Today's Message Index:
----------------------
1. 06:02 AM - Re: The weak link (Robert L. Nuckolls, III)
2. 06:49 AM - Re: transorbs (Robert L. Nuckolls, III)
3. 08:54 AM - Wild flights... 22 hr trip in an LSA over the Atlantic... (Jay Hyde)
4. 10:38 AM - Re: Voltage Drop / amp ????? (Frank Stringham)
5. 01:12 PM - Re: Wild flights... 22 hr trip in an LSA over the Atlantic... (rckol)
6. 01:36 PM - Re: Re: Wild flights... 22 hr trip in an LSA over the Atlantic... (Jay Hyde)
7. 01:36 PM - Re: Re: Wild flights... 22 hr trip in an LSA over the Atlantic... (Robert D. Taylor)
8. 01:57 PM - Re: Re: Wild flights... 22 hr trip in an LSA over the Atlantic... (Jay Hyde)
9. 02:05 PM - Re: EV200 (Eric M. Jones)
Message 1
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Subject: | Re: The weak link |
At 07:10 PM 7/21/2009, you wrote:
> >
>
>One benefit the computer programmer has is the opportunity to ponder bad
>things happening while sitting at a desk (on the ground), drinking a
>favored beverage. On the other hand, the pilot gets to ponder these bad
>things while riding through said bad things (which are often quite
>distracting). Sometimes the pilot doesn't make the right decision and
>doesn't get to take another shot at it. The computer programmer can (with
>the help of peers) consider all sorts of malfunctions.
>
>One other thought.. The act of using GPS data to correct for roll/yaw
>gyro drift is a far cry (much simpler task) from the tasks currently being
>accomplished by the current crop of EFISs. Simpler tasks mean simpler
>code, and a much easier device to debug. What amounts to be a single axis
>autopilot could be done in very few lines of code.
Absolutely! This is why the design goals I suggested
for the GPS aided wing leveler has the gps receiver
built in along with the rate sensors. No wiring other
than to power it up, hook up an antenna and pushbuttons.
If a valid gps signal isn't present, the system won't
drive. If 14v isn't present, it won't drive. Software has but
one task only . . . hold gps course of the moment
which is modified by simple push-button commands -or-
offered by external flight planning accessory over the
serial bus. VERY simple code in a one-chip microprocessor.
total parts count is very low . . . i.e. failure rates
driven by complexity go way down.
If you push all the fancy maneuvering software and
hardware out to a plug-n-play device like a palm-
computer, then the guy who keeps the airplane right
side up and pointed the right direction is not distracted
nor are his design goals plagued with CPU "business".
Let somebody else with equally constrained design goals
write the software that does the fancy steering . . .
but in a device that can be unplugged or turned off
without influencing the performance of the wing-leveler.
This distributed processing, minimalist hardware approach
offers an opportunity for a small, light, low cost
end product, and reduces probability of high-risk software.
A dual wing-leveler package has two control gps receivers
cross-checked with data from a third panel mounted receiver.
Probability for an system failure to endure unattended
by the pilot is low and plan-a/plan-b tolerance to failure
is high.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 2
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At 06:23 PM 7/21/2009, you wrote:
>Howdy folks,
>In my work we use 30v transorbs similar the ones that have been
>discussed on this list for years. We use them to limit relay
>contact arcing when switching inductive loads such as mag locks and
>electric strikes. We have hundreds in the field and until yesterday
>I would have said they never go bad - but yesterday I had a service
>call and sure enough a transorb had shorted. In our applications
>the coil currents range from 125ma to maybe an amp or so. I don't
>know why it failed, maybe a manufacturing defect, but the point
>becomes that they CAN fail.
The transorb is indeed a specialized zener. In the
zener conduction mode, the potential for dissipating
a deleterious level of heat is much higher than for
a diode rectifier. The energy available from a magnetic
field collapse is quite low and measured in millijoules.
Certainly a low risk stress to any power semiconductor.
The ability of the electrical system to deliver energy
to the transorb in a voltage transient condition is
many times higher.
>So I'm thinking, if I have one of these things across the coil on my
>master contactor and it shorts - bad things happen. Not only would
>I loose electric power but the un-fused master switch wiring would
>be overloaded. I'm thinking maybe a 30v transorb across the master
>switch - not the contactor coil may be a better choice if you are
>going to use them at all. It would still protect the switch, it
>would still allow about 15v reverse voltage to collapse the field in
>the coil (12v system - use a 45v transorb in a 24v system) and in a
>failure mode you would just be unable to shut off the power.
But there are OTHER, equally likely failure modes that
can take the battery contactor out of service. That's
what the e-bus alternate feed path is all about. The
optimum location for transient suppression is at the
contactor coil terminals.
Do I correctly deduce from your posting that your
contactor coils are protected by a single transorb?
If so, then it has to be wired as shown in -A- below.
Emacs!
In this configuration, the device HAS to be biased in
the zener conduction mode polarity while coiled power
IS APPLIED. When the switch opens, the top of the coil
swings negative . . . and the transorb is now biased
in the diode conduction mode. This configuration doesn't
take advantage of the transorb's voltage limiting function
as a specialized zener. In other words, your transorb
functionality in the coil release mode is the same as
for the simple diodes described in:
http://www.aeroelectric.com/articles/spikecatcher.pdf
The proper application of uni-polar transorbs or zeners
for SPIKE mitigation is to place them in series with
a plain vanilla rectifier as shown in -B-. In this
case, power that energizes the coil is blocked by the
diode, but the strong negative swing at switch opening
time is carried through the diode to the transorb that
conducts like a ZENER to limit the excursion to more
attractive levels (and allows the contactor to release
faster). See:
If the contactor release time (15mS versus 60 mS)
is critical the use of transorbs as shown in -B- is
indicated . . . -OR- you can use a single, bi-directional
device to keep the wiring complexity down and eliminate
device polarity concerns.
If your transorbs are implemented as in -A- then
they've offered no more functionality than the simple
rectifier diode would offer. If contactor release time
is critical, then changing to -B- or changing to
bi-directional devices is called for. See:
http://www.aeroelectric.com/Pictures/Curves/Cole-Hersee_with_Diode.gif
http://www.aeroelectric.com/Pictures/Curves/Cole-Hersee_without_Diode.gif
http://www.aeroelectric.com/Pictures/Curves/CH_w_2x18v_Transorbs.gif
http://www.aeroelectric.com/Pictures/Curves/CH_w_120_Ohm.gif
http://www.aeroelectric.com/Pictures/Curves/CH_w_1n5400.gif
>Anyway, I just wanted to bring attention to an admittedly remote
>failure mode and a possible re-configuration that would have a much
>more favorable result if a failure did occur.
Failures of the plain-vanilla diode are unknown to
me. They're simply never electrically stressed in
a manner that puts them at risk for failure. Similarly,
Transorbs wired as shown in -B- cannot be impressed with
system transients because they're isolated by the
series diode.
I'll suggest that there's more to your failure
experience than what you've related in your posting.
Bob . . .
Message 3
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Subject: | Wild flights... 22 hr trip in an LSA over the Atlantic... |
Hey there all,
I posted something similar to what I will write now but it does not seem to
have come through. Two mates of mine will attempt (and hopefully complete)
a flight across the Atlantic, from Conakry, Guinea to Belem, Brazil tomorrow
evening. They are flying an aircraft called the 'Sling' that they designed
and built here in South Africa; to be sold as a light sport kit. The
aircraft is a low wing 2 seater with a 912 Rotax engine and is specially
modified so that the whole leading edge of each wing is a fuel tank (divided
into 6 tanks), carrying 450 litres of fuel. Tomorrow evening their flight
will use 440 litres.. Its going to be a narrow thing.
The aircraft has a modified Z-16 diagram that I used from Bob's (thank you!)
lists/diagrams. In the aircraft there are 2 MGL Voyagers, a stormscope,
transponder, Garmin SL30 Nav/ Comm radio, auto pilots, and bits and pieces
including a satellite linked GPS tracker so that we can follow their
progress. This last Saturday they took off from near Johannesburg here in
South Africa and flew non-stop for 20 hours to reach Sao Tome off the west
African coast, just south of Nigeria. I was with them when James, one of
the pilots, filed an unbelievable flight plan for an LSA aircraft. He had
to repeat and confirm the distances and aircraft type several times- and
explain this to the disbelieving official at the other end.
If you're curious and would like to see more have a look at
http://www.airplanefactory.co.za/world/default.asp
You will be able to track their flight across the Atlantic tomorrow if all
goes well, and for those of you going to Oshkosh, they'll be there.
Bob, I've read your arguments and as an electrical engineer they made a lot
of sense; I used your suggestions and designs in this aircraft and so far it
has worked well and I am sure that it will continue to do so. Here's hoping
that my mates make it across the pond!
Jay from South Africa
Message 4
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Subject: | Voltage Drop / amp ????? |
I have wired my RV7A with the 13/8 revision L. I did modify it to include t
he LR3C Alternator controller in place of genric Ford Regulator and the AEC
9005-101 Low Voltage Module. In looking at the 13/8 revision Q there is an
addition of a S704-1 / diode combo added to the Main Battery Bus / Enduranc
e Bus / Endurance Bus Switch. I also have noted that a AEC9001 Schottky Dio
de can be used in place of a bridge diode.
As I notded in a previous email. 1. When the master switch is closed the vo
ltage showes around 10.8 volts with rock solid amps indication on the Dynon
D-120 EMS. When the endurance switch is closed the Voltage moves up to 12.
8 or 12.9 and the amps meter begins to fluctuate. Open the Master Switch th
us having the load go to only the endurance bus side the voltage maintains
at 12.8 to 12.9 volts and the amps still fluctuates. This situation happens
with or with out the engine running. The battery maintains charge.
Since I sent the last email I have learned that the bridge diode will cause
a drop in voltage. (Even this 62 year old guy can learn stuff....) =2C but
I would have though it would cause the endurance voltage to be less on the
endurance bus side not the main bus side with the master switch closed.???
????
Now the questions. 1. Why the addition of the S204-1 / diode combo added at
the endurance bus switch and will it be of value in my configuration to ad
ded it. 2. Would it be of value to added the Schottly in place of the bridg
e diode. I would think yes if the voltage drop is less and thus give a more
accurate voltage reading. 3. Why the higher voltage drop on the Main Bus a
s compared to the Endurance Bus? 4. Whay the conflicting amp reading betwee
n the Main vs Endurance Bus.
Thanks in advance for any help in this matter
Frank @ 1L8 ...RV7A... Phase 1 underway
_________________________________________________________________
Windows Live=99 Hotmail=AE: Celebrate the moment with your favorite sports
pics. Check it out.
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M_WL_QA_HM_sports_photos_072009&cat=sports
Message 5
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Subject: | Re: Wild flights... 22 hr trip in an LSA over the Atlantic... |
They made it to Brazil.
--------
rck
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254508#254508
Message 6
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Subject: | Re: Wild flights... 22 hr trip in an LSA over the |
Atlantic...
Yeah- its been a very anxious and scary time for all of us. I think that
they have made aviation history doing it. After Oshkosh there is still a
big journey awaiting them. They're already heroes here in SA and we are
planning a huge party when they arrive.
If you've been following the website you'll have seen the desperation,
anxiety and elation the trip has caused. I trust that y'all ;-) will give
them a great reception at Oshkosh!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jay Hyde
HH Enterprises
Aircraft Manufacture, Engineering and Flying
jay@horriblehyde.com
Mobile phone: 083 300 8675
International: +27 83 300 8675
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of rckol
Sent: 23 July 2009 10:10 PM
Subject: AeroElectric-List: Re: Wild flights... 22 hr trip in an LSA over
the Atlantic...
They made it to Brazil.
--------
rck
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254508#254508
Message 7
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Subject: | Re: Wild flights... 22 hr trip in an LSA over the |
Atlantic...
Tell 'em CONGRATULATIONS! And thanks for letting us know. Hope they have a
safe trip the rest of the way to Oshkosh.
Bob Taylor
----- Original Message -----
From: "rckol" <rckol@kaehlers.com>
Sent: Thursday, July 23, 2009 4:09 PM
Subject: AeroElectric-List: Re: Wild flights... 22 hr trip in an LSA over
the Atlantic...
>
> They made it to Brazil.
>
> --------
> rck
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=254508#254508
>
>
>
Message 8
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Subject: | Re: Wild flights... 22 hr trip in an LSA over the |
Atlantic...
If you go to their website
(http://www.airplanefactory.co.za/world/default.asp) you can leave them a
message yourself :-) - they'd really appreciate it
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jay Hyde
HH Enterprises
Aircraft Manufacture, Engineering and Flying
jay@horriblehyde.com
Mobile phone: 083 300 8675
International: +27 83 300 8675
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert D.
Taylor
Sent: 23 July 2009 10:38 PM
Subject: Re: AeroElectric-List: Re: Wild flights... 22 hr trip in an LSA
over the Atlantic...
<FLYDAD57@neo.rr.com>
Tell 'em CONGRATULATIONS! And thanks for letting us know. Hope they have a
safe trip the rest of the way to Oshkosh.
Bob Taylor
----- Original Message -----
From: "rckol" <rckol@kaehlers.com>
Sent: Thursday, July 23, 2009 4:09 PM
Subject: AeroElectric-List: Re: Wild flights... 22 hr trip in an LSA over
the Atlantic...
>
> They made it to Brazil.
>
> --------
> rck
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=254508#254508
>
>
>
Message 9
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(some repost here...) I have railed against these Type-70 contactors for years.
But they are almost obsolete. Most electronics distributors have dropped them
from their lines.
Problems--
1) Low Temperature rating. Only 122F max. You could land at Furnace Creek in Death
Valley in May and take off in October. Maybe. This is primarily due to the
Nylon innards. This is a drop-dead reason to avoid the part.
2) Not sealed. Not dust proof, or fuel proof.
3) Low interrupt capacity.
4) High hold current---16 ohm coil. Almost one amp.
5) Low hold force. The specifications call for specific orientation. 2G rating?
6) Wildly wrong for B&C to use coil suppression diodes on these. This causes short
lifetimes on the B&C parts.
7) Not designed to open against voltages above 36 volts. (So forget the B-lead
applications)
See: www.stancor.com
There are better ways to go. Omron's line of automotive contactors (CHEAP) and
Kilovac's EV200 series, Blue Sea 9012, Gigavac's GX-11. Expensive but preferred.
Can you use them? Sure. Should you use them?....not on my bird, Bubela.
Better yet, avoid all contactors and use manual switches if you can.
"Facts do not cease to exist because they are ignored."
---Aldous Huxley
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254518#254518
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