Today's Message Index:
----------------------
1. 01:44 AM - Re: Re: Minimizing audio interference (Jay Hyde)
2. 06:02 AM - Ground Wire Routing; Compass Issues (Mark Meredith)
3. 07:29 AM - Re: Re: Minimizing audio interference (Robert L. Nuckolls, III)
4. 10:53 AM - Re: Replacement Crimpers (Robert L. Nuckolls, III)
5. 02:20 PM - Re: wiring assistance (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Minimizing audio interference |
I believe that is an Op Amp - see
http://en.wikipedia.org/wiki/Operational_amplifier
Jay
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob
Verwey
Sent: 12 November 2013 09:43 AM
Subject: Re: AeroElectric-List: Re: Minimizing audio interference
Bob N, for us neophytes, please enlighten us on the triangular device in
your sketch.
Best...
Bob Verwey
IO 470 A35 Bonanza ZU-DLW
On 11 November 2013 21:05, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com> wrote:
At 08:30 AM 11/11/2013, you wrote:
I like it that Z15-3.1 shows not only the right way, but also the wrong way
to ground devices. I understand that earphones and microphones should not
be grounded locally, but should only be grounded at the panel end (intercom
or radio).
I am a little confused with the engine sensors. Grounding might be
different for different types of sensors and their display (EMS or steam
gauge). Some sensors are grounded automatically by nature of their
construction and mounting.
Yes. Many oil pressure, oil temperature, CHT, EGT sensors are
guilty of 'local grounding' . . . and for the manner in which they
were originally intended to be used . . . it didnt' matter.
But for sensors that have isolated ground, I assume that the ground wire
should terminate at the EMS or display device and not at the engine case.
Of course always follow the manufactures installation instructions.
Oh, absolutely. But absent a end-to-end design goal,
one has to play the DIY integration game. One useful
way to deal with a locally grounded signal source
looks like this:
Emacs!
There are low cost integrated circuits that do the
task of making remote voltage measurements across
hostile environments. Alternatively, one can take all
grounds for the instrument to the crankcase. The same
game is played in audio systems. I did the specification
for design of an intercom system on the Lears that
coupled all stations together by way of a transformer
coupled, twisted pair . . . Intercoms scattered about
the airplane could be grounded locally for power and
control without the worry of noises on the ground-
differences finding their way into the audio.
Bob . . .
Message 2
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| Subject: | Ground Wire Routing; Compass Issues |
Bob and Listers,
Here's a question for the group from a new guy. It's
prompted by the recent discussion (and couple of weeks ago) about minimizing
radio noise and compass deviation. What is the best routing for the ground
wire from my instrument panel forest of tabs to the firewall single point
ground?
Airplane is a modified open cockpit 1951 DeHavilland Super
Chipmunk (IO-540) rebuilt over the past 4 years. For the configuration
think Pitts S-2C: radio stack between the rear seat pilot's knees, VFR
round gages with a handful of electric instruments and a (planned) mini-iPad
portable mounted on the sidewall. Firewall forward is pure Pitts clone.
The new electrical system is pretty much finished (I hope!) except for
neatening up and securing the wire bundles. System was tested incrementally
and everything worked first try except an issue with the electric compass
noted below. I stuck exactly to the Z-11 architecture and have followed
the Connection and discussion among this group for a couple of years.
Pretty much every component is B&C (with lots of great installation guidance
from TJ).
Wire routing: I put the main and e-bus fuse blocks under
the radio/xponder with a big wire bundle running vertically up to the panel
then fanning out to instruments and switches via 18-22 AWG wires. Battery,
contactors, regulator and single point ground are at the firewall about 6
feet forward of the rear instrument panel and radio stack/fuse blocks.
Component location and wire bundle routing (either left, right or
centerline) from the firewall to the rear cockpit were aimed to keep
everything shortest from point A to point B. Radio and transponder antenna
coax run aft centerline from the radio stack under the control stick and
pilot's seat, bundled with the power wires for the lights, strobes, fuel
pump and a remote compass detector. The lights, strobes and fuel pump are
the only devices grounded locally; everything else grounds at the firewall.
My main question is about the 6 AWG panel ground wire: it
runs from the forest of tabs behind the right side of the panel, up the
right sidewall then under the floor to the firewall ground. It's WIDELY
separated from the 6 AWG main power wire that runs straight down the middle
from the battery contactor to the fuse blocks between the pilot's knees.
Was that routing a bad decision?
A possible rerouting to ensure a clean radio and minimal
compass deviation (I may not always have the portable GPS): collocate/twist
together the 6 AWG ground fat wire with the 6 AWG main power wire running
fuselage center. To do so, I'd need to run a new and longer ground wire
from the right side of the panel via the bundle of small power and ground
wires to centerline, then down to the radio stack/fuse blocks where it can
join up with the 6 AWG main power wire, then forward under the centerline
floor to the firewall.
Question is prompted by this helpful info from Sacha a
couple of weeks back:
". if they're kept very close together (eg by twisting) then as long as you
are at a distance D away from
the pair, where D is much greater than d, then the magnetic field
becomes
very small. Typically d is of the order of a few millimeters so if
you're eg
a meter away, then D is hundreds of times greater than d and the
magnetic field
is for all intents and purposes zero."
"D" for my routing of panel wires is about 3 inches behind
the wet compass and remote compass indicator. There are lots of small
ground wires mixed in with power wires in this bundle; some wires go to the
switches and instruments and some to the ground forest of tabs. Would it
help to just wrap the wet compass and remote detector with shielding and
leave wire routing as is?
The electric compass indicator is fed from a remote detector
(flux valve? don't know) behind the pilot's head far from anything else
electrical. It's not a gyro, just an indicator. It had negligible
deviation and worked fine before the rebuild. Have not tested deviation now
because the airplane is still on blocks in a steel hangar. But when powered
up the indicator has a steady oscillation left and right about 10 degrees,
about once per second..if it doesn't settle out when I get the airplane out
in the open then I have another problem. Unfortunately for the compass I
installed a steel rollover bar behind the pilot's head close to the remote
detector, knowing I was likely introducing a compass problem but scored the
rollbar as priority. Well, now it's time to think about the compasses.
Perhaps I can move the remote detector farther away from the rollbar but
it's old, big (5-6 inch diameter cylinder) and heavy so space and balance
are issues. Perhaps I could buy a new and lightweight remote compass system
but would rather keep the current functioning system.
I have one more unrelated question but I'll save that for
another email. I've appreciated the expertise of the group over the past
couple of years of reading the conversations, and thank you in advance for
your suggestions!
Mark Meredith
Super Chipmunk N7DW
(Google "Super Chipmunk Restoration" for pics/story of the rebuild and
airplane's interesting history)
Message 3
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| Subject: | Re: Minimizing audio interference |
At 03:43 AM 11/12/2013, you wrote:
>I believe that is an Op Amp ' see
>http://en.wikipedia.org/wiki/Operational_amplifier
>
>Jay
>
>http://www.matni.com/Arabic/Elec-Info/LM741%20DETAILS/philk2w.j
>
Jay is correct. The "operational amplifier" has a rich
history in the evolution of electronics. Check out
the articles on Wikipedia about George Philbrick,
Bob Widlar, Jim Williams, and Bob Pease just to
name a few of the colorful pioneers of the electronic
arts and sciences.
The op-amp comes in many flavors and sizes tailored
to a constellation of tasks. I cut my op-amp teeth about
1962 on this vacuum tube version that sold for a couple hundred
dollars in 2013 money . . .
Emacs!
http://www.matni.com/Arabic/Elec-Info/LM741%20DETAILS/philk2w.j
I doubt that there were more than a few dozen
products available.
The last op-amp I stuck to a board looked like
a little brick of plastic about the size of a match
head . . .
Emacs!
. . . and costs about $2. The Digikey site offers
over 30,000 variations on the theme. We've come
a long way baby . . .
Bob . . .
Message 4
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| Subject: | Re: Replacement Crimpers |
At 08:46 PM 11/11/2013, you wrote:
>
>Bob,
>I need to replace my long serving Paladin
>crimpers, not due to wear, rather someone else
>decided they needed them more than I do. One of
>my criteria for the replacement is the use of
>field swappable dies. Having read your writings
>on crimpers for use with the common wire
>terminals Id like your opinion on the
>following dies the first one the Sargent 4100-40 is the leader in my opinion
I'm not really in a position to offer useful
information on the various products. I've
evaluated a few tools and compared with the
performance of my $high$ Amp crimpers . . . and
found most to be satisfactory alternatives.
I started to look at exchangeable die-sets
a few years back but the cost of serviceable
complete tools was so low that the idea of making
one handle do lots of jobs wasn't very attractive.
Further, the costs of loose die-sets is driven
by volume of sales . . . seems that die-sets
could easily approach the cost of a complete
tool!
Sorry I can't be more helpful . . .
Bob . . .
Message 5
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| Subject: | Re: wiring assistance |
At 02:48 PM 11/12/2013, you wrote:
Bob,
know this a long shot but i need assistance to finish wiring my
Glasair. i am hoping you know someone over this way that i could
contact. i was told that Greg Richter has done this sort of thing
but i have been unable to contact him. had a guy who was supposed to
assist me but he is too busy now. according to him i am only about
6 working hours away from being finished but i can't get him
back. i am located in the middle of South Carolina.
basically what needs to b done to finish the install is 6 circuit
breakers and connect, finish the transponder harness (it's 90%
done), finish the audio panel harness (it's 85% done), wire the new
electric tach, rehookup the old engine instruments, and calibrate the
new GRT Hxr w/autopilot.
the airplane has now been down 5 months which is absolutely
ridiculous. any direction and guidance would be most appreciated.
thanks.
Wince Holliday
N745CW
Wince, I am not personally aware of anyone in your
neighborhood who might be helpful . . . I've posted
your query to the aeroelectric-list. Perhaps someone
on the list can help or knows somebody who can.
Bob . . .
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