---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 07/30/15: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 06:49:50 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 12:48:55 PM PST US Subject: Re: AeroElectric-List: ARINC 429 wiring practices From: Charlie England 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 _____________________________________ Time: 01:50:11 PM PST US From: "Ross Home" Subject: RE: AeroElectric-List: 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 > 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 _____________________________________ Time: 02:32:03 PM PST US Subject: Re: AeroElectric-List: ARINC 429 wiring practices From: Charlie England 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 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 * > > *tp://forums.matronics.com * > > *_blank">http://www.matronics.com/contribution * > > > * > =========== www.matronics.com/Navigator?AeroElectric-List> =========== =========== om/contribution> =========== > > * > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.