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Mag switch through d-sub connector

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donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Fri Jun 13, 2014 12:19 pm Post subject: Mag switch through d-sub connector

I'm trying to clean up the connections to a switch panel that has the mag switches. Is a D-sub connector appropriate for mag switch connections?

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jun 14, 2014 6:07 am Post subject: Mag switch through d-sub connector

At 03:19 PM 6/13/2014, you wrote:

 	  Quote: 	
		  



I'm trying to clean up the connections to a switch panel that has 

the mag switches. Is a D-sub connector appropriate for mag switch connections?


	


   Are you intending to run p-leads through a

   connector with other system wires? I presume

   that you're wanting to 'unplug' all wires

   from a panel so that it can be easily removed . . .

   This practice is generally discouraged from

   the simple perspective of complexity driven

   drop in reliability . . . every connector adds

   three new joints to every wire.



   The more sanitary practice is to make your

   wire bundle to the panel of sufficient length

   that it can be removed and supported in some

   way that allows access but without breaking

   the bundle.



   If you do decide to put connectors in the

   p-leads, run them through their own separate

   connector and bring the shields through the

   connector on their own pins.

   Bob . . .

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Jun 14, 2014 10:27 am Post subject: Re: Mag switch through d-sub connector

 	  nuckolls.bob(at)aeroelect wrote: 	
		  At 03:19 PM 6/13/2014, you wrote:

 	  Quote: 	
		  



I'm trying to clean up the connections to a switch panel that has 

the mag switches. Is a D-sub connector appropriate for mag switch connections?



	


   Are you intending to run p-leads through a

   connector with other system wires? I presume

   that you're wanting to 'unplug' all wires

   from a panel so that it can be easily removed . . .

   This practice is generally discouraged from

   the simple perspective of complexity driven

   drop in reliability . . . every connector adds

   three new joints to every wire.

	




In this case, the switches that I'm using have solder lugs so there's already three joints. I'm currently using faston and spade connectors for each wire.  I was simply trying to consolidate the connections to a single DB-25 connector. 



 	  Quote: 	
		  

   The more sanitary practice is to make your

   wire bundle to the panel of sufficient length

   that it can be removed and supported in some

   way that allows access but without breaking

   the bundle. 	




That's what I'm doing now. But identifying each wire and mating it can be really tedious especially considering the location.



 	  Quote: 	
		  

   If you do decide to put connectors in the

   p-leads, run them through their own separate

   connector and bring the shields through the

   connector on their own pins. 	




I can certainly do that.  I just didn't know if the mags should be physically segregated to a different connector. 



   Bob . . .[/quote]

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jun 14, 2014 11:44 am Post subject: Mag switch through d-sub connector

 	  Quote: 	
		  

That's what I'm doing now. But identifying each wire and mating it 

can be really tedious especially considering the location.\


	


    Odds are that you can bundle the mag-wires in with

    other, low victim-potential wires, with no difficulty.

    Taking them through a connector doesn't add

    significant risk . . . the wires get pre-flight

    tested. Good compromise is run them through

    their own connector.

   Bob . . .

stearman456

Joined: 14 Aug 2010
Posts: 49

Posted: Sun Oct 05, 2014 4:38 am Post subject: Re: Mag switch through d-sub connector

If you ran the P leads through the firewall using an old fashioned Cannon plug, could you use a three pin plug and run both shields through one pin with no noise consequences, or would a separate pin for each shield be required?  Pins 1 & 2 of course would carry the P leads themselves.

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 07, 2014 2:22 pm Post subject: Mag switch through d-sub connector

At 07:38 2014-10-05, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "stearman456" <warbirds(at)shaw.ca>



 If you ran the P leads through the firewall using an old fashioned Cannon plug  could you use a three pin plug and run both shields through one pin with no noise consequences, or would a separate pin for each shield be required?



 	


   Your subject speaks to the D-subs . . . 



 [img]cid:7.1.0.9.0.20141007171425.04d77a40(at)aeroelectric.com.0[/img] 



    but you write about 'old fasion Cannon connectors

    which I take to mean something more like this . . .



  [img]cid:7.1.0.9.0.20141007171425.04d77a40(at)aeroelectric.com.1[/img] 



 

   The classic D-Sub isn't a very robust connector

   for service as a fire wall penetration but the

   MS31xx series connectors are fine. You can combine

   the shields on one pin. Ground the shields at

   engine end only. Use the shields as ground conductor

   for the "G" terminal on the mag switch.



 

 

   Bob . . .

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ceengland7(at)gmail.com
Guest

Posted: Tue Oct 07, 2014 2:27 pm Post subject: Mag switch through d-sub connector

No electrical difference, but lots more failure points. A failed-open point won't stop the engine, but can be very dangerous on the ground (engine can fire with switches off). A less than perfect job of installation (of any splice/connector installation) could cause a failed-shorted problem, which *could* stop the engine.



Charlie

On Sun, Oct 5, 2014 at 7:38 AM, stearman456 <warbirds(at)shaw.ca (warbirds(at)shaw.ca)> wrote:

[quote]--> AeroElectric-List message posted by: "stearman456" <warbirds(at)shaw.ca (warbirds(at)shaw.ca)>

 

 If you ran the P leads through the firewall using an old fashioned Cannon plug  could you use a three pin plug and run both shields through one pin with no noise consequences, or would a separate pin for each shield be required?

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=431522#431522

 

 

 

 

 

 

 

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stearman456

Joined: 14 Aug 2010
Posts: 49

Posted: Tue Oct 07, 2014 3:18 pm Post subject: Re: Mag switch through d-sub connector

Thanks Bob.   The MS31xx type of plug was what I had in mind.  I hadn't thought of grounding the switch through the shields but that makes sense.  Thanks again.



Dan

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 07, 2014 4:09 pm Post subject: Mag switch through d-sub connector

At 17:25 2014-10-07, you wrote:

 	  Quote: 	
		  No electrical difference, but lots more failure points. A 

failed-open point won't stop the engine, but can be very dangerous 

on the ground (engine can fire with switches off).


	


   A potentially latent failure than is pre-flight

   detectable during run-up . . . low risk.



   Bob . . .

ceengland7(at)gmail.com
Guest

Posted: Tue Oct 07, 2014 5:35 pm Post subject: Mag switch through d-sub connector

On 10/7/2014 7:05 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 17:25 2014-10-07, you wrote:

> No electrical difference, but lots more failure points. A failed-open 

> point won't stop the engine, but can be very dangerous on the ground 

> (engine can fire with switches off).



   A potentially latent failure than is pre-flight

   detectable during run-up . . . low risk.



An in-flight failure would be detectable prior to shutdown, too. If 
	


that's part of the shutdown procedure, but it rarely is.

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