Today's Message Index:
----------------------
1. 08:57 AM - Re: Z-12 Architecture - Parallel Master Contactors (user9253)
2. 12:46 PM - Re: Circuit protection - Amps (Carlos Trigo)
3. 04:14 PM - SD-8 self excite capacitor (Tom Barter)
4. 09:16 PM - Re: SD-8 self excite capacitor (Robert L. Nuckolls, III)
5. 09:16 PM - Re: Re: Clearing some away some fog and fuzzy logic . . . (Robert L. Nuckolls, III)
6. 09:38 PM - Re: Z13/20 (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: Z-12 Architecture - Parallel Master Contactors |
Re: A second parallel battery contactor in lieu of an E-Bus.
The cost of the E-Bus and diode and switch and relay are relatively inexpensive
and weigh less than a second contactor and associated heavy wire. When I am
faced with a decision, I ask myself, "What is best in the long run?"
Your proposal is feasible for a backup in case of contactor failure in Z-12
(two alternators). I do not see any safety issues. You have double the chance
of leaving the master switch on. :-)
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=288501#288501
Message 2
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Subject: | Circuit protection - Amps |
Thanks Ralph
I did the same as you and kept the old units (which I'll probably have to
toss when my bird will hit the weighing scales ... :-(), so I am maintaining
the same protection.
Carlos
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-
> server@matronics.com] On Behalf Of Ralph E. Capen
> Sent: sexta-feira, 26 de Fevereiro de 2010 15:58
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Circuit protection - Amps
>
> <recapen@earthlink.net>
>
> The fuse is supposed to protect the wire. Shouldn't be an issue. You can
> downsize the fuse based on expected draw and any unexpected draw will pop
the
> fuse.
>
> I had similar Whelens which I replaced with LED units...kept the same fuse
as I am
> carrying one of the old units (with both lenses) as a backup in case of
hangar rash
> at a destination....I can easily swap out to my backup and the wiring is
already set-
> up.
>
>
> My .02
>
> Ralph
>
>
> -----Original Message-----
> >From: Carlos Trigo <trigo@mail.telepac.pt>
> >Sent: Feb 26, 2010 10:01 AM
> >To: aeroelectric-list@matronics.com
> >Subject: AeroElectric-List: Circuit protection - Amps
> >
> >I had Whelen Nav lights in my RV-9A, in a circuit protected by a 7Amp
PTC.
> >
> >I replaced those by new LED nav lights, which draw about 0.5A, and should
> >need a protection device not bigger than 1A.
> >
> >
> >If I leave the circuit with the same 7A protection, what are the
> >implications?
> >
> >
> >Carlos
>
Message 3
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Subject: | SD-8 self excite capacitor |
Bob,
The SD-8 that I recently purchased was supplied with a 10K mfd capacitor.
The self excite mod in the 'Connection calls for a 20-50K mfd. I seem to
remember reading that the capacitor rating was not that critical. With the
addition of the resistors and bridge rectifier, will the supplied capacitor
be satisfactory for the SD-8 to self excite?
Tom Barter
Kesley, IA
Avid Magnum
Message 4
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Subject: | Re: SD-8 self excite capacitor |
At 06:09 PM 2/27/2010, you wrote:
>Bob,
>
>The SD-8 that I recently purchased was supplied with a 10K mfd
>capacitor. The self excite mod in the 'Connection calls for a
>20-50K mfd. I seem to remember reading that the capacitor rating
>was not that critical. With the addition of the resistors and
>bridge rectifier, will the supplied capacitor be satisfactory for
>the SD-8 to self excite?
Yes.
Bob . . .
Message 5
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Subject: | Re: Clearing some away some fog and fuzzy logic |
. . .
At 10:43 AM 2/26/2010, you wrote:
>
>The main issue in this debate seems to be whether to use fuses or
>circuit breakers. Like many decisions in life, there is more than
>one way to accomplish a goal. One way may have certain advantages
>over the other way, and visa-versa. Many times the decision boils
>down to a matter of personal preference; and I believe that is the case here.
It's always a personal preference but it's not
always a matter of 'let's take out a 5A breaker and
put in a 5A fuse'. There are even instances where
two 5A breakers can exhibit SIGNIFICANT differences.
It's not even a debate about which is better or
preferred but a reminder that what ever device
is being considered, confident compliance with
design goals may goe far beyond current ratings.
Some people might argue that fuses will blow quicker than circuit
breakers will trip, thus offering better protection. Although
technically true, I do not think the time difference is significant.
It's not necessarily better but it IS different.
The time-to-trip dynamics for the full gamut
of protective devices is huge . . . if you're
just protecting the wire to gear down indicator
LEDS, the differences may not be significant.
But as soon as the load offers high inrush or
transient characteristics like incandescent landing
lights, pump motors, pitot heaters, confident
application of the chosen device demands understanding.
One way to avoid nuisance blowing of fuses is to use a larger
size. For instance, an avionics manufacturer might recommend using a
1 amp fuse. If you use a 3 amp fuse instead, there will be a lot
less chance of it blowing.
I counsel rejection of the off-hand up-sizing
just to hedge one's bets. The prudent designer
doesn't wager, he strives for the sure thing.
>Quote from Bob,
> > "discussed, researched, and demonstrated not to be true."
> End Quote
>I am taking Bob's side here. The technician is basing his statement
>on rumors. Bob has done experiments with expensive lab
>equipment. I trust his work. Even if the technician is correct
>(which I doubt), I would rather ruin an alternator than have an
>over-voltage condition ruin thousands of dollars worth of avionics.
It's not about gathering followers into the
camp of any particular individual. We're not running
for office. It's about the physics of simple-ideas,
about lessons-learned, about failure-tolerant design
based on logic.
> Although the technician is highly critical of Bob's
> recommendations, I do not take his statements as being a personal attack.
I guess you've not been hanging around this List
very long my friend. The "technician" in another
life claims much in the way of qualifications for
his opinion . . . including engineering degrees.
He was asked to leave the List some years back
simply because he proved incapable or unwilling
to comport with list decorum. See:
http://www.aeroelectric.com/articles/gmcjetpilot.html
But since ALL our writings have been archived for
the future, I continue to be asked about certain
of his assertions years later. What was that we
read about 'sins of the fathers'?
> Still, he was expressing his opinions as fact and pooh-poohing
> Bob's, which is not a nice thing to do. If I say something that
> others disagree with, it is OK to tell me, as long as it is done
> diplomatically. LOL
I quite agree as do the vast majority of the List
members. This particular circumstance may well
bubble up to the surface for years to come . . .
Bob . . .
Message 6
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>I don't have much experience analyzing schematics but when I look at
>Z-13/20, I guess I just don't see what the issue is. Can someone
>please educate me?
It's clumsy . . . my associates would
call it a kluge. Z-12 shows a well considered
integration of the SD20 into a legacy system
with an e-bus added. I'm working on a drawing
that explores another approach to tying the
SD-20 and a main alternator onto two batteries.
Build a 13/20 if you wish. It will function as
advertised. I pulled the drawing because I'm
not proud of it and I'd prefer not to be associated
with the system when and if it is used.
Bob . . .
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