Com to intercom harness wiring question

[mruffatto]

Hello,
So I have spent a considerable amount of time staring at electrical drawings for the SV-interom-2S to SV-Com-425 and still remain confused about the grounding.

I guess my first question is will pin 1 on the intercom ultimately be terminated at my firewall ground block? It appears that way on pg 2-3 of the intercom manual.

My second question is how to tie all of the grounds/shields together that will goto pin 1? The manual mentions a pigtail. I've searched and searched for a picture/example online and could not find one in other build sites.

Third question, would daisy chaining sheilds/grounds together with solder sleeves be an alternative? This could get bulky and costly.

Last question. I'm installing two comms. The drawing on pg 2-3 of the intercom manual shows the PTT radio select switch wire as being in a shielded cable? Pin 5 on the COMs. Is this correct or do I just not understand the schematic. That is not how I am setup. I have a SPDT switch on my grip with three wires coming forward.

 

[mruffatto]

I have still been going over the manuals and have managed to come up with another possible issue.
I'm using tosten military style grips. They came with two ground output wires stubbed out. One for the hat switch(trim) and one for the rest of the switches(PTT,CWS,Flaps,Com flip,smoke). I combined those two grounds at a connector to run only one wire to my firewall ground just to save a little space. I did the same thing on the copilot side. I figured this was alright since they are all ground sense switches. No shielded wires anywhere. Will my PTT switches potential introduce noise?
Maybe I have not been planning far enough ahead.

 

[dynonsupport]

Yes, SV-INTERCOM-2S Pin 1 is THE ground for the shields on the shielded wires, and power to the SV-INTERCOM-2S.

The worst thing on audio wiring is "ground loops" - multiple paths to ground can cause hum, squeal, cross-talk, etc. So ultimately you want to terminate grounds in an audio system to only one point with the same "potential".

Hard to describe in type... When "pigtail" is mentioned in the SV-INTERCOM-2S manual, this is the technique we had in mind: http://pad2.whstatic.com/images/thumb/9/99/RG-59-9373.jpg/670px-RG-59-9373.jpg - note this is a larger diameter cable (RG-59, typically used for video) than what's typically used for audio.

So, once you've separated out the shields as pigtails, bond all of THOSE together in one bundle, and the connection to your electrical ground bus, with a single wire coming out of the bundle to be terminated at Pin 1.

You can use solder sleeves, don't "daisy chain" - bring the wire from the solder sleeve to the same point as all the others.

Hello,
So I have spent a considerable amount of time staring at electrical drawings for the SV-interom-2S to SV-Com-425 and still remain confused about the grounding.

I guess my first question is will pin 1 on the intercom ultimately be terminated at my firewall ground block? It appears that way on pg 2-3 of the intercom manual.

My second question is how to tie all of the grounds/shields together that will goto pin 1? The manual mentions a pigtail. I've searched and searched for a picture/example online and could not find one in other build sites.

Third question, would daisy chaining sheilds/grounds together with solder sleeves be an alternative? This could get bulky and costly.

Last question. I'm installing two comms. The drawing on pg 2-3 of the intercom manual shows the PTT radio select switch wire as being in a shielded cable? Pin 5 on the COMs. Is this correct or do I just not understand the schematic. That is not how I am setup. I have a SPDT switch on my grip with three wires coming forward.

 

[dynonsupport]

PTT to SV-INTERCOM-2S and SV-COM-C25/X83 - "push to ground" is correct.

CWS / Servo Disconnect - "push to ground" is correct.

Flaps - depends on your trim controller. If it's a Dynon SV-AP-PANEL, "push to ground" is correct.

"COM flip" (SV-COM-C25 flip/flop) - "push to ground" is correct.

It's unlikely that these signals will induce noise.

I have still been going over the manuals and have managed to come up with another possible issue.
I'm using tosten military style grips. They came with two ground output wires stubbed out. One for the hat switch(trim) and one for the rest of the switches(PTT,CWS,Flaps,Com flip,smoke). I combined those two grounds at a connector to run only one wire to my firewall ground just to save a little space. I did the same thing on the copilot side. I figured this was alright since they are all ground sense switches. No shielded wires anywhere. Will my PTT switches potential introduce noise?
Maybe I have not been planning far enough ahead.

 

[mruffatto]

Thanks for getting back to me so quickly. Maybe you can clarify one more thing concerning the mic jack wiring.

PTT switch wire from my grip to Intercom Pin 10(Pilot Mic PTT)
Jack Tip(PTT) not connected
Jack Ring(mic audio) to Intercom Pin 23 (Pilot Mic)
Jack sleeve(common) to Intercom Pin 2 (mic ground)
Shield pigtailed with others at intercom side

The other side of the PTT switch on the grip is already grounded to the firewall

Does that sound right?

 

[Dynon]

That sounds right!

 

[The RV8 Pilot]

Quote "You can use solder sleeves, don't "daisy chain" - bring the wire from the solder sleeve to the same point as all the others."

Why do you discourage the "daisy chain"?  just reading up on the AeroElectric Connection and Bob describes just that for this process.  Just trying to figure out how to terminate all these grounds.

Thanks, Michael

 

[dynonsupport]

Audio wiring is acutely sensitive to "ground loops" which can develop if there are multiple ground "paths" in audio wiring. Bringing all the audio grounds to a central point is a good way to ensure that there aren't any "ground loops". The pro's that wire audio harnesses are careful not to have "ground loops" so they can get away with daisy-chaining audio grounds.

A solder sleeve is a good way to terminate all the audio grounds together.

Also, there are several companies, including Aircraft Spruce, that can make you a SV-COM-C25/X83 to SV-INTERCOM-2S harness (for a fee, of course).

Quote "You can use solder sleeves, don't "daisy chain" - bring the wire from the solder sleeve to the same point as all the others."

Why do you discourage the "daisy chain"?  just reading up on the AeroElectric Connection and Bob describes just that for this process.  Just trying to figure out how to terminate all these grounds.

Thanks, Michael

 

[The RV8 Pilot]

Thanks for the reply! I will do it as described in the manual using solder sleeves!

 

[hstaton]

In all of my readings in AeroElectric, I haven't seen Bob call for daisy-chaining - just the opposite - all pigtails joined together, with one connection going to ground. On another note, I have tried dedicated pigtails in the past (those with heat-shrink tubing) and have been disappointed. Bob's website has an excellent how-to showing how to create your own pigtails. I've done it many times, and it works.

 

[The RV8 Pilot]

http://www.aeroelectric.com/articles/pigtail/pigtail.html. Down towards the end he refers to daisy-chaining

In all of my readings in AeroElectric, I haven't seen Bob call for daisy-chaining - just the opposite - all pigtails joined together, with one connection going to ground. On another note, I have tried dedicated pigtails in the past (those with heat-shrink tubing) and have been disappointed. Bob's website has an excellent how-to showing how to create your own pigtails. I've done it many times, and it works.