klehman(at)albedo.net
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 Posted: Mon Apr 11, 2011 4:40 pm Post subject: Which Diode part number to use for dual power feed? |
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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.
Ken
On 4/11/2011 5:32 PM, Robert L. Nuckolls, III wrote:
| Quote: | At 01:55 PM 4/11/2011, you wrote:
>
>
> Guys,
> Can someone point me to the right type and part no. of Diode to use in
> a circuit providing a dual power feed to a single piece of equipment?
>
> I have an EIS4000 that has a single power input. I'd like to provide
> both E-bus power and an Aux Batt power feed to it.
>
> I don't want the E-bus power backfeeding into my Aux Batt.
What does the architecture of your ship's
power system look like? How many sources
of power are available to run the EIS4000
before you added another battery?
Finally, what's the driving concerns making
supplying an engine monitoring system with 'last-
ditch' power? I'm unaware of any incident where
a plane/pilot experienced an unhappy day because
the pilot was unable to know oil pressure or any
other parameter unique to engine operations.
I've brought airplanes home with broken tach
cables because I KNEW that redline could not
be exceeded on that particular airplane at full
throttle during a climb to altitude or after
desired altitude was reached. When in doubt, back
it down some to achieve max maneuvering airspeed.
Other parameters can be considered with respect to
max ratings with similar avenues of thourght and
understanding.
If you've got a judiciously maintained main battery
and a modern alternator of any stripe, (and best
yet a second engine driven power source) you are
FAR more likely to experience failure of the
LCD display on the instrument than you are to
experience loss of power to that instrument.
A cursory study of aviation accidents and incidents
worthy of reporting to the archivists will show
that electrical systems issues are exceedingly
rare players in aircraft accidents. Even when
the occasional 'dark n stormy night' story
discusses electrical systems issues, we find
that they could have been easily avoided by judicious
architecture changes COMBINED with a pilot's
understanding of system operation and limits.
But if your heart is set on adding this feature
to your project, the bridge diode rectifier with
fast-on tabs like
http://aeroelectric.com/Pictures/Misc/s401-25.jpg
will do the job. Power to EIS comes from terminal
on the odd terminal set 90 degrees to the rest.
Power in from the two sources goes to the most
adjacent terminals. The terminal opposite the output
or (+) corner is ignored.
Suitable parts include Radio Shack 276-1185, B&C
S401-25, All Electronics FWB-252 and others. Any
diode assembly you can find that looks like this
will do the job.
Emacs!
Bob . . .
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