Today's Message Index:
----------------------
1. 08:23 AM - Re: Re: getting the horse back out in front of the cart . . . (Robinson, Chad)
2. 08:36 AM - Re: Engine cranking problem in Glasair (Richard May)
3. 10:57 AM - Garmin-AT ACU resolver questions (Ralph E. Capen)
4. 01:36 PM - 2003 List Fund Raiser - Please Support Your Lists... (Matt Dralle)
5. 02:41 PM - Dual Battery System With Standby Battery (Gabe A Ferrer)
6. 03:04 PM - Re: getting the horse back out in front . . . (Robert L. Nuckolls, III)
7. 04:31 PM - Re: Current Limiters (Ernest Kells)
8. 06:49 PM - Re: Ground wire (John Szantho)
9. 09:18 PM - Re: Garmin-AT ACU resolver questions (Alex Peterson)
10. 09:37 PM - Re: Re: getting the horse back out in front . . . (Jim Sower)
Message 1
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| Subject: | Re: getting the horse back out in front of the |
cart . . .
--> AeroElectric-List message posted by: "Robinson, Chad" <crobinson@rfgonline.com>
> "Robert L. Nuckolls, III" wrote:
> >
> > ????? That's what a shunt does for you. Let's you measure
> > current in a remote location on tiny wires irrespective of
> > how much current is being measured/monitored.
>
> Jim Sower wrote:
>
> I knew ammeters had a shunt. Are you saying that I could remove the shunt from
> the meter on the panel and remote it all the way back to the firewall (Velocity)
> and run a pair of 26 gauge wires back to the panel and connect directly to the
> movement (or something analogous to this with an off-the-shelf calibrated shunt)?
> That might solve the problem if the "movement" of the current meter was any good
> or I could obtain an easily installable substitute.
Ah-ha! The confusion becomes clear! Jim, ammeters with internal shunts are actually
not the standard practice here, or at least not in homebuilts (I don't know
what certified ships use - Bob?), and for the exact reason you describe - it's
a pain to run the wiring. You would normally use a shunt (essentially a simple
current-to-voltage converter) located in the exact spot you want to measure,
and NOT run huge 4AWG or similar wires up behind your panel. And yes, you
can then run a much smaller and lighter wire pair up to the meter.
B&C has a whole page of shunts of various sizes at:
http://www.bandcspecialty.com/cgi-bin/ez-catalog/cat_display.cgi?15X358218
Then you use an ammeter designed for an external shunt, which is really just a
voltmeter with a typical range of 0-50mV. The face of the "voltmeter" is painted
with a scale calibrated to the correct range, which you need to know. You pick
your shunt to match your meter, not your "expected" current flow - when the
shunt has 50mV across it, your meter should show full-scale, and that full scale
(suppose it's 40A) needs to be correct! That's why B&C has so many sizes
available.
You might want something bigger than 26AWG though; 22AWG might be more appropriate.
Bob, do you have a recommendation on maximum resistance in the wiring to
an ammeter? I don't remember what these meters have as an internal coil resistance
so I can't do the math on errors associated with wiring resistance. Since
I've gone digital I don't even have one to measure.
Basically, Jim, you want the wiring to the meter to have a very small resistance
compared to the wiring inside the meter, which is the coil that creates the
electromagnet and moves the needle. This will make the meter more accurate. The
more resistance the wire has, the greater the relative voltage drop across it
compared to the meter's needle, and the less accurate the meter will be. If
you care.
Regards,
Chad
Message 2
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| Subject: | Re: Engine cranking problem in Glasair |
--> AeroElectric-List message posted by: Richard May <ram45@comporium.net>
I'm building a Glasair 3, and have the Skytec High Touque starter. And it
cranks my 300hp Lyc. with enthusiasm. It's not the permanent magnet type,
like the newer Skytec's. But is still offered for sale, and I believe due
to it's more powerful cranking ability. I crank my engine over on a regular
basis to help lubricate it and push oil around inside it to help prevent
corrosion. It will crank fine with the plugs in under compression. And I
use a variety of batteries. And even connect them with copper house wiring
and it still cranks fine. I'd suspect your starter first. They are fairly
easy to change out, if you want to borrow one to see if it helps.
Message 3
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<aeroelectric-list@matronics.com>
| Subject: | Garmin-AT ACU resolver questions |
--> AeroElectric-List message posted by: "Ralph E. Capen" <recapen@earthlink.net>
Fellow listers,
I am installing a UPSAT full stack with GX-60 and SL-30 with their ACU attached
to a Century NSD-1000 HSI as the primary display indicator.
Here's my question: With the SL-30 NAV side set to output resolver signals (not
switched by the ACU - supposed to be direct connected to the display) and the
GX-60 outputting converter signalling (all it has) switched through the ACU,
with the ACU set for GPS (sending the GPS converter signalling to the display)
the SL-30 being direct connected can still send its resolver signals to the
display....what happens when the display "sees" both sets of signals? I would
think that they could cause the indicator to do weird things - especially if
they are directionally conflicting.
I have contacted the Garmin-AT folks about this...they want to look at the pinouts
for my NSD1000. Their system is configured the same way if you were to use
their display head and wire it the way their website - and documentation shows.
Maybe their gear ignores one set of signals - or favors one set over the
other.
There are a pair of take-offs from the ACU that I could use to pick a set of relays
to prevent this from happening...or figure out a way to set the SL-30 NAV
side to an off configuration while I'm using the GPS.
What are your thoughts on this? I'm puzzled.
Ralph Capen
RV6A - wiring..........
Message 4
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| Subject: | 2003 List Fund Raiser - Please Support Your Lists... |
--> AeroElectric-List message posted by: Matt Dralle <dralle@matronics.com>
Dear Listers,
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Message 5
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| Subject: | Dual Battery System With Standby Battery |
--> AeroElectric-List message posted by: "Gabe A Ferrer" <ferrergm@bellsouth.net>
Bob and all:
I'm helping a friend with his rotary powered RV9A's electrical system.
He wants an all electric system with dual batteries.
But he would like one of the batteries to be on standby and isolated from the alternator
and charging system. The battery would be charged on the ground by
a battery charger every couple of months.
Assume that the battery is new when installed.
Can a voltmeter reading, before each fllight, of the standby battery predict its
ampere hour capacity for the next year or two?
Thanks
Gabe A Ferrer
RV6 N2GX 83 hours
South Florida
Email: ferrergm@bellsouth.net
Cell: 561 758 8894
Night Phone: 561 622 0960
Fax: 561 622 0960
Message 6
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| Subject: | Re: getting the horse back out in front . . . |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
This is a long post . . .I wanted to leave several exchanges of
the thread intact along with sketches I've added to illustrate points.
I may convert this to an illustrated .html document and post on
the website. I think it's a good illustration of the value of getting
ALL the questions identified and asked before we begin gluing too
many of the answers together.
========================================================================================
At 09:40 PM 10/31/2003 -0600, you wrote:
>--> AeroElectric-List message posted by: Jim Sower <canarder@frontiernet.net>
>
>
>"Robert L. Nuckolls, III" wrote:
>
> > ????? That's what a shunt does for you. Let's you measure
> > current in a remote location on tiny wires irrespective of
> > how much current is being measured/monitored.
>
>I knew ammeters had a shunt. Are you saying that I could remove the shunt
>from the meter on
>the panel and remote it all the way back to the firewall (Velocity) and
>run a pair of 26
>gauge wires back to the panel and connect directly to the movement (or
>something analogous to
>this with an off-the-shelf calibrated shunt)? That might solve the
>problem if the "movement"
>of the current meter was any good or I could obtain an easily installable
>substitute.
Yup, that's the big ADVANTAGE of a shut . . . you can keep fat wires
out of the instrument environment yet do measurements on huge current
values on small wires (26 is pretty small and not fun to work with -
22AWG is recommended as the smallest practical airframe wire). Now,
if you increase the ammeter extension wires to 20AWG, then you can
take advantage of the fusible link kits now offered by B&C where
you get some silicone jacketed, fiberglas sleeving, some but splices
and 24AWG (sometimes hard to find) wire for use as shown at:
http://www.aeroelectric.com/articles/fuselink/fuselink.html
Virtually ALL ammeters of any quality are DESIGNED to work with
EXTERNAL shunts. These instruments have a 50 mv full scale movement
and can be marked to depict ANY desired full scale value in amperes
while in fact, the REAL current flowing through the instrument is
perhaps at most a few milliamps. This was the sum and substance of
on of the earlier replies in this thread.
> >
> > What is the basis for your distrust? If you have a loadmeter now
> > that behaves as you describe, it COULD be entirely accurate. A soggy
> > battery recharges at relatively slow rates (especially if your
> > bus voltage is set too low) and the "constant charge reading"
> > may simply be the sum total of equipment loads (relatively
> > constant) + a small charging value for battery.
>
>Actually, it reads 15-20 amps charge with everything in the airplane
>turned off (like that's
>where it lives). It shows a much smaller movement toward discharge than I
>believe is
>actually happening when I turn everything on, and shows maybe 25-30 amps
>(5-10 net) charge in
>flight. Very small indications zeroed at 15-20 amps. Charging voltage
>OTOH starts at
>13-13.5 after start after long period of inactivity and builds toward
>14.5. Ammeter doesn't
>move much. Shows maybe 10 A max charge when alternator (interpreting
>charging voltage)
>appears to be pretty much at capacity.
Very good. I don't recall reading that earlier. Forgive me if you included
that data in an earlier post. I try to hit the list 5-10 times a day
and in the haste of attempting to address as many items as possible
it's easy to miss some of the more salient points . . . Based on what
you've stated above, I'll suggest that your current instrument is trash.
> > Lack of trust simply means "lack of understanding" . . . if
> > you know the instrument is bogus, why leave it in the airplane?
>
>The power supply to most of the airplane passes through this ammeter. If
>I took it out, I
>would have to install a terminal stud very nearby to house the cables
>going to/from the
>meter. It's basically a terminal block right now, and not at all an easy
>one to get at.
A important feature of the current collection of Z-drawings currently
published in the 'Connetion is the notion of tying the alternator b-lead
into the system right at the starter contactor on the firwall. The fat
wires associated with alternator output are a couple of feet long at
most and easy to access for installation/maintenance/inspection any time
the cowl is off.
> > If you haven't checked it for proper operation, then it may
> > very well be trying to tell you something useful about
> > what's going on in your airplane.
>
>I described above what I've observed. I don't believe it's telling me
>anything particularly
>useful. I was hoping one of the inductive units would come with all that
>was needed to play
>including display. No such luck.
I agree . . . it's time to pitch that dead dog . . .
> > > As you say, besides the sensor, I'd have to have a power supply and
> > > display device. Way more trouble than it's worth.
> > >Don't guess there is a solution simple enough to meet my meager electronic
> > >abilities ... Jim S.
> >
> > I'm not sure that's true. Your earliest postings on this
> > thread was "how do I do this?" . . . for which you received
> > some useful and lucid replies. Now, I sense from your
> > responses that you've not yet explored "what do I need?"
>
>Agreed. I was not forthcoming with all the facts, guessing that they
>weren't pivotal
>considerations.
No big problem here . . . I see it all the time in my "other life" . . .
I suggested earlier that questions are more important than answers. The
focus of thought my dozens of helpful folks can be charging off in the
wrong direction or slaying dragons that don't need slaying because not
all of the right questions have been asked. If I had asked a simple
question in March of '98, "where is the shaft breaking", I could have
avoided over two years of jousting the wrong dragons while searching the
cause for a series of failures that were costing us $millions$.
Now, three years after identifying the right dragon, the problem
still isn't fixed but that's another story.
> > "how is it useful to me as a pilot/maintainer of an airplane"
> > and "what is the most efficient way of achieving that
> > performance?"
>
>It would be nice to have a loadmeter, but charging voltage is enough
>information to get by so
>absence of a loadmeter is an inconvenience but certainly not a show
>stopper. Since all of
>the output of the alternator goes to the firewall mounted Alt relay and
>thence to the Master
>relay and on to either the battery or the busses, that area is the only
>place to
>reaslitically measure current flow. Gathering that data and remoting it
>to an appropriate
>display on the panel is my challenge.
Very good. I've suggested that things like ammeters and voltmeters are
most useful for diagnostics. Given that they display exactly the same
data 999 times out of 1000, they become very poor warning devices
because of two common traits of the human condition (1) since we're
quite used to seeing the same readings for countless observations
is easy to miss an out-of-the-ordinary reading when it does happen
and/or (2) since the information received 99.9% of the time is essentially
un-interesting, we tend to look at those instruments less often. The
ammeter on most airplanes I fly is tucked in an out-of-the-way corner
of the panel so as not to use up "valuable" real estate for so lowly
an instrument . . .
>OK. You asked for it. Here's [the mess] that came at me with the plane:
> From the Alt side of the split master switch, there's a 2-conductor
> shielded 24-26 AWG wire
>that originally went (both conductors wired in parallel) to the "F"
>terminal of an internally
>regulated 40 amp alternator (which went south). I replaced that unit with
>an externally
>regulated (generic Ford regulator) also 40 amp unit that I owned, using
>the in-place parallel
>wires to excite the regulator.
If the shielded pair runs directly from the split-rocker master switch
to the alternator, do I correctly infer that the master switch was wired
as shown in:
http://www.aeroelectric.com/articles/Thread/Figure_1.gif
> Output from the alternator runs about 10" through 8- or
>10-gauge cable and passes through a 1.5" x 1.5" x 0.5" metal box with 1/4"
>terminals on each
>side and a mounting flange (I'm told this is a fusible link)
Is this a commercially produced unit? Do you know what
it really contains? I've seen builders shun the rather fat
ANL limiters and bases in favor of building an automotive
mini-ANL into their own enclosure thusly:
http://www.aeroelectric.com/articles/Thread/Figure_2.gif
I DON'T recommend this. The metal box is usually grounded
to the firewall. The mechanical integrity of the insulating
washers is at risk here. They are relatively thin and not
robust. This assembly puts very small clearances between
fat wires carrying lots of current adjacent to hard-ground
enclosures. I couldn't certify this arrangement. This is
one case where those-who-know-more-about-airplanes-than-we-do
make sense.
Yes, the ANL+base combo is pretty honky. If you just gotta
have a smaller part, consider the Littlefuse MIDI style
or some of the Bussman miniature high current fuses but
when fabricating a base, bandsaw out a piece of Delrin
or phenonic, drill holes for brass fuse studs and for mounting
base to airframe. Counter bore holes for fuse studs so
that heads of screws are under-flush to bottom surface.
see http://www.aeroelectric.com/articles/Thread/Figure_3.gif
After installing studs, pot the counter-bore with expoxy
to capture screw head and insulate the screw from electrical
contact. Hex headed screws are really good here . . . lets
the epoxy get a good grip on it. Also, steel is probably
okay since your ring terminal that carries current on and
off the fuseholder is bolted right against the fuse
tab . . . the bolt will carry only a tiny percentage
of total current flow.
> and thence for about 10' to the
>ammeter in the instrument panel. From the ammeter, another 10' run of 10
>gauge wire returns
>to the firewall mounted master solenoid and another foot or so to the
>battery. That's about
>a 20' run of 10 gauge wire to charge the battery (I didn't like that at
>all on account of
>line losses). There was no over voltage protection on the original
>internally regulated
>alternator and only what the Ford regulator gave me on the other unit.
Your misgivings about this are well founded for reasons cited and for
a few more that I could add. It would be better that the alternator
b-lead were replaced with a hunk of 4AWG running from b-terminal
through a shunt, b-lead fuse and then to starter contactor.
>What I've done:
>I have split the two conductors from the Alt switch to the
>alternator. One circuit goes from
>the essential buss through a small LED indicator and connects to the "A"
>conductor of the
>pair. At the other end (in the engine compartment) it goes straight to
>the "I" spade
>terminal on the alternator where it is grounded (and lights the light)
>until the alternator
>comes on line and then is reversed biased to no voltage and the light goes
>out.
Understand. This tells me that you now have an internally regulated
alternator and that voltage from the panel to tell the alternator when
to go to work carries no field current.
> The original
>output from the Alt switch connects to the "B" conductor of the pair at
>the instrument
>panel. In the engine compartment near the alternator the "B" lead splits,
>one lead going to
>the "F" terminal on the alternator, the other back to the forward
>firewall, through a fuze to
>the Alt relay. The B&C crowbar goes from that terminal to ground. I ran
>a 10 gauge cable
>from the alternator B+ to the Alt relay. and a short #10 from the output
>side of the Alt
>relay to the output side of the Master relay. From there the original
>alternator output
>cable as well as the charging cable run in parallel to the ammeter on the
>panel.
What size is your alternator?
>Charging current from the alternator goes pretty much the most direct
>route (through the Alt
>relay) to the battery. I have parallel 10 gauge cables carrying current
>to the instrument
>panel area.. Since there were two #10 cables in place as well as the
>2-conductor #24 run
>from panel to firewall, I didn't have to run any additional wire through the
>difficult-to-work-with chase from the firewall to the instrument
>panel. An event that drove
>me NUTS for the past two days is the Alt relay. I ordered a master relay
>from Wick's and
>finally figured out that the activating terminal is not (as I had assumed)
>grounded to the
>relay case, but to one of the current carrying posts. The crowbar circuit
>as well as the
>indicator needs it to be grounded to the case. That will set me back
>about a week, finding
>and obtaining a suitable unit.
B&C stocks the S702-1, 4-terminal contactors I illustrate in all
of the applications where this contactor is suitable. They
can get one in your hands post-hasty
If it were my airplane and I elected not to replace the pair of 10AWG wires,
then I'd probably wire pretty much like:
http://www.aeroelectric.com/articles/Thread/Figure_4.gif
Here you see that we use the original shielded pair of conductors
together as alternator control. Forget the "I" terminal . . . there
are alternator failure modes that may not illuminate the bulb driven
from this terminal. However, the alternator may not start up unless
you wire a 150 ohm, 2w resistor from "F" to "I" . . . try it without
and add resistor if alternator doesn't come on line.
Buy or build a low-voltage warning sensor like our
AEC9005-101 shown at
http://www.aeroelectric.com/Catalog/AEC/9005/9005.html
or build your own per
http://www.aeroelectric.com/articles/lvwarn/LVWarn-ABMM.html
and
http://www.aeroelectric.com/articles/lvwarn/9021-620.pdf
Either one installs per
http://www.aeroelectric.com/Catalog/AEC/9005/9005-701B.pdf
Parallel the two 10AWG wires for a main bus feed. Two strands of
10AWG, 10' long gives you a wiring resistance of about 5 milliohms.
So if you loaded a 60A alternator to 100% of capacity, would give
you 0.3 volts drop in your main bus feed. You won't be loading
the system to 60a so this is an acceptable compromise.
Now, let's talk about loadmeters, voltmeters, et. als.
As I mentioned earlier, these are poor warning devices and
by-and-large, useful only for troubleshooting. If your low
voltage warning light came on before you cranked the engine
and went out after the engine was started and alternator is
running then you KNOW that it's carrying all of the present
loads. If the light comes on, in what way could you use
ANY readings from a loadmeter, battery ammeter or voltmeter
to drive decisions for the balance of the flight?
Of course you're going to have a battery with enough
KNOWN capacity to get you to airport of intended destination
powering only useful stuff. I'll suggest that under
these conditions, whatever readings you get from a
voltmeter or ammeter of any kind are of no value
to you as a pilot.
Soooo . . . if you built your airplane with NO panel
mounted electrical instrumentation other than active
notification of low voltage, I've have no heartburn
with it. Of course, you DO have a hole in the panel
were the ammeter used to go. Rather than plug it with
a piece of sheet aluminum, I suppose you could put
something useful in there like an OAT indicator, perhaps
a 760VHF second comm radio. Or, what the heck, a voltmeter
certainly wouldn't hurt. While voltmeter and ammeter
data are useful to mechanics trying to troubleshoot
a mis-behaving system, they are P.S. (panel schmaltz) to
the pilot. So, if you leave the shunt out, you don't need
to run any new wires to the panel. Existing wires will
suffice . . .
Bob . . .
Message 7
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| Subject: | Re: Current Limiters |
--> AeroElectric-List message posted by: "Ernest Kells" <ernest.kells@sympatico.ca>
> You've admitted to some "bad judgement" where I'm having
> trouble figuring out what's bad about it. As I've suggested
> to others, lets see what you have in hand, what you want to
> achieve in the finished product and then figure out the
> most attractive combination of parts and techniques will
> get this done. My perception is that you're belabored with
> some erroneous or at least mis-understood concepts....Bob . . .
>
Hello, Bob: You're right - bad judgement with weak skills. I used your
book for general reading throughout my project. I should have ramped up at
this stage on the electrical knowledge, before starting this work.
This is what I have done. I installed the 70 amp alternator although I need
less than 35 amps (VFR only). I "assumed" that if I installed a 35 amp
breaker on the alternator switch that I would be protected from the
summation of the electricity drawn by the systems. I penetrated the
firewall, etc., with wire based upon 40 amps, using a 40 amp shunt/ammeter.
I finally determined that on a low charge battery that the alternator would
deliver more than the wire could handle - on the wire from the alternator.
It seems to me that the significant change would involve replacing the #8
wire from the alternator to the contactor with #4. No ANL fuse/limiter? ? ?
If I have the 35 amp breaker for the alternator switch it seems that I would
NOT have to replace the #8 wire from the battery contactor to the main bus
with #4 (per Z-2). I have #2awg for the battery positive and negative,
engine ground, master and starter relays and the starter.
Of course, I must swallow my pride and learn, then analyze requirements,
then revise the design. BTW: I got into trouble using the Vans electrical
diagram (OP-10). On a call today they said what I did was alright. HMMM!
They have sold a lot of RV-6s. Thanks for the tremendous help - Matt too!
Message 8
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--> AeroElectric-List message posted by: "John Szantho" <szantho@usa.com>
I am working on the landing light, recognition light, strobe and roll servo
wiring for my RV9-A wings. What is the best way to wire the ground? Should I
go directly from each device to the wing front spar (multiple ground points
(faston tabs?)), or should I run a #10 wire (would this be the optimum
size?) for the entire length of the wing to a common ground point in the
fuselage/wings and connect to this common ground wire? I could run this wire
in a conduit I have in each wing. I feel somewhat lost, may be there are
other options? Can anyone help?
John Szantho (RV9-A wings)
Message 9
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| Subject: | Garmin-AT ACU resolver questions |
--> AeroElectric-List message posted by: "Alex Peterson" <alexpeterson@usjet.net>
>
> I am installing a UPSAT full stack with GX-60 and SL-30 with
> their ACU attached to a Century NSD-1000 HSI as the primary
> display indicator.
>
> Here's my question: With the SL-30 NAV side set to output
> resolver signals (not switched by the ACU - supposed to be
> direct connected to the display) and the GX-60 outputting
> converter signalling (all it has) switched through the ACU,
> with the ACU set for GPS (sending the GPS converter
> signalling to the display) the SL-30 being direct connected
> can still send its resolver signals to the display....what
> happens when the display "sees" both sets of signals? I
> would think that they could cause the indicator to do weird
> things - especially if they are directionally conflicting.
Ralph, I cannot understand your question. Please clarify a couple
things.
What is an ACU?
When you talk about resolver stuff, are you perhaps talking about the
course deviation indicator signals? My understanding of the resolver is
that it is the method by which the Nav radio knows what direction you
have the OBS pointed.
In any case, it would seem not right to have a situation where more than
one signal can get to anything.
Alex Peterson
Maple Grove, MN
RV6-A N66AP 397 hours
www.usfamily.net/web/alexpeterson
Message 10
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| Subject: | Re: getting the horse back out in front . . . |
--> AeroElectric-List message posted by: Jim Sower <canarder@frontiernet.net>
"Robert L. Nuckolls, III" wrote:
This is a long post . . .I wanted to leave several exchanges of
the thread intact along with sketches I've added to illustrate points.
I feel like I'm really getting somewhere now. I'll try to shorten the post.
>
> Yup, that's the big ADVANTAGE of a shut . . . (26 is pretty small and not
fun to work
> with -
> 22AWG is recommended as the smallest practical airframe wire).
If I had too-small wire already in the chase, and bought an indicator a size too
small for
the shunt, would the line losses tend to make them match better? I don't need
precision
current flow - just a good indication of what the alternator's putting out.
Based on what you've stated above, I'll suggest that your current instrument is
trash.
Agreed. For some time it's being used only as a terminal block for all them #10
cables.
>
> ... tying the alternator b-lead
> into the system right at the starter contactor on the firwall.
I'm tying it to either the "low" side of the master relay or the "high" side of
the starter
relay as soon as it clears the Alt relay..
>
>
> If the shielded pair runs directly from the split-rocker master switch
> to the alternator, do I correctly infer that the master switch was wired
> as shown in:
>
> http://www.aeroelectric.com/articles/Thread/Figure_1.gif
Not quite. When Alt rocker is on (output hot) it follows conductor "A" to (near)
alternator
where a "Y" branches: to "F" terminal on Alt; to control terminal on Alt relay.
The "B"
strand is not connected to Alt rocker (as it used to). Wire from some fused power
terminal
nearby goes through warning light and attaches to "B" conductor. In engine compartment,
"B"
conductor goes to "I" terminal on alternator.
New related question:
Since Alt rocker switch switches both B+ (through relay) and internal regulator
(through "F"
terminal) could I simplify wiring by switching ONLY the Alt relay, and stringing
a 3" 22 ga
jumper from B+ to "F"? If Alt rocker is OFF, Alternator B+ is connected to nothing.
If Alt
Rocker is ON, Alternator B+ is connected to hot post on Starter or Master relay
and jumper
turns on the internal regulator. Does this make sense, particularly around eliminating
one
more piece of wire in engine compartment?
> > Output from the alternator runs ... (I'm told this is a fusible link)
>
> Is this a commercially produced unit? Do you know what
> it really contains?
No and No. No labels, no nothing, just a sealed unit.
> I've seen builders shun the rather fat
> ANL limiters and bases in favor of building an automotive
> mini-ANL into their own enclosure thusly:
>
> http://www.aeroelectric.com/articles/Thread/Figure_2.gif
>
> I DON'T recommend this. ... the ANL+base combo is pretty honky. ... consider
the
> Littlefuse MIDI style or some of the Bussman miniature high current fuses
> see http://www.aeroelectric.com/articles/Thread/Figure_3.gif
That's my plan. 50-70 amp Bussman or whatever looks good at Autozone, properly
mounted.
> It would be better that the alternator
> b-lead were replaced with a hunk of 4AWG running from b-terminal
> through a shunt, b-lead fuse and then to starter contactor.
Sounds like a plan.
> What size is your alternator?
60 or 70 amp ND. Most likely out of a Mitsubishi (unless that's who owns ND).
> B&C stocks the S702-1, 4-terminal contactors I illustrate in all
> of the applications where this contactor is suitable. They
> can get one in your hands post-hasty
On the 4-terminal units, is one terminal connected to Alt rocker and the other
to ground? Or
is it grounded to the case? Or what?
Guess I need to ask B&C that question :o)
When I found out what my relay was doing, I cursed and stomped my foot and took
some doofus
engineers' names in vain. Here I thought ALL master relays were grounded to the
case since
there's (in my mind) no assurance of a path to ground downstream of the relay.
Imagine my
surprise when the builder in the next hangar informed me that the control terminal
is
supposed to be switched to GROUND. Weird.
> If it were my airplane and I elected not to replace the pair of 10AWG wires,
> then I'd probably wire pretty much like:
>
> http://www.aeroelectric.com/articles/Thread/Figure_4.gif
That's pretty much where I've already ended up (as soon as I install my shunt and
new fuze
:o)
> Here you see that we use the original shielded pair of conductors
> together as alternator control. Forget the "I" terminal . . . there
> are alternator failure modes that may not illuminate the bulb driven
> from this terminal.
Here I went and installed that light because a) I had a conductor for it (arguably
stooopid
reasoning), and b) because I'd heard (I thought on this list) that some alternators
get
squirrley if the "I" isn't used.
> However, the alternator may not start up unless
> you wire a 150 ohm, 2w resistor from "F" to "I" . . . try it without
> and add resistor if alternator doesn't come on line.
What if I jump from B+ to "F" and thence (through the resistor above) to "I"?.
That would
give me NO wires to Alternator except B+ and a couple of little jumpers on the
unit :o)
> Buy or build a low-voltage warning sensor like our
> AEC9005-101 shown at
>
> http://www.aeroelectric.com/Catalog/AEC/9005/9005.html
>
> or build your own per
>
> http://www.aeroelectric.com/articles/lvwarn/LVWarn-ABMM.html
>
> and
>
> http://www.aeroelectric.com/articles/lvwarn/9021-620.pdf
>
> Either one installs per
>
> http://www.aeroelectric.com/Catalog/AEC/9005/9005-701B.pdf
I think I will do that. Could mount warning light where current Alt warn resides
:o)
Deferrable I think.
> Parallel the two 10AWG wires for a main bus feed. Two strands of
> 10AWG, 10' long gives you a wiring resistance of about 5 milliohms.
> So if you loaded a 60A alternator to 100% of capacity, would give
> you 0.3 volts drop in your main bus feed. You won't be loading
> the system to 60a so this is an acceptable compromise.
That's GOOD news.
> Now, let's talk about loadmeters, voltmeters, et. als.
>
> As I mentioned earlier, these are poor warning devices and
> by-and-large, useful only for troubleshooting. ... If the light comes on,
in what way
> could you use
> ANY readings from a loadmeter, battery ammeter or voltmeter
> to drive decisions for the balance of the flight?... under
> these conditions, whatever readings you get from a
> voltmeter or ammeter of any kind are of no value
> to you as a pilot.
Hadn't thought of it that way. Makes sense. And I could likely have it for about
what B&C
gets for shunt and meter indicator :o)
> Soooo . . . if you built your airplane with NO panel
> mounted electrical instrumentation other than active
> notification of low voltage, I've have no heartburn
> with it. Of course, you DO have a hole in the panel
> were the ammeter used to go. Rather than plug it with
> a piece of sheet aluminum, I suppose you could put
> something useful in there like an OAT indicator,
I already have that :o)
> perhaps
> a 760VHF second comm radio.
Have that in my GPS/Comm :o)
> Or, what the heck, a voltmeter
Have that too :o((
> While voltmeter and ammeter
> data are useful to mechanics trying to troubleshoot
> a mis-behaving system, they are P.S. (panel schmaltz) to
> the pilot. So, if you leave the shunt out, you don't need
> to run any new wires to the panel. Existing wires will
> suffice . . .
More good news :o)
Thanks a whole bunch. This really REALLY helps.
Now if I could only figure out why that *#%&# engineer designed that relay the
way he did ...
Jim S.
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