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Shielded wire for wingtip strobe

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dalemed

Joined: 25 Dec 2007
Posts: 46

Posted: Mon Aug 31, 2009 8:06 am Post subject: Shielded wire for wingtip strobe

I'm getting ready to install an Aveo wingtip LED stobe on my all-aluminum wing.  I ran some bench tests and found quite a bit of switching noise on the stobe wire.  I'm assuming I should use shielded wire for this line and I'm assuming I should ground the shield on only one end.



Which end of the shield should I ground or does it matter?



I'm new to this list so I apologize if this question has been asked and answered a lot of times.  I did a search of the list but nothing jumped out at me.



Thanks!

_________________
Dale
Zenith Zodiac CH650

nuckollsr

Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Mon Aug 31, 2009 11:04 am Post subject: Re: Shielded wire for wingtip strobe

Shielding has a VERY limited, VERY specific effect on the propagation of noise from one wire to another. How did you 'measure' switching noise? Just holding your hand-held transceiver close to the product or its leadwires is not a very telling experiment. Your handheld can and will detect close proximity noises that have little or nothing to do with operational aspects of making your 'noisy' device co-exist with potential 'victims' of that noise.



What does the manufacturer say about noise issues? Email them and ASK if they're aware of any customers that have encountered noise issues and what they did about them. It's a 99% bet that an inline filter would be necessary to take care of noise that is CONDUCTED on the power wires. These are not the kinds of noises that will couple from one wire to the next because there is no shielding.



Bob . . .

doug.ilg(at)verizon.net
Guest

Posted: Mon Aug 31, 2009 1:24 pm Post subject: Shielded wire for wingtip strobe

I also have a set of these lights.  I am not to the point of installing and I have not conducted any experiments, but the manufacturer says that no shielding is needed.  It's one of their selling points.  All the flashy bits for the LEDs are inside the idividual light heads, so all you need to supply is 7-32 VDC.  I guess that doesn't guarantee that no noise can leak out onto the power leads, but they claim it's a "noise free" installation.



FWIW

 

Doug Ilg

Grumman Tiger N74818, College Park Airport (KCGS), Maryland

Challenger II LSS (N641LG reserved) - kit underway at Laurel Suburban (W18)

dalemed

Joined: 25 Dec 2007
Posts: 46

Posted: Mon Aug 31, 2009 4:47 pm Post subject: Re: Shielded wire for wingtip strobe

I ran about 15 feet of wire from a battery to the strobe.  When an AM weather Band radio was anywhere within 10 feet of the circuit, there was considerable noise in the radio.



I didn't get any information with my lights.  Any info I got was from their website.  Where did you read that they are "noise free"?  The spikes I see on the power lines using an oscilloscope would indicate otherwise.



In any event, I don't see where the use of shielded wire would hurt.  I'd like to know the best way/place to ground the shield.



Thanks for your feedback!

_________________
Dale
Zenith Zodiac CH650

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Aug 31, 2009 6:32 pm Post subject: Shielded wire for wingtip strobe

At 07:48 PM 8/31/2009, you wrote:

 	  Quote: 	
		  



I ran about 15 feet of wire from a battery to the strobe.  When an 

AM weather Band radio was anywhere within 10 feet of the circuit, 

there was considerable noise in the radio.



I didn't get any information with my lights.  Any info I got was 

from their website.  Where did you read that they are "noise 

free"?  The spikes I see on the power lines using an oscilloscope 

would indicate otherwise.



In any event, I don't see where the use of shielded wire would 

hurt.  I'd like to know the best way/place to ground the shield.


	


   Shielded wire may not hurt . . . but it most certainly

   won't help. Shielding is NOT a radio frequency interference

   fix. If there is CONDUCTED noise on your strobe supply

   leads then adding a shielded wire only insures that any

   noise present is carried with better efficiency to the

   bus an on to the rest of the airplane. Conducted noise

   must be filtered at the antagonist. This and similar

   products are called for if the devices prove to be troublesome.



http://www.aeroelectric.com/Catalog/AEC/9006/9006-700A.pdf



   Here's a noisy LED driver that has been upgraded with

   an appropriate RF noise filter.



http://www.aeroelectric.com/Catalog/AEC/9051/9051-700A.pdf



   Shielding is more weight, more installed complexity

   and essentially ineffectual on anything except electro-

   statically coupled noises in wire bundles.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Tue Sep 01, 2009 4:52 am Post subject: Shielded wire for wingtip strobe

Somewhat related question. I have the Whelen Comet system for my RV-7A, It

has shielded cable, of course, the power unit out to the wingtip strobe,

with the shield grounded at the power unit.



But, because there's a chance I won't be able to fly my project off the

field where it's now being built, I may hve to take the wings off and truck

it to anothre airport, so I want to use a terminal strip at the inboard wing

root, so that the wires can be disconnected. What should I do with the

shield wire at that location. Should I treat it like any other wire and

connect it at the terminal strip and continue it out to the wing tip? Or

should I just terminate it at the wing root? 



--

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

FisherPaulA(at)johndeere.
Guest

Posted: Tue Sep 01, 2009 5:51 am Post subject: Shielded wire for wingtip strobe

Bob,

I treated it like any other wire at the Molex connectors in the wing root.  Seems to be working so far.  Full disclosure - I've only got 19 hours on it, but I don't have any problems with audio, communications, or navigation equipment.



Paul A. Fisher

RV-7A N18PF

--

dalemed

Joined: 25 Dec 2007
Posts: 46

Posted: Tue Sep 01, 2009 2:05 pm Post subject: Re: Shielded wire for wingtip strobe

Since everyone (including the manufacturer) says I shouldn't need shielded wire, I'm going to go with standard wire and save the weight.



Thanks, everybody!

_________________
Dale
Zenith Zodiac CH650

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Sep 02, 2009 3:22 am Post subject: Shielded wire for wingtip strobe

9/2/2009



Hello Bob, You wrote: "What should I do with the shield wire at that 

location?"



Below is a copy of my 2/16/2005 posting from the archives addressing this 

question.



'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."



==============================================



2/16/2005



Hello Jay, Here is how I solved that problem.



1) I bought some additional connectors and pins of the type that plugs into

the Whelen power supply. They are available from Terminal Town and other

sources.



2) I ran a cut end of the Whelen provided cables in a continuous snake from

each wing tip light all the way to my single power supply in the fuselage

leaving a coil of excess cable in the fuselage near each wing  root.



3) Then I installed the connectors on the cable cut end and plugged into the

power supply.



4) If I ever have to remove my one piece wing I will just unplug the two

cable connectors from the power supply, cut the connectors off the cable

ends, and pull the cables out of the fuselage.##



5) When I reinstall the wing I just go through the same process as when

originally installing the wing by snaking the cable ends dangling from the

wing root into the power supply, reinstalling the connectors, and plugging

back into the power supply.



Considering how seldom one pulls the wings off and how little effort and

cost is involved in cutting off and reinstalling the cable end connectors

this is the best solution for me. It also eliminates an additional cable

connection junction at the wing root.



OC



##PS: If one were a really fastidious and pecunious type one could not cut

off the connectors, but rather just extract the pins from the connectors for

wing removal, and then reinsert the pins upon wing reinstall.



End Msg: #136

=============================================================



Time: 05:52:52 AM PST US

From: "Bob Collins" <bcollinsrv7a(at)comcast.net>

Subject: RE: Re: Shielded wire for wingtip strobe



Somewhat related question. I have the Whelen Comet system for my RV-7A, It

has shielded cable, of course, the power unit out to the wingtip strobe,

with the shield grounded at the power unit.

But, because there's a chance I won't be able to fly my project off the

field where it's now being built, I may hve to take the wings off and truck

it to anothre airport, so I want to use a terminal strip at the inboard wing

root, so that the wires can be disconnected. What should I do with the

shield wire at that location. Should I treat it like any other wire and

connect it at the terminal strip and continue it out to the wing tip? Or

should I just terminate it at the wing root?

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 02, 2009 4:41 am Post subject: Shielded wire for wingtip strobe

At 06:20 AM 9/2/2009, you wrote:

 	  Quote: 	
		  



9/2/2009



Hello Bob, You wrote: "What should I do with the shield wire at that 

location?"



Below is a copy of my 2/16/2005 posting from the archives addressing 

this question.


	


   <snip>



   I think we're talking two different systems here. The

   classic strobe systems are xenon flash tubes supplied

   with high voltage (300v) to light up and triggered by still

   higher voltage (10Kv) to flash. These systems come with

   shielded wire in the installation kit.



   The strobe that is the subject of this tread is an

   LED device. We're not talking about the wires

   between a hv power supply and strobe heads but the

   14v ship's power wire to the device.



   Unless the manufacture calls out shielded wire

   (and this should NEVER happen on a 14v supply

   wire) then potential victim/antagonist pairs

   have been identified and shielding is not useful.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Wed Sep 02, 2009 5:48 am Post subject: Shielded wire for wingtip strobe

Appreciate that but the question isn't whether I should or shouldn't have

connectors. The question is only on the fate of the shielded cable at the

connector. 



--

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Wed Sep 02, 2009 5:49 am Post subject: Shielded wire for wingtip strobe

Mine is the Xenon type.. The manufacturer instructions do not address the

question.http://minnesota.publicradio.org/collections/special/columns/news_c

ut/archive/the_unemployed_series/ 



--

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

rv8iator

Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR

Posted: Wed Sep 02, 2009 6:20 am Post subject: Shielded wire for wingtip strobe

Bob...



You can cut the shielded cable and use a two pin connector of your choosing (molex style, amp mate n loc).  It should be a polarized connector to prevent connection reversal. The short distance that is unshielded at the connector will have no negatve impact on performance nor will it create noise problems for other devices.  

The total unshielded length created by the connector is a fraction of the total system length.



Chris Stone

RV-8

Newberg, OR



--

_________________
C. Stone (RV8iator)

mprather(at)spro.net
Guest

Posted: Wed Sep 02, 2009 6:44 am Post subject: Shielded wire for wingtip strobe

If you choose to insert a connector at the wing joint, it's fine to route

any shielding through that connector.  Dedicate one pin in the connector

for each shield that goes through the connector.  If there's a 'bleeder'

wire with foil shield, just route the bleeder through the connector.  If

the shield is braid, separate the braid from the center, bundle/trim the

braid as necessary to install it in the connector pin, and install the pin

in the connector body.



Unlike coax (RG-5, it's not important for the shielding to be

uninterrupted.  A short length where the shield doesn't surround the

'signal' wire(s) won't  have any impact on noise ingress or egress.  True

coax feedline depends on maintaining controlled impedance along the

transmission line in order to avoid leakage, reflection, and detuning. 

Shielded wire doesn't have the same requirements, as it isn't designed to

offer a controlled impedance environment in the first place.

Regards,



Matt-



[quote] 

 <bcollinsrv7a(at)comcast.net>



 Appreciate that but the question isn't whether I should or shouldn't have

 connectors. The question is only on the fate of the shielded cable at the

 connector.



 --

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 02, 2009 6:52 am Post subject: Shielded wire for wingtip strobe

At 07:47 AM 9/1/2009, you wrote:

 	  Quote: 	
		  

<bcollinsrv7a(at)comcast.net>



Somewhat related question. I have the Whelen Comet system for my RV-7A, It

has shielded cable, of course, the power unit out to the wingtip strobe,

with the shield grounded at the power unit.



But, because there's a chance I won't be able to fly my project off the

field where it's now being built, I may hve to take the wings off and truck

it to anothre airport, so I want to use a terminal strip at the inboard wing

root, so that the wires can be disconnected. What should I do with the

shield wire at that location. Should I treat it like any other wire and

connect it at the terminal strip and continue it out to the wing tip? Or

should I just terminate it at the wing root?


	


    You can use the terminal strip or any of several

    practical connectors. Treat the shield ground like

    a 4th wire in the bundle and favor it with its

    own splice at the terminal strip or in the

    connector.



        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Wed Sep 02, 2009 7:29 am Post subject: Shielded wire for wingtip strobe

//    You can use the terminal strip or any of several

    practical connectors. Treat the shield ground like

    a 4th wire in the bundle and favor it with its

    own splice at the terminal strip or in the

    connector.

Will do. Many thanks!

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Sep 02, 2009 7:50 am Post subject: Shielded wire for wingtip strobe

At 07:40 AM 9/2/2009, you wrote:



 	  Quote: 	
		     <snip>



   I think we're talking two different systems here. . .


	


   Oops . . . I see there were two threads of discussion

   on similar topics. Got my mouse cord tangled around

   my SEND button. The response was accurate with

   respect to the simple-ideas, just not well tied

   to the thread  . . .



   Bob . . .

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Sep 02, 2009 6:36 pm Post subject: Shielded wire for wingtip strobe

9/2/2009



Hello Bob, Yes I understand that. But why not finesse the problem regarding 

the fate of the cable shield at the connectors and also the requirement for 

any connectors at all when they are not necessary with the technique that I 

described?



In this case simpler is both better and cheaper.



'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."



PS: Recall one of the axioms of building: "That which you leave out cannot 

cause you problems later on."



======================================



---

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Thu Sep 03, 2009 3:14 am Post subject: Shielded wire for wingtip strobe

//PS: Recall one of the axioms of building: "That which you leave out cannot

cause you problems later on."



Heh heh. You know, though, that's not a very good axiom. (g)

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

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