Today's Message Index:
----------------------
1. 04:45 AM - Re: Power, signal, and Coax - How should they be bundled? (Matthew S. Whiting)
2. 07:41 AM - Re: Power, signal, and Coax - How should they be bundled? (wsimpso1)
3. 09:31 AM - Re: Power, signal, and Coax - How should they be bundled? (Robert L. Nuckolls, III)
4. 11:55 AM - Re: Power, signal, and Coax - How should they be bundled? (user9253)
5. 04:04 PM - OVM-14 MkIII development program (Robert L. Nuckolls, III)
6. 04:04 PM - Re: Re: Power, signal, and Coax - How should they be bundled? (Robert L. Nuckolls, III)
7. 04:56 PM - Re: OVM-14 MkIII development program (Peter Campo)
8. 07:05 PM - Re: OVM-14 MkIII development program (Robert L. Nuckolls, III)
9. 09:42 PM - Re: OVM-14 MkIII development program (Jeff Luckey)
Message 1
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| Subject: | Re: Power, signal, and Coax - How should they be |
bundled?
In general, I agree with Bob that this issue is overblown by some, but I am n
ot quite as cavalier as is Bob in this regard. I don=99t have any exp
erience with aircraft wiring, but I do have 30+ years of experience with ind
ustrial controls and data acquisition and we had a lot of issues with EMI/EM
C and noise over the years.
In the airplane I am building, I am running power wires down one side of the
fuselage and signal wires down the other where possible. I also try to avo
id bundling power wires with signal wires and also where they cross try to c
ross them at 90 degrees, again where possible and not a huge inconvenience.
I am not saying to jump through hoops, but no reason to run a GPS cable bes
ide the cable to the A/P servo in most cases as it can easily be avoided.
At least one manufacturer, Garmin, does provide guidelines and warnings in r
egard to wiring. Here is a short except, shouldn=99t invoke copyright
concerns since this is short and for education, from the Garmin G3X install
ation manual. This is from chapter 2 Installation Preparation:
=9C2.3.1 Wiring Harness Installation
Use cable meeting the applicable aviation regulation for the interconnect wi
ring. Any cable meeting specifications is acceptable for the installation. W
hen routing cables, observe the following precautions:
=A2 All cable routing should be kept as short and as direct as possibl
e.
=A2 Check that there is ample space for the cabling and mating connect
ors.
=A2 Avoid sharp bends in cabling.
=A2 Avoid routing near aircraft control cables.
=A2 Avoid routing cables near heat sources, RF sources, EMI interferen
ce sources, power sources (e.g., 400 Hz generators, trim motors, etc.) or ne
ar power for fluorescent lighting.
=A2 Route the GPS antenna cable as far as possible away from all COM t
ransceivers and antenna cables.
=A2 Analog Input wires routed too close to spark plugs, plug wires, or
magnetos may result in erratic readings.=9D
There are also special precautions for the magnetomers, as Bob mentioned, th
at are covered elsewhere in the manual, but the above are the general sugges
tions for wiring of all Garmin LRUs.
Most equipment is fairly tolerant, but I will also say that the 60s and 70s v
intage Cessna and Pipers that I have owned and flown were train wrecks in re
gards to EMC/EMI. I don=99t think I=99ve flown one that didn
=99t have issues such as hearing the beacon faintly in the headsets or ge
neral static and poor audio quality. These may have been caused by repairs a
nd field modifications, but I don=99t know as I=99ve never had t
he privilege to fly a brand new GA airplane. On my build I am trying to do t
hings reasonably in accordance with Garmin=99s recommendations above a
nd also in accordance with what I learned several decades ago in a course ca
lled =9CGrounding and Shielding=9D taught by Dr. Tom Van Doren f
rom the University of Missouri-Rolla. I brought him in to teach his course a
t the Fortune 500 company I worked for as we always had issues in the field w
ith large installations that had hundreds of sensors and high voltage and hi
gh current industrial heaters and motors.
Tom showed us that very simple practices that add virtually no cost to the i
nstallation (using twisted wires for power and ground for example) add huge b
enefit.
So, no need to obsess as Bob says, but I do think it pays to do a few good p
ractices such as what Garmin recommends. Particularly with devices like GPS
antennas and cables that are dealing with very, very small signals and even
with standard audio signals if you want a clean signal with minimal backgro
und static.
Matt
Sent from my iPad
> On Nov 15, 2023, at 9:19=AFPM, Robert L. Nuckolls, III <nuckolls.bob
@aeroelectric.com> wrote:
>
> =EF=BB At 04:29 PM 11/15/2023, you wrote:
>
>>
>> Here is my little problem. I am trying to wire my fiberglass airplane wit
h internal antennas properly. I have little insight on electromagnetic compa
tibility. Please help.
>>
>> I know that I am supposed to keep wiring for DC power to stuff like motor
s and electronics separated from data, but am struggling with knowing what i
s what and how much they matter.
>
> Not true. "Data" carried on RS or CAN style
> serial signals are DESIGNED to live happily
> with other energy paths in a complex system.
> That's what good data management is all about . . .
> if a product is qualified to go into an airplane,
> it is assumed to be TESTED per some agreed
> upon protocol for RESISTANCE to EXPECTED
> antagonists.
>
> I worked in general aviation electrical/avionics
> systems for 40 plus years. Not once did
> I encounter a situation where the manufacturer
> warned against routing any of their products
> wiring separate from any other wires in the
> airplane. To do so would be a written admission
> of their failure to design a product INCOMPATIBLE
> with their target market.
>
> Same thing goes for cars, over the road trucks,
> all manner of heavy machines. High speed data
> systems are EVERYWHERE. Do installation
> instructions for any accessories proposed for
> use in your project include such warnings? Yeah,
> flux gates are a special case cause they're
> task is to resolve VERY TINY angular position
> of earth's magnetic field. But signal paths
> out to the flux gate should require no special
> treatment for electro-magnetic compatibility
> with the rest of ship's systems.
>
> Throughout my experience in experimental aviation,
> I've encountered several instances where a
> product was adversely affected by radio
> frequency energy from transmitters. Poorly
> designed products.
>
> On the certified side of the house, I had
> a case on Hawker-Beech 800 aircraft where
> a poorly conceived HF antenna caused a
> gross failure of every starter generator
> controller in the airplane. Turns out that
> the 30+ year old controllers were grand-fathered
> onto current production never having been
> qualified to ANY reasonable compatibility
> requirements! Spent a week in Little Rock
> getting some brand new aircraft sold off
> before a Dec 31 deadline to meed sales
> targets! Man . . . that was a can of
> worms!
>
> Bottom line is that much of what's circulated
> as sage advice for configuring wire bundles
> in your project is not founded in good
> engineering or physics. Ignore it. Concentrate
> on good craftsmanship and don't worry about
> things that go squeak and bump in the night.
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
=
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ========================
========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
Message 2
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| Subject: | Re: Power, signal, and Coax - How should they be bundled? |
Before we get too far into implying that I listen to poor sources, my one and only
source of advice on all of this has been "The AeroElectric Connection" by
Bob Nuckolls, 12th edition. Specifically Chapter 16, page 16-16
"(3) Avionics and audio systems should not share wire bundles with DC power distribution"
Am I to ignore that? Antenna cables and GPS data seem to be avionics, while the
lights and servos and ELT seem to be DC power stuff...
There was also talk within chapter 16 of interference between audio and other systems,
magnetic field interference, high currents in COAX, and lots of other
examples including the warning that shielding will not keep down magnetic field
interference.
Now I am asking for help from this forum on details of exactly how to wire some
potentially noisy DC power, some DC potentiometer signal, and some RF so they
do not mess with each other. I have padded clamps, mounting studs, terminals,
spools of wire and cable, etc. Advice received will be acted upon and soon.
Since the aft fuselage is a difficult place to rearrange wiring in later, I want
to arrange it now so it is unlikely to ever need rearrangement later.
Details in the aft fuselage:
My trim motors are DC power, and like all of the others are only certified for
splash/condensation resistance. No data bus. They each have a DC electric motor
with a stall current draw of 1 amp fed with two 24AWG leads, a high and low
reference voltage and a sense wire. I suspect the DC power feeds, while modest
current, could be noisy. I do not know or even begin to understand if EM interference
could begin to be an issue with the potentiometer wiring adjacent to
any of the rest of this stuff.
My aft position/flashing light are LED's, not certified. All switching is done
in the cabin - the LED set is cycled between low and high power. The manufacturer
(FlyLEDS) tells us the wiring is noisy, and so recommends a two wire shielded
cable, with the shield grounded in the cabin.
My ELT is aircraft certified hardware. There is a single conductor for GPS position
data to the ELT inside a shielded cable with power and ground wires, and
the shield is grounded in the cabin. I have no doubt that this hardware and cable
is fine by itself.
Three RG400 cables from two COM and one GS antenna. Antenna are copper tape and
ferrite balun per common practice in fiberglass airplanes.
So my question for aft fuselage stuff: Would I be wise to isolate any of these
from any of the others?
Best case - everything can go in one bundle;
Easily accepted case - two bundles and please say which conductors/cables in each
bundle;
Difficult case - three bundles with DC power in one, servo potentiometer leads
in one, and coax in third.
Does anything else require shielding?
Going forward to the baggage bay, we include lots of DC power including batteries,
contactors, starter and ground cables, Dynon's ADS-B, COM radio, data platforms,
transponder, data bus, etc. Again, three bundles going around the people
to the instrument panel is more difficult to execute, two is way doable.
What wires/cables should not be bundled with what other wires? Will I be at low
likelihood of noisy radios and messed up signals with two bundles? Do I really
have to figure out a third path between panel and baggage bay?
Billski
nuckolls.bob(at)aeroelect wrote:
> At 04:29 PM 11/15/2023, you wrote:
>
> Bottom line is that much of what's circulated
> as sage advice for configuring wire bundles
> in your project is not founded in good
> engineering or physics. Ignore it. Concentrate
> on good craftsmanship and don't worry about
> things that go squeak and bump in the night.
>
>
> Bob . . .
>
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=512309#512309
Message 3
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| Subject: | Re: Power, signal, and Coax - How should they be |
bundled?
At 06:43 AM 11/16/2023, you wrote:
>In general, I agree with Bob that this issue is
>overblown by some, but I am not quite as
>cavalier as is Bob in this regard. I don=99t
>have any experience with aircraft wiring, but I
>do have 30+ years of experience with industrial
>controls and data acquisition and we had a lot
>of issues with EMI/EMC and noise over the years.
As have I. The majority of my 'fire fighting' tasks
in airplanes involved EMC issues. But not once did
I encounter a problem that was resolved by resorting
any wires in their respective bundles.
Every problem had roots in poor integration
practices by the SYSTEM designer (ground loops,
bonding, etc), craftsmanship (pushed back pin,
broken shield ground, etc) -or- fundamental
errors or omissions in the performance of the
appliance (like those generator controllers
and annunciator signal conditioners in the
HB800). The 'fix' always went to correcting
shortcomings in the appliance . . . never
needed to move a wire to a different bundle.
Discovered many issues having root cause in failure
of some presumably 'qualified' appliance to comply
with legacy functional and/or environmental issues.
It's too bad that Garmin would include that
broad-brush, boilerplate narrative in their installation
manuals. But yeah, one is well advise to
hold lawyers at arms length with as many magic
words as justifies their salaries in corporate
legal departments.
Have you noticed that the first several to many
pages of instructions for a new purchase include
a library of warnings, do's and don'ts some of
which are not even applicable to how the product
works?
The 'Connection is in need of some serious
updating. I'd like to get started on that pretty
soon . . . not getting any younger!
Bob . . .
////
(o o)
===========o00o=(_)=o00o=======
=
< Go ahead, make my day . . . >
< show me where I'm wrong. >
========================
========
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 4
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| Subject: | Re: Power, signal, and Coax - How should they be bundled? |
A trim servo position potentiometer is extremely unlikely to cause any
interference because the output signal changes very slowly as the motor
runs. When the motor stops running, the position signal is steady DC. Other
antagonists that transmit pulsing signals are more likely to cause
interference. Since both the positive and negative signal wires of the trim
position sensor are run together in one cable, any transmitted or received
interference in one wire is canceled by the other wire.
In other words, don't worry about the trim position indicator circuit.
Circuits that are more likely to cause interference are the magneto P leads
and strobe light power wires. Also make sure that audio circuits are
grounded at one end only. Microphone jacks should NOT be grounded locally.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=512311#512311
Message 5
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| Subject: | OVM-14 MkIII development program |
The ECBs and parts are all in. Shouldn't take
long to put one together. Promises to be fun . . .
the boards are tiny and rather densely populated.
But putting the parts in rows like this reduces
the error rate for getting parts put in
the right spot.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 6
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| Subject: | Re: Power, signal, and Coax - How should they |
be bundled?
At 01:54 PM 11/16/2023, you wrote:
>
>A trim servo position potentiometer is extremely unlikely to cause any
>interference because the output signal changes very slowly as the motor
>runs. When the motor stops running, the position signal is steady DC.
<snip>
Exactly.
I might add that coax cables for radios are also
very low on the list for potential victim or antagonist.
The magic thing about coax is its ability to keep
signals on the inside IN; signals on the outside OUT.
This magic goes away should the shield connections
at the connector become undone. In these cases,
you might WANT the fault to raise a ruckus of some
variety with another system . . . else how would
you become aware of the need for maintenance? I've
only encountered a couple instances of loose shields
on a coax . . . and those involved UG-88 connectors with
threaded clamps. Crimped connectors are pretty immune
from this ailment.
Another consideration for making wire routing
decisions is the fact that potential victims
are largely confined to stuff behind the panel.
Even if gizmos scattered about the airplane
were potential antagonists (mostly not), they
don't share environs with the most vulnerable
systems behind the panel.
Everything off the panel will happily
coexist in wire
bundles.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 7
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| Subject: | Re: OVM-14 MkIII development program |
Bob,
If you are looking for field testers let me know (I have an RV6 with auto al
ternator, external regulator, and AGM battery - and no OVP - eeek!). I can c
ertainly install and test it, but have no surface mount experience, so assem
bly is probably a bridge too far.
Peter
> On Nov 16, 2023, at 4:16=AFPM, Robert L. Nuckolls, III <nuckolls.bob
@aeroelectric.com> wrote:
>
> =EF=BB The ECBs and parts are all in. Shouldn't take
> long to put one together. Promises to be fun . . .
> the boards are tiny and rather densely populated.
>
> But putting the parts in rows like this reduces
> the error rate for getting parts put in
> the right spot.
>
>
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
==
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ========================
========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
>
Message 8
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| Subject: | Re: OVM-14 MkIII development program |
At 06:55 PM 11/16/2023, you wrote:
>Bob,
>If you are looking for field testers let me know (I have an RV6 with
>auto alternator, external regulator, and AGM battery - and no OVP -
>eeek!). I can certainly install and test it, but have no surface
>mount experience, so assembly is probably a bridge too far.
Thank you for the offer! You're on the list for
first article. As soon as I'm satisfied with the
performance, I'll be looking for some 'victims'
willing to add their experience/observations
to the development of this product.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 9
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| Subject: | Re: OVM-14 MkIII development program |
Bob,
I'd like to be on the list of Beta testers, too.
-Jeff
On Thursday, November 16, 2023 at 07:10:55 PM PST, Robert L. Nuckolls,
III <nuckolls.bob@aeroelectric.com> wrote:
At 06:55 PM 11/16/2023, you wrote:
Bob,
If you are looking for field testers let me know (I have an RV6 with autoal
ternator, external regulator, and AGM battery - and no OVP -eeek!).=C2- I
can certainly install and test it, but have no surfacemount experience, so
assembly is probably a bridge too far.
=C2- Thank you for the offer!=C2- You're on the list for
=C2- first article. As soon as I'm satisfied with the
=C2- performance, I'll be looking for some 'victims'
=C2- willing to add their experience/observations
=C2- to the development of this product.
=C2- Bob . . .
=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2
-=C2-=C2-=C2-=C2-=C2-////
=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2-=C2
-=C2-=C2-=C2-=C2-(o o)
=C2-=C2- ===========o00o=(_)=o00o====
=====
=C2-=C2- < Go ahead, make my day . . .=C2-=C2- >
=C2-=C2- < show me where I'm wrong.=C2-=C2-=C2-=C2-=C2->
=C2-=C2- ====================
============
=C2-
=C2-=C2- In the interest of creative evolution
=C2-=C2- of the-best-we-know-how-to-do based
=C2-=C2- on physics and good practice.
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