Automotive Circuit Protection - Part 1

[Garfield Willis]

On Sat, 24 Jun 2000 10:06:30 +0800 (WST), Bernd Felsche
<bernie at innovative.iinet.net.au> wrote:

>> >When the connection between battery and alternator fails, the
>> >alternator's unsmoothed ripple voltage is seen by electrical
>> >consumers...
>> > ... the resulting ripple is only a couple of volts; enough
>> >to confuse ECUs, but hardly enough to cause damage to electrical
>> >consumers designed for automotive use.

>> (2) Contrary to the second person's glib dismissal of LoadDump as merely
>> minutae ripple on the output of the bridge (which is complete nonsense),
>> it IS a very REAL threat that SAE and ISO have sped'd out extensively.
>
>I said no such thing. I was responding to the initial question of
>the transorb being capable of smoothing the ripple in the absence of
>a battery.

Gee, BF, I didn't mention your name, but since you admit to owning that
quote above (it is a verbatim quote, BTW)...

Here we go again,

That's EXACTLY my point, you thot (still think?) that disconnecting the
battery just creates only a couple volts of ripple. Nobody asked any
"initial question of the transorb being capable of smoothing ripple".
You constructed that outta thin air yourself, as an "answer" to the
first poster's question, which was:

>2. Battery wire not properly connected to battery and battery becomes
>disconnected.  Alternator and entire electrical system experience high
>voltage. Would not the fuel pump provide enough of a load to keep the
>alternator voltage low enough or safety?  Would Transorb be any better?

Your direct, verbatim answer, which I quoted above, was:

>When the connection between battery and alternator fails, the
>alternator's unsmoothed ripple voltage is seen by electrical
>consumers. Note that most alternators supply at least 3 phases (6
>diodes) and the resulting ripple is only a couple of volts; enough
>to confuse ECUs, but hardly enough to cause damage to electrical
>consumers designed for automotive use.

That's YOU talking, BF. It's directly UNDER the quote of the first
poster's question, which I included above. SO, to his restating the Load
Dump phenom, because he wanted to ask more, YOU respond that ... well
read the frigging quotation yourself. That IS what you claimed, "hardly
enough to cause damage to electrical consumers..."

The first poster is replaying the definition of a Load Dump, as
described earlier in the thread, and first cited in the linked article
recommending transorbs. That term, which you obviously knew NOTHING
about, you just ignored and blew off as "no problemo". I quoted your
response to the above point, VERBATIM. You claim to have "said no such
thing". Let the jury of your peers take note.

Your quote above about "ripple" is a DIRECT contradiction of the idea
that disconnecting the battery could cause serious damage. It can, it
does, it's called a "load dump" event. That was mentioned in the thread
from the get-go. You chose to poo-poo it, as if you knew better.

You even stated, which I didn't call you on, tiring as I was of washing
more diapers, that:

>The alternator's control circuitry should protect against such an
>over-voltage situation anyway by manipulating the excitation
>current.  There's typically a Zener diode to sense over-voltage.
>Such a circuit can react quickly enough to protect the rest of the
>vehicle's electrics.

That's EXACTLY what the ALT regulator is NOT capable of doing, and
that's WHY Load Dump occurs. You say, "oh, thus should be so", and since
a Zener can quickly sense over-voltage, surely there is "no problem". Is
such shooting off at the mouth, responsible behavior?

>You weren't around to respond, and I think some answer (even if it's
>not authoritative) is better than no answer at all.

You missed the point about the "A-word", BF. We don't care if the answer
is given in an authoritative tone or not, a "radio voice" means nothing
to most of us; we just want a correct answer, or at least one based on
SOME knowledge of the subject. The primary problem is the bullshit
answer; giving it out in an authoritative/matterOfact tone only adds
insult to injury.

I was around; but even if I wasn't, how does it possibly matter?; when
YOU don't know what you're talking about BF, then WAIT/listen for
someone who does, OR ask a further question about the subject so you too
can learn something. And if no one seems to know, then GO FIND OUT,
instead of inventing "some answer". You didn't say, "gee, I'm puzzled
how merely disconnecting the battery could cause such damaging output
levels from the ALT; what IS this Load Dump thing, anyway?", nor did you
even suggest your own "theory" about "ripple" was "all you could imagine
would be the worst happening, and wonder what this Load Dump stuff is
all about". And you certainly didn't pay ANY attention to the linked
articles OR my reference to such a danger; you just blew them BOTH off
matter-of-factly as being no worse than "ripple".

An answer given from actual knowledge of the subject is ALWAYS
preferred. "Some answer" constructed without knowledge of even the
rudiments of the subject, is NEVER better than "no answer at all". If
you don't know about something, may I suggest that you kindly shut the
sock up and LISTEN, instead of conjecturing pontifically as you're want
to do. Granted, you're free to blather, blather all you want; I'm not
trying to restrain your freedom of speech. But you WILL be held
accountable for any bullshit you spray around, you WILL be called on it;
we're here to both contribute AND learn, me as well as anyone else, but
we are NOT here to construct fake "infodrivel" as a by-product of a
college education gone wrong. That doesn't help ANYONE to learn
anything. Somebody who read YOUR "answer" as the last response on what I
was warning about, would have not given a moments pause to disconnecting
a battery cable whilst the engine's running. After all, what harm can a
few volts of mere "ripple" do?

The thread was started by a posting about the merits of using transorbs
in harsh automotive environments, and pointed to a link. That link, and
my response, BOTH used the term "Load Dump" and how disconnecting the
battery can lead to such, and yet you suggested that battery disconnect
would only introduce a wee ripple, surely harmless.

>If we all knew everything, this list wouldn't exist.

Nobody is claiming to "know everything". Get real, and forget the straw
man arguments. All that anyone asks for in human collaboration is to
make reasonably sure you know what the frig you're talking about before
you construct "some answer". Nature may abhore a vacuum, but
understanding doesn't abhore an unanswered question so badly as it
abhores a bullshit concocted "some answer".

Criminee, we've had several public lamentations of late about how the
bullshit and bogosity level of the list have risen, from several others
not just me, whom I could name by name. These are old-timers shaking
their heads, feeling like it's more than half the battle just cleaning
up after the mis/disinformation spread by others who like yourself, feel
that "some answer" (read any answer), is better than none.

It's so simple, BF; contribute when you KNOW you know something, or
contribute a QUESTION or further inquiry, when you don't. But don't hand
out "some answer" when the room goes quiet for more than a few moments.

>You're suggesting that a *Zener* diode at the ALT output is
>insufficient protection to prevent the bridge output from exceeding
>safe levels during such transients?

Have you read ANYTHING about the phenomenon called "Load Dump", BF? If
you want to discuss this topic, why don't you check it out some, eh?

If you can't learn from the offer of discussion based on knowledge and
references to subjects already discussed in automotive technical, then
may I suggest you go study some.

>Thank you for your diplomatic comments.

The initial rudeness occurs when you offer "some answer" and contradict
already discussed information, as if you know better, when you clearly
don't know squat. I think phoneys are one of the RUDEST kinds of people
on the planet. What do you think, BF?

We are here to learn, and to help each other. Nobody learns or is helped
by a bullshit artist.

Gar


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