Today's Message Index:
----------------------
1. 06:38 AM - Fuse Sizing (Jeff Page)
2. 07:22 AM - Re: Nippondenso alternator question (Paul)
3. 08:11 AM - Flight Test Architecture (lee.logan@gulfstream.com)
4. 10:46 AM - Re: power to handheld gps. (Larry L. Tompkins, P.E.)
5. 01:11 PM - power to handheld gps (bob noffs)
6. 07:15 PM - Re: power to handheld gps. (Joe)
Message 1
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I just looked through Chapter 10 and didn't find any guidance on
selecting the size of a fuse.
I am quite sure that a 10A fuse is designed to blow at, or barely
above, 10A and thus would be unsuitable for protecting a circuit with
an actual current flow of 10A.
In my case, I have a landing light circuit totalling 9.2A. Mostly it
is 4.6A to each bulb, but there are some common wires at the switch
that carry both loads.
Looking at Bob's Wire Size Selection chart with 10C Rise (which makes
wire selection incredibly easy, compared to the graphs in 43-13-1B), I
could use 18 gauge wire in the wings and 14 gauge wire where both
currents are common.
I can't use a double pole switch to wire each light independently with
separate fuses, because I am already using a double pole switch to
give me off, on or wig wag.
So I need a single circuit with a single fuse. The fuse needs to be
sufficient for the total current. This also means upgrading the 18
gauge wire in the wings to 14 gauge, to avoid having a fuse too big
for the wire.
So my gut feel is to use the 35C Rise part of the table to pick a
current rating for the fuse, which would give me 15A fuse for 14 gauge
wire. Correct ?
Also, the calculations quite clearly include the return to ground part
of the current when calculating wire losses due to resistance. What
equivalent resistance value would be typical of the frame of aluminum
aircraft when used for the ground return ?
Thanks for your advice,
Jeff Page
Dream Aircraft Tundra #10
Message 2
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Subject: | Re: Nippondenso alternator question |
Depends on the specific ND alternator. The ones I have experience with have
a switch (internal to the regulator) that provides a ground at the "L"
terminal where (in automobiles) an "Idiot Light" is connected across the "L"
to the"IG" and indicates the alternator is getting power to the "IG terminal
but the Alternator's "B" lead Voltage is not high enough to charge the
battery. The ground is removed (and the light goes out) when the alternator
starts supplying power. There are apparently some ND alternators that use
the "L" terminal to power the internal regulator and in that case the "L"
must have a specific light connected to provide starting voltage. In that
case the light is powered by the regulator current before the power from the
"B" lead takes over and the light goes out indicating the alternator is
working properly. I have never seen that type of ND alternator but there are
a few people on other groups who state the Light is required or the
alternator will not provide power. If your alternator requires a light it
should be the light specified in the original application. This provides the
proper current to the regulator.
The only ND alternators I have data for shows the "L" terminal as a simple
switch to ground and personal testing shows the alternator can be turned on
and off while running with no connection to the "L" lead (simply switching
power to the "IG" connection. Turning the alternator off under power is not
recommended as that causes an alternator "load dump" which may damage the
alternator if its disconnected under higher amp charging current. Hasent
happened to me up to a tested 40 amp load dump but still to be avoided
except when the alternator regulator fails high "B" terminal voltage. The
addition of a transorb of sufficient power will shunt the load dump and
protect the alternator but that is a different topic.
ND alternators come in many versions of internal regulators, some sense the
charging voltage thru the IG terminal to accurately charge the battery based
on the battery terminal voltage not the "B: lead voltage.
Thus as originally designed for auto use, the "B" lead is hard wired
directly to the battery. The IGN switch is turned on before starting and the
"idiot light" is powered by the "IG" power input and the regulator internal
ground. There is no requirement for the "L" terminal to be connected to
anything (at least with the ND alternators I have evaluated). If there is a
connection it must limit the current as the internal ground switch may
require external current limiting. In an aircraft application generally
there is no need for any connection to the "L" terminal as the alternator
wiring and its current generation is monitored in a different method. Be
sure your design provides a connection to the battery before starting the
engine.
Sorry but perhaps the supplier of the alternator can tell you. If you
purchased the add on alternator as a specific Kit for your engine. In any
event If the light is required you must install the proper one. Do not
connect the "L" terminal to any thing else other than the proper bulb. Not
an LED as if a light is required the LED with limiting resistor will not
pass enough current and clearly nothing else. If the light is not required
(my personal experience its not) then there is no need if you have other
ways to tell if the alternator is functioning properly like current monitor
or bus voltage. The ND alternator generally requires approx 1500 alternator
RPM to start generation. In an automobile this is generally around the just
above idle rpm of the engine and again in an auto the idiot light can turn
on at slow idle and go out just above that rpm.
Paul
----- Original Message -----
From: "darinh" <gerns25@netscape.net>
Sent: Sunday, July 06, 2008 10:35 PM
Subject: AeroElectric-List: Nippondenso alternator question
>
> This is my last question...at least for tonight. I have a Rotax 914 and
> the onboard generator is not enough so I added a optional 40 amp
> nippondenso alternator. It has the alt. output and a plug labeled "L" and
> "IG". I assume the "IG" is the field circuit and the "L" is obviously the
> lamp circuit.
>
> The question is this: I have been told that the alt. must have the
> indicator lamp installed for it to charge the battery. I don't really
> want to add another "idiot" light to my panel as I already had two for the
> turbo control unit and one for my GRT EIS. Can I run it through the EIS
> light or will this screw it up? If I have to have a light, I may just
> mount it behind the panel. Lastly, I was told this light cannot be an
> LED...is this also correct?
>
> --------
> Darin Hawkes
> Series 7 (Final Assembly)
> 914 Turbo
> Kaysville, Utah
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=191541#191541
>
>
Message 3
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Subject: | Flight Test Architecture |
Good information, Bob, thanks for taking the time to answer my questions
about electrical system performance. Good point too, that Z-13/8 with a
big battery back-up is really designed to get you to destination, not just
back on the ground safely. As I said, "...I would already be headed for
good weather/divert/home base/whatever if the SD-8 let go" too, but that is
clearly situationally dependant (the "whatever" clause).
You also said you think a voltmeter indicating SD-8 performance would be
useful. Are there any schematics/parts recommendations available for that?
I'd prefer to have the voltmeter on my EDM-900C do double duty depending
upon which alternator were supplying power to the system, but don't know if
that is possible or not.
Thanks again for the recommendations.
Lee...
Message 4
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Subject: | Re: power to handheld gps. |
Bob:
My experience is the smallest connectors are ones used in RC aircraft
and car models. They are sort of a mini Molex connector. I was able to
obtain then at a local hobby shop.
Hope this helps.
Larry Tompkins
Message 5
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Subject: | power to handheld gps |
thanks to all who offered good solutions to my power outlet question. i
finally settled on a power jack assembly similar to what you find on the
business end of a 12 volt transformer used to power just about you name
it!
my new dilemma is now the gps. the large screen on the airmap 2000
which is great for viewing also makes the unit about the size of a 2 car
garage. i now am having second thoughts about where to mount it! but
when i decide , i know how to get power to it!
bob noffs
Message 6
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Subject: | Re: power to handheld gps. |
Bob Noffs,
Here are some Radio Shack parts that might work for you:
Size N Coaxial DC Power Plug (2-Pack)
$2.99
Model: 274-1573
Catalog #: 274-1573
http://www.radioshack.com/product/index.jsp?productId=2102488&cp=&sr=
1&origkw=dc+plug&kw=dc+plug&parentPage=search
Size N Panel-Mount Coaxial DC Power Jack
$2.99
Model: 274-1576
Catalog #: 274-1576
http://www.radioshack.com/product/index.jsp?productId=2102489&cp=&sr=
1&origkw=dc+jack&kw=dc+jack&parentPage=search
Joe
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