in 2cm lengths, no other length, and they only had
three of those. And no Grade 8 bolts at all. And no stainless either.
Radio Shack's marketing must really understand their market, because I have
never seen any of the local stores go out of business. Clearly, they can
make enough money selling cell phones, cordless phones, stereos, alarms,
smoke detectors and batteries. The square footage of the stores devoted to
component sales seems to shrink every so often, till now there's just a
couple of metal tray bins and a short wall of plastic bagged stuff.
I don't attack the RS people. I just try to avoid them, because interaction
with their store personnel is painfully embarrassing. I wouldn't expect the
NAPA guys to know what a BNC is, so why should I expect the RS people to
know either? Sure, there's that "radio" in the name, and "shack" harkens
back to the built-it-yourself ham radio days, but you don't seriously expect
to find royalty at Burger King, do you?
Times change, salmon die after the upstream swim. Good parts are still
available on the Web (Mouser, Digikey, Newark, Allied). Acquire Zen.
Ultimately, WGASA?
Ed
wb6wsn
Ed Price
"Daniel J. Stern" <das...@127.0.0.1> wrote in message
news:Pine.GSO.4.58.04...@alumni.engin.umich.edu...
Elitist scum!
Haute cuisine is anyplace you can drive through!
Ed
Ed Price
"Dick C" <foo.d...@comcast.net> wrote in message
news:Xns956DBE86232DD...@216.196.97.136...
> pgtr wrote in rec.autos.tech
>
>> Thanks for the response - OK I found it in a text book - that's
>> precisely it - a condensor must be 'properly matched' to the
>> application and prevents sparks from potentially jumping across the
>> points as contact is broken. (which in turn would lead to pitting and
>> a dramatic reduction in points life). E.g. it 'absorbs' the volts that
>> might otherwise 'jump' across the opening points.
>>
>> Now what about if you converted an existing standard ignition to
>> electronic ignition. The 'switching' occurs 'electronically' thru some
>> sort of solid state circuit but would a condensor help the electronics
>> life or longevity or is it simply no longer necessary at all? I'm
>> speaking of a generic electronic conversion kit for points - say
>> magnetic induction triggering.
>
> With a conventional points and condensor ignition system you have
> quite a bit of voltage going through the points.
The reason for the voltage at the points is that, when the points open,
there is a current flowing in the primary of the coil. The coil, by it's
design, is very inductive. When a flowing current is suddenly stopped in an
inductor, you get a high reverse voltage. This is technically called counter
EMF, or inductive kick, or Yeeowch! (Anybody who would like to experience
inductive kick can just hold the wire of an inductive device, like a fan
blower, while you brush the wire over the battery terminal. See the arcing?
Feel the zaps?)
This voltage is in series with the opening contacts of the points, and
breaks down the air gap resistance, causing an arc to jump across the
points. This is bad, because the arc erodes the points contact surface, and
will cause the points to fail very early. The capacitor acts to divert the
energy from the points, damping the transient energy.
The size of the capacitor should be matched to the size of the coil, since
the energy in the coil is handed to the capacitor, and then handed back to
the coil. This back and forth handoff happens a lot of times, with a little
bit of energy being lost each time, until everything has calmed down. The
trick is to get everything calmed down before the next cycle happens, even
at the maximum RPM.
The Kettering ignition system is simple and reliable, and was a towering
advance over the old Ford spark coils. It also erodes its points, wastes
energy, causes electronic noise, and isn't accurate or adjustable enough for
modern engine design.
Ed
Ed Price
"Christopher Green" <cj.g...@worldnet.att.net> wrote in message
news:c31fa7b1.04092...@posting.google.com...
> "Tegger®" <teggerati...@changetheobvious.invalid> wrote in message
>> pgtr <pgtr(deletethisnsubsatsymbol>bigfoot[ddot]com> muttered darkly in
>> news:ggb4l0hemg7gblevu...@4ax.com:
>>
>> > ignition system?
>> >
>> > conversion 'kit' in an older 'points' based ignition system?
>> >
>> > cars for RF reduction - but rather the condensor connected to points
>> > in the distributor.
>>
>>
>>
>> current wants to keep flowing. The current flows from + to -.
>
> No. When the points open, the magnetic field in the coil collapses.
> This creates a negative voltage much greater than the battery voltage.
> This is what causes the arc.
>
> The condenser had been charging, as had the coil, while the points
> were closed.
I'm sure you meant to say that the capacitor is discharged, as the capacitor
is in parallel with the points contacts and is shorted to ground when the
contacts close.
And if everyone would try to call a condenser a capacitor, the world would
be a more perfect place. Kumbiyaaaahhhhhhh..............
Ed
Ed Price
"Tegger®" <teggerati...@changetheobvious.invalid> wrote in message
> cj.g...@worldnet.att.net (Christopher Green) muttered darkly in
> news:c31fa7b1.04092...@posting.google.com:
>
>> "Tegger®" <teggerati...@changetheobvious.invalid> wrote in
>> message news:<Xns956D3D68D37...@207.14.113.17>...
>
>
>>>
>>> Current is flowing through the points as they open. As they open, the
>>> current wants to keep flowing. The current flows from + to -.
>>
>> No. When the points open, the magnetic field in the coil collapses.
>> This creates a negative voltage much greater than the battery voltage.
>> This is what causes the arc.
>>
>> The condenser had been charging, as had the coil, while the points
>> fed, and its field collapses. It is the collapse that induces the
>> spark voltage in the secondary, but it also produces a high back
>> voltage in the primary. The condenser opposes the collapse by
>> discharging into the coil.
>>
>
> <snip>
>
>>
>> The condenser is not so much a low-resistance path (actually, its DC
>> resistance is effectively infinite) as a small energy source used as a
>> kind of snubber.
>
>
> Hmm. If I am to use a physical analogy then, the back voltage from the
> collapsed primary speeds south. The condenser's storage heads north at the
> same time and the two crash into each other, resulting in zero voltage?
>
> 'Scuse me if that sounds dumb, I'm trying to understand this better.
A better analogy would be that the current heading south looses a little
lunch money as it pushes against a spring (the capacitor), and then rebounds
north back to the coil (buying lunch again), and then rebounds back to the
capacitor. After a lot of trips, it doesn't have any more lunch money, and
it starves to death.
Then the points open, and it starts all over again.
Ed
Ed Price
"Christopher Green" <cj.g...@att.net> wrote in message
news:58d7l0hmp46lo0ttg...@4ax.com...
> On 24 Sep 2004 00:37:47 GMT, "Tegger®"
SNIP
> Close...
>
> The coil is an inductor, so the voltage induced is proportional to the
> rate of change of current. Without a condenser, the current through
> the primary falls from maximum to zero in almost no time at all. But
> there's a charged condenser across the ponts, and it discharges
> through the coil when the points open, providing enough current to
> limit the induced voltage and prevent arcing.
Now you keep saying that thing about the capacitor being charged when the
points open. Just how does the capacitor get charged while the points are
closed (shorting the capacitor to ground)?
Ed
Ed Price
"Tegger®" <teggerati...@changetheobvious.invalid> wrote in message
> Christopher Green <cj.g...@att.net> muttered darkly in
> news:58d7l0hmp46lo0ttg...@4ax.com:
>
> <snip>
>
>> The coil is an inductor, so the voltage induced is proportional to the
>> rate of change of current. Without a condenser, the current through
>> the primary falls from maximum to zero in almost no time at all. But
>> there's a charged condenser across the ponts, and it discharges
>> through the coil when the points open, providing enough current to
>> limit the induced voltage and prevent arcing.
>
>
>
> mean:
> 1) The field collapse in the coil would be *delayed* for too long,
> resulting in a weak secondary voltage, or
> 2) would it mean the field would collapse *too slowly*?
>
> Are you trying to delay the field collapse only until the points are too
> far apart for the arc to form?
>
> Silly question now, but could you not put a diode in the feed from the
> points to the coil, and use that to prevent the back-voltage from getting
> to the points?
A nice, fast acting diode that could conduct 50 amps or so (peak) and
withstand the transient voltage environment was not available when Mr.
Kettering developed the system. Besides, the diode would create more RFI,
because it would turn on and off very abruptly, causing it's own spectral
distribution of energy. Not the right way to go.
Ed
Ed Price
"Christopher Green" <cj.g...@worldnet.att.net> wrote in message
news:c31fa7b1.04092...@posting.google.com...
> news:<beudnZ9eAdY...@pghconnect.com>...
SNIP
> The condenser in a Kettering (inductive discharge) ignition system
> with mechanical breaker points is merely a snubber. In a Kettering
> ignition, the points are susceptible to arcing when they begin to
> open. Charge stored in the (small, compared to the coil or to the
> capacitor of a CDI system) condenser is fed into the coil to slow the
> collapse of the field and thus reduce the voltage that appears across
> the points after the points open.
>
> --
> Chris Green
You could find a schematic of a Kettering system at
http://users.mrbean.net.au/~rover/ketterin.htm
and then you wouldn't keep saying that the capacitor is charged at the time
the points open.
Ed
Al
"Ed Price" <edp...@cox.net> wrote:
Let's face it. Few people do electronic hobbies anymore. When I was a
kid in the 50s, I built my own transistor radio before anyone else had
one. You could actually build something which was not available
commercially. Often if it was available, what you built could be
superior. This is hardly the case anymore. And it's not just
electronics. When was the last time to saw a kit for a stick built model
airplane with tissue paper fabric. Why bother building when you can buy
something for less than 50 bucks on the internet and it flies out of the
box?
Radio Shack is surviving by selling what most people want to buy,
pre-built electronic toys. And the realy trouble started when a woman
took over as CEO. At least the stock holders are somewhat happy.
I needed a couple of -12VDC 3-terminal regulators recently. The only way
to get them is by mail order. I lucked out when my son found some at the
MIT Flea Market. I won't be surprised is soon DIP parts will no longer
be available anywhere. And how are hobbiests able to deal with SMDs.
Al
Daniel J. Stern
>>>> You've got questions, we've got blank stares. Despite being something
>>>> of a cliche, it's dead-on accurate in the huge majority of RS stores.
>>> Why just RS? Include McD and BK in there too.
>> The critical key difference is that Shit Shack *used* to be useful.
>> McDeath and Booger King have *always* sold crapola.
> Elitist scum! Haute cuisine is anyplace you can drive through!
Naw it ain't. Haute cuisine is the kind that comes out of the oven or off
of the stove, as opposed to caulde cuisine, which comes out of the fridge
or freezer.
Rich Webb
>Radio Shack used to be (maybe 30 years ago) an intriguing place to browse
>and buy project parts. But for whatever reason, the selection and quality of
>discrete components has plummeted to the joke level. It was bad 10 years
>ago, and it's even worse now.
>
>My proof? Well, I can go into any store in the San Diego region, and get the
>same level of cheap parts. From what I hear on Usenet, this is typical
>everywhere else. You could refute my experience, if you could cite a Radio
>Shack that sells RG-214 coax, type N coax fittings, or switches that have
>tin-plated terminals and a good "feel."
I don't have a citation/link (it's been several weeks since I read it)
but a recent industry rag had an article commenting that Radio Shack
might be returning at least partway to its roots. They apparently had a
"D'Oh!" moment and realized that there's no possible way to compete with
the warehouse retailers for the big ticket items. A typical RS has less
total shelf space than in just the notebook PC aisle at CompUSA.
On the other hand, a customer driving to CompUSA (or fill-in-the-blank)
probably passes at least a couple RS stores en route. So they're looking
to capture the "I need a ..." market for smaller items and piece parts.
I wish them luck. It is, perhaps, a sign of uber-geek sophistication to
dump on Radio Shack. But, even in the days of on-line ordering and
overnight delivery, it's pretty handy to be able to walk a couple of
blocks to the local RS and pick up a spool of wire-wrap wire.
--
Rich Webb Norfolk, VA
clifto
> you might get some puzzled looks if you go into a parts store
> and ask for a capacitor instead of calling it a condenser.
Not at all. They'll just pull out the high-capacitor battery pack for
the latest LG cell phone.
--
At the end of the new Kerry ad: "I'm John Kerry, and I approved of this
ad before I voted against it."
Bob Ward
>
>Let's face it. Few people do electronic hobbies anymore. When I was a
>kid in the 50s, I built my own transistor radio before anyone else had
>one. You could actually build something which was not available
>commercially. Often if it was available, what you built could be
>superior. This is hardly the case anymore. And it's not just
>electronics. When was the last time to saw a kit for a stick built model
>airplane with tissue paper fabric. Why bother building when you can buy
>something for less than 50 bucks on the internet and it flies out of the
>box?
That would be when I stopped into the Hobby Lobby store in Chino Hills
last week - they still have a full selection of advanced level kits
for RC hobbyists.
Why bother building a high performance aircraft when you can buy RTF
junk on the Internet? You tell me.
Tim Auton
[snip]
>Let's face it. Few people do electronic hobbies anymore. When I was a
>kid in the 50s, I built my own transistor radio before anyone else had
>one.
Was it better (cheaper, smaller, sounded better...) than a
commercially available non-transistor radio?
>You could actually build something which was not available
>commercially.
You still can. Things have moved on, so we build different things
these days. The components are much better though. I built a PVR
(digital video recorder). I didn't make the motherboard, or the CPU,
or the RAM and I didn't write most of the code (I did write some
though, and I spent a whole lot of time making the damn thing work) -
but I bet you didn't make your own transistors or capacitors or invent
much of the circuit topology for your radio either. I also build
boards for my robots - not from discrete components, but from micro
controllers, integrated H-bridge drivers, packaged power regulators
and the like. Why not make it all from discretes? Same reason you
didn't make your own transistors.
>Often if it was available, what you built could be
>superior. This is hardly the case anymore. And it's not just
>electronics. When was the last time to saw a kit for a stick built model
>airplane with tissue paper fabric.
All the time! Go to an R/C hobby shop, the place is full of 'em. Go to
a place they fly gliders, the sky is full of 'em.
>Why bother building when you can buy
>something for less than 50 bucks on the internet and it flies out of the
>box?
Perhaps because the cheap planes suck?
Tim
--
Guns Don't Kill People, Rappers Do.
E. Rosten
>>The only hope RS (or any other retailer) has, is its customer base.
>>With condescending assholes in the field, it can only get worse.
>>I'll tell you: Every time I walk into a RS store, I express my feelings,
>>and they are not ALL good. For instance: They are carrying less and less in
>>the way of discreet electronics components, like IC's, connectors, small
>>accessories, and even resistors and capacitors. I tell them that. But I do
>>it constructively. Will it get better? Probably not. It's largely driven by
>>the market trend.
>
>
>
> Is there a discreet way to point out the difference between "discrete"
> and "discreet"?
I want discreet components. You know, ones that do the job quietly
without making a fuss or goddiping or any of that stuff. Resistors
should be seen and not heard. Incedentelly that is why I prefer
resistors to, say, capacitors. At worst a resiztor makes a small fizzing
sound (but that is rare). My capacitors on the other hand often make
loud bangs. That is about as indiscreet as it gets.
-Ed
--
(You can't go wrong with psycho-rats.) (er258)(@)(eng.cam)(.ac.uk)
/d{def}def/f{/Times findfont s scalefont setfont}d/s{10}d/r{roll}d f 5/m
{moveto}d -1 r 230 350 m 0 1 179{1 index show 88 rotate 4 mul 0 rmoveto}
for /s 15 d f pop 240 420 m 0 1 3 { 4 2 1 r sub -1 r show } for showpage
Ed Price
"Rich Webb" <bbe...@mapson.nozirev.ten> wrote in message
news:46qdl0det9etq6864...@4ax.com...
Not dumping on them, it's more like wondering how an old friend went over to
the dark side. RS just might have some wire-wrap wire. Do you think they
also have wrapping tools, suitable DIP sockets, switches with WW compatible
terminals, and maybe even an IC or two? Analog & logic stuff is not mutually
incompatible with RF, but I just notice the RS lack of RF components more
acutely.
Thus far, based on my last visit of a week ago, there's no evidence of any
new emphasis on component selection or quality. Fortunately for me, I have a
nearby Gateway, and a couple of big surplus stores too. Each has their
strengths, and I try my best to keep them all profitable. NAPA too! <g>
Ed
wb6wsn
RV
wrote:
>
>"Dick C" <foo.d...@comcast.net> wrote in message
>news:Xns956DBE86232DD...@216.196.97.136...
>> pgtr wrote in rec.autos.tech
>>
>>> Thanks for the response - OK I found it in a text book - that's
>>> precisely it - a condensor must be 'properly matched' to the
>>> application and prevents sparks from potentially jumping across the
>>> points as contact is broken. (which in turn would lead to pitting and
>>> a dramatic reduction in points life). E.g. it 'absorbs' the volts that
>>> might otherwise 'jump' across the opening points.
Half of what it does, not just to stop burning points.
You could do that with a reverse biased diode if that was all you
wanted to do but that would dump the back emf as it does in other
applications such as solenoids and elec motors.
>>>
>>> Now what about if you converted an existing standard ignition to
>>> electronic ignition. The 'switching' occurs 'electronically' thru some
>>> sort of solid state circuit but would a condensor help the electronics
>>> life or longevity or is it simply no longer necessary at all?
no longer needed.
> I'm
>>> speaking of a generic electronic conversion kit for points - say
>>> magnetic induction triggering.
>>
>> With a conventional points and condensor ignition system you have
>> quite a bit of voltage going through the points.
You mean current.
In fact the elec system uses more current than the 4amp point systems.
Usualy 8amps for elec ig.
Youll note a HEI oil filled ignition coil for example is about half
the resistance of a points system coil = twice the current flows.
>
>
>
>The reason for the voltage at the points is that, when the points open,
>there is a current flowing in the primary of the coil. The coil, by it's
>design, is very inductive. When a flowing current is suddenly stopped in an
>inductor, you get a high reverse voltage.
>This is technically called counter
>EMF
Back EMF.
>, or inductive kick, or Yeeowch! (Anybody who would like to experience
>inductive kick can just hold the wire of an inductive device, like a fan
>blower, while you brush the wire over the battery terminal. See the arcing?
>Feel the zaps?)
The starter solenoid wire as the starter is released is a better
example ;)
>
>This voltage is in series with the opening contacts of the points, and
>breaks down the air gap resistance, causing an arc to jump across the
>points. This is bad, because the arc erodes the points contact surface, and
>will cause the points to fail very early. The capacitor acts to divert the
>energy from the points, damping the transient energy.
The condensor ensures that the field collapses as rapidly as possible
into the secondary.
Without a condensor the rate would be too slow, specially at low
engine speeds.
The condensor is like an EMF "reflector" that works in 2 directions.
One way it sinks more current in the time space than without it, in
the other coil oscillation direction it becomes a source that reflects
the EMF back the other way aiding the current flowing back to the coil
more than without it.
It does the job of a reverse biased diode, but it follows the coil
oscilations in both directions unlike the diode, and doesnt shunt the
EMF to earth like a diode would wasting the energy to earth not
sending it back on the reverse coil oscillation..
This is less and less important the faster the points open.
If they where electronically switched and very rapid you wouldnt need
a condensor at all, in fact in those cases you dont.
So in essence the fundamental purpose fo the condensor is to
compensate for the poor switching time of points.
If the swithing time is high enough at all engine speeds (as it is n
elec ig) then the condensor simply isnt required.
>
>The size of the capacitor should be matched to the size of the coil,
Yes
Any changes to coil impedance effects the peak of oscilations or
"ringing" and will require rematching of the condensor..
>since
>the energy in the coil is handed to the capacitor, and then handed back to
>the coil. This back and forth handoff happens a lot of times, with a little
>bit of energy being lost each time, until everything has calmed down.
The coil oscillates with or without a condensor, the condensor just
follows the coils AC like oscillation by reflecting the EMF, sinking
and being a source in each direction instead of dumping to earth.
That ensures the speed of the lines of flux collapsing in the field
are kept at a high rate and current to ensure maxuimum energy to the
secondary throughout the spark time.
> The
>trick is to get everything calmed down before the next cycle happens, even
>at the maximum RPM.
No, time is only relevant to the resistance, more resistance = slower
condensor charge and discharge rate.
A condensor charging and discarging is instant, more resistance in the
line slows the rate of charging and discharging..
Spark time is related to the seondary impedance present.
The time it takes for the coil oscillations to decay completely after
the spark time and induced voltage peak has ended (at which point they
slow greatly in frequency) is irrelevant, if you saw a scope pattern
and noted the oscillations decayed all the way to the next time the
points closed it wouldnt mean sqaut, other than being quite unusual.
After the points shut you are in dwell period charging the coil
primary and the condensor at that point until the points open again is
shorted to earth via the points.
The only oscillation you may note after that is a reflection the scope
pickup sees from the condensor residual primary voltage discharging
when the points shut but thats just a blip in firing time, youll note
elec switching system does not have this small oscillation at the
electronic equivelant of points closing time.
But thats here nor there, the spark period is the only period that
matters really, what you see after that just indicates the condition
of the coil oscillations (according to coil resistance and capacitance
of the condensor) by seeing the residual at a much lower frequency at
the residual end, that or lack of, is fair indication of what is going
on during the spark time.
If the residual falls in a single slope with no oscillation there is a
resistance or capacitance problem and you can assume the ringing of
the coil is as poor during spark time when its so fast you can hardly
see it on the scope,
If the resitance is ok then it only leaves the condensor left to
replace.
In addition to that a lack of the small reflection of the condensor
when the points close is an indcator the condensor is not well.
Or you have electronic ignition ;-)
Anyway thats all old shiite from ye olden days when we used a scope
that looked like then end of a beer bottle.
Now with the end of oil filled coils for E pole wound coils running
high primary current, dead spark systems and remote coils there is
little to see on the scope outside of spark time, peak KV and pattern
uniformity..
Coil ringing is too fast to see and the rest of the picture we used
just aint there anymore.
sol...@londontaxiweddings.com.au
> What is the role of ignition condenser in a traditional 'points' based
> ignition system?
>
> And what is the role (if any) of a condenser in an electronic
> conversion 'kit' in an older 'points' based ignition system?
>
> Note I'm not asking about the capacitor installed off the coil in some
> cars for RF reduction - but rather the condensor connected to points
> in the distributor.
>
I am so glad none of the above were involved in wiring up the USA shuttle vehicles,
the kettering ignition, is under engineered, as any electronic tech will tell you, one definition of an ARC is- too much energy in the component, and the size and rating should be increased or reconfigured until arcing stops,
why is there no arcing in my dashboard when I turn off my high powered headlights ? hmm,
every dc circuit needs a return path, every AC circuit also needs a return path,
The coil should always have had 4 terminals not 3, dc in, dc out, ac out , and ac return,
if the distributor had been put before the coil and not after, the 3 terminal -ve terminal to ground would work, esp as both ground for dc out, and ac return,
Everyone is quick to talk about rising and collapsing magnetic fields, but never mention, this is a sine wave signal with countless frequency variation, ask your electronic tech, nothing DC about it, the condensor over the points, IS the AC return path for the spark generated, any number of condensers on the same wire, would reduce the strangulation of the AC return path, leading to a better and short spark, I tried it, wow, the RF condenser on the -ve terminal is one and the same issue, now forgotten about because every electronic device installed in cars has a condenser as filter circuit- on the power input -inside to the device,
a high tension leads takes away the spark to the spark plug, but none suppied to return the spark to the coil? why?, designers(bad)said so lets just cook the battery, and the rest of the car as every spark blasts it way through everything, to return,to the coil.
No electronic ignition circuit would have been created if enough AC return had ALWAYS been suppied, so please keep your hands off the SHuttle and other things.
J.B. Wood
plenty of correct info on line these days to address your questions. An
electronic technician (one who diagnoses and provides required repairs)
may not have sufficient grasp of the physics and relevant applied
mathematics to provide a correct response. Most EE undergrad courses
cover the stuff you asked about.
You might start with what happens when you quickly interrupt the flow of
current (DC or AC) through an inductor (coil). Folks like Nikola Tesla
and Michael Faraday before him understood this quite well including the
behavior of circuits containing both condensers (capacitors) and an
inductor(s). Such behavior made possible radiotelegraphy prior to the
invention of vacuum tube amplification. As an aside, when I was a young
lad many decades ago we used to construct "shock boxes" using a junked
car ignition coil, some flashlight batteries and mercury switches.
BTW, the circuit path from the high-voltage secondary of the induction
(ignition) coil is through the spark plug cap to the chassis ground of
the vehicle and back to the the other (grounded) terminal of the
secondary. The ignition coil is a low-to-high voltage transformer with
the primary and secondary windings sharing a common (chassis ground)
terminal. Sincerely, from a humble EE,
--
J. B. Wood e-mail: arl_1...@hotmail.com