Today's Message Index:
----------------------
1. 12:26 AM - Re: Shunt insulation (John MacCallum)
2. 04:46 AM - Radio Coax (paul wilson)
3. 05:23 AM - Re: Radio Coax (Robert L. Nuckolls, III)
4. 05:36 AM - Re: Shunt insulation (Robert L. Nuckolls, III)
5. 05:51 AM - Re: Developing the initial software for the wig-wag project (Robert L. Nuckolls, III)
6. 06:44 AM - Re: Shunt insulation (Stuart Hutchison)
7. 07:40 AM - Re: Shunt insulation (Jared Yates)
8. 08:11 AM - Re: Radio Coax (paul wilson)
9. 09:31 AM - Re: Shunt insulation (Robert L. Nuckolls, III)
10. 11:19 AM - Re: Shunt insulation (Jared Yates)
11. 04:32 PM - Re: Secrets Techniques (John Loram)
12. 05:14 PM - Re: Shunt insulation (Robert L. Nuckolls, III)
13. 05:56 PM - Re: Shunt insulation (Jared Yates)
14. 06:05 PM - A peek into the pages of aviation history (Robert L. Nuckolls, III)
15. 06:10 PM - Re: Shunt insulation (Robert L. Nuckolls, III)
16. 10:32 PM - Ignition Interference (messydeer)
Message 1
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| Subject: | Shunt insulation |
G'day Stu,
No it won't be affected by temperature enough to be a problem. A shunt is a
low value resistor in series with the circuit you want to measure the
current in.
An ammeter is a sensitive volt meter that measure the voltage being dropped
across the shunt (resistor).
The calibration of the shunt will the depend on the Full scale deflection
current required by the Ammeter.
Needless to say just use the shunt supplied with the engine monitor package
and you will be ok.
Cheers
John MacCallum
VH-DUU
RV10 #41016
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Stuart
Hutchison
Sent: Sunday, 29 April 2012 1:54 PM
Subject: AeroElectric-List: Shunt insulation
G'day Bob,
My shunt is mounted in the 'hot' wire between the live post of the starter
contactor (not measuring start currents) and the main and avionics busses.
The B-lead is upstream (so to speak - depends whether we're talking
electrons or holes !), so I can read the current into and out of the
battery. I've already 1A fused the signal leads (which go to my EFIS), but
I wanted additional insulation around the shunt to protect from shorts
should anything metalic fall between it and the fuselage during aerobatics.
I don't really understand how a shunt is calibrated, so I'm wondering if
clear heatshrink and having the shunt on the back of the firewall will alter
the temperature environment of the shunt enough to affect it's calibration?
You may be able to see the heatshrink in the photo ... which has holes
punched for the terminals to screw down.
Kind regards, Stu
F1 Rocket VH-FLY <http://www.mykitlog.com/RockFLY>
http://www.mykitlog.com/RockFLY <about:www.teamrocketaircraft.com>
www.teamrocketaircraft.com
Message 2
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Is there physics to the comment below?
I happened to pick up the comment on a jeep forum where the guys buy
an antenna with a stock length of coax and don't have the ability to
change the length.
Apperciate any comments. Thanks, Paul
DO NOT coil your antenna coax lead or let it cross over itself, to
get the best reception and transmission from your radio. I have now
tried this and found significant increases for both. Run your lead
around the seat, around the roof, or whatever you have to do to
prevent crossover of the lead, next to itself. You will find much
improvement in your reception.
Message 3
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At 06:39 AM 4/29/2012, you wrote:
Is there physics to the comment below?
I happened to pick up the comment on a jeep forum where the guys buy
an antenna with a stock length of coax and don't have the ability to
change the length.
Apperciate any comments. Thanks, Paul
DO NOT coil your antenna coax lead or let it cross over itself, to
get the best reception and transmission from your radio. I have now
tried this and found significant increases for both. Run your lead
around the seat, around the roof, or whatever you have to do to
prevent crossover of the lead, next to itself. You will find much
improvement in your reception.
No validity to this idea at all. This narration suggests
that there are things going on OUTSIDE the coaxial feedline
that can have an effect on things that go on INSIDE
the feedline. In fact, the very nature of an idealized
feedline (low SWR and artful construction) calls for
keeping all good things in and bad things out.
When I worked at Boeing there was an analog computer
associated with the terrain avoidance radar that had
perhaps a dozen coax cables of critical length running
between a couple of the black boxes. The lengths were
adjusted on installation to achieve the desired performance.
It took about three shifts to get this thing tuned up
and had a system MTBF on the order of 10 hours.
During a tune up procedure in the airplane, we could
count on going to the lab with two or three circuit
cards. But the point to be made here is after they
were all measured and verified for performance NOT
bundled, the last chore was to coil them up and
string tie them into a neat and secure installation.
No shifts in performance of the radar was experienced
or expected for having repositioned the coax cables.
We don't often see "too long" cables in a TC aircraft.
They are cut to ideal installed length on installation.
But the idea that system performance would suffer because
the feedlines are coiled or 'cross over themselves'
is bogus.
If the writer had some demonstrable variations in
performance due to feedline positioning, there was
something seriously wrong with the installation
and the feedline was acting more like a piece of
wire than a coax cable.
Bob . . .
Message 4
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| Subject: | Shunt insulation |
At 02:22 AM 4/29/2012, you wrote:
G'day Stu,
No it won't be affected by temperature enough to be a problem. A
shunt is a low value resistor in series with the circuit you want to
measure the current in. An ammeter is a sensitive volt meter that
measure the voltage being dropped across the shunt (resistor).
The calibration of the shunt will the depend on the Full scale
deflection current required by the Ammeter.
Needless to say just use the shunt supplied with the engine monitor
package and you will be ok.
Cheers
John MacCallum
VH-DUU
RV10 #41016
I will expand on John's righteous answer to add that GOOD shunts
are made of a strange metal called manganin. This is an alloy of
multiple metals designed to give the shunt a zero, or near-zero
coefficient of resistance versus temperature. Obviously, a shunt
carries current through a resistance which heats it up. Further,
shunts may be situated in environmental extremes of temperature.
It's desirable to have a very low temperature coefficient
for resistance so that the instrument reads correctly under all
operating extremes.
Hence, any additional heating that might be attributed to
the added insulation is of no consequence.
I will add also that concerns for loose pieces of metal
getting into things electric are probably not well founded.
TC aircraft have had many, many examples of exposed, high
current conductors go out the production line door. The
design goals are better served by making sure things are
well bolted down as opposed to insulating the bus bars
(etc) from the effects things flying around unrestrained.
Bob . . .
Bob . . .
Message 5
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| Subject: | Re: Developing the initial software for the wig-wag |
project
At 05:23 PM 4/28/2012, you wrote:
>
>Here is the document I put together describing the work involved with
>the development of the initial software for the wig-wag controller. It
>should give those who are interested some idea of what is involved
>in the process. Hopefully others will jump into the pool and get
>involved with putting together software for this project and future
>follow-on projects. Take a look and, as always, I welcome any and
>all feedback...
>
>Greg McHugh
>
Greg,
Thank you for this illuminating narrative of the
software development process. I've appended it to
the project data bundle and posted to
http://tinyurl.com/6w9vndk
as revision P3. This is exciting stuff gentlemen.
If this gets the juices flowing for any of you byte-
herders out there, you are encouraged to participate
at what ever level is appropriate to your needs
and desires.
Bob . . .
Message 6
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| Subject: | Shunt insulation |
Thanks Bob & John.
Excellent ... good news, thank you.
I think my 20 mintues to mitigate the low risk to next to zero was worth
it. I have seen some incredible collections of spare washers, swarf and
lockwire offcuts etc in the bellies of TC aircraft ... probably a good
thing they're not rolled inverted as often as my Rocket will be :)
Kind regards, Stu
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Sent: Sunday, April 29, 2012 10:34 PM
Subject: RE: AeroElectric-List: Shunt insulation
At 02:22 AM 4/29/2012, you wrote:
G=EF=BDday Stu,
No it won=EF=BDt be affected by temperature enough to be a problem. A
shunt is a low value resistor in series with the circuit you want to
measure the current in. An ammeter is a sensitive volt meter that
measure the voltage being dropped across the shunt (resistor).
The calibration of the shunt will the depend on the Full scale
deflection current required by the Ammeter.
Needless to say just use the shunt supplied with the engine monitor
package and you will be ok.
Cheers
John MacCallum
VH-DUU
RV10 #41016
I will expand on John's righteous answer to add that GOOD shunts
are made of a strange metal called manganin. This is an alloy of
multiple metals designed to give the shunt a zero, or near-zero
coefficient of resistance versus temperature. Obviously, a shunt
carries current through a resistance which heats it up. Further,
shunts may be situated in environmental extremes of temperature.
It's desirable to have a very low temperature coefficient
for resistance so that the instrument reads correctly under all
operating extremes.
Hence, any additional heating that might be attributed to
the added insulation is of no consequence.
I will add also that concerns for loose pieces of metal
getting into things electric are probably not well founded.
TC aircraft have had many, many examples of exposed, high
current conductors go out the production line door. The
design goals are better served by making sure things are
well bolted down as opposed to insulating the bus bars
(etc) from the effects things flying around unrestrained.
Bob . . .
Bob . . .
Message 7
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| Subject: | Re: Shunt insulation |
I shorted mine the other day while trying to install a prop oil line. Note t
o self, don't forget to disconnect the negative battery lead when waving lon
g metal bits around under the cowl.
On Apr 29, 2012, at 8:34, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectr
ic.com> wrote:
> At 02:22 AM 4/29/2012, you wrote:
> G=EF=BDday Stu,
>
> No it won=EF=BDt be affected by temperature enough to be a problem. A s
hunt is a low value resistor in series with the circuit you want to measure t
he current in. An ammeter is a sensitive volt meter that measure the voltage
being dropped across the shunt (resistor).
>
> The calibration of the shunt will the depend on the Full scale deflection c
urrent required by the Ammeter.
> Needless to say just use the shunt supplied with the engine monitor packag
e and you will be ok.
>
> Cheers
>
> John MacCallum
> VH-DUU
> RV10 #41016
>
> I will expand on John's righteous answer to add that GOOD shunts
> are made of a strange metal called manganin. This is an alloy of
> multiple metals designed to give the shunt a zero, or near-zero
> coefficient of resistance versus temperature. Obviously, a shunt
> carries current through a resistance which heats it up. Further,
> shunts may be situated in environmental extremes of temperature.
> It's desirable to have a very low temperature coefficient
> for resistance so that the instrument reads correctly under all
> operating extremes.
> Hence, any additional heating that might be attributed to
> the added insulation is of no consequence.
> I will add also that concerns for loose pieces of metal
> getting into things electric are probably not well founded.
> TC aircraft have had many, many examples of exposed, high
> current conductors go out the production line door. The
> design goals are better served by making sure things are
> well bolted down as opposed to insulating the bus bars
> (etc) from the effects things flying around unrestrained.
> Bob . . .
>
>
>
>
> Bob . . .
>
>
==========================
=========
==========================
=========
==========================
=========
==========================
=========
>
Message 8
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Thanks for your input
Paul
========
At 06:22 AM 4/29/2012, you wrote:
>At 06:39 AM 4/29/2012, you wrote:
>Is there physics to the comment below?
>
>I happened to pick up the comment on a jeep forum where the guys buy
>an antenna with a stock length of coax and don't have the ability to
>change the length.
>
>Apperciate any comments. Thanks, Paul
>
>DO NOT coil your antenna coax lead or let it cross over itself, to
>get the best reception and transmission from your radio. I have now
>tried this and found significant increases for both. Run your lead
>around the seat, around the roof, or whatever you have to do to
>prevent crossover of the lead, next to itself. You will find much
>improvement in your reception.
>
>No validity to this idea at all. This narration suggests
>that there are things going on OUTSIDE the coaxial feedline
>that can have an effect on things that go on INSIDE
>the feedline. In fact, the very nature of an idealized
>feedline (low SWR and artful construction) calls for
>keeping all good things in and bad things out.
>When I worked at Boeing there was an analog computer
>associated with the terrain avoidance radar that had
>perhaps a dozen coax cables of critical length running
>between a couple of the black boxes. The lengths were
>adjusted on installation to achieve the desired performance.
>It took about three shifts to get this thing tuned up
>and had a system MTBF on the order of 10 hours.
>During a tune up procedure in the airplane, we could
>count on going to the lab with two or three circuit
>cards. But the point to be made here is after they
>were all measured and verified for performance NOT
>bundled, the last chore was to coil them up and
>string tie them into a neat and secure installation.
>No shifts in performance of the radar was experienced
>or expected for having repositioned the coax cables.
>We don't often see "too long" cables in a TC aircraft.
>They are cut to ideal installed length on installation.
>But the idea that system performance would suffer because
>the feedlines are coiled or 'cross over themselves'
>is bogus.
>If the writer had some demonstrable variations in
>performance due to feedline positioning, there was
>something seriously wrong with the installation
>and the feedline was acting more like a piece of
>wire than a coax cable.
>
> Bob . . .
>
>
><http://www.matronics.com/Navigator?AeroElectric-List>http://www.matronics.com/Navigator?AeroElectric-List
><http://www.matronics.com/contribution>http://www.matronics.com/contribution
>
Message 9
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| Subject: | Re: Shunt insulation |
At 09:40 AM 4/29/2012, you wrote:
>I shorted mine the other day while trying to install a prop oil
>line. Note to self, don't forget to disconnect the negative battery
>lead when waving long metal bits around under the cowl.
How did you have a 'hot' shunt with the battery
contactor OFF?
Bob . . .
Message 10
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| Subject: | Re: Shunt insulation |
Thanks for asking Bob, your question inspired me to pull out z13/8
again to make sure I hadn't hooked it up wrong! If I understand
correctly though, it looks like the shunt for the SD8 goes from the
always-hot side of the battery contactor via a 20AWG fuse link. Is
that not correct? It's been a little while since I hooked all of
those wires up.
On Sun, Apr 29, 2012 at 12:28 PM, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com> wrote:
> <nuckolls.bob@aeroelectric.com>
>
>
> At 09:40 AM 4/29/2012, you wrote:
>>
>> I shorted mine the other day while trying to install a prop oil line. Note
>> to self, don't forget to disconnect the negative battery lead when waving
>> long metal bits around under the cowl.
>
>
> How did you have a 'hot' shunt with the battery
> contactor OFF?
>
>
> Bob . . .
>
>
Message 11
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| Subject: | Secrets Techniques |
Well, that works like a charm!... I've spent so many years trying not to
melt the insulation that I was not taking full advantage of the properties
of Tefzel. I've encountered solder sleeves in the past, but never appreciate
their purpose.
onward and upward (someday), -john-
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Thursday, April 19, 2012 9:39 PM
Subject: Re: AeroElectric-List: Secrets Techniques
At 11:12 PM 4/19/2012, you wrote:
Sixty years I've been doing this! Built all my own ham radio gear as a
teenager in the 50's, got a EE degree from a prestigious university, spent
my adult life as a development engineer designing medical and laboratory
instruments. You'd think I could strip a multiconductor shield Tefzel
insulated cable in my sleep, but it's a bit@h! I make a mess of the shield
when I try to remove the Tefzel. What is the secret trick to it!
The secret is go ahead and 'trash' the shield.
I have a bunch of 22AWG, 3-conductor shielded
that a common Stripmaster more-or-less strips
the outer jacket and probably 80% of the shield
strands. Then I use a solder-sleeve
to put a neat pigtail on the damaged shielding.
There are normally no currents flowing in the
shield. If your grounding pig-tail gets good
electrical connection with only one of of the
strands, you're good to go. More than likely
you can get good connection with 10% or more
of the shield stranding. The neat thing
is that the pigtail under heat shrink covers
the carnage.
I'll see if I can dig some of the stuff up
and do a comic-book series of pictures on the
process tomorrow.
Bob . . .
Message 12
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| Subject: | Re: Shunt insulation |
At 01:17 PM 4/29/2012, you wrote:
Thanks for asking Bob, your question inspired me to pull out z13/8
again to make sure I hadn't hooked it up wrong! If I understand
correctly though, it looks like the shunt for the SD8 goes from the
always-hot side of the battery contactor via a 20AWG fuse link. Is
that not correct? It's been a little while since I hooked all of
those wires up.
Oh . . . THAT shunt. Yes, Z-13/8Q does show that
sequence of connection which was shuffled around
in Revision R when we deleted the "self excitation"
feature for the SD-8 and replaced the 20AWG fusible
link with a 30A fuse thusly:
Emacs!
But I understand how it came to be on your airplane and it's
no really big deal. I wouldn't change it now. But it did
strike me strangely and I had to ask. I should probably
add a note to Z-13/8 to elaborate on the 30A in-line fuse.
The picture I had in my head at the time suggested that
leads supplied on the COTS fuse-holder would place the SD-8
control relay close to the battery contactor. The note would
speak to this design goal and suggest that the leads not be
spliced. In fact, I did mark the upstream lead as being in
the 6-inch-or-less category.
I've just discovered an rather slick, in-line holder for
the plastic fuses. It's offered by marine electrical suppliers
(among others). It's not only waterproof by virtue of the
now ubiquitous bellows gasket but the snap-on cover features
a mounting tab. Pretty cool.
Emacs!
Is the system still working since the "shorting" event? It
must have been a really short duration event not to take out
the fuse. In any case, I'd replace the fuse. "Teasing"
events on fuses can be cumulative and your present fuse might
have been re-calibrated downward.
If the fuse IS still intact, I'd like to have it. I'm
working an accident case where a sequence of fuse-teasing
events accumulated over some 15-20 hours of flight before
the fuse gave up. It would be interesting to look at your
fuse under a microscope to see if it shows signs of teasing.
If the fuse is not intact, well . . . that's what fuses
do when they are doing what they do best.
Bob . . .
Message 13
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| Subject: | Re: Shunt insulation |
In my installation I have a 20AWG fuse link instead of an inline fuse. I
haven't had any reason to turn the master on recently so I haven't
reconnected the battery to see if things are still working. The battery is
a mostly dead PC680 that I've used just for testing purposes, so that might
have also limited the amount of current available. I got the usual pop and
a little spark or two but the fuse link didn't seem to smoke. It's in a
bit of that fiberglass insulating stuff so perhaps I should pull that back
and make sure it's all still good. Should I replace it with a fuse? That
nifty inline holder looks a lot like a weatherpack connector.
On Sun, Apr 29, 2012 at 8:13 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 01:17 PM 4/29/2012, you wrote:
> >
>
> Thanks for asking Bob, your question inspired me to pull out z13/8
> again to make sure I hadn't hooked it up wrong! If I understand
> correctly though, it looks like the shunt for the SD8 goes from the
> always-hot side of the battery contactor via a 20AWG fuse link. Is
> that not correct? It's been a little while since I hooked all of
> those wires up.
>
> Oh . . . THAT shunt. Yes, Z-13/8Q does show that sequence of connection
> which was shuffled around in Revision R when we deleted the "self
> excitation" feature for the SD-8 and replaced the 20AWG fusible link with
> a 30A fuse thusly:
>
> [image: Emacs!]
>
> But I understand how it came to be on your airplane and it's no really
> big deal. I wouldn't change it now. But it did strike me strangely and I
> had to ask. I should probably add a note to Z-13/8 to elaborate on the
> 30A in-line fuse. The picture I had in my head at the time suggested that leads
> supplied on the COTS fuse-holder would place the SD-8 control relay close
> to the battery contactor. The note would speak to this design goal and
> suggest that the leads not be spliced. In fact, I did mark the upstream
> lead as being in the 6-inch-or-less category.
> I've just discovered an rather slick, in-line holder for the plastic
> fuses. It's offered by marine electrical suppliers (among others). It's
> not only waterproof by virtue of the now ubiquitous bellows gasket but
> the snap-on cover features a mounting tab. Pretty cool.
>
>
> [image: Emacs!]
>
> Is the system still working since the "shorting" event? It must have
> been a really short duration event not to take out the fuse. In any case,
> I'd replace the fuse. "Teasing" events on fuses can be cumulative and
> your present fuse might have been re-calibrated downward.
>
> If the fuse IS still intact, I'd like to have it. I'm working an accident
> case where a sequence of fuse-teasing events accumulated over some 15-20
> hours of flight before the fuse gave up. It would be interesting to look
> at your fuse under a microscope to see if it shows signs of teasing. If
> the fuse is not intact, well . . . that's what fuses do when they are
> doing what they do best.**
>
> **
> Bob . . .
>
Message 14
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| Subject: | A peek into the pages of aviation history |
A cousin of mine who retired from Boeing Seattle's
spacecraft programs is also a pilot. He sent me this
fascinating link today. Don't start until you have about
an hour to spend on it. It's a real journey of the
mind.
http://tinyurl.com/7ct4umu
Bob . . .
Message 15
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| Subject: | Re: Shunt insulation |
At 07:55 PM 4/29/2012, you wrote:
In my installation I have a 20AWG fuse link instead of an inline
fuse. I haven't had any reason to turn the master on recently so I
haven't reconnected the battery to see if things are still working.
Okay, fusible links are VERY robust fuses. They'll take a
pretty heavy hit without breathing hard.
The battery is a mostly dead PC680 that I've used just for testing
purposes, so that might have also limited the amount of current
available. I got the usual pop and a little spark or two but the
fuse link didn't seem to smoke. It's in a bit of that fiberglass
insulating stuff so perhaps I should pull that back and make sure
it's all still good. Should I replace it with a fuse? That nifty
inline holder looks a lot like a weatherpack connector.
You got it. Yeah, if it were my airplane, I'd go
for the fuse. Simple, fast, inexpensive and continuing
to evolve . . . sort of like the elegant hammer . . .
I'll do some poking around to see if I can find a bulk
source for those fuse-holders. Either B&C or AeroElectric
should stock that one.
Bob . . .
Message 16
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| Subject: | Ignition Interference |
My test pilot flew my plane for the first time today. Yeah! But now I have to fix
all the problems that we've ignored. First on the list is the RFI issue. I
have a Jabiru 3300 in my Sonex. Wired it more or less like Bob's diagrams, with
a filter capacitor. Ran all my power in on the right side and the two mag wires
in on the left. Mag wires are 1-conductor shielded, with the braid pulled
out the last 2 or 3 inches on either end. Seems like it's the left mag, cuz when
it's turned off, the noise disappears. Suggestions?
--------
Dan
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http://forums.matronics.com/viewtopic.php?p=372121#372121
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