Today's Message Index:
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0. 01:47 PM - A List Contribution - It's Your Personal Squelch Button... (Matt Dralle)
1. 09:40 AM - Re: bad fuses (Robert L. Nuckolls, III)
2. 02:10 PM - Re: Re: bad fuses (Matthew S. Whiting)
3. 02:29 PM - Power, signal, and Coax - How should they be bundled? (wsimpso1)
4. 06:17 PM - Re: Power, signal, and Coax - How should they be bundled? (Robert L. Nuckolls, III)
Message 0
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| Subject: | A List Contribution - It's Your Personal Squelch Button... |
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Message 1
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Received my amazon order of 'cheap fuses'. Don't have time
to gather fine-grained data right now but just for grins:
Connected a 2A fuse directly across a CV/CC power supply
set up for 24v @ 5A. Turned on power supply and got tired
of waiting for the fuse to blow after a minute or so.
Increased to 10A and repeated test. Took video of the
results. Fuse blew in ~400 milliseconds. Okay,
would we wire a 2A circuit with anything less that
22AWG? I wouldn't. I demonstrated 22AWG ability
to carry 20A for an indefinite interval without
putting the insulation at risk.
http://aeroelectric.com/Pictures/Wire/22AWG_20A.pdf
Yeah, this fuse is a bit more robust than a
name-brand device . . . but would it put a 22AWG
feeder at risk?
Need to build some instrumentation support shelves
over the workbench before I can set up a really
good examination of these devices.
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: re: bad fuses |
Yes, one wire in room temp air will carry a fair bit of current. However, b
undle a few wires at 12,000 feet and the capacity will be a fair bit less.
It is good the fuse blew at 10 A. I have seen videos of 2 A Chinese fuses t
hat carried 30 A for a fair bit of time.
Some Chinese fuses MAY protect wire adequately, but in my airplane I want fu
ses that WILL protect my wires adequately.
Matt
Sent from my iPad
> On Nov 15, 2023, at 12:42=AFPM, Robert L. Nuckolls, III <nuckolls.bo
b@aeroelectric.com> wrote:
>
> =EF=BB Received my amazon order of 'cheap fuses'. Don't have time
> to gather fine-grained data right now but just for grins:
>
> Connected a 2A fuse directly across a CV/CC power supply
> set up for 24v @ 5A. Turned on power supply and got tired
> of waiting for the fuse to blow after a minute or so.
>
> Increased to 10A and repeated test. Took video of the
> results. Fuse blew in ~400 milliseconds. Okay,
> would we wire a 2A circuit with anything less that
> 22AWG? I wouldn't. I demonstrated 22AWG ability
> to carry 20A for an indefinite interval without
> putting the insulation at risk.
>
> http://aeroelectric.com/Pictures/Wire/22AWG_20A.pdf
>
> Yeah, this fuse is a bit more robust than a
> name-brand device . . . but would it put a 22AWG
> feeder at risk?
>
> Need to build some instrumentation support shelves
> over the workbench before I can set up a really
> good examination of these devices.
>
> 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 3
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| Subject: | Power, signal, and Coax - How should they be bundled? |
Here is my little problem. I am trying to wire my fiberglass airplane with internal
antennas properly. I have little insight on electromagnetic compatibility.
Please help.
I know that I am supposed to keep wiring for DC power to stuff like motors and
electronics separated from data, but am struggling with knowing what is what and
how much they matter.
So first issue is we are supposed to keep DC power separated from signal lines.
I know which are power and which are data, and I know which are coax resonating
at RF frequencies. What do I with coax? I have three antennas back there with
cables going forward and another antenna going a foot or so to the ELT box.
Here is what we have in the aft fuselage:
Position signal from my trim servos is data. The maker puts the two power
wires to an electric motor and three wires for servo position on the same cable
with no shielding. Five wires 24AWG, with a max 1 amp for power. Three sets
of these;
ELT, has power and GPS position data signal, all 22 AWG, 1 amp fuse, plus
an RJ11 connector cable to the control box forward. No motors, just electronics;
Three coax antenna cables, two TX/RX for COM, One RX for GS;
LED continuous and flashing - continuous 1 amp and momentary 6 amp, and recommend
shield grounded at airframe ground.
So, how do I bundle this stuff to stay quiet on signal and radios?
Do we consider antenna coax to be power or signal or a third category?
Does it work OK to bundle coax with power wires? Or will electric motors mess
up the Voice and GS stuff?
The makers of the servos and ELT seem to bundle up power and signal will
they be OK if I keep them that way or is it way better to separate power from
signals as close to the servos as I can, run power together then bundle signals
together and run them separately?
Do I run coax cables together but away from a power bundle for ELT and LED
and servos and away from signal bundles?
I have a dipole on each fuselage wall that tends to use the whole vertical
height available. I plan to run my wiring along the fuselage walls and through
the center of the dipoles. That gives me a place for two bundles. Putting a
third bundle at say top or bottom of the fuselage has been warned against - Jim
Weir says it will mess with my COM antennas.
I could suspend a run of wiring down the middle of the fuselage, next to the
big push-pull tube for the elevators. That only gets me about 4 separation
between center and sides with three bundles and would get interesting to work
the support. A fiberglass wand supported at bulkheads and a some triads along
the length. I do not have any desire to do that
It all gets more interesting as we go forward, but the answers to the above questions
should help with insight. The only antennas from the baggage bay through
the cockpit are transponder and ADS-B on the floor with their own ground planes
and two GPS antennas at the top of the roof that need no ground planes. I
still only have two paths around the seats, so I suspect I must decide if my signals
from the trim servos can be bundled up with the power wires or the coax.
My center console is really crowded as we pass over the spar. Maybe I could
run the signal bundle outside the console and put a cover over it. Ugh.
What say you guys? It sure would help if I can bundle the servo position signals
with either the power wires or with the coax cables and still have it behave
nicely.
Billski
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=512304#512304
Message 4
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| Subject: | Re: Power, signal, and Coax - How should they be |
bundled?
At 04:29 PM 11/15/2023, you wrote:
>
>Here is my little problem. I am trying to wire my fiberglass
>airplane with internal antennas properly. I have little insight on
>electromagnetic compatibility. Please help.
>
>I know that I am supposed to keep wiring for DC power to stuff like
>motors and electronics separated from data, but am struggling with
>knowing what is 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.
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