Today's Message Index:
----------------------
1. 07:20 AM - Re: capacitor and music jack help needed (luckymacy@comcast.net (lucky))
2. 07:21 AM - Re: capacitor and music jack help needed (Rodney Dunham)
3. 08:50 AM - antennas ()
4. 09:48 AM - Re: Re: Why are wire strands tinned ? (Dan Morrow)
5. 10:06 AM - Re: capacitor and music jack help needed (Eric M. Jones)
6. 10:06 AM - Re: capacitor and music jack help needed (Eric M. Jones)
7. 10:06 AM - Re: capacitor and music jack help needed (Eric M. Jones)
8. 10:22 AM - Re: capacitor and music jack help needed (Matt Prather)
9. 10:46 AM - Re: Re: capacitor and music jack help needed (Matt Prather)
10. 11:29 AM - AW: Re: Was antennas Now Fuse Block Location (Europa (Alfred Buess))
11. 11:34 AM - Re: Re: capacitor and music jack help needed (luckymacy@comcast.net (lucky))
12. 11:47 AM - Re: AW: Re: Was antennas Now Fuse Block Location (Gilles Thesee)
13. 12:13 PM - Re: antennas (Dave Morris \)
14. 12:46 PM - AW: AW: Re: Was antennas Now Fuse Block Location (Europa (Alfred Buess))
15. 01:46 PM - Re: Second OVP as backup (Robert L. Nuckolls, III)
16. 09:24 PM - 'lectric lockwashers (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
Thanks Matt.
Yesterday I was only able to find manufacturers marketing their capacitors with
these specs or wholesalers who wanted to sell you at least 50 at a time or foreign
companies whose shipping cost would have probably been as much as the capacitor.
Seems to be a lot of hobbiest companies in the UK. But a new search
today turned up Surplus Sales of Nebraska and maybe they have it in stock...
http://www.surplussales.com/
I was hoping a 16VDC would be acceptable since I have a 12 volt system. I was
assuming the 25V spec was a worst case recommendation based upon a 24V aircraft
electrical design.
I just don't see any email traffic on this radio. It seems to be a really good
one as far as features/size/weight goes. Are Rotax type engines inherently
electrically "noisier" than Lycomings/Conts? I would think ignition noise could
have been eliminated at the sources on these smaller engines. I think that's
where these radios have been most popular to install.
Lucky
do not archive
-------------- Original message --------------
> --> AeroElectric-List message posted by: "Matt Prather"
>
> Hello Lucky,
>
> See below.
>
> > --> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
> >
> > I have a XCOM 760 radio and I just checked into their website for the
> > first time in a long time and leared that they now insist all their
> > radios must be fitted with a 22,000uF/25VDC electrolytic capacitor,
> > 85C. But I can't find that exact match using google, e-bay or any of
> > the couple of electronic web site catalogs I bookmarked.
> >
>
> It would be perfectly safe to substitute a cap with a higher voltage
> rating. Googling around, I found several different caps in the 30-50VDC
> rating range. To be honest with you though, this seems like ridulously
> large cap for a 5W radio. These caps are cheap and plentiful however, so
> there's no harm in doing as the manufacture specifies. At the same time,
> I'd be tempted to install and test the radio without the cap (there's no
> risk to the radio). If you have a performance problem (noise), then
> consider adding the cap.
>
> snip
>
> > thanks,
> > Lucky
> >
>
> Regards,
>
> Matt-
>
>
>
>
>
>
Thanks Matt.
Yesterday I was only able to find manufacturers marketing their capacitors with
these specs or wholesalers who wanted to sell you at least 50 at a time or foreign
companies whose shipping cost would have probably been as much as the capacitor.
Seems to be a lot of hobbiest companies in the UK. But a new search today
turned up Surplus Sales of Nebraska and maybe they have it in stock...
http://www.surplussales.com/
I was hoping a 16VDC would be acceptable since I have a 12 volt system. I was assuming
the 25V spec was a worst case recommendation based upon a 24V aircraft
electrical design.
I just don't see any email traffic on this radio. It seems to be a really good
one as far as features/size/weight goes. Are Rotax type engines inherently electrically
"noisier" than Lycomings/Conts? I would think ignition noise could have
been eliminated at the sources on these smaller engines. I think that's where
these radios have been most popular to install.
Lucky
do not archive
-------------- Original message --------------
-- AeroElectric-List message posted by: "Matt Prather" <MPRATHER@SPRO.NET>
Hello Lucky,
See below.
-- AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
I have a XCOM 760 radio and I just checked into their website for the
first time in a long time and leared that they now insist all their
radios must be fitted with a 22,000uF/25VDC electrolytic capacitor,
85C. But I can't find that exact match using google, e-bay or any of
the couple of electronic web site catalogs I bookmarked.
It would be perfectly safe to substitute a cap with a higher voltage
rating. Googling around, I found several different caps in the 30-50VDC
rating range. To be honest with you though, this seems like ridulously
large cap for a 5W radio. These caps are cheap and plentiful however, so
there's no harm in doing as the manufacture specifies. At the same time,
I'd be tempted to install and test the radio without the cap (there's no
risk to the radio). If you have a performance problem (noise), then
consider adding the cap.
snip
thanks,
Lucky
Regards,
Matt-
Message 2
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Subject: | capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Rodney Dunham" <rdunhamtn@hotmail.com>
Lucky,
Matt is right, you may not need a capacitor at all IF you don't have a noise
problem. BUT you may not recognize your noise problem! It might not be noise
in your ear. It might be a GPS that loses satellite lock or some other
equally esoteric and unrecognizable anomaly in your avionics! Also, PM
alternators like it there for their own health. 22,000 mF is arrived at
using a "rule-of-thumb" conversion which depends on the ALT output (Amps) to
be filtered, not the consumer's amp rating. Mine filters an 18 Amp PM
alternator. Rotax calls for the same 22K mF capacitor. I used a 47K mF
capacitor included in an overvolt protection kit purchased from B&C
Specialty Products online. While you're at it, do your avionics another big
favor and install Bob's OVP system available from the same site,
bandcspecialty.com.
That's the short answer. For the long answer keep reading.
The 22,000 microFarad capacitor is used to filter the ALT output.The ALT
produces AC current . The waveform of the AC current resembles a sine wave.
Imagine a single-line dollar sign tipped over on its side. One half of the
sine wave above 0 volts the other below it, ie. 0 to +14 back to 0 to -14
back to 0 and so on. This is dutifully converted to DC current by the
rectifier by chopping off the bottom half of the sine waves. The result is a
bunch of overlapping top halves and is very close to
14VDC current except for a "ripple" of voltage varying from, say, +13 to +14
volts.* This current is passed to your power distribution bus and is
available to the various electric "consumers" such as the BAT and your very
nice XCOM 760. If you didn't have any avionionics, you'd be done wiring.
The problem with this unfiltered energy is that the ripple, that little AC
current from +13 to +14*, causes a constantly expanding and collapsing
magnetic field which in turn causes a matching AC current to be established
in any unshielded wires within its sphere of influence, ie... your XCOM. A
small amplitude, say 1/2 volt AC current is now supermiposed onto the 14VDC
supply current from your fuse block to your radio. This causes "noise" in
your set, your headphones, your GPS, etc... and you're NOT done wiring.
Sooo.... The first step is to connect the VR output to the aforementioned
22K mF capacitor on its way to the battery and power distribution bus. The
capacitor attenuates and slightly delays the ripple. In other words it makes
it smaller. Smaller (less amplitude) ripple equals weaker magnetic field
equals smaller ripple voltage induced in your XCOM. Notice, however, that it
does NOT eliminate the ripple. There is no noise-free power (save your BAT
alone) but it does make things "quieter", so to speak. One caveat... The
capacitor can be bigger than the one recommended. See above. Mine is 47K mF
and the power leads from the VR go to it on the + terminal then from the +
terminal to the OV relay then to the starter contactor hot side and on to
the battery. This produces the "cleanest" DC power one can produce from such
a system. I think! :o)
Next.... Shield the power supply wires from the fuse block to the "load" ie,
your XCOM and any other wires subject to RFI such as phones, GPS, etc...
Also note, a linear ground bus system as designed by our fearless leader
(and available at B&C Specialty Products**) will add to your electrical
hygeine by preventing the legendary ground loop!
Rodney in Tennessee
* Numbers not to be considered actual, real life, scientifically produced,
ie valid numbers. Just pulled 'em out of my posterior for the purpose of
illustration.
**I do not work for or receive compensation from B&C in any way. I just love
their stuff because it works, it's relatively inexpensive and I can
understand it!
Message 3
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--> AeroElectric-List message posted by: <bakerocb@cox.net>
<< hi all, i have bobs book but i was looking for a detailed ''how to''
set of directions
for building a comm antenna. bobs drawings leave too much to my
imagination
and i end up with more questions than when i started . i am not at all
familiar
with electronics. that i can even send this e mail is a miracle. anything
on
a web site anyone knows of? from bobs book it seems that the antenna is
very
basic stuff but i need more help shopping for parts for one
thing.....skip..... bob noffs>>
10/02/2005
Hello Bob Noffs, Bob Nuckolls' advice to buy a ready made antenna is very
sound. But it is possible to roll your own inexpensively and quickly.
Go to this web site for specifices. http://www.rst-engr.com/
Many of us have good working copper tape nav and comm antennas inside our
composite airplanes.
OC
Message 4
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Subject: | Re: Why are wire strands tinned ? |
--> AeroElectric-List message posted by: "Dan Morrow" <DanFM01@butter.toast.net>
Having owned a sailboat used in salt water for many years, I can comment
on this. Copper sheathing was used on ships in the 18th and 19th centuries
to control barnacles and other growth. The sheathing was sacrificial in
nature and could be replaced. I am not aware of copper sheathing being used
on boats or ships in the last century. The modern technique is to use
antifouling paints that contain materials poisonous to marine life. Copper
and tin compounds were the most common before the environmentalists started
banning them.
Salt water is death to most unprotected metals. Stainless steel and bronze
are the only metals that can be used topside under salt water spray.
Aluminum and other metals can only be used if protected by paint or
anodyzing. Brass can be used in the cabin. It needs to be laquered or
otherwise protected if it is to look good.
My sailboat, which was built in 1974, was wired with plain copper wires.
I have had problems with corrosion of the wire. The salt air penetrates
anywhere there is a break in the insulation and eats up the wire.
An airplane is typically in a much more benign environment unless it is
based near salt water. Nonetheless, I think tinned wire is a real good
idea.
----- Original Message -----
From: "Eric M. Jones" <emjones@charter.net>
Subject: AeroElectric-List: Re: Why are wire strands tinned ?
> --> AeroElectric-List message posted by: "Eric M. Jones"
> <emjones@charter.net>
>
> There is not much reason to plate the copper wire. I have seen cables
> where
> some wire was plated only for identification (apparently), while audio
> buffs
> claim that copper oxide causes diode effects and thus all audio wire
> should
> be plated. Of course, all real audiophiles are insane.
>
> Marine types say it is to prevent corrosion. So they have tinned copper
> cables yet put copper bottoms on their boats. Copper and brass are good in
> saltwater.
>
> One could surmise that some high-frequency effects are improved because of
> skin effect.
>
> There are local old houses hereabouts wired in IRON wire.
>
> My guess is it's just floccinaucinihilipilification.
>
> By the way I will gladly sample my Super-4-CCA to interested parties.
> Email
> me off list.
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> (508) 764-2072
>
> "The problem with the world is that only the intelligent people want to be
> smarter, and only the good people want to improve."
> - Eolake Stobblehouse
>
>
> --
>
>
Message 5
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Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
>I have a XCOM 760 radio and I just checked into their website for the first
>time
>in a long time and leared that they now insist all their radios must be
>fitted
>with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find that
>exact match using google, e-bay or any of the couple of electronic web site
>catalogs
>I bookmarked.
Hi Lucky,
The general rule in capacitors is that you can always use a higher voltage
one; a bigger one unless it's a timing circuit. But as they say the devil is
in the details.
My computer motherboard had a dozen failed electrolytics (of the TRILLIONS
[YIKES!] made by a dozen Oriental companies for Abit, Asus, Aopen, Dell, HP,
etc.,etc.,etc.; this may have been one of the greatest engineering disasters
of the decade, and there is an interesting tale as to how it happened
involving stolen R&D secrets that didn't really work out. There are some
truly monster lawsuits in the works. But I digress....). I replaced most of
my motherboard's electrolytic capacitors "E-caps"...but this is not for the
faint-hearted.
I mention this as general information to spur thinking on using E-caps when
you can avoid it. But my opinion of using a 22,000 uF/25V cap to eliminate
noise from the B+ supply to the XCOM radio or any other system is that this
is a very poor way to do things. The capacitor itself is an inch in diameter
and two inches long and weighs over three ounces. At 14V it contains a
couple joules of energy. Most E-caps are not rated for altitude cycling and
temperature cycling unless you buy the expensive military versions.
Hmmm......
A far better technique than using a single fat electrolytic cap is to use an
in-line inductor and a capacitor. Certainly this is within the ability of
XCOM or anyone else with some knowledge of the subject. It goes without
saying...so I will say it...that several parts should be added for the thing
to work well:
1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency brush
noise.
2-An 18 volt zener across the capacitor to protect it from fast HV
transients.
3-Maybe a solid state resettable fuse in case the cap shorts.
4-Note that XCOM has the cap before the fuse. This needs some thinking.
Bob N. has a good paper on this:
http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It could
be expanded to remedy this XCOM patch-job and provide a number of user
friendly filters.
A really robust and useful filter that is hardly ever used is an LM317
voltage regulator (or better yet some of its newer sisters). These voltage
regulators can do a much better filtering job than a pound of capacitor and
inductor, especially at audio frequencies.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"Every act of conscious learning requires the willingness to suffer an
injury to one's self-esteem...."
-Thomas Szasz
Message 6
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Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
>I have a XCOM 760 radio and I just checked into their website for the first
>time
>in a long time and leared that they now insist all their radios must be
>fitted
>with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find that
>exact match using google, e-bay or any of the couple of electronic web site
>catalogs
>I bookmarked.
Hi Lucky,
The general rule in capacitors is that you can always use a higher voltage
one; a bigger one unless it's a timing circuit. But as they say the devil is
in the details.
My computer motherboard had a dozen failed electrolytics (of the TRILLIONS
[YIKES!] made by a dozen Oriental companies for Abit, Asus, Aopen, Dell, HP,
etc.,etc.,etc.; this may have been one of the greatest engineering disasters
of the decade, and there is an interesting tale as to how it happened
involving stolen R&D secrets that didn't really work out. There are some
truly monster lawsuits in the works. But I digress....). I replaced most of
my motherboard's electrolytic capacitors "E-caps"...but this is not for the
faint-hearted.
I mention this as general information to spur thinking on using E-caps when
you can avoid it. But my opinion of using a 22,000 uF/25V cap to eliminate
noise from the B+ supply to the XCOM radio or any other system is that this
is a very poor way to do things. The capacitor itself is an inch in diameter
and two inches long and weighs over three ounces. At 14V it contains a
couple joules of energy. Most E-caps are not rated for altitude cycling and
temperature cycling unless you buy the expensive military versions.
Hmmm......
A far better technique than using a single fat electrolytic cap is to use an
in-line inductor and a capacitor. Certainly this is within the ability of
XCOM or anyone else with some knowledge of the subject. It goes without
saying...so I will say it...that several parts should be added for the thing
to work well:
1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency brush
noise.
2-An 18 volt zener across the capacitor to protect it from fast HV
transients.
3-Maybe a solid state resettable fuse in case the cap shorts.
4-Note that XCOM has the cap before the fuse. This needs some thinking.
Bob N. has a good paper on this:
http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It could
be expanded to remedy this XCOM patch-job and provide a number of user
friendly filters.
A really robust and useful filter that is hardly ever used is an LM317
voltage regulator (or better yet some of its newer sisters). These voltage
regulators can do a much better filtering job than a pound of capacitor and
inductor, especially at audio frequencies.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"Every act of conscious learning requires the willingness to suffer an
injury to one's self-esteem...."
-Thomas Szasz
Message 7
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Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
>I have a XCOM 760 radio and I just checked into their website for the first
>time
>in a long time and leared that they now insist all their radios must be
>fitted
>with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find that
>exact match using google, e-bay or any of the couple of electronic web site
>catalogs
>I bookmarked.
Hi Lucky,
The general rule in capacitors is that you can always use a higher voltage
one; a bigger one unless it's a timing circuit. But as they say the devil is
in the details.
My computer motherboard had a dozen failed electrolytics (of the TRILLIONS
[YIKES!] made by a dozen Oriental companies for Abit, Asus, Aopen, Dell, HP,
etc.,etc.,etc.; this may have been one of the greatest engineering disasters
of the decade, and there is an interesting tale as to how it happened
involving stolen R&D secrets that didn't really work out. There are some
truly monster lawsuits in the works. But I digress....). I replaced most of
my motherboard's electrolytic capacitors "E-caps"...but this is not for the
faint-hearted.
I mention this as general information to spur thinking on using E-caps when
you can avoid it. But my opinion of using a 22,000 uF/25V cap to eliminate
noise from the B+ supply to the XCOM radio or any other system is that this
is a very poor way to do things. The capacitor itself is an inch in diameter
and two inches long and weighs over three ounces. At 14V it contains a
couple joules of energy. Most E-caps are not rated for altitude cycling and
temperature cycling unless you buy the expensive military versions.
Hmmm......
A far better technique than using a single fat electrolytic cap is to use an
in-line inductor and a capacitor. Certainly this is within the ability of
XCOM or anyone else with some knowledge of the subject. It goes without
saying...so I will say it...that several parts should be added for the thing
to work well:
1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency brush
noise.
2-An 18 volt zener across the capacitor to protect it from fast HV
transients.
3-Maybe a solid state resettable fuse in case the cap shorts.
4-Note that XCOM has the cap before the fuse. This needs some thinking.
Bob N. has a good paper on this:
http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It could
be expanded to remedy this XCOM patch-job and provide a number of user
friendly filters.
A really robust and useful filter that is hardly ever used is an LM317
voltage regulator (or better yet some of its newer sisters). These voltage
regulators can do a much better filtering job than a pound of capacitor and
inductor, especially at audio frequencies.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"Every act of conscious learning requires the willingness to suffer an
injury to one's self-esteem...."
-Thomas Szasz
Message 8
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Subject: | capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Rodney,
I generally agree with what you have said here. A couple of comments
though. Big caps on the input of a device are generally there to provide
better performance against transient demand. That is, when a consumer
needs a big burst of electrons (say it's a comm radio and you push the
transmit button), the extra capacitance helps support the bus voltage by
being a local reservoir. Additionally, this reservoir effect means that
the transient load causes less noise elsewhere in the system.
Conversely, to reduce the effects of ripple on the output of the
alternator, the big cap should be placed at the regulator (as you
suggest). A capacitor only is an effective filter when it's placed close
to the device causing the bus transient (be it load or source). The
further from the offending device the cap is wired, the more R and L
effects reduce it's ability.
So, I wonder which reason the XCOM needs the cap. Is it that it needs
less ripple on the input, or less sag when you push the transmit button,
or is it that the XCOM is a noisy resident on a power buss. If it's a
noisy consumer, place the cap as close to the radio as possible (so that
it doesn't disturb the GPS or other devices). If it's sensitive to
ripple, then place the big cap close the output of the alternator.
Regards,
Matt-
> --> AeroElectric-List message posted by: "Rodney Dunham"
> <rdunhamtn@hotmail.com>
>
> Lucky,
>
> Matt is right, you may not need a capacitor at all IF you don't have a
> noise problem. BUT you may not recognize your noise problem! It might
> not be noise in your ear. It might be a GPS that loses satellite lock
> or some other equally esoteric and unrecognizable anomaly in your
> avionics! Also, PM alternators like it there for their own health.
> 22,000 mF is arrived at using a "rule-of-thumb" conversion which
> depends on the ALT output (Amps) to be filtered, not the consumer's amp
> rating. Mine filters an 18 Amp PM alternator. Rotax calls for the same
> 22K mF capacitor. I used a 47K mF capacitor included in an overvolt
> protection kit purchased from B&C Specialty Products online. While
> you're at it, do your avionics another big favor and install Bob's OVP
> system available from the same site,
> bandcspecialty.com.
>
> That's the short answer. For the long answer keep reading.
>
> The 22,000 microFarad capacitor is used to filter the ALT output.The ALT
> produces AC current . The waveform of the AC current resembles a sine
> wave. Imagine a single-line dollar sign tipped over on its side. One
> half of the sine wave above 0 volts the other below it, ie. 0 to +14
> back to 0 to -14 back to 0 and so on. This is dutifully converted to DC
> current by the rectifier by chopping off the bottom half of the sine
> waves. The result is a bunch of overlapping top halves and is very
> close to
> 14VDC current except for a "ripple" of voltage varying from, say, +13 to
> +14 volts.* This current is passed to your power distribution bus and
> is available to the various electric "consumers" such as the BAT and
> your very nice XCOM 760. If you didn't have any avionionics, you'd be
> done wiring.
>
> The problem with this unfiltered energy is that the ripple, that little
> AC current from +13 to +14*, causes a constantly expanding and
> collapsing magnetic field which in turn causes a matching AC current to
> be established in any unshielded wires within its sphere of influence,
> ie... your XCOM. A small amplitude, say 1/2 volt AC current is now
> supermiposed onto the 14VDC supply current from your fuse block to your
> radio. This causes "noise" in your set, your headphones, your GPS,
> etc... and you're NOT done wiring.
>
> Sooo.... The first step is to connect the VR output to the
> aforementioned 22K mF capacitor on its way to the battery and power
> distribution bus. The capacitor attenuates and slightly delays the
> ripple. In other words it makes it smaller. Smaller (less amplitude)
> ripple equals weaker magnetic field equals smaller ripple voltage
> induced in your XCOM. Notice, however, that it does NOT eliminate the
> ripple. There is no noise-free power (save your BAT alone) but it does
> make things "quieter", so to speak. One caveat... The capacitor can be
> bigger than the one recommended. See above. Mine is 47K mF and the
> power leads from the VR go to it on the + terminal then from the +
> terminal to the OV relay then to the starter contactor hot side and on
> to the battery. This produces the "cleanest" DC power one can produce
> from such a system. I think! :o)
>
> Next.... Shield the power supply wires from the fuse block to the "load"
> ie, your XCOM and any other wires subject to RFI such as phones, GPS,
> etc... Also note, a linear ground bus system as designed by our
> fearless leader (and available at B&C Specialty Products**) will add to
> your electrical hygeine by preventing the legendary ground loop!
>
> Rodney in Tennessee
>
> * Numbers not to be considered actual, real life, scientifically
> produced, ie valid numbers. Just pulled 'em out of my posterior for the
> purpose of illustration.
> **I do not work for or receive compensation from B&C in any way. I just
> love their stuff because it works, it's relatively inexpensive and I
> can understand it!
>
>
Message 9
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Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
The thing that is slightly frustrating about this whole discussion is that
when you buy the XCOM (or whatever else), presumably you are buying a comm
transceiver that is designed to be installed in an aircraft. And that it
will be wired into the aircraft power buss. Why the heck wasn't the radio
designed to perform correctly in that environment (without adding
additional "stuff")??
Eric, I agree that a LM317 or something more modern is a great way to
provide clean power to a device, but the XCOM's go for something like $1k.
I'm sure it has a regulated power supply built in...
Matt-
> --> AeroElectric-List message posted by: "Eric M. Jones"
> <emjones@charter.net>
>
> --> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
>
>>I have a XCOM 760 radio and I just checked into their website for the
>> first time
>>in a long time and leared that they now insist all their radios must be
>> fitted
>>with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find
>> that exact match using google, e-bay or any of the couple of electronic
>> web site catalogs
>>I bookmarked.
>
> Hi Lucky,
>
> The general rule in capacitors is that you can always use a higher
> voltage one; a bigger one unless it's a timing circuit. But as they say
> the devil is in the details.
>
> My computer motherboard had a dozen failed electrolytics (of the
> TRILLIONS [YIKES!] made by a dozen Oriental companies for Abit, Asus,
> Aopen, Dell, HP, etc.,etc.,etc.; this may have been one of the greatest
> engineering disasters of the decade, and there is an interesting tale
> as to how it happened involving stolen R&D secrets that didn't really
> work out. There are some truly monster lawsuits in the works. But I
> digress....). I replaced most of my motherboard's electrolytic
> capacitors "E-caps"...but this is not for the faint-hearted.
>
> I mention this as general information to spur thinking on using E-caps
> when you can avoid it. But my opinion of using a 22,000 uF/25V cap to
> eliminate noise from the B+ supply to the XCOM radio or any other
> system is that this is a very poor way to do things. The capacitor
> itself is an inch in diameter and two inches long and weighs over three
> ounces. At 14V it contains a couple joules of energy. Most E-caps are
> not rated for altitude cycling and temperature cycling unless you buy
> the expensive military versions. Hmmm......
>
> A far better technique than using a single fat electrolytic cap is to
> use an in-line inductor and a capacitor. Certainly this is within the
> ability of XCOM or anyone else with some knowledge of the subject. It
> goes without saying...so I will say it...that several parts should be
> added for the thing to work well:
>
> 1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency
> brush noise.
> 2-An 18 volt zener across the capacitor to protect it from fast HV
> transients.
> 3-Maybe a solid state resettable fuse in case the cap shorts.
> 4-Note that XCOM has the cap before the fuse. This needs some thinking.
>
> Bob N. has a good paper on this:
> http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It
> could be expanded to remedy this XCOM patch-job and provide a number of
> user friendly filters.
>
> A really robust and useful filter that is hardly ever used is an LM317
> voltage regulator (or better yet some of its newer sisters). These
> voltage regulators can do a much better filtering job than a pound of
> capacitor and inductor, especially at audio frequencies.
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> (508) 764-2072
>
> "Every act of conscious learning requires the willingness to suffer an
> injury to one's self-esteem...."
> -Thomas Szasz
>
>
Message 10
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|
Subject: | Re: Was antennas Now Fuse Block Location |
--> AeroElectric-List message posted by: "Europa (Alfred Buess)" <ykibuess@bluewin.ch>
Hi Bob,
Have a look at this solution (kit: Europa XS)
http://www.europaowners.org/Fuse-panel-in-picnic-tray
Regards,
Alfred
Alfred Buess
Laenggasse 81, CH-3052 Zollikofen, Switzerland
Tel.: +41 (0)31 911 63 32, Fax: +41 (0)31 911 56 32
E-Mail: ykibuess@bluewin.ch
Europa XS #097, Monowheel, Foam shortwing, Rotax 912S, Airmaster 332 CS
bob noffs <icubob@newnorth.net> wrote:
--> AeroElectric-List message posted by: "bob noffs"
hi all,
i was just looking and thinking about the best place for my fuse panel.
---------------------------------
Click here to donate to the Hurricane Katrina relief effort.
Message 11
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|
Subject: | Re: capacitor and music jack help needed |
--> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
What if I just got something like the one at
http://www.sphere.bc.ca/test/inductors.html
Fair Rite Snap-It RFI Ferrite Suppressors....Fits wires/bundles up to 10mm/0.390
inch in diameter, easily opens and snaps shut, fantastic for quenching EMI/RFI
emissions from already existing equipment, power cords, cables, and connections.
Type 0443167251, approx. 225 ohms impedance at 100Mhz, very efficient and
inexpensive emission solution.
Seems like it would be easy to install and remove if it didn't work.
-------------- Original message --------------
> --> AeroElectric-List message posted by: "Matt Prather"
>
> The thing that is slightly frustrating about this whole discussion is that
> when you buy the XCOM (or whatever else), presumably you are buying a comm
> transceiver that is designed to be installed in an aircraft. And that it
> will be wired into the aircraft power buss. Why the heck wasn't the radio
> designed to perform correctly in that environment (without adding
> additional "stuff")??
>
> Eric, I agree that a LM317 or something more modern is a great way to
> provide clean power to a device, but the XCOM's go for something like $1k.
> I'm sure it has a regulated power supply built in...
>
>
> Matt-
>
> > --> AeroElectric-List message posted by: "Eric M. Jones"
> >
> >
> > --> AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
> >
> >>I have a XCOM 760 radio and I just checked into their website for the
> >> first time
> >>in a long time and leared that they now insist all their radios must be
> >> fitted
> >>with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find
> >> that exact match using google, e-bay or any of the couple of electronic
> >> web site catalogs
> >>I bookmarked.
> >
> > Hi Lucky,
> >
> > The general rule in capacitors is that you can always use a higher
> > voltage one; a bigger one unless it's a timing circuit. But as they say
> > the devil is in the details.
> >
> > My computer motherboard had a dozen failed electrolytics (of the
> > TRILLIONS [YIKES!] made by a dozen Oriental companies for Abit, Asus,
> > Aopen, Dell, HP, etc.,etc.,etc.; this may have been one of the greatest
> > engineering disasters of the decade, and there is an interesting tale
> > as to how it happened involving stolen R&D secrets that didn't really
> > work out. There are some truly monster lawsuits in the works. But I
> > digress....). I replaced most of my motherboard's electrolytic
> > capacitors "E-caps"...but this is not for the faint-hearted.
> >
> > I mention this as general information to spur thinking on using E-caps
> > when you can avoid it. But my opinion of using a 22,000 uF/25V cap to
> > eliminate noise from the B+ supply to the XCOM radio or any other
> > system is that this is a very poor way to do things. The capacitor
> > itself is an inch in diameter and two inches long and weighs over three
> > ounces. At 14V it contains a couple joules of energy. Most E-caps are
> > not rated for altitude cycling and temperature cycling unless you buy
> > the expensive military versions. Hmmm......
> >
> > A far better technique than using a single fat electrolytic cap is to
> > use an in-line inductor and a capacitor. Certainly this is within the
> > ability of XCOM or anyone else with some knowledge of the subject. It
> > goes without saying...so I will say it...that several parts should be
> > added for the thing to work well:
> >
> > 1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency
> > brush noise.
> > 2-An 18 volt zener across the capacitor to protect it from fast HV
> > transients.
> > 3-Maybe a solid state resettable fuse in case the cap shorts.
> > 4-Note that XCOM has the cap before the fuse. This needs some thinking.
> >
> > Bob N. has a good paper on this:
> > http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It
> > could be expanded to remedy this XCOM patch-job and provide a number of
> > user friendly filters.
> >
> > A really robust and useful filter that is hardly ever used is an LM317
> > voltage regulator (or better yet some of its newer sisters). These
> > voltage regulators can do a much better filtering job than a pound of
> > capacitor and inductor, especially at audio frequencies.
> >
> > Regards,
> > Eric M. Jones
> > www.PerihelionDesign.com
> > 113 Brentwood Drive
> > Southbridge MA 01550-2705
> > (508) 764-2072
> >
> > "Every act of conscious learning requires the willingness to suffer an
> > injury to one's self-esteem...."
> > -Thomas Szasz
> >
> >
>
>
>
>
>
>
What if I just got something like the one at
http://www.sphere.bc.ca/test/inductors.html
Fair Rite Snap-It RFI Ferrite Suppressors....Fits wires/bundles up to 10mm/0.390
inch in diameter, easily opens and snaps shut, fantastic for quenching EMI/RFI
emissions from already existing equipment, power cords, cables, and connections.
Type 0443167251, approx. 225 ohms impedance at 100Mhz, very efficient and
inexpensive emission solution.
Seems like it would be easy to install and remove if it didn't work.
-------------- Original message --------------
-- AeroElectric-List message posted by: "Matt Prather" <MPRATHER@SPRO.NET>
The thing that is slightly frustrating about this whole discussion is that
when you buy the XCOM (or whatever else), presumably you are buying a comm
transceiver that is designed to be installed in an aircraft. And that it
will be wired into the aircraft power buss. Why the heck wasn't the radio
designed to perform correctly in that environment (without adding
additional "stuff")??
Eric, I agree that a LM317 or something more modern is a great way to
provide clean power to a device, but the XCOM's go for something like $1k.
I'm sure it has a regulated power supply built in...
Matt-
-- AeroElectric-List message posted by: "Eric M. Jones"
<EMJONES@CHARTER.NET>
<B
R> -- AeroElectric-List message posted by: luckymacy@comcast.net (lucky)
I have a XCOM 760 radio and I just checked into their website for the
first time
in a long time and leared that they now insist all their radios must be
fitted
with a 22,000uF/25VDC electrolytic capacitor, 85C. But I can't find
that exact match using google, e-bay or any of the couple of electronic
web site catalogs
I bookmarked.
Hi Lucky,
The general rule in capacitors is that you can always use a higher
voltage one; a bigger one unless it's a timing circuit. But as they say
the devil is in the details.
My computer motherboard had a dozen failed electrolytics (of the
TRILLIONS [YIKES!] made by a dozen Oriental comp
anies for Abit, Asus,
Aopen, Dell, HP, etc.,etc.,etc.; this may have been one of the greatest
engineering disasters of the decade, and there is an interesting tale
as to how it happened involving stolen RD secrets that didn't really
work out. There are some truly monster lawsuits in the works. But I
digress....). I replaced most of my motherboard's electrolytic
capacitors "E-caps"...but this is not for the faint-hearted.
I mention this as general information to spur thinking on using E-caps
when you can avoid it. But my opinion of using a 22,000 uF/25V cap to
eliminate noise from the B+ supply to the XCOM radio or any other
system is that this is a very poor way to do things. The capacitor
itself is an inch in diameter and two inches long and weighs over three
ounces. At 14V it contains a co
uple joules of energy. Most E-caps are
not rated for altitude cycling and temperature cycling unless you buy
the expensive military versions. Hmmm......
A far better technique than using a single fat electrolytic cap is to
use an in-line inductor and a capacitor. Certainly this is within the
ability of XCOM or anyone else with some knowledge of the subject. It
goes without saying...so I will say it...that several parts should be
added for the thing to work well:
1-A 0.1 uF ceramic cap across the big capacitor to stop high-frequency
brush noise.
2-An 18 volt zener across the capacitor to protect it from fast HV
transients.
3-Maybe a solid state resettable fuse in case the cap shorts.
4-Note that XCOM has the cap before the fuse. This needs some thinking.
<
BR> Bob N. has a good paper on this:
http://www.aeroelectric.com/articles/filter/RS_Noise_Filters.pdf , It
could be expanded to remedy this XCOM patch-job and provide a number of
user friendly filters.
A really robust and useful filter that is hardly ever used is an LM317
voltage regulator (or better yet some of its newer sisters). These
voltage regulators can do a much better filtering job than a pound of
capacitor and inductor, especially at audio frequencies.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"Every act of conscious learning requires the willingness to suffer an
injury to one's self-esteem...."
-Thomas Szasz
&g
t;
Message 12
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|
Subject: | Re: Was antennas Now Fuse Block Location |
--> AeroElectric-List message posted by: Gilles Thesee <Gilles.Thesee@ac-grenoble.fr>
Europa (Alfred Buess) a crit :
>--> AeroElectric-List message posted by: "Europa (Alfred Buess)" <ykibuess@bluewin.ch>
>
>Hi Bob,
>
>Have a look at this solution (kit: Europa XS)
>
>http://www.europaowners.org/Fuse-panel-in-picnic-tray
>
>
>
Alfred,
According to the photos there is an "always hot" bus along with the main
and essential bus. Is there a fuse protecting the feeder from the
battery to this bus under the panel ?
In our airplane (MCR 4S), the "always hot" busses are next to their
respective batteries and so do not need such a protection.
Just out of curiosity,
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 13
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|
--> AeroElectric-List message posted by: "Dave Morris \"BigD\"" <BigD@DaveMorris.com>
If you have a composite ship and would like to try a different idea in
antennas that does not require a ground plane, and your tail cone is around
31 inches in diameter, check out the Morris Com Loop antenna
http://www.DaveMorris.com/MorrisComLoop.cfm
Dave Morris
At 10:48 AM 10/2/2005, you wrote:
>--> AeroElectric-List message posted by: <bakerocb@cox.net>
>
> << hi all, i have bobs book but i was looking for a detailed ''how to''
>set of directions
> for building a comm antenna. bobs drawings leave too much to my
>imagination
> and i end up with more questions than when i started . i am not at all
>familiar
> with electronics. that i can even send this e mail is a miracle. anything
>on
> a web site anyone knows of? from bobs book it seems that the antenna is
>very
> basic stuff but i need more help shopping for parts for one
>thing.....skip..... bob noffs>>
> 10/02/2005
>
> Hello Bob Noffs, Bob Nuckolls' advice to buy a ready made antenna is very
>sound. But it is possible to roll your own inexpensively and quickly.
>
> Go to this web site for specifices. http://www.rst-engr.com/
>
> Many of us have good working copper tape nav and comm antennas inside our
>composite airplanes.
>
> OC
>
>
Message 14
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|
Subject: | Re: Was antennas Now Fuse Block Location |
--> AeroElectric-List message posted by: "Europa (Alfred Buess)" <ykibuess@bluewin.ch>
Gilles,
You are right: The always hot bus is protected by a fuse just after the
battery. My battery is back in the fuselage and I wanted all the fuses
in the same place, that's why I have chosen this solution. In addition I
have a switch in the always hot bus feed wire just after the battery,
which is remotly operated from the cockpit. It allows me in case of an
emergency to cut all electric power just at the place of the battery.
Meilleures salutations,
Alfred
-----Ursprngliche Nachricht-----
Von: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] Im Auftrag von
Gilles Thesee
Gesendet: Sonntag, 2. Oktober 2005 19:46
An: aeroelectric-list@matronics.com
Betreff: Re: AW: AeroElectric-List: Re: Was antennas Now Fuse Block
Location
--> AeroElectric-List message posted by: Gilles Thesee
--> <Gilles.Thesee@ac-grenoble.fr>
Europa (Alfred Buess) a crit :
>--> AeroElectric-List message posted by: "Europa (Alfred Buess)"
>--> <ykibuess@bluewin.ch>
>
>Hi Bob,
>
>Have a look at this solution (kit: Europa XS)
>
>http://www.europaowners.org/Fuse-panel-in-picnic-tray
>
>
>
Alfred,
According to the photos there is an "always hot" bus along with the main
and essential bus. Is there a fuse protecting the feeder from the
battery to this bus under the panel ?
In our airplane (MCR 4S), the "always hot" busses are next to their
respective batteries and so do not need such a protection.
Just out of curiosity,
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
Message 15
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|
Subject: | Re: Second OVP as backup |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
Thank you for sharing these thoughts with me. I'm going to publish
your original along with my reply on the AeroElectric List (of course
with your name removed) because it raises some important issues
which should be addressed an shared with all
>Hi Bob, I have installed in my GlaStar the B & C L-60 alternator and
>the LR3C-14 regulator wired as your recommend. I have added a second
>solenoid in series with the output of the alternator. This solenoid is
>activated by connecting the coil lead to ground. I have installed a
>power P MOS transistor with its gate lead connected to the (+)
>lead of one of your OVP modules. Added a 1000 ohm resistor from this
>gate lead to ground. Connected the source lead of the transistor to ground.
>Connected the drain to the solenoid coil. Your OVP unit is connected to
>the main power bus with a 5 amp breaker so that when the airplane is
>normally powered up the alternator solenoid is turned on. If there is
>an over voltage (I set this OVP at 16.0 volts) the OVP will blow the 5 amp
>breaker and disconnect the alternator via the transistor.
"Backup" systems are good when there is an unacceptable probability
that some "primary" system might cease to function and at the least,
increase pilot workload and at worst, cause catastrophic failures to
propagate across multiple systems.
A hand-held, totally independent GPS receiver is an EXCELLENT
example of what is nearly a bullet-proof backup for a device
that's mounted the panel, has 1000's of parts, depends on ship's
DC for power and is subject to severe damage if ship's power
is having a really bad day.
We've had some recent discussions about voltage regulators internal
to alternators wherein the block diagram or schematic of exemplar
regulators have a section labeled "OV Protection". I've cited
a rational for discounting this feature as adequate to the task
when the established (or uncertain) reliability of the regulator
section suggests that "backup" OV protection is warranted. It has
to do with the fact that OV protection is included on the same die
with the rest of the regulator chip's operating features.
The problem with this architecture is two-fold. I've never seen
a chip where there was any attempt to isolate the OVP function
to the extent that some failures of the voltage REGULATION loop
did not ALSO affect the ability of the OVP section to function.
This has always mystified me as to the thought processes of the
chip designers. The fact that they INCLUDE OV protection is a tacit
suggestion that it's a GOOD thing to do. I.e., the designer
recognizes that (1) there are failure modes within his/her product
capable of producing the OV condition and (2) there is no rational
methodology for stating that probability of regulator failure is
less than 10 to the minus -6 failure rates. THEREFORE: We'll
ADD the OVP feature. The reasoning then fails because it depends
on some of the same sense paths that the regulator uses for
operation (?????). If the designers know what they're doing, I
must assume that it's good marketing hype to put the little box
in there an mark it "OV Protection." However, when subjected to
well developed techniques for doing failure mode effects analysis
(FMEA) AND deducing mean time between failures (MTBF), this
little suite of components within the chip's topology do not
satisfy the design goals which have been adopted by the aviation
industry.
This is like analyzing the topology of a microprocessor's
arithmetic logic unit and deciding that an add, multiply,
divide and subtract section may be DEPENDED upon for proper
operation even if one of the other three sections on the
same chip has failed.
As systems designers and integrators we are faced with
a conundrum:
(1) Is the MTBF of EVERY chip offered to the automotive
industry so high that probability of an OV condition is sufficiently
remote as to be ignored?
(2) If the chip designer includes OV protection in his/her
design, then was it done to "back up" a questionable result
to the answer for (1) or was it included just so that the
marketing hype at the top of the chip's data sheet can include
"Over Voltage Protection is included on the die"?
Without good answers to these issues, I am driven by my
experiences and education in the certified side of aviation
to suggest that some form of TOTALLY INDEPENDENT OV protection
be included in OBAM aircraft designs that I recommend and
professionally stand behind as "the best I know how to do."
It appears that you've perceived some level of risk in the
LR-3/L60 combination that suggests some level of additional
backup is called for. Let us consider the facts that we
have to work with:
The L60 is a wound field, externally regulated alternator
that depends on a current supply to the "F" pin in order
to generate ANY output whatsoever. Hmmm . . . there IS
a condition to consider where a fault might occur between
the "F" and "B" leads INTERNALLY to the alternator. I have
seen this happen one time on a Mooney about 30 years ago.
The Electrical Systems Lead was all over his alternator
supplier for the way he bundled certain conductors within
the alternator which opened the doors for this possibility.
I don't believe this is an issue with the L60.
So, assuming that there IS value in adding a second OVP
system, I'll suggest there is no need to add a contactor
in series with the b-lead to effect a reliable shutdown.
Adding a smaller, much less stressed, relay or other solid
state device in series with the field supply to the LR-3
would suffice. Since the LR-3 now uses REMOTE but voltage
sensing separate from the field supply pin, there are no
risks to regulation stability for having inserted extra
components in series with the field power lead.
Now that we've down-sized the size of the task with
respect to stresses and need for robust components, let
us consider the value added by a decision to stack
OVP systems:
Consider this extreme. Suppose we had 10 OVP systems
any one of which would shut down a runaway alternator.
One might very comfortably state that this airplane will
NEVER suffer from catastrophic propagation of an OV
event. Now one has the task of keeping apprised of
LATENT failures. How many of the 10 systems are inoperative
after say 2,000 hours of inattention. Well, if only
one or two of the 10 have crapped, who cares? Okay,
lots of protection may offer one more restful sleep
but what are the trade-offs? What is the probability
of system failure NOT due to a real OV event but for
a failure within one of the OVP systems that produces
an unnecessary system shutdown?
All other things being equal, you're X times as likely
to suffer this condition where X is the number of OVP
systems installed.
Now, the real engineer works to optimize return on
investment for the decision as to how many OVP systems
are called for. This is something like sending your
elected officials to Washington but only after asking
and getting a rational answer to the following question:
"Sir . . . government needs cash to operate. Fine.
If taxation rates are zero percent, revenue to
government is obviously zero. If taxation rates
are 100%, revenues to government are still zero.
It stands to reason that somewhere between zero
and 100% taxation, revenues to government will
peak. It's like having just the right mixture in
your carburetor, having just the right amount of
salt or sugar in a recipe. Tell us sir. What is
the proper rate of taxation for the economy to
grow? How much can government confiscate in order
to maximize the support of government programs
without overburdening the economy such that any
INCREASE in taxation REDUCES revenues to government?"
I doubt that a single soul in government with any
power has an answer to that question supported on a
foundation of simple-ideas.
We have a similar problem. Too many protective
components and systems drives up cost of acquisition,
cost of ownership, weight, volume, complexity. All
of these things are good to minimize. Adding protection
to excess actually drives system reliability down.
Too few protective devices (that cost a few dollars
to install) expose us to risks of failure that have
very expensive and perhaps dangerous consequences
(one of the reasons I carry enough stuff in my flight
bag to continue flight to intended destination with
the panel completely dark). So, like adjusting levels
of taxation to achieve optimum cash flow, we need to
adjust levels of complexity with an eye toward the
"elegant solution": Highest acceptable reliability
with lowest cost of ownership.
Let us consider the LR-3's design. OV protection
shares no components or wiring with any other
functionality of the regulator assembly. In fact,
OVP, LV Warn, Voltage regulation are three independent
systems that share only a common enclosure. If
you were to split them into separate enclosures,
the rational is that system reliability would not
go up but down due to increase in numbers of wires
and installer fabricated connections. Therefore,
it was deduced about 20 years ago that the LR-3
should take its present form and aside from any
value added by modernizing the LR-3 to take advantage
of new technologies, I can see no compelling reasons
be concerned about reliability of the current
offering.
The OVP and Regulation sections would have MTBF
numbers on the order of 20,000 and 5,000 hours
each. The probability of having simultaneous
regulation AND over voltage protection failures
is extremely small. If you follow the recommended
manual testing of the OVP system every annual or
every oil change, that number gets better yet.
So, armed with this understanding, your decision
about adding more "protection" becomes one of deciding
whether (1) to err on the side of "safety" but to
tolerate reduced functional reliability and increased
cost or (2) is there sufficient confidence in the
design of the LR-3 as offered to use it "barefoot".
The LR-3 is a mature product with lineage going
back 20 years and somewhere around 5000 units
in service. Less than 5% of the fleet hardware has
been returned for service with most returns to repair
owner induced damage. Some have experienced circuit
failures but I've not heard of any COMPOUND failures
that resulted in an uncontrolled runaway. I've not
had feedback on the status of LR-3 returns for
a couple of years. I need to call up and get an
update.
It would seem that your first task is to see if your
concerns are rational. Is your departure from the
recommended optimal configuration driven by real,
rumored or imagined concerns?
> I also pre load the alternator
>with a 20 ohm resistor to stabilize the alternator when it is
>disconnected due to an OVP occurrence.
Not sure what this does for you. If you're wanting to
pre-load a load-dump event, know that the for the milliseconds
between onset of event and opening of the b-lead contactor,
field excitation and output current are building with alternator
output current bounded only by the machine's magnetics.
You could see a 70A+ dump into your 20 ohm resistor which
would only being to subdue the alternator at b-lead voltages
on the order of 70 * 20 or 1400 volts!
>Do you think this setup will give added protection in case
>the internal LR3C-14 OVP fails?
To have this be a concern, you'll FIRST have to experience
a runaway condition in the REGULATOR combined with a new
or latent failure in the OVP that's unable to react to the
regulator failure. This is statistically a very remote
event.
>The rational for this is to totally disconnect the alternator to provide
>a second level of protection for my $25,000.00 electronics in the
>airplane. Also could you provide the schematic for your latest OVP
>circuit. I believe the ones in your AeroElectric Connection manual
>are not the latest versions.
If you perceive some unacceptable levels of risk associated with
a single layer of OV protection, perhaps your concerns would be better
served with good preventative maintenance in an RG battery
that will stand off a runaway alternator for some period of time.
Unlike the 20 ohm resistor you proposed, a new 17 a.h. RG battery
will load a runaway 60A alternator to levels under 20 volts long enough
for a pilot to react to a big red, OV warning light and allow
manual shut-down of the system before damage occurs to any DO-160
qualified devices in the airplane.
There are no schematics in the 'Connection intended to guide the
builder in fabricating a functional OVP system. These are conceptual
only and offered to illustrate philosophies and not practice.
The article at
http://aeroelectric.com/articles/Crowbar_OV_Protection/Crowbar_C.pdf
was recently updated based on feedback from an astute builder who
correctly identified a deficiency in the original design.
I'll suggest you join us on the AeroElectric List for further
discussion of this or any other concerns you may have. See:
http://aeroelectric.com/consulting.html
Bob . . .
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Subject: | 'lectric lockwashers |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
>Comments/Questions: I just went through Chapters 8 and 9 and found no
>specific call out. Is there a preference between split lock washers and
>internal star lock washers for electrical connections? I'm talking about
>master and starter relays, battery posts and the starter, those big
>"honkers." I have noticed that the circuit breakers came with split lock
>washers, but those are #6 and #8. RV6A w/O-360.
Internal tooth star washers are preferred. Beryllium-Copper
or Phosphor_Bronze if you can get them . . . otherwise,
plated steel. Split-ring lockwashers are one step above spit
for locking and a half step above a flat washer for improved
condutivity.
Bob . . .
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