Today's Message Index:
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1. 06:49 AM - Re: ARINC 429 wiring practices (Robert L. Nuckolls, III)
2. 12:48 PM - Re: ARINC 429 wiring practices (Charlie England)
3. 01:50 PM - Re: ARINC 429 wiring practices (Ross Home)
4. 02:32 PM - Re: ARINC 429 wiring practices (Charlie England)
Message 1
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Subject: | Re: ARINC 429 wiring practices |
At 04:34 PM 7/27/2015, you wrote:
Thanks to David & Bob.=C2
Bob,
My question about the 'extra' ground wire was
related to the serial port(s), not ARINC. IIRC,
serial stuff is typically unbalanced, with a
signal line and a shield/ground return. In the
case of the AFS docs, they show in one case (to
external GPS) a pair of signal wires
(bi-directional data), and a ground wire, all
wrapped in a shield. In another case
(magnetometer) they show a pair of RS422 signal
wires, a power wire, and a ground wire, all
wrapped in a shield. That's the practice of
embedding an extra ground wire inside a shield
(when the shield can serve as ground) that I was really questioning.
The 'extra' wire you're describing . . . is it bare?
. . . and what is the nature of the shield material?
. . . what you are describing is reminiscent
of a product from Belden Wire called "Beldfoil"
shielded wire. Instead of braiding strands of wire
over the bundle, they wrap an aluminum foil shield
over it. VERY effective shielding but electrical
connection to thin aluminum is hard to make up.
The solution was to bundle a bare stranded wire
in with the other wires. Given that it is not
insulated, it makes connection with the shielding
at innumerable places along the length of the cable.
http://tinyurl.com/nhpjmup
Given that electro-static shield currents are
very low, it matters not that the ground connection
to the foil is not gas-tight. Hence, the shield ground
has a hi order of integrity to the task and the foil
shielding is electro-statically superior and much
less expensive than braid . . . a kind of win-win.
Unfortunately, this technology is not generally
offered in combination with our favorite insulations
so you don't see this wire used in TC or military
aircraft . . . but it's fine for our purposes.
That 'extra' wire CAN be used as a part of the
power path as long as it's 22AWG current ratings
are observed . . . with the caveat that the
return path power wire be included in the bundle
so that you get parallel path cancellation for
electro-magnetic coupling. But as a general rule,
you're almost never wrong to use the shield
for electro-static decoupling and attach it
to ground one time only at either end.
Bob . . .
Message 2
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Subject: | Re: ARINC 429 wiring practices |
Understand about Belfoil shielded wire; I've built my share of cables using
it in one of my previous lives as a sound engineer & audio tech. It's
unrelated to my question. As a reminder, my question is about the AFS
*documents*, not actual wire. I should have attached an image of the
diagram with the 1st post. Image attached now.
See the wiring from the 'EFIS Main Cable' connector to the Nav Radio,
Altitude Encoder Output to Transponder, GPS, and Magnetometer. All are
shown with a separate ground wire, drawn within the shield. None of the
devices draw significant current, and all the 'ground' return pins shown in
the EFIS Main Connector are electrically common to the chassis of the EFIS
itself. My question is about the 'extra' ground wire, drawn within the
shield for each of these destinations.
The only connection that does make sense to me is the 'EFIS Audio Output',
which logically shows a signal wire and a shield return, without the extra
ground wire.
On Thu, Jul 30, 2015 at 8:48 AM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 04:34 PM 7/27/2015, you wrote:
> Thanks to David & Bob.=C3=82
>
> Bob,
>
> My question about the 'extra' ground wire was related to the serial
> port(s), not ARINC. IIRC, serial stuff is typically unbalanced, with a
> signal line and a shield/ground return. In the case of the AFS docs, they
> show in one case (to external GPS) a pair of signal wires (bi-directional
> data), and a ground wire, all wrapped in a shield. In another case
> (magnetometer) they show a pair of RS422 signal wires, a power wire, and
a
> ground wire, all wrapped in a shield. That's the practice of embedding an
> extra ground wire inside a shield (when the shield can serve as ground)
> that I was really questioning.
>
>
> The 'extra' wire you're describing . . . is it bare?
> . . . and what is the nature of the shield material?
>
> . . . what you are describing is reminiscent
> of a product from Belden Wire called "Beldfoil"
> shielded wire. Instead of braiding strands of wire
> over the bundle, they wrap an aluminum foil shield
> over it. VERY effective shielding but electrical
> connection to thin aluminum is hard to make up.
>
> The solution was to bundle a bare stranded wire
> in with the other wires. Given that it is not
> insulated, it makes connection with the shielding
> at innumerable places along the length of the cable.
>
> http://tinyurl.com/nhpjmup
>
> Given that electro-static shield currents are
> very low, it matters not that the ground connection
> to the foil is not gas-tight. Hence, the shield ground
> has a hi order of integrity to the task and the foil
> shielding is electro-statically superior and much
> less expensive than braid . . . a kind of win-win.
> Unfortunately, this technology is not generally
> offered in combination with our favorite insulations
> so you don't see this wire used in TC or military
> aircraft . . . but it's fine for our purposes.
>
> That 'extra' wire CAN be used as a part of the
> power path as long as it's 22AWG current ratings
> are observed . . . with the caveat that the
> return path power wire be included in the bundle
> so that you get parallel path cancellation for
> electro-magnetic coupling. But as a general rule,
> you're almost never wrong to use the shield
> for electro-static decoupling and attach it
> to ground one time only at either end.
>
>
> Bob . . .
>
> *
>
===========
www.matronics.com/Navigator?AeroElectric-List>
===========
===========
om/contribution>
===========
>
> *
>
>
Message 3
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Subject: | ARINC 429 wiring practices |
I just got done installing a 5600. I wired it as shown. Each Serial
Port bundle has a RX, TX, Gnd and shield. The shields for the four
ports are all connected together at the main harness connector with a
black wire coming out of the connector that gets grounded to the
chassis. I used whatever TX, RX wires I needed for the particular
instrument. I ran all of the Gnd wires to my ground block since that is
where all of my instruments are grounded. Everything works great ever
since I got rid of the 18=9D length of unused OAT cable.
If your question is why they want us to ground each serial port, I
can=99t tell you. I just did it. Have you called AFS and asked
them?
Ross
N9PT
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Charlie England
Sent: Thursday, July 30, 2015 12:47 PM
Subject: Re: AeroElectric-List: ARINC 429 wiring practices
Understand about Belfoil shielded wire; I've built my share of cables
using it in one of my previous lives as a sound engineer & audio tech.
It's unrelated to my question. As a reminder, my question is about the
AFS *documents*, not actual wire. I should have attached an image of the
diagram with the 1st post. Image attached now.
See the wiring from the 'EFIS Main Cable' connector to the Nav Radio,
Altitude Encoder Output to Transponder, GPS, and Magnetometer. All are
shown with a separate ground wire, drawn within the shield. None of the
devices draw significant current, and all the 'ground' return pins shown
in the EFIS Main Connector are electrically common to the chassis of the
EFIS itself. My question is about the 'extra' ground wire, drawn within
the shield for each of these destinations.
The only connection that does make sense to me is the 'EFIS Audio
Output', which logically shows a signal wire and a shield return,
without the extra ground wire.
On Thu, Jul 30, 2015 at 8:48 AM, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com> >
wrote:
At 04:34 PM 7/27/2015, you wrote:
Thanks to David & Bob.=C3=82
Bob,
My question about the 'extra' ground wire was related to the serial
port(s), not ARINC. IIRC, serial stuff is typically unbalanced, with a
signal line and a shield/ground return. In the case of the AFS docs,
they show in one case (to external GPS) a pair of signal wires
(bi-directional data), and a ground wire, all wrapped in a shield. In
another case (magnetometer) they show a pair of RS422 signal wires, a
power wire, and a ground wire, all wrapped in a shield. That's the
practice of embedding an extra ground wire inside a shield (when the
shield can serve as ground) that I was really questioning.
The 'extra' wire you're describing . . . is it bare?
. . . and what is the nature of the shield material?
. . . what you are describing is reminiscent
of a product from Belden Wire called "Beldfoil"
shielded wire. Instead of braiding strands of wire
over the bundle, they wrap an aluminum foil shield
over it. VERY effective shielding but electrical
connection to thin aluminum is hard to make up.
The solution was to bundle a bare stranded wire
in with the other wires. Given that it is not
insulated, it makes connection with the shielding
at innumerable places along the length of the cable.
http://tinyurl.com/nhpjmup
Given that electro-static shield currents are
very low, it matters not that the ground connection
to the foil is not gas-tight. Hence, the shield ground
has a hi order of integrity to the task and the foil
shielding is electro-statically superior and much
less expensive than braid . . . a kind of win-win.
Unfortunately, this technology is not generally
offered in combination with our favorite insulations
so you don't see this wire used in TC or military
aircraft . . . but it's fine for our purposes.
That 'extra' wire CAN be used as a part of the
power path as long as it's 22AWG current ratings
are observed . . . with the caveat that the
return path power wire be included in the bundle
so that you get parallel path cancellation for
electro-magnetic coupling. But as a general rule,
you're almost never wrong to use the shield
for electro-static decoupling and attach it
to ground one time only at either end.
Bob . . .
ist"
target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
Message 4
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Subject: | Re: ARINC 429 wiring practices |
I haven't asked them yet, because I already have a strong suspicion of what
their answer will be: 'to shield the ground from noise'. Serial data needs
a ground return, but since the ground return pins in the connector are all
bonded to the case of the EFIS, any noise on the shield is also on those
ground return pins. Which begs the question: why have the extra ground
wire? My suspicion is that they are following some 'certified aircraft'
practice that was started back in mythological times and hasn't been
updated with current knowledge. That's why I've been asking here; we've
seen other 'stuff' in certified a/c that can be done better or simpler,
based on current knowledge.
Glad to hear that you've got yours working noise-free.
Charlie
On Thu, Jul 30, 2015 at 3:48 PM, Ross Home <rossmickey@comcast.net> wrote:
> I just got done installing a 5600. I wired it as shown. Each Serial Por
t
> bundle has a RX, TX, Gnd and shield. The shields for the four ports are
> all connected together at the main harness connector with a black wire
> coming out of the connector that gets grounded to the chassis. I used
> whatever TX, RX wires I needed for the particular instrument. I ran all
of
> the Gnd wires to my ground block since that is where all of my instrument
s
> are grounded. Everything works great ever since I got rid of the 18
=9D
> length of unused OAT cable.
>
>
> If your question is why they want us to ground each serial port, I can
=99t
> tell you. I just did it. Have you called AFS and asked them?
>
>
> Ross
>
> N9PT
>
>
> *From:* owner-aeroelectric-list-server@matronics.com [mailto:
> owner-aeroelectric-list-server@matronics.com] *On Behalf Of *Charlie
> England
> *Sent:* Thursday, July 30, 2015 12:47 PM
> *To:* aeroelectric-list@matronics.com
> *Subject:* Re: AeroElectric-List: ARINC 429 wiring practices
>
>
> Understand about Belfoil shielded wire; I've built my share of cables
> using it in one of my previous lives as a sound engineer & audio tech. It
's
> unrelated to my question. As a reminder, my question is about the AFS
> *documents*, not actual wire. I should have attached an image of the
> diagram with the 1st post. Image attached now.
>
>
> See the wiring from the 'EFIS Main Cable' connector to the Nav Radio,
> Altitude Encoder Output to Transponder, GPS, and Magnetometer. All are
> shown with a separate ground wire, drawn within the shield. None of the
> devices draw significant current, and all the 'ground' return pins shown
in
> the EFIS Main Connector are electrically common to the chassis of the EFI
S
> itself. My question is about the 'extra' ground wire, drawn within the
> shield for each of these destinations.
>
>
> The only connection that does make sense to me is the 'EFIS Audio Output'
,
> which logically shows a signal wire and a shield return, without the extr
a
> ground wire.
>
>
> On Thu, Jul 30, 2015 at 8:48 AM, Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
> At 04:34 PM 7/27/2015, you wrote:
> Thanks to David & Bob.=C3=82
>
> Bob,
>
> My question about the 'extra' ground wire was related to the serial
> port(s), not ARINC. IIRC, serial stuff is typically unbalanced, with a
> signal line and a shield/ground return. In the case of the AFS docs, they
> show in one case (to external GPS) a pair of signal wires (bi-directional
> data), and a ground wire, all wrapped in a shield. In another case
> (magnetometer) they show a pair of RS422 signal wires, a power wire, and
a
> ground wire, all wrapped in a shield. That's the practice of embedding an
> extra ground wire inside a shield (when the shield can serve as ground)
> that I was really questioning.
>
>
> The 'extra' wire you're describing . . . is it bare?
> . . . and what is the nature of the shield material?
>
> . . . what you are describing is reminiscent
> of a product from Belden Wire called "Beldfoil"
> shielded wire. Instead of braiding strands of wire
> over the bundle, they wrap an aluminum foil shield
> over it. VERY effective shielding but electrical
> connection to thin aluminum is hard to make up.
>
> The solution was to bundle a bare stranded wire
> in with the other wires. Given that it is not
> insulated, it makes connection with the shielding
> at innumerable places along the length of the cable.
>
> http://tinyurl.com/nhpjmup
>
> Given that electro-static shield currents are
> very low, it matters not that the ground connection
> to the foil is not gas-tight. Hence, the shield ground
> has a hi order of integrity to the task and the foil
> shielding is electro-statically superior and much
> less expensive than braid . . . a kind of win-win.
> Unfortunately, this technology is not generally
> offered in combination with our favorite insulations
> so you don't see this wire used in TC or military
> aircraft . . . but it's fine for our purposes.
>
> That 'extra' wire CAN be used as a part of the
> power path as long as it's 22AWG current ratings
> are observed . . . with the caveat that the
> return path power wire be included in the bundle
> so that you get parallel path cancellation for
> electro-magnetic coupling. But as a general rule,
> you're almost never wrong to use the shield
> for electro-static decoupling and attach it
> to ground one time only at either end.
>
>
> Bob . . .
>
>
> *ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-L
ist <http://www.matronics.com/Navigator?AeroElectric-List>*
>
> *tp://forums.matronics.com <http://forums.matronics.com>*
>
> *_blank">http://www.matronics.com/contribution <http://www.matronics.com/
contribution>*
>
>
> *
>
===========
www.matronics.com/Navigator?AeroElectric-List>
===========
===========
om/contribution>
===========
>
> *
>
>
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