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Mag switch through d-sub connector

 
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donjohnston



Joined: 13 Dec 2009
Posts: 203

PostPosted: Fri Jun 13, 2014 12:19 pm    Post subject: Mag switch through d-sub connector Reply with 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?

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nuckolls.bob(at)aeroelect
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PostPosted: Sat Jun 14, 2014 6:07 am    Post subject: Mag switch through d-sub connector Reply with quote

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 . . .


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donjohnston



Joined: 13 Dec 2009
Posts: 203

PostPosted: Sat Jun 14, 2014 10:27 am    Post subject: Re: Mag switch through d-sub connector Reply with quote

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]


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nuckolls.bob(at)aeroelect
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PostPosted: Sat Jun 14, 2014 11:44 am    Post subject: Mag switch through d-sub connector Reply with quote

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 . . .


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stearman456



Joined: 14 Aug 2010
Posts: 49

PostPosted: Sun Oct 05, 2014 4:38 am    Post subject: Re: Mag switch through d-sub connector Reply with quote

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.

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PostPosted: Tue Oct 07, 2014 2:22 pm    Post subject: Mag switch through d-sub connector Reply with quote

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
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PostPosted: Tue Oct 07, 2014 2:27 pm    Post subject: Mag switch through d-sub connector Reply with 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 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?




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stearman456



Joined: 14 Aug 2010
Posts: 49

PostPosted: Tue Oct 07, 2014 3:18 pm    Post subject: Re: Mag switch through d-sub connector Reply with quote

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


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PostPosted: Tue Oct 07, 2014 4:09 pm    Post subject: Mag switch through d-sub connector Reply with quote

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 . . .


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PostPosted: Tue Oct 07, 2014 5:35 pm    Post subject: Mag switch through d-sub connector Reply with quote

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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