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Adelk123



Joined: 04 Aug 2018
Posts: 2

PostPosted: Sat Aug 04, 2018 5:42 pm    Post subject: Power Reply with quote

I’ve got a question for the group. I’m currently powering dual board ECU through a DPDT switch with each side of the switch switching different power sources.

I’ve decided I don’t want to use two different power sources for the ECUs. I prefer to just power the ECUs directly off of my engine Bus. This bus is an always hot battery bus mounted at the aft end of the Aircraft. With the floors being closed up, access is challenging but not impossible. I had considered the idea of each ECU having its own circuit powered off of the same bus. I am currently out of additional circuits on that fuse box though. I have considered combining with a circuit that I can readily access. I have two small led baggage lights powered off of that same bus that I could tie in to fairly easily. If there is no real benefit to having two circuits on the same bus due to the switch still being a single point of failure, would it be acceptable to stack the terminals on one side of the switch to power both ECUs from one source? The current for both combined is less than 1/2 of an amp.

I realize that doing so still creates a single point of failure so I’m looking for advice finding a solution that I might not of already thought of.

Thanks for any advice.


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nuckolls.bob(at)aeroelect
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PostPosted: Sat Aug 04, 2018 6:02 pm    Post subject: Power Reply with quote

This bus is an always hot battery bus mounted at the aft end of the Aircraft. With the floors being closed up, access is challenging but not impossible. I had considered the idea of each ECU having its own circuit powered off of the same bus.

Depending on how 'orderly' the lay of wires
is in the bundle carrying the current feeder,
it may be possible to lap solder TWO wires to
the end of the single wire thus converting the
single wire into a 'tag line' for installation
of a new pair.

I am currently out of additional circuits on that fuse box though. I have considered combining with a circuit that I can readily access. I have two small led baggage lights powered off of that same bus that I could tie in to fairly easily.

Use one of those . . . separating them
eliminates the single point of failure
for one ECU (or intermediate wiring faults)
from tripping both systems off line.

If there is no real benefit to having two circuits on the same bus due to the switch still being a single point of failure, would it be acceptable to stack the terminals on one side of the switch to power both ECUs from one source? The current for both combined is less than 1/2 of an amp.

Your choice . . . but I couldn't sell that
idea onto a TC aircraft. I presume you
currently have a 2nd source on a bus up
front? I think I'd leave it there. The
'plum' in your FMEA pudding is the exceedingly
remote probability of loosing BOTH sources
during the consumption of ONE tank of gas.
Exactly what those sources are is irrelevant
as long as they too do not suffer a 'cow pie'
in their FMEA.

This leaves JUST the switch which, in an
OBAM aircraft, will see perhaps a couple
hundred actuations per year . . . at your
stated load, the electrical life is infinite.
The mechanical life will be more environmentally
driven than service driven. I'd just replace
the switch for grins every 5 years or so . . .

I've seen more switches (even the $high$ mil-spec
devices) fail due to chronological AGE in
a less than pleasant environment than
from service life . . .




Bob . . .


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Adelk123



Joined: 04 Aug 2018
Posts: 2

PostPosted: Sat Aug 04, 2018 8:10 pm    Post subject: Re: Power Reply with quote

Ok, thanks for the feedback.

Yes, I currently have the secondary ECU powered another bus in the front of the airplane. What I failed to think out completely was the load shedding side of things. My intent was to have the ability to load shed everything except the critical engine items, the second ECU not being critical. The problem is the switchology has become more complex than I like due to the injector relays and their relationship with the ECUs. I feel it’s a safer and a more simplified solution just to have the same power source with both ECUs and leaving no possibility to inadvertently shut down the engine during load shedding.


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PostPosted: Sun Aug 05, 2018 7:33 am    Post subject: Power Reply with quote

At 11:10 PM 8/4/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "Adelk123" <andydelk(at)mac.com>

Ok, thanks for the feedback.

Yes, I currently have the secondary ECU powered another bus in the front of the airplane. What I failed to think out completely was the load shedding side of things. My intent was to have the ability to load shed everything except the critical engine items, the second ECU not being critical. The problem is the switchology has become more complex than I like due to the injector relays and their relationship with the ECUs. I feel it’s a safer and a more simplified solution just to have the same power source with both ECUs and leaving no possibility to inadvertently shut down the engine during load shedding.


Hmmmm . . . perhaps we can help sort the
sands of your FMEA. Can you describe the
current architecture . . . or better yet
. . . post a drawing? What is your base
architecture . . . one of the z-figures?
Have you done a load analysis to define
your actions upon loss of alternator?



Bob . . .


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BARRY CHECK 6



Joined: 15 Mar 2011
Posts: 687

PostPosted: Sun Aug 05, 2018 10:46 am    Post subject: Power Reply with quote

Scotty:
"The more they overtake the plumbing the easier it is to stop up the drain."

On Sun, Aug 5, 2018 at 11:38 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

Quote:
At 11:10 PM 8/4/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "Adelk123" <andydelk(at)mac.com (andydelk(at)mac.com)>

Ok, thanks for the feedback.

Yes, I currently have the secondary ECU powered another bus in the front of the airplane.  What I failed to think out completely was the load shedding side of things. My intent was to have the ability to load shed everything except the critical engine items, the second ECU not being critical. The problem is the switchology has become more complex than I like due to the injector relays and their relationship with the ECUs. I feel it’s a safer and a more simplified solution just to have the same power source with both ECUs and leaving no possibility to inadvertently shut down the engine during load shedding.


  Hmmmm . . . perhaps we can help sort the
  sands of your FMEA. Can you describe the
  current architecture . . . or better yet
  . . . post a drawing?  What is your base
  architecture . . . one of the z-figures?
  Have you done a load analysis to define
  your actions upon loss of alternator?



  Bob . . .


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yellowduckduo(at)gmail.co
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PostPosted: Sun Aug 05, 2018 3:03 pm    Post subject: Power Reply with quote

15 years ago when I was making similar decisions I picked up a second
set of injectors and fuel rail from the local auto wrecker and welded
them in.
It simplified the "switchology" quite a bit.
Both ecu's run all the time and are hard wired to the negative side of
their dedicated injectors.
Manual toggle switches send positive power to whichever set of injectors
I wish to operate.
Z-14 allowed independent powering of the two systems without using any
diodes or relays.
Same thing with the ignitions.
(Now Scotty has to stop up two drains to spoil my day...)
Ken

On 05/08/2018 2:45 PM, FLYaDIVE wrote:
Quote:
Scotty:

"The more they overtake the plumbing the easier it is to stop up the
drain."

On Sun, Aug 5, 2018 at 11:38 AM Robert L. Nuckolls, III
<nuckolls.bob(at)aeroelectric.com <mailto:nuckolls.bob(at)aeroelectric.com>>
wrote:

At 11:10 PM 8/4/2018, you wrote:
>
> <andydelk(at)mac.com <mailto:andydelk(at)mac.com>>
>
> Ok, thanks for the feedback.
>
> Yes, I currently have the secondary ECU powered another bus in
> the front of the airplane. What I failed to think out completely
> was the load shedding side of things. My intent was to have the
> ability to load shed everything except the critical engine items,
> the second ECU not being critical. The problem is the switchology
> has become more complex than I like due to the injector relays
> and their relationship with the ECUs. I feel it’s a safer and a
> more simplified solution just to have the same power source with
> both ECUs and leaving no possibility to inadvertently shut down
> the engine during load shedding.
>

Hmmmm . . . perhaps we can help sort the
sands of your FMEA. Can you describe the
current architecture . . . or better yet
. . . post a drawing? What is your base
architecture . . . one of the z-figures?
Have you done a load analysis to define
your actions upon loss of alternator?
Bob . . .



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nuckolls.bob(at)aeroelect
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PostPosted: Sun Aug 05, 2018 3:54 pm    Post subject: Power Reply with quote

Quote:
I feel it’s a safer and a more simplified solution just to have the same power source with both ECUs and leaving no possibility to inadvertently shut down the engine during load shedding.


This was a component of the philosophy for the
E-bus. The idea was to have maximum endurance
loads on the e-bus and battery bus. If the alternator
quits you (1) close alternate e-feed, (2) open battery
master contactor.

There are no switch ops associated with an appliance
or system, hence the probability of inadvertently
shutting down and endurance load was essentially
zero.



Bob . . .


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