Dynon SV-ARINC-429 to 430W wiring help

[larrynew]

If I may ask the electric gurus a few questions on the Dynon SV-ARINC-429 connection to a GNS 430W. I attached a picture and drew in what I thought it should be.

1. Should the wires be shielded twisted pair?

2. Should they be grounded on both ends like in the picture in red? If so, is the ARINC side ground just attached to the airframe?

3. Is the GPS RS 232 OUT just a single non-shielded wire?

Here's what makes me think it should be shielded wiring. Although not Dynon, this page in the 400W series install manual shows ARINC connections with shielded twisted pair. All the other 400W to ARINC connections also show the same.

 

[airguy]

I just ran twisted pair on mine, without shield. They talk to each other now, but I haven't flown yet and haven't transmitted on the comm radio yet to see if that causes a problem.

 

[JDanno]

Shielded is always better BUT in most cases really won't matter. Its not like it is not gonna work. If you have an autopilot this is a good time to wire one with these wires so that you can control it from the EFIS or the GPS. I was wiring up my -10 yesterday with this very same task.

 

[krw5927]

I hope Dynon weighs in on this one. I just ran these very wires to/from my Garmin 480 and Dynon ARINC box. Didn't twist, didn't shield. Don't remember seeing anything in the Dynon instructions to do so.

 

[larrynew]

Talked to Dynon tech support. They said to use twisted pairs but don't worry about shielding. Said certified avionics folks have to use shielding but they don't see any difference. Talked to a certified avionics installer and he recommended shielded twisted pair. I have shielded twisted pair so that's what I'm going to use as I have to justify sourcing and buying all those card edge connectors for grounding on the back plate of the 430.

 

[johnbright]

 

[GalinHdz]

FWIW I used shielded twisted pairs because I wanted to err on the safe side. I would rather do it once instead of maybe having to rip everything out and do it all for a second time. Besides, the difference in wire price is small compared to the man hours needed if you have to replace everything.

YMMV

 

[RV7A Flyer]

Here's what Stein did when I ordered my avionics with wire harness terminated at one end (I did the wire runs and connectors on the other end). This is a 430W to SV ARINC. (Ignore the split to D6/XPDR line, I added that and ended up not needing the XPDR connection anyway). You can see the lines that are shielded on one end only, at the 430W.

 

[AZSteve053]

The single conductor (RS232 Out) should be a single conductor SHIELDED wire, shield grounded at the source end and floating at the receiving end. This is a high speed digital signal susceptible to interference from other stuff including Transponder RF output pulses from antenna etc. As others have pointed out Twisted shielded pair is the cable of choice for Arinc 429 interfaces. The Stein diagram above shows exactly this type industry std implemented.

 

[Cumulo]

The single conductor (RS232 Out) should be a single conductor SHIELDED wire, shield grounded at the source end and floating at the receiving end. This is a high speed digital signal susceptible to interference from other stuff including Transponder RF output pulses from antenna etc. As others have pointed out Twisted shielded pair is the cable of choice for Arinc 429 interfaces. The Stein diagram above shows exactly this type industry std implemented.

If you use shielded cable to reduce EMI, you are likely just making an antenna system for EMI if you only ground a one end: and particularly if the currents are unbalanced as they would be with a single shielded wire.
Standard Rule for Shields:
AUDIO: One point ground. (an audio wavelength is miles long, and no ground loops with one ground)
RADIO FREQUENCIES: Ground early and often. At least a ground at each end.

ron ( did 2 FAA radio+ repair stations from scratch in the day)