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nuckolls.bob(at)aeroelect
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 Posted: Tue Apr 12, 2011 8:09 am Post subject: Which Diode part number to use for dual power feed? |
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At 07:36 PM 4/11/2011, you wrote:
| Quote: |
If the EIS is to be your primary voltage monitor and low voltage
warning don't forget that it will read low by around 0.6 volts if
powered through a silicon diode. That said I think any 1N5400 series
(1N5401, 1N5402, etc.) would be sufficient as I think I only have a
2 or 3 amp fuse on my EIS4000.
Further with the diodes you will not get a low voltage warning from
the main EIS voltmeter if the main supply fails. AUX inputs can be
used for that purpose though.
Another approach is a two position power switch if you really want
it. I can see some comfort value in having a voltage reading if
operating an electric dependent engine after an alternator failure
but I did not consider it essential.
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Excellent points . . .
Even when such multi-purpose instruments are operated
from the e-bus, normal voltage readings would be at
some level below real voltage readings. Which is not
a particularly relevant fact.
When architecture decisions are finalized, the effects
to CALIBRATION can and should be considered. Your
'normal' voltage readings for standard ops might now
be 13.5 volts as opposed to 14.2 . . . this is an
entry into the POH, not a fact that calls for any
agonizing over making tweaks to architecture or work-
arounds (like substituting switches for diodes).
If the EIS4000 is your only source for low voltage
annunciation, then you might consider running the
EIS from the main bus. If you loose the alternator
in cruising flight and your plan-B calls for
shutting down the main bus for ENDURANCE, I see
no increase in risks for having the EIS be dark.
Leave the engine settings alone and guess what?
They'll be the same when you bring the main bus
back up for approach to landing.
This discussion highlights the reason way we changed
the E-bus from "essential" to "endurance" some years
back. Essential goodies are those necessary to
get you back on the ground under present conditions.
Way back when, if your Narco VT-1 Super-Homer went
TU just before you intended to shoot a LOC approach,
your plan-B called for an airport in VMC . . . unless
you were really "uptown" with two VOR/LOC radios.
The point is that critical equipment be (1) backed
up with an independent substitute or (2) change
of flight plans to work around criticality of that
piece of equipment.
Providing multiple power sources in an already
failure tolerant architecture assumes that the
highest risk of failure is loss of power. Lots
of band-aid on top of band-aid while assuming
that the system itself is impervious to all other
failures.
Bob . . .
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plevyakh
Joined: 10 Jan 2011
Posts: 39
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| Posted: Tue Apr 12, 2011 9:49 am Post subject: Re: Which Diode part number to use for dual power feed? |
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After considering your points I simplified and stayed with the Z10/8.
My EIS4000 is on the Endurance bus along with my dual EFIS/AHRS. I'll flip the EBus Alternate feed on prior to engine start, eliminating the brown out potential, which will give the AHRS time to align prior to shaking the airplane around with engine start....and have my EIS on line to show oil pressure right after engine start.
I've attached my latest architecture version. If anyone sees an error in wiring, please let me know. I'm learning tons here and greatly appreciate your inputs.
Thank-you.
Howard
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| Description: |
| Four page printable version |
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Download |
| Filename: |
PRINTABLE_Electric GlaStar w_dual lightspeeds architecture v04_12Apr2011.pdf |
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220.85 KB |
| Downloaded: |
264 Time(s) |
| Description: |
| Al electric GlaStar w/ Dual Lightspeeds, Dual GRT EFIS, EIS4000 (Based on Z10/8). |
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Download |
| Filename: |
Electric GlaStar w_dual lightspeeds architecture v04_12Apr2011.pdf |
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321 Time(s) |
_________________
Howard Plevyak
GlaStar / Cincinnati, Ohio |
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