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2 Grounds

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sam(at)fr8dog.net
Guest

Posted: Mon Feb 26, 2007 12:14 pm Post subject: 2 Grounds

Do I need a separate ground for the Avionics, including the phones. Or 

will the ganged firewall (cool side) ground block be satisfactory for 

all my grounds? I think the audio panel (GMA 340) has a ground block.

Thanks,

Sam Marlow

steerr(at)bellsouth.net
Guest

Posted: Tue Feb 27, 2007 8:43 am Post subject: 2 Grounds

Did you ever get an answer to this, Sam?  I don't know if it applies to your 

situation, but I'm using an intercom in addition to my Microaire 760 radio. 

Bob kindly gave me a wiring diagram for hooking up the two together.  That 

diagram specifically separated the signal ground from the power ground.



Hope this helps.



Bill



---

sam.marlow

Joined: 25 Feb 2006
Posts: 99

Posted: Tue Feb 27, 2007 4:47 pm Post subject: 2 Grounds

No, I didn't get an answer, and my grounds are just hanging waiting to be connected. If I just knew where?



---- Bill Steer <steerr(at)bellsouth.net> wrote: 

[quote] 

 

 Did you ever get an answer to this, Sam?  I don't know if it applies to your 

 situation, but I'm using an intercom in addition to my Microaire 760 radio. 

 Bob kindly gave me a wiring diagram for hooking up the two together.  That 

 diagram specifically separated the signal ground from the power ground.

 

 Hope this helps.

 

 Bill

 

 ---

john(at)ballofshame.com
Guest

Posted: Tue Feb 27, 2007 9:20 pm Post subject: 2 Grounds

Bleary eyed, but still almost thinking straight, I'll take a shot at 

this....

Ground is ground is ground...however, the best grounding schemes would 

use wiring with 0 resistance and 0 length.  Since we have to use real 

wire, the second best choice is to keep the avionics ground wires as 

short as possible to a single grounding point.  That ground point then 

gets grounded to the firewall ground.  This is good because it keeps 

everything very short AND it makes wiring a lot more convenient (only 1 

wire going to the firewall).  What you DON'T want to do is mount a piece 

of copper on the instrument panel, for example, and then tie that to the 

firewall ground because then you'll have caused a ground loop (you'll 

have ground coming from the panel metal also in this example).  Wherever 

you tie them together, the only metal it should be touching (other than 

the other avionic ground wires) is the firewall ground.

As far as a "signal" ground, I'm assuming we're talking about the serial 

lines?  Anything that communicates with each other should have their 

signal grounds tied together.  I'm not up to my avionics install yet but 

if avionics are anything like the real word, how you do this, exactly, 

is dependent on the specific thingy you're installing.  In a perfect 

world, you would have a signal ground pin somewhere but I believe some 

avionics don't quite work this way.  If you list the avionics you're 

trying to make play with each other, I'm sure someone probably has a 

good answer.

-John

www.ballofshame.com

sam.marlow(at)adelphia.net wrote:

[quote] 

 No, I didn't get an answer, and my grounds are just hanging waiting to be connected. If I just knew where?

 ---- Bill Steer <steerr(at)bellsouth.net> wrote: 

> 

>

> Did you ever get an answer to this, Sam?  I don't know if it applies to your 

> situation, but I'm using an intercom in addition to my Microaire 760 radio. 

> Bob kindly gave me a wiring diagram for hooking up the two together.  That 

> diagram specifically separated the signal ground from the power ground.

>

> Hope this helps.

>

> Bill

>

> ---

nuckollsr(at)cox.net
Guest

Posted: Wed Feb 28, 2007 10:42 am Post subject: 2 Grounds

At 11:32 AM 2/26/2007 -0500, you wrote:



 	  Quote: 	
		  



Do I need a separate ground for the Avionics, including the phones. Or 

will the ganged firewall (cool side) ground block be satisfactory for all 

my grounds? I think the audio panel (GMA 340) has a ground block.

Thanks,

Sam Marlow


	


     See chapter on Grounds in the 'Connection and in

     particular the suggested architectures illustrated

     in Figure Z-15 in . . .



http://aeroelectric.com/articles/Rev11/AppZ_R11J.pdf



     The term "need" is not quantifiable. There are tens

     of thousands of vehicles including airplanes where

     various systems in power distribution and signal

     handling are "grounded" willy-nilly without consideration

     for the physics



     For every builder that touts a "need" there will be

     a half dozen who cite observations based on their

     own experiences that contradict the notion of "need".



     Bottom line is that there are reasons based in physics

     that show now potential for noise and/or degraded operation

     can be elevated by inattention to grounding. It's easy

     to do but if you don't wish to do it, probability of

     a PERCEIVED degradation of performance is low. HOWEVER

     when a build comes on the list citing some anomalous or

     noisy behavior, the first question that enters my mind

     is, "How are your grounds architectured?".



     If things are stuck down to the airframe without regard

     to practices and principles KNOWN to reduce risk, then

     identifying and fixing the problem can be much harder.



     None of us can tell you that you NEED to do anything

     but plenty of us who will sympathize with you should

     some noise problem present itself at some time in the

     future.



     Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Wed Feb 28, 2007 6:02 pm Post subject: 2 Grounds

Bob,



To quote you, chapter 18 page 11 of the connection (hope I am not 

violating your copy write)

"The forest-of-ground-tabs technique described in Chapter 5 is entirely 

suitable and convenient for most equipment in the electrical system.  

However, while it is electrically correct to wire all the panel mounted 

equipment to the same ground block the total number of wires can be 

significant.



Further, given that there are a number of small signal systems 

vulnerable to noise concentrated on the panel, it makes sense to create 

separate and co-located ground system for these potential victims.  ..."



Are you saying that the separate and co-located avionics ground system 

is acceptable because the potential for noise from this design is 

minimal, and the advantage of not running many separate grounds from all 

the avionics to the ground bus outweighs the minimal noise potential.



Can I then make the conclusion, that if the ground bus were near the 

avionics, running the wires a single bus would be minimally superior?



Larry Rosen

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 11:32 AM 2/26/2007 -0500, you wrote:



> 

>

> Do I need a separate ground for the Avionics, including the phones. 

> Or will the ganged firewall (cool side) ground block be satisfactory 

> for all my grounds? I think the audio panel (GMA 340) has a ground 

> block.

> Thanks,

> Sam Marlow



     See chapter on Grounds in the 'Connection and in

     particular the suggested architectures illustrated

     in Figure Z-15 in . . .



 http://aeroelectric.com/articles/Rev11/AppZ_R11J.pdf



     The term "need" is not quantifiable. There are tens

     of thousands of vehicles including airplanes where

     various systems in power distribution and signal

     handling are "grounded" willy-nilly without consideration

     for the physics



     For every builder that touts a "need" there will be

     a half dozen who cite observations based on their

     own experiences that contradict the notion of "need".



     Bottom line is that there are reasons based in physics

     that show now potential for noise and/or degraded operation

     can be elevated by inattention to grounding. It's easy

     to do but if you don't wish to do it, probability of

     a PERCEIVED degradation of performance is low. HOWEVER

     when a build comes on the list citing some anomalous or

     noisy behavior, the first question that enters my mind

     is, "How are your grounds architectured?".



     If things are stuck down to the airframe without regard

     to practices and principles KNOWN to reduce risk, then

     identifying and fixing the problem can be much harder.



     None of us can tell you that you NEED to do anything

     but plenty of us who will sympathize with you should

     some noise problem present itself at some time in the

     future.



     Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

N1DeltaWhiskey(at)comcast
Guest

Posted: Thu Mar 01, 2007 8:26 am Post subject: 2 Grounds

Larry,



I'll take a stab at attempting to clarify this.  It makes sense to run all 

ground wires to a single ground point, including the avionics.  What I 

believe Bob is saying is that common ground point for the avionics may be 

established near the avionics, then a single wire connects the avionics 

ground point to the "forest of tabs" on the firewall.



In effect, this method uses the same ground point and the circuitry is 

virtually identical from a current flow standpoint. It precludes the 

possibility of alternate feed paths for the ground current, and may, to some 

miniscule degree, reduce the possibility of electromagnetic crosstalk.  The 

avionics to firewall ground wire needs to be large enough to handle the 

combined current demand of all of the avionics.



I see plusses and minuses with the remote avionics ground point.  On the 

plus side is that the amount of wires from the panel to the firewall is 

reduced making, possibly, for a cleaner wiring job, lower weight 

(minimally), and so on.  On the minus side is that failure of the connection 

between the avionics ground and the firewall ground wipes out all of the 

avionics (but a good installation should preclude this from being a 

significant concern).  It is a wash in my view, and therefore, neither 

arrangement is necessarily "superior" to the other.  Weigh your concerns and 

use the system you feel most comfortable with.



Hope this helps.



Doug Windhorn

---

sam(at)fr8dog.net
Guest

Posted: Thu Mar 01, 2007 9:09 am Post subject: 2 Grounds

Thanks Doug for clarification!

Sam Marlow



Doug Windhorn wrote:

[quote] 

 <N1DeltaWhiskey(at)comcast.net>



 Larry,



 I'll take a stab at attempting to clarify this.  It makes sense to run 

 all ground wires to a single ground point, including the avionics.  

 What I believe Bob is saying is that common ground point for the 

 avionics may be established near the avionics, then a single wire 

 connects the avionics ground point to the "forest of tabs" on the 

 firewall.



 In effect, this method uses the same ground point and the circuitry is 

 virtually identical from a current flow standpoint. It precludes the 

 possibility of alternate feed paths for the ground current, and may, 

 to some miniscule degree, reduce the possibility of electromagnetic 

 crosstalk.  The avionics to firewall ground wire needs to be large 

 enough to handle the combined current demand of all of the avionics.



 I see plusses and minuses with the remote avionics ground point.  On 

 the plus side is that the amount of wires from the panel to the 

 firewall is reduced making, possibly, for a cleaner wiring job, lower 

 weight (minimally), and so on.  On the minus side is that failure of 

 the connection between the avionics ground and the firewall ground 

 wipes out all of the avionics (but a good installation should preclude 

 this from being a significant concern).  It is a wash in my view, and 

 therefore, neither arrangement is necessarily "superior" to the 

 other.  Weigh your concerns and use the system you feel most 

 comfortable with.



 Hope this helps.



 Doug Windhorn

 ---

nuckollsr(at)cox.net
Guest

Posted: Thu Mar 01, 2007 9:46 am Post subject: 2 Grounds

At 12:08 PM 3/1/2007 -0500, you wrote:



 	  Quote: 	
		  



Thanks Doug for clarification!

Sam Marlow



Doug Windhorn wrote:

>

><N1DeltaWhiskey(at)comcast.net>

>

>Larry,

>

>I'll take a stab at attempting to clarify this.  It makes sense to run 

>all ground wires to a single ground point, including the avionics.

>What I believe Bob is saying is that common ground point for the avionics 

>may be established near the avionics, then a single wire connects the 

>avionics ground point to the "forest of tabs" on the firewall.

>

>In effect, this method uses the same ground point and the circuitry is 

>virtually identical from a current flow standpoint. It precludes the 

>possibility of alternate feed paths for the ground current, and may, to 

>some miniscule degree, reduce the possibility of electromagnetic 

>crosstalk.  The avionics to firewall ground wire needs to be large enough 

>to handle the combined current demand of all of the avionics.

>

>I see plusses and minuses with the remote avionics ground point.  On the 

>plus side is that the amount of wires from the panel to the firewall is 

>reduced making, possibly, for a cleaner wiring job, lower weight 

>(minimally), and so on.  On the minus side is that failure of the 

>connection between the avionics ground and the firewall ground wipes out 

>all of the avionics (but a good installation should preclude this from 

>being a significant concern).  It is a wash in my view, and therefore, 

>neither arrangement is necessarily "superior" to the other.  Weigh your 

>concerns and use the system you feel most comfortable with.

>

>Hope this helps.

>

>Doug Windhorn


	


     Right on Doug. Thanks. The single-point failure issue

     is addressed by the notation you'll find on Figure Z-15

     illustrations for the panel ground bus where I show

     five separate, 20AWG wires to run from the panel ground

     bus down to the firewall ground.



     Bob . . .

dennis.glaeser(at)eds.com
Guest

Posted: Thu Mar 01, 2007 10:16 am Post subject: 2 Grounds

I ran Power grounds for each radio to the forest of tabs, and used the

'remote ground' for all of the signal connection 'lows' and shields.

With this setup, I believe that the connection from the remote ground to

the forest of tabs is non-critical (although I agree it's failure

potential rivals my chances of winning the lottery 



Dennis Glaeser



----------------------------------------------------

From:		Doug Windhorn 	

  --- <-snip-> ---

On the minus side is that failure of the connection 

between the avionics ground and the firewall ground wipes out all of the



avionics (but a good installation should preclude this from being a 

significant concern).  It is a wash in my view, and therefore, neither 

arrangement is necessarily "superior" to the other.  Weigh your concerns

and 

use the system you feel most comfortable with.



Hope this helps.



Doug Windhorn

LarryRosen

Joined: 16 Jan 2006
Posts: 415
Location: Medford, NJ

Posted: Thu Mar 01, 2007 3:27 pm Post subject: 2 Grounds

Thanks you all for the clarification

Larry

Do not archive



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 12:08 PM 3/1/2007 -0500, you wrote:



> 

>

> Thanks Doug for clarification!

> Sam Marlow

>

> Doug Windhorn wrote:

>> 

>> <N1DeltaWhiskey(at)comcast.net>

>>

>> Larry,

>>

>> I'll take a stab at attempting to clarify this.  It makes sense to 

>> run all ground wires to a single ground point, including the avionics.

>> What I believe Bob is saying is that common ground point for the 

>> avionics may be established near the avionics, then a single wire 

>> connects the avionics ground point to the "forest of tabs" on the 

>> firewall.

>>

>> In effect, this method uses the same ground point and the circuitry 

>> is virtually identical from a current flow standpoint. It precludes 

>> the possibility of alternate feed paths for the ground current, and 

>> may, to some miniscule degree, reduce the possibility of 

>> electromagnetic crosstalk.  The avionics to firewall ground wire 

>> needs to be large enough to handle the combined current demand of 

>> all of the avionics.

>>

>> I see plusses and minuses with the remote avionics ground point.  On 

>> the plus side is that the amount of wires from the panel to the 

>> firewall is reduced making, possibly, for a cleaner wiring job, 

>> lower weight (minimally), and so on.  On the minus side is that 

>> failure of the connection between the avionics ground and the 

>> firewall ground wipes out all of the avionics (but a good 

>> installation should preclude this from being a significant 

>> concern).  It is a wash in my view, and therefore, neither 

>> arrangement is necessarily "superior" to the other.  Weigh your 

>> concerns and use the system you feel most comfortable with.

>>

>> Hope this helps.

>>

>> Doug Windhorn



     Right on Doug. Thanks. The single-point failure issue

     is addressed by the notation you'll find on Figure Z-15

     illustrations for the panel ground bus where I show

     five separate, 20AWG wires to run from the panel ground

     bus down to the firewall ground.



     Bob . . .

_________________
Larry Rosen
#40356
N205EN (reserved)
<http>

enewton57(at)cableone.net
Guest

Posted: Thu Mar 01, 2007 4:33 pm Post subject: 2 Grounds

I have a decidedly small and low tech avionics  system.  A single radio (ICOM A200) a single transponder (Colllins) and a  single intercom (PS 1000).  So with that simple of a system, I'll  probably just run the ground wire from each component to the forest of tabs  on the firewall.  If I'm reading your post right, that's perfectly  acceptable, right?

  

 Eric Newton - Long Beach, MS

BH #682

http://mybearhawk.com

 [quote]   ---

N1DeltaWhiskey(at)comcast
Guest

Posted: Thu Mar 01, 2007 8:53 pm Post subject: 2 Grounds

Eric,

  

 Certainly a way that I could feel comfortable with  (and the way I did mine).

  

 Doug

 [quote]   ---

rv9jim(at)juno.com
Guest

Posted: Fri Mar 02, 2007 6:16 am Post subject: 2 Grounds

Yup!  That is what I did.  Just get a large enough ground tab block.  I

had to run several wires thru the fire wall pass thru and use the ground

tabs on the fire wall side.  That is OK as there was a lot of unused tabs

on that side anyway.   I think I got the 24/24 block. Working out fine

and I still have about a dozen empty tabs on the fire wall side to be

used as necessary.

Jim

RV9-A QB (FWF bout done)

klehman(at)albedo.net
Guest

Posted: Fri Mar 02, 2007 6:53 am Post subject: 2 Grounds

Me too however the radio, intercom, and my strobe power supplies are all 

also grounded to their respective cases (as well as their ground pins) 

and therefore to the metal airframe. I can not hear the strobe whine in 

flight but it is obvious on the ground.  Since various capacitors and 

chokes on the 12v strobe power supply did not help, I decided that this 

was a "feature" to remind me to turn them off after landing  



Fortunately there is no transponder reply noise which has annoyed me on 

some other airplanes.



Ken



Doug Windhorn wrote:



[quote] Eric,

  

 Certainly a way that I could feel comfortable with (and the way I did 

 mine).

  

 Doug



     ---

nuckollsr(at)cox.net
Guest

Posted: Fri Mar 02, 2007 1:02 pm Post subject: 2 Grounds

At 06:31 PM 3/1/2007 -0600, you wrote:



 	  Quote: 	
		  I have a decidedly small and low tech avionics system.  A single radio 

(ICOM A200) a single transponder (Colllins) and a single intercom (PS 

1000).  So with that simple of a system, I'll probably just run the ground 

wire from each component to the forest of tabs on the firewall.  If I'm 

reading your post right, that's perfectly acceptable, right?


	


    Yes. Taking all wires to the single point is

    a perfectly good thing to do. Extending the

    ground system up to the panel is useful for

    more complex installation where the total number

    of grounds gets up to a dozen or more.



    Bob .. .

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