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Why multiple skinny power wires?

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millner(at)me.com
Guest

Posted: Sun Sep 16, 2012 11:44 am Post subject: Why multiple skinny power wires?

On 9/14/2012 10:26 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   Redundancy is not well addressed

    . . . one of the wires could be bad and you\

    wouldn't know it


	


Bob, on the GNS480 (nee CNX80) IImorrow/Apollo (now Garmin) addressed 

that by inhibiting certain functions of the radio if both leads weren't 

hot.  For instance, I think the comm radio or the VOR receiver quits if 

both leads aren't hot.



Of course, if you didn't know that, you'd think you'd have a bad 

radio... and nowadays, Garmin will happily relieve of you $1000 to 

advise that "bench tests OK"... 



Paul



-- 

Please note my new email address!

millner(at)me.com

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tim2542(at)sbcglobal.net
Guest

Posted: Sun Sep 16, 2012 12:59 pm Post subject: Why multiple skinny power wires?

The 430 does this with nav and comm functions. Not sure why you would ever want only one of functions but the option is there. 

Tim

Sent from my iPhone

On Sep 16, 2012, at 12:42 PM, Paul Millner <millner(at)me.com> wrote:

 	  Quote: 	

 On 9/14/2012 10:26 AM, Robert L. Nuckolls, III wrote:

> Redundancy is not well addressed

>   . . . one of the wires could be bad and you\

>   wouldn't know it

 Bob, on the GNS480 (nee CNX80) IImorrow/Apollo (now Garmin) addressed that by inhibiting certain functions of the radio if both leads weren't hot.  For instance, I think the comm radio or the VOR receiver quits if both leads aren't hot.

 Of course, if you didn't know that, you'd think you'd have a bad radio... and nowadays, Garmin will happily relieve of you $1000 to advise that "bench tests OK"... 

 Paul

 -- 

 Please note my new email address!

 millner(at)me.com

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grosseair(at)comcast.net
Guest

Posted: Sun Sep 16, 2012 1:55 pm Post subject: Why multiple skinny power wires?

Those are multiple wires to multiple pins, not multiple wires to the 

SAME pin as in the original post from the SkyRadar installer.



The 430 specifies a 10A CB on the com and a 5A CB for the Nav. I suppose 

they could have used one 15A circuit, but that would require larger wire 

that wouldn't fit in the connector pins. That makes sense.



John Grosse



 	  Quote: 	
		   Tim Andres <mailto:tim2542(at)sbcglobal.net>

 September 16, 2012 3:58 PM

 

 <tim2542(at)sbcglobal.net>



 The 430 does this with nav and comm functions. Not sure why you would 

 ever want only one of functions but the option is there.

 Tim



 Sent from my iPhone

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Sep 16, 2012 2:53 pm Post subject: Re: Why multiple skinny power wires?

I have no idea. 



However...consider the case where several high-current devices are driven off a single power source simultaneously. In that case a substantial amount of weight can be saved by using "tree" architecture for the wiring harness, instead of "bus" architecture. Essentially each high current device likely to be on simultaneously has it's own smaller conductor. All these are bundled into the main trunk, which gets larger and larger the closer to the battery you get. At the battery, the tree has many separate circuit breakers and perhaps remote switches.



Advantage: Lighter weight.

Disadvantage: Greater complexity.



The fraction of aircraft weight attributed to wiring is reasonably small. However, if you're going to Jupiter...or building a multi-engine electric airplane, it's a big concern.

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 17, 2012 11:18 am Post subject: Why multiple skinny power wires?

At 04:53 PM 9/16/2012, you wrote:




Those are multiple wires to multiple pins, not multiple wires to the 

SAME pin as in the original post from the SkyRadar installer.



   Yes, the original thread was discussing twin ground

   and twin power wires to a single function device.



The 430 specifies a 10A CB on the com and a 5A CB for the Nav. I 

suppose they could have used one 15A circuit, but that would require 

larger wire that wouldn't fit in the connector pins. That makes sense.



   When you have lots of capability built into a single

   box, it should be expected that some features be

   powered separately from each other. In this case

   we might see multiple paralleled ground wires but

   multiple, independent power feeders.



   There is no common convention for these decisions.

   When in doubt, do what the manufacturer's instructions

   call out.

The 430 does this with nav and comm functions. Not sure why you would 

ever want only one of functions but the option is there.



   Not so much for WANTING only one at a time but a

   deliberate isolation such that failure of one system

   doesn't pop the protection and take down multiple

   systems.

   Bob . . .

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