---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 05/28/09: 24 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:54 AM - 12V Power Socket (Andrew Butler) 2. 06:08 AM - Re: Engine mount as starter ground path (Tom Hanaway) 3. 06:45 AM - Re: 12V Power Socket (jay@horriblehyde.com) 4. 07:10 AM - Re: 12V Power Socket (Richard Girard) 5. 07:10 AM - Re: Alternator with built-in regulator (Wade Roe) 6. 07:11 AM - Re: 12V Power Socket (James H Nelson) 7. 07:21 AM - Grounding philosophy (Johnson, Phillip (EXP)) 8. 07:26 AM - Reading Potentiometer Values () 9. 07:44 AM - Re: 12V Power Socket () 10. 07:44 AM - Re: Alternator with built-in regulator () 11. 08:20 AM - Re: Alternator with built-in regulator (Hinde, Frank George (Corvallis)) 12. 08:38 AM - Re: State of the art - then and now (Chris Stone) 13. 09:13 AM - Re: Reading Potentiometer Values (Bob White) 14. 09:15 AM - Re: 12V Power Socket (Greg Young) 15. 10:40 AM - Grey code output to multiple devices (Ralph E. Capen) 16. 10:40 AM - Re: Reading Potentiometer Values () 17. 01:12 PM - Re: Reading Potentiometer Values (Robert L. Nuckolls, III) 18. 01:18 PM - Re: Alternator with built-in regulator (Robert L. Nuckolls, III) 19. 02:07 PM - Re: Grounding philosophy (Robert L. Nuckolls, III) 20. 02:11 PM - Re: Re: Engine mount as starter ground path (Robert L. Nuckolls, III) 21. 05:42 PM - Re: Re: Engine mount as starter ground path (Tom Hanaway) 22. 06:03 PM - Re: Re: Engine mount as starter ground path (Robert L. Nuckolls, III) 23. 06:12 PM - Re: Re: Engine mount as starter ground path (Kelly McMullen) 24. 09:31 PM - Re: KX-125 Installation Manual? (iconoclast) ________________________________ Message 1 _____________________________________ Time: 05:54:10 AM PST US From: Andrew Butler Subject: AeroElectric-List: 12V Power Socket Hello, I am wiring up a 12V (cigarette lighter) power socket into my panel. Can anyone tell me the convention for the +ve and -terminals on these things? Thanks, Andrew. ________________________________ Message 2 _____________________________________ Time: 06:08:51 AM PST US From: "Tom Hanaway" Subject: AeroElectric-List: Re: Engine mount as starter ground path Bob, My first post to this site. I'm working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. One and two are clear. I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit. In a later post, you advise "any bonding jumpers across the engine mounts are best removed" to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? Thanks, Tom Hanaway Boynton Beach, FL Robert L. Nuckolls, III wrote: > > > > At 11:35 PM 5/26/2009, you wrote: >> > >> >> t 08:47 PM 5/26/2009, you wrote: >> > >> >> The Z-14 I've put into my RV10 follows the best practices as >> described in the Connection with one oversight.... I have the 2 sided >> forest of tabs on the firewall but I only have an AWG 8 cable >> running to it from the rear batteries instead of an AWG2 fat wire. >> And it's too late to swap it out without significant re-work. > > Bill, re-reading my posting from last night I'm not > sure I conveyed a clear image of my recommendations. > In a nutshell: > > Add local grounds to airframe for the batteries if > you don't already have them. > > Add crankcase to firewall ground stud for engine. > > Leave jumpers across the engine mount biscuits. > > You can cut the 8AWG wire out if you wish and > if it is practical. It adds only weight and > offers no significant electrical function. > > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) ________________________________ Message 3 _____________________________________ Time: 06:45:00 AM PST US From: "jay@horriblehyde.com" Subject: Re: AeroElectric-List: 12V Power Socket The positive is the centre post and negative the outer shell. Jay -----Original Message----- From: "Andrew Butler" [andrewbutler@ireland.com] Subject: Re: AeroElectric-List: 12V Power Socket Hello, I am wiring up a 12V (cigarette lighter) power socket into my panel. Can anyone tell me the convention for the +ve and -terminals on these things? Thanks, Andrew. ________________________________ Message 4 _____________________________________ Time: 07:10:53 AM PST US Subject: Re: AeroElectric-List: 12V Power Socket From: Richard Girard Positive is the center (spring loaded plunger on the plug), ground is the shell (two flat connectors along the side of the plug). Rick On Thu, May 28, 2009 at 7:45 AM, Andrew Butler wrote: > andrewbutler@ireland.com> > > Hello, > > I am wiring up a 12V (cigarette lighter) power socket into my panel. > > Can anyone tell me the convention for the +ve and -terminals on these > things? > > Thanks, > > Andrew. > > ________________________________ Message 5 _____________________________________ Time: 07:10:53 AM PST US From: Wade Roe Subject: Re: AeroElectric-List: Alternator with built-in regulator Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as backup. Wade Roe IPhone message On May 27, 2009, at 10:38 PM, "Robert L. Nuckolls, III" wrote: > > > > >> >> >> The plane will be IFR and all electric. >> >> Wade Roe >> > > Wade, would it be a fair assumption then that > a second alternator will go onto the vacuum > pump pad? > > > Bob . . . > > ----------------------------------------) > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > ---------------------------------------- > > ________________________________ Message 6 _____________________________________ Time: 07:11:38 AM PST US Subject: Re: AeroElectric-List: 12V Power Socket From: James H Nelson Andrew, The usual center is positive and the shell goest to ground. You should wire the scocket to powerthe panel with out turning the master on. I have mine that way so I can play with the panel with out using the aircraft battery. I have a little cpmpressor / battery unit that I take to the hanger and keeps the tires up and lets me run my glass panel for setting up a trip etc. Jim ____________________________________________________________ Compete with the big boys. Click here to find products to benefit your business. http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTI97zF6gFxJRmQXuZsZBzUiPEnqkuoiaMthATKQtsww5EJAaYCWxa/ ________________________________ Message 7 _____________________________________ Time: 07:21:11 AM PST US From: "Johnson, Phillip (EXP)" Subject: AeroElectric-List: Grounding philosophy Time: 09:21:48 AM PST US From: "Robert L. Nuckolls, III" Subject: At 09:05 AM 5/27/2009, you wrote: Bob, >I read your message and went to your web link indicated below and I >can't accept that it is a good design. The problem that I see is that >your design does not create a single ground reference. >Yes it does. The architectures discussed in Figure Z-15 and >other writings suggeste the stud at the forest of tabs on the >firewall is the central point ground for the aircraft. So Ground point number one is the "forest of tabs" and ground point number two is the engine crankcase when the alternator, starter motor, and most engine sensors make their ground. I.e. there is not a single point ground. In an ideal world where #2 gauge wires and interconnections have zero resistance but, as you point out in your document, this is not the case. >>Ideally you want >>the engine block to be the ground reference with all currents flowing >>through it. To this end you need to connect the battery -ve to the >>crankcase and then make all grounds connect, either directly or >>indirectly, to the crankcase as well. In doing this there will be no >>ground potential differences to upset the instrumentation. >Instrumentation is a special case where grounded automotive >sensors are at risk for suffering ground loop interference. >This has been discussed at length in various writings. If the >problem presents itself (usually manifest by a shift in >instrumentation readings in response to alternator loads), >then the "ground" leads for panel mounted instruments need >to be extended to the crankcase. However, if one has a very >low resistance net between he crankcase and the firewall >ground stud . . . then the "problem" may be reduced to >insignificant if not completely unobservable. They should not have to be a special case if wired correctly. When everything references the crankcase there is no special case. The problem is that when the installation is done all the connections are clean and the installer usually knows what he is doing. A few years down the road an unknowledgeable person does not prepare the electrical bonding surface as well as he should and then problems start happening when current starts to flow through the circuit. Using the philosophy that I have given, these problems are reduced significantly, which in my opinion makes for a better design. >>The pilot now tries to start the engine and all of >>the current tries to flow through this instrumentation ground. This >>causes a melt down of the wiring and a potential ground fire and risk to >>those expensive electronics. >Again, discussed in past publications and postings . . . >"Smoking ground returns" is easily avoided by not closing >the returns. Common occurrences include the risk of >instrumentation grounds for instruments not designed >to live in the real world of aircraft. Another common >risk happens when builders attached p-lead shields to >crankcase at one end and airframe at the other end. >All of my drawings illustrate technique for avoiding >that loop as well. Again, "Smoking ground returns" are avoided if you use my design solution. >>It is my opinion, and I believe that the automotive industry also adopts >>this philosophy, that you connect the battery ground to the crankcase >>and then strap the engine to the airframe/car body and system ground so >>that the high current grounds pass only through the engine. Charging >>ground currents, which can be extremely high, also only pass through the >>engine block thereby preventing erroneous instrumentation and potential >>fire risk. >Batteries go to crankcases in cars because the battery >always sits right next to the engine. In the old days the battery ground went straight to the bodywork and then there was an engine strap in a different location which coupled the body to the engine. I'm not sure when the change occurred but I would guess that it occurred somewhere soon after the first electronic systems were implemented. I changed the battery on my neighbours Audi a couple of years ago and that had the battery under the rear seats. The ground lead did not go straight to the body but I can't be sure that it went all the way to the front either. I surmise that if it did not go directly to the body it would probably make the full journey to the engine. >The automotive >industry has adopted the same philosophy as every other >industry for minimizing the numbers of joints, fasteners >and pieces of wire in the fat-wire conduction paths. Agreed >Now, if one had a battery on the forward side of >the firewall then there is no electrical reason >NOT to ground the battery right to the crankcase. >There are mechanical reasons not to . . . we've >already established the value of a 2AWG equivalent >jumper from crankcase to ground stud. This same stud >becomes a practical spot to ground a battery as >well . . . and the 2AWG bonding strap makes sure >that voltage differences between the crankcase >and the ground stud are insignificantly small. I have a Cozy MK IV with the battery on the cockpit side of the firewall. I have approximately two feet of cable connecting the -ve to crankcase ground so length cant be an issue. The issue is that there are two additional connections and a couple of feet of #2 cable separating the engine ground from the "forest of tabs". Using the numbers from your paper this gives 1.3 mohm of resistance. Assuming you have an alternator sourcing say 40 amps you now have 50 mV ground difference which is also rectified AC i.e. noise. Now as you have said it is difficult to get better than 0.5miliohm per connection and with time and sloppy maintenance the number grows to something that is unacceptable. All this just because the ground reference was not defined appropriately. >If the battery is aft of the firewall, then the >most practical battery ground is the firewall >ground stud . . . or to the airframe on an all >metal airplane. OK I have a plastic aeroplane so airframe is not an option but I still feel the firewall is a bad choice. >>OK I've now started to run and get my flame suit on. >Zero risk from me sir . . . Bob . . . ________________________________ Message 8 _____________________________________ Time: 07:26:00 AM PST US Subject: AeroElectric-List: Reading Potentiometer Values From: I have a handful of potentiometers at home and I want to verify the ohms rating of each. What is the best/easiest or cheapest way to determine their rating? The only real equipment I have is a simple DC tester with ohms values. I will be using one to control the audio volume between my D180 & GMA340. Thanks, Glenn ________________________________ Message 9 _____________________________________ Time: 07:44:33 AM PST US Subject: RE: AeroElectric-List: 12V Power Socket From: Absolutely, if you think about it for just a second, these things are no different than a standard light bulb socket. Touch the center contact and you'll light up; touch the ring and your still here. When people used to smoke everyone knew the center contact had to touch to make the heat and the cool ground was the outside. After too many cigarettes you got stinky fingers and the contact would begin to fail and loose heat thus becoming less of a conductor between the center and the shell. If the shell were a on the + side of the ship, your 63 Chevy's steel panel would still be smoking. Glenn From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Richard Girard Sent: Thursday, May 28, 2009 9:44 AM Subject: Re: AeroElectric-List: 12V Power Socket Positive is the center (spring loaded plunger on the plug), ground is the shell (two flat connectors along the side of the plug). Rick On Thu, May 28, 2009 at 7:45 AM, Andrew Butler wrote: Hello, I am wiring up a 12V (cigarette lighter) power socket into my panel. Can anyone tell me the convention for the +ve and -terminals on these things? Thanks, Andrew. -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List http://forums.matronics.com le, List Admin. ="_blank">http://www.matronics.com/contribution ________________________________ Message 10 ____________________________________ Time: 07:44:42 AM PST US Subject: RE: AeroElectric-List: Alternator with built-in regulator From: One caveat on P & P alts. The one I had came with what I'll call a cheap Molex connector for the field wire etc. I replaced it with sold wiring after it vibrated and sheared itself off for the second time. I now use and internal job and have not had any issues. It's all about the core quality. Alternators are one of the biggest scams in automotive history. They cost about $10.00 to rebuild and the vendors charge you an arm and a leg. As Frank mentioned, start with a good core and stick with it. I'm using one off a Porsche and it works like a champ. Glenn -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Hinde, Frank George (Corvallis) Sent: Wednesday, May 27, 2009 5:45 PM Subject: RE: AeroElectric-List: Alternator with built-in regulator (Corvallis)" In that case send that alternator back to Vans and exchange it for the plane power unit...Trying to use the B&C regulator (which it was not designed for) is a bit like putting lipstick on a pig..Its still a pig! I futzed with a rebuilt alternator for a while and had a couple of scary moments in IMC..then I changed to the Plane power and its been faultless ever since. They come with a wonderful reputation. No electrical noise, just fit (with the supplied brackets) and forget it. On An all electric IFR airplane the alternator is not the place to be making shortcuts!!!..The extra couple of hundred bucks is WELL spent. Frank RV7a..all electric IFR including 2* EI's and the fuel pumps! -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Wade Roe Sent: Wednesday, May 27, 2009 2:20 PM Subject: RE: AeroElectric-List: Alternator with built-in regulator The alternator from Vans is a reconditioned Japanese automobile unit (Honda?) that came with the firewall forward kit. I figured the B&C linear regulator to be a superior/cleaner product than that on the alternator. The plane will be IFR and all electric. Wade Roe ________________________________ Message 11 ____________________________________ Time: 08:20:36 AM PST US From: "Hinde, Frank George (Corvallis)" Subject: RE: AeroElectric-List: Alternator with built-in regulator Me too..I found that the SD8 was adequate and remember I run electric fuel pumps..One of them MUST be running or I become a glider. I have a GNS 430W, transponder etc etc and found that with sensible load management the SD8 would maintian the battery volts at 12..Not enough to charge the battery but it would keep up with the load. Frank -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Wade Roe Sent: Thursday, May 28, 2009 6:52 AM Subject: Re: AeroElectric-List: Alternator with built-in regulator Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as backup. Wade Roe IPhone message ________________________________ Message 12 ____________________________________ Time: 08:38:58 AM PST US From: Chris Stone Subject: Re: AeroElectric-List: State of the art - then and now Great stuff Bob! "The more things change the more they stay the same." Thanks for sharing... C. Stone I'm in possession of several issues of the Electrical Experimenter circa 1916. This hobbyist/amateur/semi- professional publication offered a newsstand source for both understanding and state of the art news in a range of technologies. I'm using one of these magazines as reference for a science history presentation I'm doing. I've scanned it for sharing and thought I would post it for those having an interest in such things. See: http://tinyurl.com/ofbj3c It's interesting to see the depth and scope of interests illustrated on these pages. It's also interesting to see a level of hucksterism and quackery not unlike that which pours forth in today's video and print media! See pdf pages 7, 25, 62 (violet rays), 65 (Pandiculator). But the casually discriminating eye can easily identify and appreciate the good stuff of which there is plenty. Hope you enjoy browsing this piece of technological history. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 13 ____________________________________ Time: 09:13:32 AM PST US From: Bob White Subject: Re: AeroElectric-List: Reading Potentiometer Values Hi Glenn, It sounds like you have what you need. Measure the resistance (ohms) between the two outside pins. That will tell you what the resistance of the pot is. There is another consideration when selecting a pot. There linear and "audio" taper pots. A linear pot will change resistance linearly with pot rotation. Turn it half way between CCW and CW will give a reading of 1/2 the total resistance. An audio taper will change exponentially. Rotating half way between CCW and CW will result in a lower resistance between the center pin and the CCW pin and a higher resistance between the center pin and the CW pin. The audio taper is probably the best choice for your application. Also, there should be some markings on the pot that will tell you what value the pot is. Picking up a couple of random pots from by work bench, one is marked "200 (ohm) LIN" which is pretty straightforward to decode. the other is marked "A100K" which clearly indicates it is a 100 kohm pot, and I would guess the "A" means audio taper but I would have to check. (There are pots that aren't configured quite as described, but it should work for most run of the mill pots.) Bob W. On Thu, 28 May 2009 10:23:23 -0400 wrote: > > I have a handful of potentiometers at home and I want to verify the ohms > rating of each. What is the best/easiest or cheapest way to determine > their rating? The only real equipment I have is a simple DC tester with > ohms values. I will be using one to control the audio volume between my > D180 & GMA340. > > Thanks, > Glenn > > > > > -- N93BD - Rotary Powered BD-4 - http://www.bob-white.com 3.8 Hours Total Time and holding Cables for your rotary installation - http://roblinstores.com/ ________________________________ Message 14 ____________________________________ Time: 09:15:53 AM PST US From: "Greg Young" Subject: RE: AeroElectric-List: 12V Power Socket It depends on what you want to accomplish. If you wire it to the buss side of the master you can power your panel from it during the build. But if you wire it to the battery side of the master you can power accessories or trickle charge the battery without turning on the master. There are pluses & minuses both ways. Think it through and decide what's best for you. Regards, Greg Young > -----Original Message----- > ground. You should wire the scocket to powerthe panel with > out turning the master on. > I have mine that way so I can play with the panel with out > using the aircraft battery. I have a little cpmpressor / > battery unit that I take to the hanger and keeps the tires > up and lets me run my glass panel for setting up a trip etc. > > > ________________________________ Message 15 ____________________________________ Time: 10:40:29 AM PST US From: "Ralph E. Capen" Subject: AeroElectric-List: Grey code output to multiple devices Folks, I have a Narco AR 850 grey code altitude reporter. I would like to connect it to two devices (GPS and transponder) instead of just the transponder. The serial port on the GPS is being used for something else and it has grey code lines also. Both the GPS and transponder have diode suppression in the grey code lines in order to prevent an off unit from dropping the signal to low. What say ye.....can I do this - or will smoke escape....? Thanks, Ralph Capen ________________________________ Message 16 ____________________________________ Time: 10:40:29 AM PST US Subject: RE: AeroElectric-List: Reading Potentiometer Values From: Excellent, Thanks Bob. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bob White Sent: Thursday, May 28, 2009 12:00 PM Subject: Re: AeroElectric-List: Reading Potentiometer Values Hi Glenn, It sounds like you have what you need. Measure the resistance (ohms) between the two outside pins. That will tell you what the resistance of the pot is. There is another consideration when selecting a pot. There linear and "audio" taper pots. A linear pot will change resistance linearly with pot rotation. Turn it half way between CCW and CW will give a reading of 1/2 the total resistance. An audio taper will change exponentially. Rotating half way between CCW and CW will result in a lower resistance between the center pin and the CCW pin and a higher resistance between the center pin and the CW pin. The audio taper is probably the best choice for your application. Also, there should be some markings on the pot that will tell you what value the pot is. Picking up a couple of random pots from by work bench, one is marked "200 (ohm) LIN" which is pretty straightforward to decode. the other is marked "A100K" which clearly indicates it is a 100 kohm pot, and I would guess the "A" means audio taper but I would have to check. (There are pots that aren't configured quite as described, but it should work for most run of the mill pots.) Bob W. On Thu, 28 May 2009 10:23:23 -0400 wrote: > > I have a handful of potentiometers at home and I want to verify the ohms > rating of each. What is the best/easiest or cheapest way to determine > their rating? The only real equipment I have is a simple DC tester with > ohms values. I will be using one to control the audio volume between my > D180 & GMA340. > > Thanks, > Glenn > > > > > -- N93BD - Rotary Powered BD-4 - http://www.bob-white.com 3.8 Hours Total Time and holding Cables for your rotary installation - http://roblinstores.com/ ________________________________ Message 17 ____________________________________ Time: 01:12:09 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Reading Potentiometer Values At 09:23 AM 5/28/2009, you wrote: > >I have a handful of potentiometers at home and I want to verify the ohms >rating of each. What is the best/easiest or cheapest way to determine >their rating? The only real equipment I have is a simple DC tester with >ohms values. I will be using one to control the audio volume between my >D180 & GMA340. For simple volume control duties, simply knowing the resistance value is sufficient. Further, it's unlikely that the exact value is critical. Potentiometers with values ranging from 500 to perhaps as high as 10000 ohms would work for you. It's an easy experiment and zero risk to the rest of your system. Digital multi-meters are inexpensive. Harbor Freight has one that seems to be perpetually on sale for under $5. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 18 ____________________________________ Time: 01:18:13 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Alternator with built-in regulator At 08:51 AM 5/28/2009, you wrote: > >Roger that. I plan to use the B&C 8 amp alternator or the 20 amp as >backup. Most builders find the SD-8 to be adquate to the task. Consider Figure Z-13/8. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 19 ____________________________________ Time: 02:07:14 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Grounding philosophy So Ground point number one is the "forest of tabs" and ground point number two is the engine crankcase when the alternator, starter motor, and most engine sensors make their ground. I.e. there is not a single point ground. In an ideal world where #2 gauge wires and interconnections have zero resistance but, as you point out in your document, this is not the case. Let's not get wrapped around the axle for defining "single point ground". The better term is perhaps a central ground point from which the rest of the ground system radiates. Now, there can be and often is further spreading from nodes remote from the central ground. One example is the crankcase from which numerous grounded sensors find a reference. See Figure Z-15 (three sheets). Risks of system performance degrading due to currents circulating in the ground system are reduced if not eliminated by first avoiding multiple grounds within any single system that are not co-located. In the case of engine instruments with grounded sensors, taking the ground returns for panel mounted instruments back to the crankcase makes the crankcase a "single point ground" for that suite of instruments. Figure Z-15 speaks to a variety of grounding options for accessories located all over the airplane. None of those illustrations suggests that ALL grounds be brought to a single-point be it the crankcase or forest of tabs. What those drawing DO illustrate is making a distinction between potential noise victims, noise antagonists and breaking the ground loop coupling mode. They should not have to be a special case if wired correctly. When everything references the crankcase there is no special case. The problem is that when the installation is done all the connections are clean and the installer usually knows what he is doing. A few years down the road an unknowledgeable person does not prepare the electrical bonding surface as well as he should and then problems start happening when current starts to flow through the circuit. Using the philosophy that I have given, these problems are reduced significantly, which in my opinion makes for a better design. Define "wired correctly". In the TC aviation world we're very much aware of the problems associated with engine sensors conforming to legacy automotive conventions of grounding to the block. In the 1957 Chevy, the grounded oil pressure "sender" is "wired correctly". In a 1995 Beechjet, this product would not be considered for a host of reasons not the least of which is "incorrect wiring" for design goals imposed on the project. But if my boss says "Put this 1957 oil pressure gage in that airplane" I can get 'er done with zero risk of degraded performance induced by poor grounding decisions. Again, "Smoking ground returns" are avoided if you use my design solution. I'm not suggesting that there is but one solution for avoiding smoking grounds or ground loop induced noise. If you choose to use the crankcase as your "single point ground" . . . is it your intention to take all the ground wires from ship's electro-whizzies to the crankcase? That could make for a really big bundle of wires through the firewall. If you grounded EVERYTHING to the crankcase, would you still ground the p-lead shields at both ends? >Batteries go to crankcases in cars because the battery >always sits right next to the engine. In the old days the battery ground went straight to the bodywork and then there was an engine strap in a different location which coupled the body to the engine. I'm not sure when the change occurred but I would guess that it occurred somewhere soon after the first electronic systems were implemented. I changed the battery on my neighbours Audi a couple of years ago and that had the battery under the rear seats. The ground lead did not go straight to the body but I can't be sure that it went all the way to the front either. I surmise that if it did not go directly to the body it would probably make the full journey to the engine. Which is anecdotal to what we're discussing here. Exactly how you achieve low resistance, minimum parts count, no-loop architecture for grounds in your airplane has many recipes for success as long as the components are assembled with understanding. But let us take care that we don't confuse 1800+ readers of this List with some notion that the crankcase is the touchstone of grounds . . . this simply isn't so. I have a Cozy MK IV with the battery on the cockpit side of the firewall. I have approximately two feet of cable connecting the -ve to crankcase ground so length cant be an issue. The issue is that there are two additional connections and a couple of feet of #2 cable separating the engine ground from the "forest of tabs". Using the numbers from your paper this gives 1.3 mohm of resistance. Assuming you have an alternator sourcing say 40 amps you now have 50 mV ground difference which is also rectified AC i.e. noise. Now as you have said it is difficult to get better than 0.5miliohm per connection and with time and sloppy maintenance the number grows to something that is unacceptable. All this just because the ground reference was not defined appropriately. I think you're sifting the sand here. There is NO electrical system for any vehicle that is not plagued with beeps, burps, hums, spikes and assorted perturbations of voltage a LOT bigger than your hypothesis. In the TC aircraft world we KNOW that those noises exist and we design to live with them. See: http://www.aeroelectric.com/articles/DO-160.pdf The voltage levels you hypothesize are of no significance if potentially vulnerable systems don't see them because ground loops have been eliminated. Making sure the loops don't exist is easy if you understand your system integration task. It matters not whether the system follows legacy automotive design goals or modern aviation design goals. BOTH technologies can be successfully integrated into the OBAM aircraft. >If the battery is aft of the firewall, then the >most practical battery ground is the firewall >ground stud . . . or to the airframe on an all >metal airplane. OK I have a plastic aeroplane so airframe is not an option but I still feel the firewall is a bad choice. A "bad choice" only if you allow ground loops to exist without evaluating their potential for influencing system performance. Please wire in any manner that gives you comfort. All I'm offering is a constellation of options based on many recipes for success. Virtually ALL of those recipes call for elimination of ground loops that offer a potential for problems. NONE of those recipes treats any location or component of the ground system as the Nirvana of grounds. The forest-of-tabs offers a level of convenience for the majority of system grounds for devices both sides of the firewall. Having this device be 'central' to the ship's ground system makes sense . . . especially if the engine sensors are "wired correctly" in observance of modern aircraft design goals. But even if they are not, the third sheet of Z15 suggests how the 1950's design goals can be accommodated in a 2009 RV. Bob . . . ________________________________ Message 20 ____________________________________ Time: 02:11:02 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Engine mount as starter ground path At 07:58 AM 5/28/2009, you wrote: >Bob, > >My first post to this site. I'm working on an rv-10. I thought I >understood the grounding once you gave the below explanation to Bill W. > >One and two are clear. I read #3 as putting a jumper across an >individual mount t0 both sides of a single biscuit. In a later >post, you advise "any bonding jumpers across the engine mounts are >best removed" to avoid parallel grounds. Equally, the Connection >speaks of a single point ground at firewall. Is this a contradiction >or does it refer to not having jumpers between two completely separate mounts? No, I was referencing a project-in-process where an already too-small 8AWG battery(-) wire was installed. Upsizing that wire was not an attractive option. The work-around involved the used of jumper straps around the shock mount biscuits and local battery grounds. Now, if you're starting from scratch and your battery is located near the firewall, that posting was not applicable to you. Use NO JUMPERS on the engine mount biscuits. Wire as suggested in chapter 5 and Figure Z-15. Welcome to the List! Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 21 ____________________________________ Time: 05:42:50 PM PST US From: "Tom Hanaway" Subject: RE: AeroElectric-List: Re: Engine mount as starter ground path Thanks Bob. Sorry to beat a dead horse but I need one more clarification. Your response mentions "if battery near firewall". The batteries are actually both in the aft area. Can the battery be locally grounded to airframe at site of battery (metal frame craft) with B&C tab forest on firewall for grounds and engine ground? Or is best solution still to run a 2awg ground wire up to firewall and proceed with grounding to tab forest as above? Thanks, Tom _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Thursday, May 28, 2009 5:10 PM Subject: Re: AeroElectric-List: Re: Engine mount as starter ground path At 07:58 AM 5/28/2009, you wrote: Bob, My first post to this site. I=12m working on an rv-10. I thought I understood the grounding once you gave the below explanation to Bill W. One and two are clear. I read #3 as putting a jumper across an individual mount t0 both sides of a single biscuit. In a later post, you advise =13any bonding jumpers across the engine mounts are best removed=14 to avoid parallel grounds. Equally, the Connection speaks of a single point ground at firewall. Is this a contradiction or does it refer to not having jumpers between two completely separate mounts? No, I was referencing a project-in-process where an already too-small 8AWG battery(-) wire was installed. Upsizing that wire was not an attractive option. The work-around involved the used of jumper straps around the shock mount biscuits and local battery grounds. Now, if you're starting from scratch and your battery is located near the firewall, that posting was not applicable to you. Use NO JUMPERS on the engine mount biscuits. Wire as suggested in chapter 5 and Figure Z-15. Welcome to the List! Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 22 ____________________________________ Time: 06:03:49 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Re: Engine mount as starter ground path At 07:34 PM 5/28/2009, you wrote: >Thanks Bob. >Sorry to beat a dead horse but I need one more clarification. Your >response mentions "if battery near firewall". The batteries are >actually both in the aft area. Can the battery be locally grounded >to airframe at site of battery (metal frame craft) with B&C tab >forest on firewall for grounds and engine ground? > >Or is best solution still to run a 2awg ground wire up to firewall >and proceed with grounding to tab forest as above? > >Thanks, >Tom > >---------- You say "both batteries". Which Z-figure are you crafting? Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 23 ____________________________________ Time: 06:12:41 PM PST US From: Kelly McMullen Subject: Re: AeroElectric-List: Re: Engine mount as starter ground path The RV-10 by necessity and design has the battery(s) located in the tailcone to partly offset the weight of the IO-540 up front. Given that the structure from the battery location to the firewall is all riveted aluminum in the lower half of the fuselage there likely is a solid ground path. Running a fat wire to parallel that ground path, or to replace it doesn't appear to be all that good an option. Kelly Robert L. Nuckolls, III wrote: > > No, I was referencing a project-in-process where an > already too-small 8AWG battery(-) wire was installed. > Upsizing that wire was not an attractive option. > The work-around involved the used of jumper straps > around the shock mount biscuits and local battery grounds. > > Now, if you're starting from scratch and your > battery is located near the firewall, that > posting was not applicable to you. Use NO > JUMPERS on the engine mount biscuits. Wire > as suggested in chapter 5 and Figure Z-15. > > ________________________________ Message 24 ____________________________________ Time: 09:31:57 PM PST US Subject: AeroElectric-List: Re: KX-125 Installation Manual? From: "iconoclast" If it's not too much trouble, can you please PM me the KX 125 manual also? I'm adding a second com and need to patch into the harness for my 125. 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