Today's Message Index:
----------------------
1. 05:54 AM - 12V Power Socket (Andrew Butler)
2. 06:08 AM - Re: Engine mount as starter ground path (Tom Hanaway)
3. 06:45 AM - Re: 12V Power Socket (jay@horriblehyde.com)
4. 07:10 AM - Re: 12V Power Socket (Richard Girard)
5. 07:10 AM - Re: Alternator with built-in regulator (Wade Roe)
6. 07:11 AM - Re: 12V Power Socket (James H Nelson)
7. 07:21 AM - Grounding philosophy (Johnson, Phillip (EXP))
8. 07:26 AM - Reading Potentiometer Values ()
9. 07:44 AM - Re: 12V Power Socket ()
10. 07:44 AM - Re: Alternator with built-in regulator ()
11. 08:20 AM - Re: Alternator with built-in regulator (Hinde, Frank George (Corvallis))
12. 08:38 AM - Re: State of the art - then and now (Chris Stone)
13. 09:13 AM - Re: Reading Potentiometer Values (Bob White)
14. 09:15 AM - Re: 12V Power Socket (Greg Young)
15. 10:40 AM - Grey code output to multiple devices (Ralph E. Capen)
16. 10:40 AM - Re: Reading Potentiometer Values ()
17. 01:12 PM - Re: Reading Potentiometer Values (Robert L. Nuckolls, III)
18. 01:18 PM - Re: Alternator with built-in regulator (Robert L. Nuckolls, III)
19. 02:07 PM - Re: Grounding philosophy (Robert L. Nuckolls, III)
20. 02:11 PM - Re: Re: Engine mount as starter ground path (Robert L. Nuckolls, III)
21. 05:42 PM - Re: Re: Engine mount as starter ground path (Tom Hanaway)
22. 06:03 PM - Re: Re: Engine mount as starter ground path (Robert L. Nuckolls, III)
23. 06:12 PM - Re: Re: Engine mount as starter ground path (Kelly McMullen)
24. 09:31 PM - Re: KX-125 Installation Manual? (iconoclast)
Message 1
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Subject: | 12V Power Socket |
Hello,
I am wiring up a 12V (cigarette lighter) power socket into my panel.
Can anyone tell me the convention for the +ve and -terminals on these things?
Thanks,
Andrew.
Message 2
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Subject: | Re: Engine mount as starter ground path |
Bob,
My first post to this site. I'm working on an rv-10. I thought I understood
the grounding once you gave the below explanation to Bill W.
One and two are clear. I read #3 as putting a jumper across an individual
mount t0 both sides of a single biscuit. In a later post, you advise "any
bonding jumpers across the engine mounts are best removed" to avoid parallel
grounds. Equally, the Connection speaks of a single point ground at
firewall. Is this a contradiction or does it refer to not having jumpers
between two completely separate mounts?
Thanks,
Tom Hanaway
Boynton Beach, FL
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com
<mailto:nuckolls.bob@aeroelectric.com?subject=Re:%20Engine%20mount%20as%20st
arter%20ground%20path&replyto=4A1D8274.5020609@nc.rr.com> >
>
> At 11:35 PM 5/26/2009, you wrote:
>> <nuckolls.bob@aeroelectric.com
<mailto:nuckolls.bob@aeroelectric.com?subject=Re:%20Engine%20mount%20as%20st
arter%20ground%20path&replyto=4A1D8274.5020609@nc.rr.com> >
>>
>> t 08:47 PM 5/26/2009, you wrote:
>> <MauleDriver@nc.rr.com
<mailto:MauleDriver@nc.rr.com?subject=Re:%20Engine%20mount%20as%20starter%20
ground%20path&replyto=4A1D8274.5020609@nc.rr.com> >
>>
>> The Z-14 I've put into my RV10 follows the best practices as
>> described in the Connection with one oversight.... I have the 2 sided
>> forest of tabs on the firewall but I only have an AWG 8 cable
>> running to it from the rear batteries instead of an AWG2 fat wire.
>> And it's too late to swap it out without significant re-work.
>
> Bill, re-reading my posting from last night I'm not
> sure I conveyed a clear image of my recommendations.
> In a nutshell:
>
> Add local grounds to airframe for the batteries if
> you don't already have them.
>
> Add crankcase to firewall ground stud for engine.
>
> Leave jumpers across the engine mount biscuits.
>
> You can cut the 8AWG wire out if you wish and
> if it is practical. It adds only weight and
> offers no significant electrical function.
>
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
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Subject: | Re: 12V Power Socket |
The positive is the centre post and negative the outer shell.
Jay
-----Original Message-----
From: "Andrew Butler" [andrewbutler@ireland.com]
Subject: Re: AeroElectric-List: 12V Power Socket
Hello,
I am wiring up a 12V (cigarette lighter) power socket into my panel.
Can anyone tell me the convention for the +ve and -terminals on these things?
Thanks,
Andrew.
Message 4
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Subject: | Re: 12V Power Socket |
Positive is the center (spring loaded plunger on the plug), ground is the
shell (two flat connectors along the side of the plug).
Rick
On Thu, May 28, 2009 at 7:45 AM, Andrew Butler <andrewbutler@ireland.com>wrote:
> andrewbutler@ireland.com>
>
> Hello,
>
> I am wiring up a 12V (cigarette lighter) power socket into my panel.
>
> Can anyone tell me the convention for the +ve and -terminals on these
> things?
>
> Thanks,
>
> Andrew.
>
>
Message 5
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Subject: | Re: Alternator with built-in regulator |
Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as
backup.
Wade Roe
IPhone message
On May 27, 2009, at 10:38 PM, "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com
> wrote:
> >
>
>
>>
>>
>> The plane will be IFR and all electric.
>>
>> Wade Roe
>>
>
> Wade, would it be a fair assumption then that
> a second alternator will go onto the vacuum
> pump pad?
>
>
> Bob . . .
>
> ----------------------------------------)
> ( . . . a long habit of not thinking )
> ( a thing wrong, gives it a superficial )
> ( appearance of being right . . . )
> ( )
> ( -Thomas Paine 1776- )
> ----------------------------------------
>
>
Message 6
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Subject: | Re: 12V Power Socket |
Andrew,
The usual center is positive and the shell goest to ground. You
should wire the scocket to powerthe panel with out turning the master on.
I have mine that way so I can play with the panel with out using the
aircraft battery. I have a little cpmpressor / battery unit that I take
to the hanger and keeps the tires up and lets me run my glass panel for
setting up a trip etc.
Jim
____________________________________________________________
Compete with the big boys. Click here to find products to benefit your business.
http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTI97zF6gFxJRmQXuZsZBzUiPEnqkuoiaMthATKQtsww5EJAaYCWxa/
Message 7
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Subject: | Grounding philosophy |
Time: 09:21:48 AM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Subject:
At 09:05 AM 5/27/2009, you wrote:
<phillip.johnson@lmco.com>
Bob,
>I read your message and went to your web link indicated below and I
>can't accept that it is a good design. The problem that I see is that
>your design does not create a single ground reference.
>Yes it does. The architectures discussed in Figure Z-15 and
>other writings suggeste the stud at the forest of tabs on the
>firewall is the central point ground for the aircraft.
So Ground point number one is the "forest of tabs" and ground point
number two is the engine crankcase when the alternator, starter motor,
and most engine sensors make their ground. I.e. there is not a single
point ground. In an ideal world where #2 gauge wires and
interconnections have zero resistance but, as you point out in your
document, this is not the case.
>>Ideally you want
>>the engine block to be the ground reference with all currents flowing
>>through it. To this end you need to connect the battery -ve to the
>>crankcase and then make all grounds connect, either directly or
>>indirectly, to the crankcase as well. In doing this there will be no
>>ground potential differences to upset the instrumentation.
>Instrumentation is a special case where grounded automotive
>sensors are at risk for suffering ground loop interference.
>This has been discussed at length in various writings. If the
>problem presents itself (usually manifest by a shift in
>instrumentation readings in response to alternator loads),
>then the "ground" leads for panel mounted instruments need
>to be extended to the crankcase. However, if one has a very
>low resistance net between he crankcase and the firewall
>ground stud . . . then the "problem" may be reduced to
>insignificant if not completely unobservable.
They should not have to be a special case if wired correctly. When
everything references the crankcase there is no special case. The
problem is that when the installation is done all the connections are
clean and the installer usually knows what he is doing. A few years
down the road an unknowledgeable person does not prepare the electrical
bonding surface as well as he should and then problems start happening
when current starts to flow through the circuit. Using the philosophy
that I have given, these problems are reduced significantly, which in my
opinion makes for a better design.
>>The pilot now tries to start the engine and all of
>>the current tries to flow through this instrumentation ground. This
>>causes a melt down of the wiring and a potential ground fire and risk
to
>>those expensive electronics.
>Again, discussed in past publications and postings . . .
>"Smoking ground returns" is easily avoided by not closing
>the returns. Common occurrences include the risk of
>instrumentation grounds for instruments not designed
>to live in the real world of aircraft. Another common
>risk happens when builders attached p-lead shields to
>crankcase at one end and airframe at the other end.
>All of my drawings illustrate technique for avoiding
>that loop as well.
Again, "Smoking ground returns" are avoided if you use my design
solution.
>>It is my opinion, and I believe that the automotive industry also
adopts
>>this philosophy, that you connect the battery ground to the crankcase
>>and then strap the engine to the airframe/car body and system ground
so
>>that the high current grounds pass only through the engine. Charging
>>ground currents, which can be extremely high, also only pass through
the
>>engine block thereby preventing erroneous instrumentation and
potential
>>fire risk.
>Batteries go to crankcases in cars because the battery
>always sits right next to the engine.
In the old days the battery ground went straight to the bodywork and
then there was an engine strap in a different location which coupled the
body to the engine. I'm not sure when the change occurred but I would
guess that it occurred somewhere soon after the first electronic systems
were implemented. I changed the battery on my neighbours Audi a couple
of years ago and that had the battery under the rear seats. The ground
lead did not go straight to the body but I can't be sure that it went
all the way to the front either. I surmise that if it did not go
directly to the body it would probably make the full journey to the
engine.
>The automotive
>industry has adopted the same philosophy as every other
>industry for minimizing the numbers of joints, fasteners
>and pieces of wire in the fat-wire conduction paths.
Agreed
>Now, if one had a battery on the forward side of
>the firewall then there is no electrical reason
>NOT to ground the battery right to the crankcase.
>There are mechanical reasons not to . . . we've
>already established the value of a 2AWG equivalent
>jumper from crankcase to ground stud. This same stud
>becomes a practical spot to ground a battery as
>well . . . and the 2AWG bonding strap makes sure
>that voltage differences between the crankcase
>and the ground stud are insignificantly small.
I have a Cozy MK IV with the battery on the cockpit side of the
firewall. I have approximately two feet of cable connecting the -ve to
crankcase ground so length cant be an issue. The issue is that there
are two additional connections and a couple of feet of #2 cable
separating the engine ground from the "forest of tabs". Using the
numbers from your paper this gives 1.3 mohm of resistance. Assuming you
have an alternator sourcing say 40 amps you now have 50 mV ground
difference which is also rectified AC i.e. noise. Now as you have said
it is difficult to get better than 0.5miliohm per connection and with
time and sloppy maintenance the number grows to something that is
unacceptable. All this just because the ground reference was not
defined appropriately.
>If the battery is aft of the firewall, then the
>most practical battery ground is the firewall
>ground stud . . . or to the airframe on an all
>metal airplane.
OK I have a plastic aeroplane so airframe is not an option but I still
feel the firewall is a bad choice.
>>OK I've now started to run and get my flame suit on.
>Zero risk from me sir . . .
Bob . . .
Message 8
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Subject: | Reading Potentiometer Values |
I have a handful of potentiometers at home and I want to verify the ohms
rating of each. What is the best/easiest or cheapest way to determine
their rating? The only real equipment I have is a simple DC tester with
ohms values. I will be using one to control the audio volume between my
D180 & GMA340.
Thanks,
Glenn
Message 9
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Subject: | 12V Power Socket |
Absolutely, if you think about it for just a second, these things are no
different than a standard light bulb socket. Touch the center contact
and you'll light up; touch the ring and your still here. When people
used to smoke everyone knew the center contact had to touch to make the
heat and the cool ground was the outside. After too many cigarettes you
got stinky fingers and the contact would begin to fail and loose heat
thus becoming less of a conductor between the center and the shell. If
the shell were a on the + side of the ship, your 63 Chevy's steel panel
would still be smoking.
Glenn
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Richard Girard
Sent: Thursday, May 28, 2009 9:44 AM
Subject: Re: AeroElectric-List: 12V Power Socket
Positive is the center (spring loaded plunger on the plug), ground is
the shell (two flat connectors along the side of the plug).
Rick
On Thu, May 28, 2009 at 7:45 AM, Andrew Butler
<andrewbutler@ireland.com> wrote:
<andrewbutler@ireland.com>
Hello,
I am wiring up a 12V (cigarette lighter) power socket into my panel.
Can anyone tell me the convention for the +ve and -terminals on these
things?
Thanks,
Andrew.
-List"
target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
http://forums.matronics.com
le, List Admin.
="_blank">http://www.matronics.com/contribution
Message 10
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Subject: | Alternator with built-in regulator |
One caveat on P & P alts. The one I had came with what I'll call a cheap
Molex connector for the field wire etc. I replaced it with sold wiring
after it vibrated and sheared itself off for the second time. I now use
and internal job and have not had any issues. It's all about the core
quality. Alternators are one of the biggest scams in automotive history.
They cost about $10.00 to rebuild and the vendors charge you an arm and
a leg.
As Frank mentioned, start with a good core and stick with it. I'm using
one off a Porsche and it works like a champ.
Glenn
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Hinde, Frank George (Corvallis)
Sent: Wednesday, May 27, 2009 5:45 PM
Subject: RE: AeroElectric-List: Alternator with built-in regulator
(Corvallis)" <frank.hinde@hp.com>
In that case send that alternator back to Vans and exchange it for the
plane power unit...Trying to use the B&C regulator (which it was not
designed for) is a bit like putting lipstick on a pig..Its still a pig!
I futzed with a rebuilt alternator for a while and had a couple of scary
moments in IMC..then I changed to the Plane power and its been faultless
ever since. They come with a wonderful reputation. No electrical noise,
just fit (with the supplied brackets) and forget it.
On An all electric IFR airplane the alternator is not the place to be
making shortcuts!!!..The extra couple of hundred bucks is WELL spent.
Frank
RV7a..all electric IFR including 2* EI's and the fuel pumps!
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Wade
Roe
Sent: Wednesday, May 27, 2009 2:20 PM
Subject: RE: AeroElectric-List: Alternator with built-in regulator
The alternator from Vans is a reconditioned Japanese automobile unit
(Honda?) that came with the firewall forward kit. I figured the B&C
linear regulator to be a superior/cleaner product than that on the
alternator.
The plane will be IFR and all electric.
Wade Roe
Message 11
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Subject: | Alternator with built-in regulator |
Me too..I found that the SD8 was adequate and remember I run electric fuel pumps..One
of them MUST be running or I become a glider.
I have a GNS 430W, transponder etc etc and found that with sensible load management
the SD8 would maintian the battery volts at 12..Not enough to charge the
battery but it would keep up with the load.
Frank
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Wade Roe
Sent: Thursday, May 28, 2009 6:52 AM
Subject: Re: AeroElectric-List: Alternator with built-in regulator
Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as backup.
Wade Roe
IPhone message
Message 12
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Subject: | Re: State of the art - then and now |
Great stuff Bob!
"The more things change the more they stay the same."
Thanks for sharing...
C. Stone
I'm in possession of several issues of the Electrical
Experimenter circa 1916. This hobbyist/amateur/semi-
professional publication offered a newsstand source
for both understanding and state of the art news in
a range of technologies.
I'm using one of these magazines as reference for a
science history presentation I'm doing. I've scanned it
for sharing and thought I would post it for those
having an interest in such things. See:
http://tinyurl.com/ofbj3c
It's interesting to see the depth and scope of interests
illustrated on these pages. It's also interesting to
see a level of hucksterism and quackery not unlike
that which pours forth in today's video and print media!
See pdf pages 7, 25, 62 (violet rays), 65 (Pandiculator).
But the casually discriminating eye can easily identify
and appreciate the good stuff of which there is plenty.
Hope you enjoy browsing this piece of technological history.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 13
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Subject: | Re: Reading Potentiometer Values |
Hi Glenn,
It sounds like you have what you need. Measure the resistance (ohms)
between the two outside pins. That will tell you what the resistance
of the pot is. There is another consideration when selecting a pot.
There linear and "audio" taper pots. A linear pot will change
resistance linearly with pot rotation. Turn it half way between CCW
and CW will give a reading of 1/2 the total resistance. An audio taper
will change exponentially. Rotating half way between CCW and CW will
result in a lower resistance between the center pin and the CCW pin and
a higher resistance between the center pin and the CW pin. The audio
taper is probably the best choice for your application.
Also, there should be some markings on the pot that will tell you what
value the pot is. Picking up a couple of random pots from by work
bench, one is marked "200 (ohm) LIN" which is pretty straightforward to
decode. the other is marked "A100K" which clearly indicates it is a
100 kohm pot, and I would guess the "A" means audio taper but I would
have to check.
(There are pots that aren't configured quite as described, but it
should work for most run of the mill pots.)
Bob W.
On Thu, 28 May 2009 10:23:23 -0400
<longg@pjm.com> wrote:
>
> I have a handful of potentiometers at home and I want to verify the ohms
> rating of each. What is the best/easiest or cheapest way to determine
> their rating? The only real equipment I have is a simple DC tester with
> ohms values. I will be using one to control the audio volume between my
> D180 & GMA340.
>
> Thanks,
> Glenn
>
>
>
>
>
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/
Message 14
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Subject: | 12V Power Socket |
It depends on what you want to accomplish. If you wire it to the buss side
of the master you can power your panel from it during the build. But if you
wire it to the battery side of the master you can power accessories or
trickle charge the battery without turning on the master. There are pluses &
minuses both ways. Think it through and decide what's best for you.
Regards,
Greg Young
> -----Original Message-----
> ground. You should wire the scocket to powerthe panel with
> out turning the master on.
> I have mine that way so I can play with the panel with out
> using the aircraft battery. I have a little cpmpressor /
> battery unit that I take to the hanger and keeps the tires
> up and lets me run my glass panel for setting up a trip etc.
>
>
>
Message 15
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Subject: | Grey code output to multiple devices |
Folks,
I have a Narco AR 850 grey code altitude reporter. I would like to connect it
to two devices (GPS and transponder) instead of just the transponder. The serial
port on the GPS is being used for something else and it has grey code lines
also.
Both the GPS and transponder have diode suppression in the grey code lines in order
to prevent an off unit from dropping the signal to low.
What say ye.....can I do this - or will smoke escape....?
Thanks,
Ralph Capen
Message 16
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Subject: | Reading Potentiometer Values |
Excellent,
Thanks Bob.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob
White
Sent: Thursday, May 28, 2009 12:00 PM
Subject: Re: AeroElectric-List: Reading Potentiometer Values
Hi Glenn,
It sounds like you have what you need. Measure the resistance (ohms)
between the two outside pins. That will tell you what the resistance
of the pot is. There is another consideration when selecting a pot.
There linear and "audio" taper pots. A linear pot will change
resistance linearly with pot rotation. Turn it half way between CCW
and CW will give a reading of 1/2 the total resistance. An audio taper
will change exponentially. Rotating half way between CCW and CW will
result in a lower resistance between the center pin and the CCW pin and
a higher resistance between the center pin and the CW pin. The audio
taper is probably the best choice for your application.
Also, there should be some markings on the pot that will tell you what
value the pot is. Picking up a couple of random pots from by work
bench, one is marked "200 (ohm) LIN" which is pretty straightforward to
decode. the other is marked "A100K" which clearly indicates it is a
100 kohm pot, and I would guess the "A" means audio taper but I would
have to check.
(There are pots that aren't configured quite as described, but it
should work for most run of the mill pots.)
Bob W.
On Thu, 28 May 2009 10:23:23 -0400
<longg@pjm.com> wrote:
>
> I have a handful of potentiometers at home and I want to verify the
ohms
> rating of each. What is the best/easiest or cheapest way to determine
> their rating? The only real equipment I have is a simple DC tester
with
> ohms values. I will be using one to control the audio volume between
my
> D180 & GMA340.
>
> Thanks,
> Glenn
>
>
>
>
>
--
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/
Message 17
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Subject: | Re: Reading Potentiometer Values |
At 09:23 AM 5/28/2009, you wrote:
>
>I have a handful of potentiometers at home and I want to verify the ohms
>rating of each. What is the best/easiest or cheapest way to determine
>their rating? The only real equipment I have is a simple DC tester with
>ohms values. I will be using one to control the audio volume between my
>D180 & GMA340.
For simple volume control duties, simply
knowing the resistance value is sufficient.
Further, it's unlikely that the exact value
is critical. Potentiometers with values
ranging from 500 to perhaps as high as
10000 ohms would work for you. It's an
easy experiment and zero risk to the rest
of your system.
Digital multi-meters are inexpensive. Harbor
Freight has one that seems to be perpetually
on sale for under $5.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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Subject: | Re: Alternator with built-in regulator |
At 08:51 AM 5/28/2009, you wrote:
>
>Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as
>backup.
Most builders find the SD-8 to be adquate to the
task. Consider Figure Z-13/8.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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Subject: | Re: Grounding philosophy |
So Ground point number one is the "forest of tabs" and ground point
number two is the engine crankcase when the alternator, starter motor,
and most engine sensors make their ground. I.e. there is not a single
point ground. In an ideal world where #2 gauge wires and
interconnections have zero resistance but, as you point out in your
document, this is not the case.
Let's not get wrapped around the axle for defining
"single point ground". The better term is perhaps
a central ground point from which the rest of the
ground system radiates. Now, there can be and often
is further spreading from nodes remote from the
central ground. One example is the crankcase from which
numerous grounded sensors find a reference. See
Figure Z-15 (three sheets).
Risks of system performance degrading due to currents
circulating in the ground system are reduced if not
eliminated by first avoiding multiple grounds within
any single system that are not co-located. In the
case of engine instruments with grounded sensors,
taking the ground returns for panel mounted instruments
back to the crankcase makes the crankcase a "single
point ground" for that suite of instruments.
Figure Z-15 speaks to a variety of grounding options
for accessories located all over the airplane. None
of those illustrations suggests that ALL grounds
be brought to a single-point be it the crankcase
or forest of tabs. What those drawing DO illustrate
is making a distinction between potential noise
victims, noise antagonists and breaking the ground
loop coupling mode.
They should not have to be a special case if wired correctly. When
everything references the crankcase there is no special case. The
problem is that when the installation is done all the connections are
clean and the installer usually knows what he is doing. A few years
down the road an unknowledgeable person does not prepare the electrical
bonding surface as well as he should and then problems start happening
when current starts to flow through the circuit. Using the philosophy
that I have given, these problems are reduced significantly, which in my
opinion makes for a better design.
Define "wired correctly". In the TC aviation world
we're very much aware of the problems associated
with engine sensors conforming to legacy automotive
conventions of grounding to the block. In the 1957
Chevy, the grounded oil pressure "sender" is
"wired correctly". In a 1995 Beechjet, this product
would not be considered for a host of reasons not
the least of which is "incorrect wiring" for design
goals imposed on the project. But if my boss says
"Put this 1957 oil pressure gage in that airplane"
I can get 'er done with zero risk of degraded
performance induced by poor grounding decisions.
Again, "Smoking ground returns" are avoided if you use my design
solution.
I'm not suggesting that there is but one solution
for avoiding smoking grounds or ground loop induced
noise. If you choose to use the crankcase as your
"single point ground" . . . is it your intention to
take all the ground wires from ship's electro-whizzies
to the crankcase? That could make for a really big
bundle of wires through the firewall. If you grounded
EVERYTHING to the crankcase, would you still ground
the p-lead shields at both ends?
>Batteries go to crankcases in cars because the battery
>always sits right next to the engine.
In the old days the battery ground went straight to the bodywork and
then there was an engine strap in a different location which coupled the
body to the engine. I'm not sure when the change occurred but I would
guess that it occurred somewhere soon after the first electronic systems
were implemented. I changed the battery on my neighbours Audi a couple
of years ago and that had the battery under the rear seats. The ground
lead did not go straight to the body but I can't be sure that it went
all the way to the front either. I surmise that if it did not go
directly to the body it would probably make the full journey to the
engine.
Which is anecdotal to what we're discussing here.
Exactly how you achieve low resistance, minimum
parts count, no-loop architecture for grounds in
your airplane has many recipes for success as long
as the components are assembled with understanding.
But let us take care that we don't confuse 1800+
readers of this List with some notion that the crankcase
is the touchstone of grounds . . . this simply isn't so.
I have a Cozy MK IV with the battery on the cockpit side of the
firewall. I have approximately two feet of cable connecting the -ve to
crankcase ground so length cant be an issue. The issue is that there
are two additional connections and a couple of feet of #2 cable
separating the engine ground from the "forest of tabs". Using the
numbers from your paper this gives 1.3 mohm of resistance. Assuming you
have an alternator sourcing say 40 amps you now have 50 mV ground
difference which is also rectified AC i.e. noise. Now as you have said
it is difficult to get better than 0.5miliohm per connection and with
time and sloppy maintenance the number grows to something that is
unacceptable. All this just because the ground reference was not
defined appropriately.
I think you're sifting the sand here. There
is NO electrical system for any vehicle that is
not plagued with beeps, burps, hums, spikes and
assorted perturbations of voltage a LOT bigger
than your hypothesis. In the TC aircraft world
we KNOW that those noises exist and we design
to live with them. See:
http://www.aeroelectric.com/articles/DO-160.pdf
The voltage levels you hypothesize are of
no significance if potentially vulnerable
systems don't see them because ground loops have
been eliminated. Making sure the loops don't exist
is easy if you understand your system integration
task. It matters not whether the system follows
legacy automotive design goals or modern aviation
design goals. BOTH technologies can be successfully
integrated into the OBAM aircraft.
>If the battery is aft of the firewall, then the
>most practical battery ground is the firewall
>ground stud . . . or to the airframe on an all
>metal airplane.
OK I have a plastic aeroplane so airframe is not an option but I still
feel the firewall is a bad choice.
A "bad choice" only if you allow ground
loops to exist without evaluating their potential
for influencing system performance. Please
wire in any manner that gives you comfort.
All I'm offering is a constellation of options
based on many recipes for success. Virtually
ALL of those recipes call for elimination of
ground loops that offer a potential for problems.
NONE of those recipes treats any location or
component of the ground system as the Nirvana
of grounds.
The forest-of-tabs offers a level of convenience
for the majority of system grounds for devices
both sides of the firewall. Having this device
be 'central' to the ship's ground system
makes sense . . . especially if the engine
sensors are "wired correctly" in observance of
modern aircraft design goals. But even if they
are not, the third sheet of Z15 suggests how the
1950's design goals can be accommodated in a 2009
RV.
Bob . . .
Message 20
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Subject: | Re: Engine mount as starter ground path |
At 07:58 AM 5/28/2009, you wrote:
>Bob,
>
>My first post to this site. I'm working on an rv-10. I thought I
>understood the grounding once you gave the below explanation to Bill W.
>
>One and two are clear. I read #3 as putting a jumper across an
>individual mount t0 both sides of a single biscuit. In a later
>post, you advise "any bonding jumpers across the engine mounts are
>best removed" to avoid parallel grounds. Equally, the Connection
>speaks of a single point ground at firewall. Is this a contradiction
>or does it refer to not having jumpers between two completely separate mounts?
No, I was referencing a project-in-process where an
already too-small 8AWG battery(-) wire was installed.
Upsizing that wire was not an attractive option.
The work-around involved the used of jumper straps
around the shock mount biscuits and local battery grounds.
Now, if you're starting from scratch and your
battery is located near the firewall, that
posting was not applicable to you. Use NO
JUMPERS on the engine mount biscuits. Wire
as suggested in chapter 5 and Figure Z-15.
Welcome to the List!
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Subject: | Re: Engine mount as starter ground path |
Thanks Bob.
Sorry to beat a dead horse but I need one more clarification. Your
response
mentions "if battery near firewall". The batteries are actually both in
the
aft area. Can the battery be locally grounded to airframe at site of
battery (metal frame craft) with B&C tab forest on firewall for grounds
and
engine ground?
Or is best solution still to run a 2awg ground wire up to firewall and
proceed with grounding to tab forest as above?
Thanks,
Tom
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L.
Nuckolls, III
Sent: Thursday, May 28, 2009 5:10 PM
Subject: Re: AeroElectric-List: Re: Engine mount as starter ground path
At 07:58 AM 5/28/2009, you wrote:
Bob,
My first post to this site. I=12m working on an
rv-10. I thought I understood the grounding once you gave the below
explanation to Bill W.
One and two are clear. I read #3 as putting a
jumper across an individual mount t0 both sides of a single
biscuit. In a later post, you advise =13any bonding jumpers across
the engine mounts are best removed=14 to avoid parallel grounds.
Equally,
the Connection speaks of a single point ground at firewall. Is this a
contradiction or does it refer to not having jumpers between two
completely separate mounts?
No, I was referencing a project-in-process where an
already too-small 8AWG battery(-) wire was installed.
Upsizing that wire was not an attractive option.
The work-around involved the used of jumper straps
around the shock mount biscuits and local battery grounds.
Now, if you're starting from scratch and your
battery is located near the firewall, that
posting was not applicable to you. Use NO
JUMPERS on the engine mount biscuits. Wire
as suggested in chapter 5 and Figure Z-15.
Welcome to the List!
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Subject: | Re: Engine mount as starter ground path |
At 07:34 PM 5/28/2009, you wrote:
>Thanks Bob.
>Sorry to beat a dead horse but I need one more clarification. Your
>response mentions "if battery near firewall". The batteries are
>actually both in the aft area. Can the battery be locally grounded
>to airframe at site of battery (metal frame craft) with B&C tab
>forest on firewall for grounds and engine ground?
>
>Or is best solution still to run a 2awg ground wire up to firewall
>and proceed with grounding to tab forest as above?
>
>Thanks,
>Tom
>
>----------
You say "both batteries". Which Z-figure are
you crafting?
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Subject: | Re: Engine mount as starter ground path |
The RV-10 by necessity and design has the battery(s) located in the
tailcone to partly offset the weight of the IO-540 up front.
Given that the structure from the battery location to the firewall is
all riveted aluminum in the lower half of the fuselage there likely is a
solid ground path. Running a fat wire to parallel that ground path, or
to replace it doesn't appear to be all that good an option.
Kelly
Robert L. Nuckolls, III wrote:
>
> No, I was referencing a project-in-process where an
> already too-small 8AWG battery(-) wire was installed.
> Upsizing that wire was not an attractive option.
> The work-around involved the used of jumper straps
> around the shock mount biscuits and local battery grounds.
>
> Now, if you're starting from scratch and your
> battery is located near the firewall, that
> posting was not applicable to you. Use NO
> JUMPERS on the engine mount biscuits. Wire
> as suggested in chapter 5 and Figure Z-15.
>
>
Message 24
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Subject: | Re: KX-125 Installation Manual? |
If it's not too much trouble, can you please PM me the KX 125 manual also? I'm
adding a second com and need to patch into the harness for my 125.
Thanks,
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=245836#245836
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