AeroElectric-List Digest Archive

Sun 07/21/13


Total Messages Posted: 8



Today's Message Index:
----------------------
 
     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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    Time: 12:06:20 AM PST US
    From: "JOHN TIPTON" <jmtipton@btopenworld.com>
    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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    Time: 06:19:49 AM PST US
    Subject: Re: Battery capacity tester-was flyback diode, now
    clock source
    From: "Eric M. Jones" <emjones@charter.net>
    > 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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    Time: 07:48:44 AM PST US
    Subject: Re: jumpimg gauge needles
    From: bob noffs <icubob@gmail.com>
    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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    Time: 01:04:09 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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    Time: 01:24:12 PM PST US
    From: "Christopher Skelt" <cskelt@earthlink.net>
    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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    Time: 06:01:52 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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    Time: 06:34:25 PM PST US
    From: Daniel Hooper <enginerdy@gmail.com>
    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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    Time: 07:32:50 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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