Today's Message Index:
----------------------
0. 11:15 AM - Make Sure You're Listed! List of Contributors Coming Soon! (Matt Dralle)
1. 09:24 AM - Re: EFII System32 (Robert L. Nuckolls, III)
2. 02:36 PM - Re: EFII System32 (Charlie England)
3. 03:02 PM - Re: EFII System32 (Robert L. Nuckolls, III)
4. 07:17 PM - Over Voltage Crowbar (dj_theis)
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| Subject: | Make Sure You're Listed! List of Contributors Coming |
Soon!
Dear Listers,
There's just a few more days left in this year's List Fund Raiser and that means
the List of Contributors (LOC) is just around the corner! In December I post
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Or, drop a personal check in the mail to:
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Matt Dralle
Matronics Email List Administrator
Message 1
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| Subject: | Re: EFII System32 |
>
>OK, for a start, here's a marked up copy of that page from the install
>manual. I've likely overlooked some stuff in the quick run-through I
>did, and could be more accurate with an internal schematic + board
>layout of the Bus Manager. But I've marked six ways the system can kill
>the engine, and highlighted a seventh *possible* way; I'd want to see
>exactly how up to twelve fusible links are installed within the
>backshell of the BM connector. Fusible links may or may not generate
>enough heat to be a factor in any wire near them. They're typically
>thermally insulated to protect other wires around them but they're
>typically not tightly confined in an enclosure (the backshell, in this
>case).
Fusible links are NOT replacements for fuses.
Fusible links are ROBUST protection against
hard faults and are used in power distribution
feeders like alternator b-leads, extension feeders
between busses, some battery installations, etc.
They are RARELY suited for protection of
individual loads.
What is the rational for protecting these
feeders individually in the first place?
Manufacturer's recommendations? Consider
REAL fuses if a FMEA warrants such protection.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: EFII System32 |
On Wed, Nov 17, 2021 at 11:28 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
>
> OK, for a start, here's a marked up copy of that page from the install
> manual. I've likely overlooked some stuff in the quick run-through I
> did, and could be more accurate with an internal schematic + board
> layout of the Bus Manager. But I've marked six ways the system can kill
> the engine, and highlighted a seventh *possible* way; I'd want to see
> exactly how up to twelve fusible links are installed within the
> backshell of the BM connector. Fusible links may or may not generate
> enough heat to be a factor in any wire near them. They're typically
> thermally insulated to protect other wires around them but they're
> typically not tightly confined in an enclosure (the backshell, in this
> case).
>
>
> Fusible links are NOT replacements for fuses.
>
> Fusible links are ROBUST protection against
> hard faults and are used in power distribution
> feeders like alternator b-leads, extension feeders
> between busses, some battery installations, etc.
>
> They are RARELY suited for protection of
> individual loads.
>
> What is the rational for protecting these
> feeders individually in the first place?
> Manufacturer's recommendations? Consider
> REAL fuses if a FMEA warrants such protection.
>
>
> Bob . . .
>
I'll take another swing, since I wrote the quoted text (it should be
obvious from the text that I don't care for the actual product being
discussed).
My yet-to-fly EFI (NOT FlyEFII) has separate fuses for each injector and
each coil. The reason I did it is that it's dirt simple to do, weighs only
a few ounces, and isolates each item from all the rest in case of a
failure. No doubt that's why FlyEFII used individual fusible links, too.
Logic: If running a carb, you can't isolate fuel delivery to each cylinder;
you're stuck with one delivery point. Not much difference with
'traditional' a/c fuel injection. But with electronic injection and dual
controllers, it's relatively easy to isolate the feed to each device so
that a failure along one path will not cause the entire system to go down.
That kind of issue is what I was trying to describe in the marked-up
version of the wiring diagram; eliminating points where a single failure
takes the entire system (in this case, the engine) offline. I consider
being able to effectively isolate each cylinder (or pair of cylinders, with
some coils) to be a significant advantage with electronic injection over
traditional systems. (I do recognize that the added installation complexity
can be a negative factor.)
As to the fusible link vs fuse question: I used links in several (all?) the
places you mention, for the same reasons; they're as reliable as the wire
itself, fewer mechanical joints, and the only reason they would ever need
to act is in a catastrophic fault situation. While I haven't installed them
for my injectors & coils, I can see justification for using them there, for
the same reasons. One shorted coil or one shorted injector will almost
certainly burn itself open before either its fuse or, if used, a fusible
link would activate. So the only reason for branch protection is the
catastrophic failure mode of a shorted wire. Using the links reduces the
number of mechanical joints (transitions) in the path to the device.
FWIW,
Charlie
Message 3
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| Subject: | Re: EFII System32 |
>
>I'll take another swing, since I wrote the quoted text (it should be
>obvious from the text that I don't care for the actual product being
>discussed).
>
>My yet-to-fly EFI (NOT FlyEFII) has separate fuses for each injector
>and each coil. The reason I did it is that it's dirt simple to do,
>weighs only a few ounces, and isolates each item from all the rest
>in case of a failure. No doubt that's why FlyEFII used individual
>fusible links, too.
Okay, if that's what the mfgr wants. But generally
speaking, fusible links are in the same class of
protection as the ANL current limiters. They take
10x longer to open under same 'rated' loads . . .
and make smoke.
Also watch for situations where one fusible
link is supplied from another fusible link
upstream. You have a I(squared)R timing
dynamic to consider for series connected
circuit protection.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 4
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| Subject: | Over Voltage Crowbar |
I've noticed the stand alone overvoltage switches are not as readily available
and I asked a friend of mine if he would put together a board using an IC provided
by Analog Devices.
https://www.analog.com/media/en/technical-documentation/data-sheets/1696fb.pdf
So, my friend completed the design and is sending to me, what he says, are well
operating switches. I'll test the switches when they arrive in a few days but
I'd like to ask for any feedback on the design. (see attached pdf of the schematic).
He says the device behaves as expected, tripping is adjustable from 15 to 18 volts
and running current is less than 5 ma. The R5 is not used and is included
only to allow for a fixed trip point (rather than adjustable with the pot).
Thanks in advance for any comments.
Dan Theis
--------
Scratch building Sonex #1362
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=504545#504545
Attachments:
http://forums.matronics.com//files/overvolt_0_1_135.pdf
http://forums.matronics.com//files/image_921.png
http://forums.matronics.com//files/overvolt_0_367.jpg
http://forums.matronics.com//files/overvolt_0_1_732.pdf
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