Today's Message Index:
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1. 12:06 AM - Re: Re: Battery capacity tester-was flyback diode, now clock source (JOHN TIPTON)
2. 06:19 AM - Re: Battery capacity tester-was flyback diode, now clock source (Eric M. Jones)
3. 07:48 AM - Re: jumpimg gauge needles (bob noffs)
4. 01:04 PM - Re: jumpimg gauge needles (Robert L. Nuckolls, III)
5. 01:24 PM - Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 and Garmin SL30 (Christopher Skelt)
6. 06:01 PM - Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 and Garmin SL30 (Robert L. Nuckolls, III)
7. 06:34 PM - Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 and Garmin SL30 (Daniel Hooper)
8. 07:32 PM - Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 and Garmin SL30 (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: Battery capacity tester-was flyback diode, |
now clock source
Hi Bob
Got it: it's a 'diode' in spike catching mode
John
----- Original Message -----
From: Robert L. Nuckolls, III
To: aeroelectric-list@matronics.com
Sent: Saturday, July 20, 2013 9:17 PM
Subject: Re: AeroElectric-List: Re: Battery capacity tester-was
flyback diode, now clock source
At 01:59 PM 7/20/2013, you wrote:
That was my question John!=C2
I found this:
http://en.wikipedia.org/wiki/Flyback_diode
This is a good description. See also this
series of articles on 'spike suppression'
on our website.
http://tinyurl.com/mkcshhs
Bob . . .
Message 2
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Subject: | Re: Battery capacity tester-was flyback diode, now |
clock source
> From: "Eric M. Jones"
> Actually I've been searching the antique shops for an AC plug-in clock and haven't
been able to find one.
FYI: That was humor. Humor is a delicate thing and I never use emoticons.
Do Not Archive
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=405006#405006
Message 3
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Subject: | Re: jumpimg gauge needles |
hi bob,
ok, got the info. mitchell gauge for water temp., oil temp and oil
pressure. these 3 gauges all twitch, water temp. the worst. the electric
uma tach and the elec. vdo fuel gauge work fine. all gauges have a
separate ground wire back to a a common ground.
bob noffs
On Sat, Jul 20, 2013 at 4:15 PM, bob noffs <icubob@gmail.com> wrote:
> bob, i know the answer to some of your questions but i will track down
> arnie and get answers for them all and get back to you.
> bob noffs
>
> On Sat, Jul 20, 2013 at 3:05 PM, Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> nuckolls.bob@aeroelectric.com**>
>>
>>
>> At 01:01 PM 7/20/2013, you wrote:
>>
>>> i know this has come up before but i can't find it. a friend with a 912
>>> has the needles on his falcon engine gauges jumping and twitching while
>>> engine is running. are there places to look at to fix this? he has been
>>> told to run wire from regulator to battery terminal, not just to bus.
>>> anything else come to mind?
>>>
>>>
>> Does the jumping stop with the alternator
>> OFF?
>>
>> Can you describe the architecture of his
>> ground system? Do all the gauges wiggle
>> or just some . . . and what do they display.
>> Are there oil, coolant or fuel SENSORS
>> that ground locally . . . in others words
>> ground where they mount and then carry their
>> data off on a single wire?
>>
>>
>>
>> Bob . . .
>>
>>
>>
>>
>>
>
Message 4
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Subject: | Re: jumpimg gauge needles |
At 09:47 AM 7/21/2013, you wrote:
>hi bob,
> ok, got the info. mitchell gauge for water temp., oil temp and oil
> pressure. these 3 gauges all twitch, water temp. the worst. the
> electric uma tach and the elec. vdo fuel gauge work fine. all
> gauges have a separate ground wire back to a a common ground.
Okay, a picture is beginning to emerge. I suspect
those first three have single wires to the guages
and they ground through their threaded fittings
to the engine.
My working theory is that there is substantial
resistance between the crankcase and the "common
ground." I.e. the common ground is NOT a forest-
of-tabs on the firewall with a nice bond strap
between crankcase and forest-of-tabs.
The EASY fix is to take GAUGE grounds for the
3 twitchy instruments out to the crankcase. I'm
90% certain that the observed twitchiness will
go away.
Years ago I think I related a story about a Long-Ez
driver who had a 30A alternator on the engine but
no starter. His VERY long crankcase ground routed
to battery(-) in the nose offered substantial
voltage drop when the alternator was charging.
This cause a rather large excursion in his gauges
with local ground sensors when the alternator
was turned ON and OFF.
Bringing instrument grounds for those systems
back to the crankcase DIDN'T change the voltage
drop on the alternator ground wire, it just moved
that drop OUTSIDE the signal loop for the gauge.
Bob . . .
Message 5
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Subject: | Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 |
and Garmin SL30
Folks,
Someone must have done this, but I can=99t find any references.
The Garmin 496 can provide directional reference to the Pictorial Pilot
Directional AP, position and direction to the EFIS HSI display, and VOR
and COM frequencies to the SL30 NAV/COMM.
a.. It seems all devices can work with 9600 baud.
b.. The SL30 and D100 are OK with the 496 =9CData out=9D
setting =9CNMEA & VHF out.=9D The AP documentation
doesn=99t mention the VHF angle.
c.. The EFIS and AP can live with the 496 =9CAdvanced=9D
setting =9CNormal.=9D I don=99t know about the SL30
but doubt it matters.
Do I simply split the 496 =9Cdata out=9D wire three ways and
run to each device and hope the AP isn=99t confused by the
extraneous commands from the GPS intended for the SL30?
Any recommendations on running grounds between the devices, using
screened cable etc.?
Thanks!!
Regards, Chris.
Lancair 360, 90% done, 90% to do.
Message 6
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Subject: | Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS |
D100 and Garmin SL30
At 03:23 PM 7/21/2013, you wrote:
>Folks,
>Someone must have done this, but I can=99t find
>any references. The Garmin 496 can provide
>directional reference to the Pictorial Pilot
>Directional AP, position and direction to the
>EFIS HSI display, and VOR and COM frequencies to the SL30 NAV/COMM.
> * It seems all devices can work with 9600 baud.
> * The SL30 and D100 are OK with the 496
> =9CData out=9D setting =9CNMEA & VHF out.=9D
> The AP documentation doesn=99t mention the VHF angle.
> * The EFIS and AP can live with the 496
> =9CAdvanced=9D setting =9CNormal.=9D I don
=99t
> know about the SL30 but doubt it matters.
>
>Do I simply split the 496 =9Cdata out=9D wire
>three ways and run to each device and hope the
>AP isn=99t confused by the extraneous commands
>from the GPS intended for the SL30?
>Any recommendations on running grounds between
>the devices, using screened cable etc.?
NEMA data streams are fixed format, labeled sentences
of ordered data words. There are few devices that read
all the data from any given device. Listeners watch all
data strings starting with the right label, and then they
disassemble the sentence for the data of interest.
For example, if your listener wants to know lat,lon it looks
for a sentence formatted to carry that data. Like "GGA"
GGA - essential fix data which provide 3D location and accuracy data.
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where:
GGA Global Positioning System Fix Data
123519 Fix taken at 12:35:19 UTC
4807.038,N Latitude 48 deg 07.038' N
01131.000,E Longitude 11 deg 31.000' E
1 Fix quality: 0 = invalid
1 = GPS fix (SPS)
2 = DGPS fix
3 = PPS fix
4 = Real Time Kinematic
5 = Float RTK
6 = estimated (dead reckoning) (2.3
feature)
7 = Manual input mode
8 = Simulation mode
08 Number of satellites being tracked
0.9 Horizontal dilution of position
545.4,M Altitude, Meters, above mean sea level
46.9,M Height of geoid (mean sea level) above WGS84
ellipsoid
(empty field) time in seconds since last DGPS update
(empty field) DGPS station ID number
*47 the checksum data, always begins with *
In this case, the listener watches for $GPGGA to come along
then it parses the sentence for the second and third words
after the header.
There are proprietary sentences too. For example, Garmin
may find it useful to output a $PGRME sentence where word
pairs offer position error distances and units in which
those data are given.
Garmin
The following are Garmin proprietary sentences.
"P" denotes proprietary, "GRM" is Garmin's
manufacturer code, and "M" or "Z" indicates the
specific sentence type. Note that the PGRME
sentence is not set if the output is set to NMEA 1.5 mode.
$PGRME,15.0,M,45.0,M,25.0,M*1C
where:
15.0,M Estimated horizontal position error in meters (HPE)
45.0,M Estimated vertical error (VPE) in meters
25.0,M Overall spherical equivalent position error
So it's conceivable that your constellation of listeners
are interested in only a small port of all data offered by
the talker.
So as long as your 'talker' offers all the data needed
by all of your 'listeners', then each listener will sift
the good stuff out of the noise. Hook them all together.
Twisted pairs are good data lines. 9600 Baud is not
a bit EMC risk but shielding the wires is not a bad
idea. Ground the shield at listener end only.
Bob . . .
Message 7
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Subject: | Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS D100 |
and Garmin SL30
If you have all the pieces, the best thing to do would be to try it out
on the bench.
When I talked to Garmin a few years ago about connecting this unit, they
said it was fine to parallel it to several devices. I *think* they said
up to five.
Do you have any devices that need to talk back to the 496? If so, that
is the only device that should have its Tx line connected to the 496 Rx
line. (you can't parallel these)
Otherwise, I would use a twisted pair for 496 Data Tx and 496 Data
Ground, and run them from the Garmin to each instrument in a
star-pattern. The screen is probably optional, depending on what else is
in the wiring harness with it and how far it's going. Things that might
be sensitive to digital noise should be guarded, and it should be
guarded from strong RF sources like antenna feeds. These are just
suggestions though. In a lot of times, within reason, it's just
'whatever works best'
Bob and I differ on where to terminate the screen, but that drills into
some serious minutiae on this project. It's probably just not necessary
at all. (Bob -- I wouldn't mind hearing your thoughts on the termination
location rationale though)
Oh, and just in case you get some funny ideas, the Tx 2 and Rx 2 lines
that are in that Garmin-made wire harness are not connected in the 496!
I think they are for the 296 only..
I found an extra Garmin power data cable laying around and I've included
a drawing showing how I would wire the system and a page of the
installation manual with some useful warnings. Looking back at my notes,
though, in the install I did it looks like I didn't even connect the
serial ground to the D100. When the instruments are inches apart and
inches from the ground terminals, all this star-grounding and shielding
starts to make less difference.
http://www8.garmin.com/manuals/GPSMAP496_OwnersManual_forEurope_.pdf
On Jul 21, 2013, at 3:23 PM, Christopher Skelt wrote:
> Folks,
> Someone must have done this, but I can=92t find any references. The
Garmin 496 can provide directional reference to the Pictorial Pilot
Directional AP, position and direction to the EFIS HSI display, and VOR
and COM frequencies to the SL30 NAV/COMM.
> It seems all devices can work with 9600 baud.
> The SL30 and D100 are OK with the 496 =93Data out=94 setting =93NMEA &
VHF out.=94 The AP documentation doesn=92t mention the VHF angle.
> The EFIS and AP can live with the 496 =93Advanced=94 setting =93Normal.=94
I don=92t know about the SL30 but doubt it matters.
>
> Do I simply split the 496 =93data out=94 wire three ways and run to
each device and hope the AP isn=92t confused by the extraneous commands
from the GPS intended for the SL30?
> Any recommendations on running grounds between the devices, using
screened cable etc.?
>
> Thanks!!
>
> Regards, Chris.
> Lancair 360, 90% done, 90% to do.
>
>
>
Message 8
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Subject: | Re: Garmin 496 with Trutrak Autopilot, Dynon EFIS |
D100 and Garmin SL30
>
>Bob and I differ on where to terminate the screen, but that drills
>into some serious minutiae on this project. It's probably just not
>necessary at all. (Bob -- I wouldn't mind hearing your thoughts on
>the termination location rationale though)
Sure . . . easy . . . flip a coin.
Shielding is a prophylactic against the weakest of all
EMI propagation modes - electrostatic.
Modern serial data signals will deliberately soften
the leading and trailing edges of the data to minimize
the strength of the propagation mode in bundles.
Twisting pairs of a balanced data stream (Like RS422)
drops the coupling mode to a small fraction of and
already weak coupling mode.
Twisting an unbalanced data stream can't exploit
the common mode rejection capability of a balanced
pair receiver . . . but it still reduces electrostatic
coupling by a substantial proportion.
Shielding breaks the electrostatic propagation mode.
The currents flowing in the shield are so tiny as to be
difficult to measure . . . one can terminate the shield
at ANY low impedance node tied to signal or power ground and it's
got all the conductivity needed to do its nearly
insignificant job.
Grounding shields at the listener-end is a convention
we used most places I worked . . . a convention not
driven by significant physics.
Bob . . .
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