Today's Message Index:
----------------------
1. 05:58 AM - P-mags and the RV-7 Off Field Landing (Robert L. Nuckolls, III)
2. 06:00 AM - Re: Stripping Longer Piece of Shielded/Twisted Pair Wire (Robert L. Nuckolls, III)
3. 06:50 AM - Re: P-mags (Hinde, Frank George (Corvallis))
4. 06:53 AM - Re: P-mags and the RV-7 Off Field Landing (BobsV35B@aol.com)
5. 07:15 AM - Engine gage wiring (Danm)
6. 08:06 AM - Re: Engine gage wiring (Mike)
7. 08:30 AM - Re: P-mags (Kevin Horton)
8. 09:22 AM - Re: Engine gage wiring (Robert L. Nuckolls, III)
9. 09:54 AM - Re: Engine gage wiring (Danm)
10. 09:56 AM - Re: Full Auto (marcausman)
11. 10:15 AM - Re: Re: Engine gage wiring (Dale Ensing)
12. 10:19 AM - Re: Re: Engine gage wiring (Hinde, Frank George (Corvallis))
13. 12:24 PM - Re: Strobes (C Smith)
14. 12:44 PM - Re: Re: Full Auto ()
15. 06:36 PM - 28v switches in a 12v system? (Chris Johnston)
16. 07:23 PM - Re: 28v switches in a 12v system? (Robert L. Nuckolls, III)
17. 08:05 PM - Re: 28v switches in a 12v system? (Matt Prather)
18. 08:09 PM - Re: P-mags (Robert L. Nuckolls, III)
19. 10:29 PM - Re: P Mags (Speedy11@aol.com)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | P-mags and the RV-7 Off Field Landing |
At 01:43 AM 2/21/2007 +0000, you wrote:
>
>Frank,
>
>Help me out here, if that isn't a "failure", just what would you call
>it? In my book, any mechanical screw up that causes an unplanned landing
>sure fits the definition of a failure.
No doubt there WAS a SYSTEM failure. But accurate
investigation and diagnosis of root cause extends
FAR beyond what usually happens when unhappy events
in aviation spark public discussions.
It's inarguable that the pilot perceived a reason
to make an off-field landing. Anecdotally, we
understand that the ignition SYSTEM was misbehaving.
What do we know about how the pilot reacted to his/her
perceptions? What did your instructor tell you to
do when the engine is running badly? Were there not
words suggesting that turning the mags off one at
a time would help you isolate a recalcitrant magneto?
Is it not reasonable to expect that a similar
investigation would have been useful in this event?
What do you think the probability is that both
Emagair products became unserviceable on the
same tank full of fuel? What do we know about the
post flight discovery of facts?
I think the major point to be considered here
is that the general public is very quick to launch
lengthy and heated debate on a variety of non-news
items reported in the media. I say "non-news" because
while the stories may accurately record a happening,
the reporter rarely knows diddly-squat about the
simple-ideas that underlie the story. They're prone
to rely on the words of others who are probably
as ignorant of facts and understanding as the reporter
is.
In Chapter 17 of the 'Connection I've suggested
that the pilot subsystem is subordinate only to
the airframe in importance for having a happy
ending to an aviation experience. Those of us who
have lived and worked in the aviation venue most
of our careers are skeptical of the notion that
the aircraft featured in this story suffered an
ignition system failure that would be expected
to force an off-field landing. But lacking
more data, the best we can offer is a considered
opinion as to PROBABILITY based on our past
experience. Opinions not founded in simple-ideas
and offered by individuals who cannot teach
the significance of those ideas are suspect. This
is where the differences between teachers and
propagandists become strikingly obvious.
So before we get out the big brush and red paint
and write ACCIDENT INDUCING FAILURE across E-Magair's
reputation, let us take the time on THIS LIST
to conduct careful consideration of facts.
It's unlikely that you'll get any facts from
folks who were not there and did not put their
hands on hardware. So no matter what pot is
boiling on any other List, let us do the science
(and/or rely on others who ARE doing the science)
lest we give rise to invariably poor recommendations
that arise from equally poor conclusions.
Bob . . .
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Stripping Longer Piece of Shielded/Twisted Pair |
Wire
At 10:48 PM 2/20/2007 -0600, you wrote:
>I have a few electrical cables (e.g., from nav lights) to my panel that
>are shielded/twisted pairs. One of the wires goes to the panel switch and
>the other goes to the ground block on the firewall. Is there any easy way
>to strip of 2' to 3' of the outer cable jacket so I can reach both the
>switch and the ground block without splicing in a piece of wire to run to
>the ground block?
You have a ground block located adjacent to the switches?
Interesting. In answer to your question, try a pair of
cuticle scissors, the slim points can be pushed under the
jacket and between the twisted wires far enough to allow the
shears to cut the jacket away. Obviously, this doesn't work
on single conductor cable.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 3
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Fair point Harry,
I guess my conjecture was that one of the P mags could have been turned
off and the engine would have resumed normal operation...I just wish I'd
though of it when it happened to me...Of course my engine just ran hot,
i.e did not causean engine stoppage.
Frank
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
HCRV6@comcast.net
Sent: Tuesday, February 20, 2007 5:43 PM
Subject: RE: AeroElectric-List: P-mags
Frank,
Help me out here, if that isn't a "failure", just what would you call
it? In my book, any mechanical screw up that causes an unplanned
landing sure fits the definition of a failure.
--
Harry Crosby
RV-6 N16CX, 312 hours
-------------- Original message ----------------------
From: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
(Corvallis)"
> <frank.hinde@hp.com>
>
> Nope Dual P mags. They did NOT fail. I believe ONE of them went to
> very advanced timing. It has the effect of fouling up the timing
> completely because once the charge has been lit the second spark
> doesn't do anything.
>
> There is a long discussion on the Vansairforce website about it.
>
> Frank
> RV-7a
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> John W. Cox
> Sent: Tuesday, February 20, 2007 11:54 AM
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: P-mags
>
> --> <johnwcox@pacificnw.com>
>
> I was not aware the four cylinder P mag was yet available for Prime
> Time. Could this have been dual E mags?
>
> John Cox
>
>
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> Terry Watson
> Sent: Tuesday, February 20, 2007 10:47 AM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: P-mags
>
> <terry@tcwatson.com>
>
>
> This is an excerpt from a message to the Matronics Engines list this
> morning, posted by Mike Larkin:
>
> " As for the P-mag, I recovered an RV-7 from a highway two weekends
> ago when Both P-mags failed. Guess what, the electrical system worked
> perfectly......"
>
> Since E-mags and P-mags have been a subject on this list, I thought I
> would pass it on. Does anyone know the story?
>
> Terry
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
Message 4
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: P-mags and the RV-7 Off Field Landing |
In a message dated 2/21/2007 8:01:18 A.M. Central Standard Time,
nuckollsr@cox.net writes:
So before we get out the big brush and red paint
and write ACCIDENT INDUCING FAILURE across E-Magair's
reputation, let us take the time on THIS LIST
to conduct careful consideration of facts.
It's unlikely that you'll get any facts from
folks who were not there and did not put their
hands on hardware. So no matter what pot is
boiling on any other List, let us do the science
(and/or rely on others who ARE doing the science)
lest we give rise to invariably poor recommendations
that arise from equally poor conclusions.
Bob . . .
Good Morning 'Lectric Bob,
I realize we are not supposed to post Me Too or other confirmation messages,
but you have hit the nail so squarely that I just cannot resist.
Great post!
Do Not Archive!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Ancient Aviator
Stearman N3977A
Brookeridge Air Park LL22
Downers Grove, IL 60516
630 985-8503
<BR><BR><BR>**************************************<BR> Check out free AOL at
http://free.aol.com/thenewaol/index.adp. Most comprehensive set of free
safety and security tools, millions of free high-quality videos from across the
web, free AOL Mail and much more.
Message 5
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Engine gage wiring |
I installed a UMA oil pressure gage, PN 4-210-080 and a oil temp gage, PN 12-200-250f
in my Kitfox IV with a Jabiru 2200 engine. When I open the master switch
(split rocker), the gages have readings of approximately 25 psi oil pressure
and 120 degree oil temp. The engine hasn't been started yet (new aircraft), so
there must be something wrong with the wiring or the sending units supplied
with the engine. I check the gage wiring and looks to be correct. I suspect either
a wiring issue or a sending unit issue. I you can help me out, it would be
appreciated.
Thanks in advance
--------
Dan Mc Intyre
Kitfox Model IV, Jab 2200
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p'487#96487
Message 6
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Engine gage wiring |
Dan,
Check all of your grounds. Make sure the engine is grounded to the
airframe. Make sure that the instrument is grounded to the main ground
(airframe)or ground bus. Make sure you have a large enough ground from
the engine to the airframe.
Just my thoughts,
Mike Larkin
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Danm
Sent: Wednesday, February 21, 2007 8:14 AM
Subject: AeroElectric-List: Engine gage wiring
I installed a UMA oil pressure gage, PN 4-210-080 and a oil temp gage,
PN 12-200-250f in my Kitfox IV with a Jabiru 2200 engine. When I open
the master switch (split rocker), the gages have readings of
approximately 25 psi oil pressure and 120 degree oil temp. The engine
hasn't been started yet (new aircraft), so there must be something wrong
with the wiring or the sending units supplied with the engine. I check
the gage wiring and looks to be correct. I suspect either a wiring issue
or a sending unit issue. I you can help me out, it would be appreciated.
Thanks in advance
--------
Dan Mc Intyre
Kitfox Model IV, Jab 2200
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p'487#96487
--
2/8/2007
--
2/8/2007
Message 7
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
On 21 Feb 2007, at 09:49, Hinde, Frank George (Corvallis) wrote:
> (Corvallis)" <frank.hinde@hp.com>
>
> Fair point Harry,
>
> I guess my conjecture was that one of the P mags could have been
> turned
> off and the engine would have resumed normal operation...I just
> wish I'd
> though of it when it happened to me...Of course my engine just ran
> hot,
> i.e did not causean engine stoppage.
>
It is too much to expect for you to suddenly become very bright after
the incident occurs, and decide to try turning one ignition off. It
is far better to put that step in your Rough Running Engine and
Engine Failure checklists now. Then, whenever the problem occurs,
the fact that you are familiar with your emergency checklist should
hopefully trigger you to try turning one ignition off at a time.
Kevin Horton
RV-8 (Finishing Kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
Message 8
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Engine gage wiring |
At 07:14 AM 2/21/2007 -0800, you wrote:
>
>I installed a UMA oil pressure gage, PN 4-210-080 and a oil temp gage, PN
>12-200-250f in my Kitfox IV with a Jabiru 2200 engine. When I open the
>master switch (split rocker), the gages have readings of approximately 25
>psi oil pressure and 120 degree oil temp. The engine hasn't been started
>yet (new aircraft), so there must be something wrong with the wiring or
>the sending units supplied with the engine. I check the gage wiring and
>looks to be correct. I suspect either a wiring issue or a sending unit
>issue. I you can help me out, it would be appreciated.
>
>Thanks in advance
Without knowing details of the internal
workings for these instruments, I'll offer
the following hypothesis to explain what
you're observing:
The earliest PRECISION (meaning stable and
repeatable) instruments were crafted from a
coil of wire suspended in a magnetic field
where a current impressed on the coil would
force rotation against a spring and move a
pointer upscale. This is known as the
D'Arsonval meter movement.
http://www.triquartz.co.uk/ammeter.html
Similar devices had moving magnets held at
"zero" by a spring and suspended in a single
fixed coil.
Both of these technologies feature a
return spring that causes the instrument
to assume a familiar and expected
"zero" reading when powered down.
Modern instruments have worked past
some of the manufacturing problems with
legacy designs. A very popular, robust and
inexpensive design is also moving magnet.
But instead of one coil, there are two coils
at right angles to each other. When the
two coils are energized, the magnet (free
to move 360 degrees) will assume alignment
with the magnetic field generated by the
two coils.
This technology allows a designer to produce
instruments having very small rotational
arcs . . . up to and including 360 continuous
degrees without stops. These movements do not
have or need return springs. Therefore, the
position assumed by the pointer in a powered
down condition may be random and unpredictable
unless the designer takes special pains with
driving circuitry to make the instrument indicate
"zero" when powered down.
Given the popularity of this technology and
the very reasonable cost to manufacture, I'll
bet that what you're seeing is the predictable
behavior of a 4-quadrant, moving magnet movement
during power down. As long as the instrument is
reading correctly when powered up, there's
no reason to be concerned.
Bob . . .
For further reading see:
http://www.jewellinstruments.com/pmtheory101.htm
http://www.jewellinstruments.com/pmglossary.htm
Message 9
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Engine gage wiring |
I ment to say that the gages are at zero with no power applied, when I power up
thats when the gages go to the 25psi and 120 degree reading, engine not running.
What do you think??? Thanks for the help
--------
Dan Mc Intyre
Kitfox Model IV, Jab 2200
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p'519#96519
Message 10
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Sam, Take a look at www.verticalpower.com . It will load shed and switch alternators (nearly) automatically, and meet your KISS principles for wiring. Won't be available until August though.
Marc
--------
Marc Ausman
http://www.verticalpower.com
RV-7 IO-390 Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p'520#96520
Message 11
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Engine gage wiring |
Dan,
I remember getting an obviously erronous number on my oil pressure when
system was first turn on. Solved the problem by reversing the leads
connection at the sending unit. The sending unit had no indication of
polarity so initial connection was a 50% guess.
Dale Ensing
----- Original Message -----
From: "Danm" <danm@gangnailtruss.com>
Sent: Wednesday, February 21, 2007 12:52 PM
Subject: AeroElectric-List: Re: Engine gage wiring
>
> I ment to say that the gages are at zero with no power applied, when I
> power up thats when the gages go to the 25psi and 120 degree reading,
> engine not running. What do you think??? Thanks for the help
>
> --------
> Dan Mc Intyre
> Kitfox Model IV, Jab 2200
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p'519#96519
>
>
>
Message 12
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Engine gage wiring |
Either the wrong senders for the guages or a bad ground between the
sender and the guages.
Worng senders happen quite often.
Call the supplier and ask them what the resistnace curve looks like, i.e
get the resistance for say 55F and measure resistance with your
multimeter.
Frank
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Danm
Sent: Wednesday, February 21, 2007 9:53 AM
Subject: AeroElectric-List: Re: Engine gage wiring
I ment to say that the gages are at zero with no power applied, when I
power up thats when the gages go to the 25psi and 120 degree reading,
engine not running. What do you think??? Thanks for the help
--------
Dan Mc Intyre
Kitfox Model IV, Jab 2200
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p'519#96519
Message 13
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Fergus
Kyle
Sent: Monday, February 19, 2007 5:05 PM
Subject: AeroElectric-List: Strobes
>>Craig,
I read your latest paragraph regarding lighting and noted that's
it's all "I" and no "we". Manoeuvring around an airfield, particularly a
busy one, is very much a community thing, not a solitary event.<<
(I) speak for my self, therefore (I) don't use the term we. (I) don't see
anyone else using "we" when writing about themselves. Silly issue to pick
on.
>> While you are not bothered by another's strobes on the tarmac,
many others are, me included. If you were to sit up at 20 feet in Chicago
O'Hare and every aircraft had on strobes, you would appreciate the confusion
and wariness that occurred.<<
While (I)'m sure people get bothered by lots of things, I can't accommodate
everyone's peeve. (I) don't intend to fly into O'Hare and I wouldn't use
strobes at a busy controlled airport for taxi. My airport is uncontrolled,
and after the events mentioned, (I) determined (I) prefer to be seen.
>> Strobes don't quickly indicate speed, turns or direction. That's
why we copied ships and used coloured lamps - which do all three. Trying to
guess the progress of conflicting traffic between flashes is a mug's game
and unsafe. It is unnecessarily distracting and time-wasting when time's in
short supply.<<
(I) would challenge all of what you have written. The lighting (on aircraft)
was adopted long before strobes were in existence, and strobes are used to
capture (photography) and simulate motion (the rabbit on instrument approach
lighting) all the time. Please cite some professional study for this claim.
While observing aircraft (I) have had no trouble discerning their motion
with strobes on, and can clearly see their other running lights in spite of
the strobes. Against a static background motion is clearly accentuated by
stroboscopic effect, giving both direction and speed, the latter most
precisely.
>> Strobes are designed to be seen many miles away, not several
feet.<<
(I) beg to differ, the factory in which (I) work employs strobes on all
autonomous vehicles that operate there, and (I) believe it is an OSHA
requirement. The distances are measured in feet, from where these vehicles
operate and people work. The strobes make them virtually unmistakable. So
strobes are not distance limited.
>> Turning strobes on at Take-off clearance tells everyone who's the
primary traffic on the live runway, and the tower that the clearance has
been received and acted on.... and it does so without bothering anyone.
If the clearance wasn't issued, it draws attention to the tower that danger
is building and the take-off stopped if possible.<<<
First (I)'ve heard of this connection, it was not taught in my instrument
work. Please cite the appropriate FAR/AIM entry. (I) don't find the
reasoning for this one as unfounded as the other claims, it actually makes
some sense. If this is truly an ATC procedure (I) would like to read that in
an official document.
>>>"I'm sure the flames will start, and the name calling will follow, but
I'd rather be an a*****e than an accident statistic."
Safe, co-ordinated airport traffic is not necessarily about what
you'd rather be. It's more concerning about what you'd rather not cause.<<<
(I)'d love to see an accident report from the NTSB, or the FAA citing
"inappropriate or illegal use of strobes" as either a cause or contributing
factor of an accident. You will of course send me a link.
>> Turning landing lights on descent through 10.000 feet is not about
aircraft collisions, it's training bird flocks to avoid aircraft.
Ferg Kyle
Europa A064 914 Classic
PS: I think the argument for rotating beacons has more merit.<<
This one escapes me, pardon my misunderstanding. This is tongue in cheek? Or
a serious entreaty on use of lights.
You are entitled to your opinion, (I) respect your civil and creative
discourse, but give me facts, and (I) will then make a considered change of
mind.
Craig Smith
Message 14
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Yea, that's a great idea, but I can't until Summer, I hope to fly on the next few
weeks!
---- marcausman <marc@verticalpower.com> wrote:
>
> Sam, Take a look at www.verticalpower.com . It will load shed and switch alternators (nearly) automatically, and meet your KISS principles for wiring. Won't be available until August though.
>
> Marc
>
> --------
> Marc Ausman
> http://www.verticalpower.com
> RV-7 IO-390 Flying
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p'520#96520
>
>
>
>
>
>
>
>
>
>
Message 15
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | 28v switches in a 12v system? |
Alright smart guys... here's my dumb question of the day...
Can I use LED illuminated switches designed for a 28 volt system in a 12
volt system? Why or why not? What would theoretically happen? I
imagine that I'm fully displaying my lack of understanding in this area,
but try to be gentle.
Thanks!
cj
Message 16
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: 28v switches in a 12v system? |
At 06:32 PM 2/21/2007 -0800, you wrote:
><CJohnston@popsound.com>
>
>Alright smart guys... here's my dumb question of the day...
>
>Can I use LED illuminated switches designed for a 28 volt system in a 12
>volt system? Why or why not? What would theoretically happen? I
>imagine that I'm fully displaying my lack of understanding in this area,
>but try to be gentle.
Sure, they'll just be dim compared to the 14v illumination
level. Better get one, hook it to a battery and see if
the illumination level is still satisfactory to your needs.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 17
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: 28v switches in a 12v system? |
It won't hurt anything, but they'll be dimmmer. LED's like most diodes
have very non-linear current vs. voltage curves. Below the knee voltage
the current is nearly zero. Once the voltage goes above gets above the
knee, the current increases rapidly for small increases in voltage. A
typicl LED knee voltage is about 1.5V. Changing from 28V to 12V will
still keep the voltage applied to the LED above the knee voltage.
For the purposes of your question, let's assume that for both 12V and 28V
the voltage across the LED is 1.7V - a safe assumption, though not
perfectly accurate.
Let's also assume that the current through the LED at 28V was 20mA. That
says the switch has a dropping resistor with a value given by R = V/I
(28V - 1.7V) /20mA = 1315ohm.
Next, let's calculate the current through the circuit when running with a
12V supply. I = V/R = (12V - 1.8V) / 1315ohm = 7mA
When considering light output, the key is about power. Let's compare.
P(28V) = 20mA * 1.7V = 34mW
P(12V) = 7mA * 1.7V = 12mW
So, I would expect that when running the 28V switches at 12V, the emitted
light would be about one third. Maybe less, actually. At the lower
current, the voltage drop across the diode is going to be a little less,
so the power is going to be a little less too. At 1.5V the power is
10.5mW.
Hope that helps..
Regards,
Matt-
> <CJohnston@popsound.com>
>
> Alright smart guys... here's my dumb question of the day...
>
> Can I use LED illuminated switches designed for a 28 volt system in a 12
> volt system? Why or why not? What would theoretically happen? I
> imagine that I'm fully displaying my lack of understanding in this area,
> but try to be gentle.
>
> Thanks!
> cj
>
>
Message 18
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
At 02:49 PM 2/21/2007 +0000, you wrote:
><frank.hinde@hp.com>
>
>Fair point Harry,
>
>I guess my conjecture was that one of the P mags could have been turned
>off and the engine would have resumed normal operation...I just wish I'd
>though of it when it happened to me...Of course my engine just ran hot,
>i.e did not causean engine stoppage.
>
>Frank
Since this is a failure mode unique to the e/p-mag
products, perhaps words to guide the pilot in conducting
an in-flight diagnosis and remedy should be added to
the POH for any aircraft that carries one or more
Emagair products.
Bob . . .
Message 19
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
The initial info I have is that one P Mag advanced the timing too far
resulting in power loss since the fuel/air mixture was ignited as in entered the
cylinder. During a power loss, the pilot should cycle the ignition source to
left/right/both to check for any improvement. The P Mags don't revert to the
internal generator until electrical power is lost. Since electrical power was
available, a P Mag would not revert to the backup mode, so that means when the
faulty ignition is turned off, the engine would run normally again. Initial
indications are the pilot did not cycle the ignitions through left/right.
I will be interesting to see what Brad discovers.
Stan Sutterfield
Nope Dual P mags. They did NOT fail. I believe ONE of them went to very
advanced timing. It has the effect of fouling up the timing completely
because once the charge has been lit the second spark doesn't do
anything.
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|