---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 07/13/06: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:21 AM - Re: Ammeter Shunt (Brian Lloyd) 2. 05:03 AM - Re: Ammeter Shunt (Bob Lee) 3. 06:24 AM - Re: Ammeter Shunt (Robert L. Nuckolls, III) 4. 12:57 PM - External Power and electrical system isolation (=?iso-8859-1?Q?Mich=E8le_MS?=) 5. 01:55 PM - Phone jack conventions (John Tvedte) 6. 02:33 PM - Re: External Power and electrical system isolation (Harley) 7. 03:58 PM - Re: Grounding lugs and transponder radiation (europa flugzeug fabrik) 8. 07:37 PM - Capacitor for Z-13/8 (Bret Smith) ________________________________ Message 1 _____________________________________ Time: 04:21:58 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: Ammeter Shunt --> AeroElectric-List message posted by: Brian Lloyd On Jul 12, 2006, at 9:22 PM, Brian Lloyd wrote: > It depends on how you wire your electrical system. If I have 5 > hours of battery life including the battery contactor and I have 4 > hours of fuel on board ... > > But if you have a separate battery feed to your endurance bus you > might want a second shunt to read loads on the endurance bus. You > may want then information to load shed to increase battery endurance. A further comment: the original question was on the ammeter shunt (or hall-effect sensor). There are many ways to craft the topology of your electrical system as Bob has shown in his book and discussions herein. But there are only a few places you can put an ammeter and get meaningful information. 1. You can put one in series with any source of power (alternator, generator, dynamo) and find out how much current it is delivering. 2. You can put one in series with a battery and see either its charging current or loads when the charging current is insufficient to carry all the loads (as in when the alternator is turning too slowly or is off-line). 3. You can put one in series with a load or loads and see how much current that device or devices demand from the system. If you change the path so that the current no longer travels through the shunt then you won't get any reading. Heck, you can put the shunt permanently in the path to the battery so it always shows battery current, even starting current. Then you can always see what is going into and coming out of your battery. Just make sure your shunt is beefy enough to handle the starting currents. The above is true regardless of the number of alternators or batteries in your system. Bob makes a point that all this discussion is so you can craft your electrical system to do what YOU want it to do. You may have different reasons to measure current than Bob or I do. Bob doesn't like the center-zero battery ammeter and I understand that. I have developed new respect for this instrument in applications where one will be running from battery power. Here is another way of looking at it. If you have two sources of power (alternators/dynamos) you are never going to be running your loads off your battery. It is only needed to start the airplane. The center-zero battery ammeter is almost useless in that system. OTOH if you have a single alternator system and will depend on the battery to get you to your destination should the alternator fail, you might want to know what the loads are so you can estimate remaining battery capacity. Now the center-zero ammeter is useful. I have a boat with a 1000AH battery bank. That battery bank provides all of the boat's power when I am at sea. I have to periodically recharge it. I want to know how much capacity I have consumed so I know how much is left and I want to know when it is fully charged. In this application the battery ammeter/shunt is critical. No other tool will suffice. So it all depends on your application. Brian Lloyd 361 Catterline Way brian-yak AT lloyd DOT com Folsom, CA 95630 +1.916.367.2131 (voice) +1.270.912.0788 (fax) I fly because it releases my mind from the tyranny of petty things . . . Antoine de Saint-Exupry ________________________________ Message 2 _____________________________________ Time: 05:03:32 AM PST US From: "Bob Lee" Subject: RE: AeroElectric-List: Ammeter Shunt --> AeroElectric-List message posted by: "Bob Lee" Brian Lloyd Wrote: << But if you have a separate battery feed to your endurance bus you might want a second shunt to read loads on the endurance bus. >> If you use a hall-effect sensor rather than a shunt you could run the endurance bus feed as well as the battery bus feed through the sensor and that way the ammeter would report total of battery bus and endurance bus (depending on which one was energized). Regards, Bob Lee N52BL KR2 Suwanee, GA 91% done only 65% to go! ________________________________ Message 3 _____________________________________ Time: 06:24:00 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Ammeter Shunt --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:02 AM 7/13/2006 -0400, you wrote: >--> AeroElectric-List message posted by: "Bob Lee" > >Brian Lloyd Wrote: ><< >But if you have a separate battery feed to your endurance bus you >might want a second shunt to read loads on the endurance bus. > >> > >If you use a hall-effect sensor rather than a shunt you could run the >endurance bus feed as well as the battery bus feed through the sensor and >that way the ammeter would report total of battery bus and endurance bus >(depending on which one was energized). Battery busses and endurance busses (if wired per the z-figures) are always energized in one way or another. There is one pretty useful dual-feedline use for a hall-sensor. You can run both alternator leads thorough it and have it read total load for both machines operating either independently or together. The questions to be asked and answered are: If I want to install any form of current monitoring device on the panel, what is the design goal for utility? One can select from a variety of locations all of which will present different information and different dynamics. Keep in mind that the first task to be completed for any architecture is a load analysis based on distribution of equipment across the various busses. The load analysis tells you that for any and all operating conditions, no current limited is exceeded -OR- during "plan-b" ops, certain loads must be turned off to meet endurance goals or to observe certain PRE-DETERMINED load limits. Bottom line is that EVERY current draw for EVERY mode of operation should be known to you before your first flight. An ammeter display of any variety is but one snapshot into system performance that might have some usefulness during a future troubleshooting activity as a technician. But if one has done their homework before first flight, ammeters are 95% useless to operating the airplane as pilot. I'm not trying discourage all the discussion about where shunts/hall-sensors can be placed and what they will show. But for the 1300 or so who are not participating in the conversation, know that whatever deductions are accomplished, don't think that ANY ammeter has much utility as an aid to flight operations no matter where it's installed. Bob . . . --------------------------------------------------------- < What is so wonderful about scientific truth...is that > < the authority which determines whether there can be > < debate or not does not reside in some fraternity of > < scientists; nor is it divine. The authority rests > < with experiment. > < --Lawrence M. Krauss > --------------------------------------------------------- ________________________________ Message 4 _____________________________________ Time: 12:57:19 PM PST US From: =?iso-8859-1?Q?Mich=E8le_MS?= Subject: AeroElectric-List: External Power and electrical system isolation --> AeroElectric-List message posted by: =?iso-8859-1?Q?Mich=E8le_MS?= Listers, I have been planning on adding external power to my system (one alternator, one battery, PMag IO360). My original design was pretty simple, hook it straight onto the battery such as one does when jump starting a car. Then I added a relay so that the external power terminals would not be hot when not connected to external power. Then some knowledgeable fellow builders told me that I should only use external power for starting the engine nothing else. Then some other knowledgeable builders told me that I could install a cigar lighter jack in parallel as an external power connector for recharging the battery. Then there was the issue as to external power not being clean DC current and consequently liable to play havoc with some of my sensitive equipment. Based on this I proceeded to design a circuit which would automatically disconnect all electricals except for the starter solenoid, current to the PMags and current to my fuel pump. Whereupon another knowledgeable person suggested that I should remember the KISS principle I may be over designing my system. What do you guys suggest isolate my electrical system when external power is hot or just hook it up onto the battery via a relay? Thanks, Michele Delsol RV8 Fuselage ________________________________ Message 5 _____________________________________ Time: 01:55:20 PM PST US From: "John Tvedte" Subject: AeroElectric-List: Phone jack conventions U2F5IC0gSSd2ZSBub3RpY2VkIHRoYXQgUFMgRW5nci4gaGFzIHN3YXBwZWQgdGhlIEwvUiBvbiB0 aGUgdGlwL21pZGRsZSBzZWN0aW9uIG9mIHRoZSBqYWNrcyAtIG9uIHRoZSBQTUE4MDAwQiB2cyB0 aGUgUE1BNzAwMEIuICBUaGV5IGFsc28gY2hhbmdlZCB0aGUgZW50ZXJ0YWlubWVudCBpbnB1dHMg YXMgd2VsbCAtIHNvIEwvUiBzdGVyZW8gaW1hZ2luZyBzaG91bGQganVzdCAncGFzcyB0aHJ1Jy4N CiANCkkgYW0gdHJ5aW5nIHRvIGRvY3VtZW50IHRoZSBhY3R1YWwgTC9SIC0gY2FuIHNvbWVvbmUg aGVscCBjbGFyaWZ5IHdoYXQgcG9ydGlvbiBvZiB0aGUgamFjayByZWFsbHkgaXMgdGhlIEwgYW5k IHdoYXQgaXMgdGhlIFI/DQogDQpUaGFua3MsDQogDQpKb2huDQo ________________________________ Message 6 _____________________________________ Time: 02:33:16 PM PST US From: Harley Subject: Re: AeroElectric-List: External Power and electrical system isolation Afternoon, Michele >>hook it straight onto the battery such as one does when jump starting a car<< I'm not familiar with an RV8, as I have a Long EZ (hangar neighbor has an RV6, though), but my philosophy is as you said...the KISS principal. Fewer plugs, relays, switches, cables and wires means less weight in the plane and fewer things to fail and possibly cause problems with other devices even when the ground power is NOT connected. >>so that the external power terminals would not be hot when not connected to external power.<< You lost me here. The external terminals? Can't you just clip a trickle charger directly onto the battery? Leave the master switch off when charging, and you should be fine. Remove the charger when flying and you have a nice, light, safe craft! That way, you'll always have a full battery, and should never have problems having enough juice to start the plane. Harley Dixon Long EZ N28EZ Canandaigua, NY Michle MS wrote: > --> AeroElectric-List message posted by: =?iso-8859-1?Q?Mich=E8le_MS?= > > Listers, > > I have been planning on adding external power to my system (one alternator, > one battery, PMag IO360). My original design was pretty simple, hook it > straight onto the battery such as one does when jump starting a car. Then I > added a relay so that the external power terminals would not be hot when not > connected to external power. Then some knowledgeable fellow builders told me > that I should only use external power for starting the engine -- nothing > else. Then some other knowledgeable builders told me that I could install a > cigar lighter jack in parallel as an external power connector for recharging > the battery. Then there was the issue as to external power not being clean > DC current and consequently liable to play havoc with some of my sensitive > equipment. Based on this I proceeded to design a circuit which would > automatically disconnect all electricals except for the starter solenoid, > current to the PMags and current to my fuel pump. Whereupon another > knowledgeable person suggested that I should remember the KISS principle -- I > may be over designing my system. > > What do you guys suggest -- isolate my electrical system when external power > is hot or just hook it up onto the battery via a relay? > > Thanks, > Michele Delsol > RV8 Fuselage > > > > > > > > ________________________________ Message 7 _____________________________________ Time: 03:58:43 PM PST US From: "europa flugzeug fabrik" Subject: AeroElectric-List: Re: Grounding lugs and transponder radiation --> AeroElectric-List message posted by: "europa flugzeug fabrik" brian wrote: > ...If your transponder puts out a peak power of 200W we have: > > 200 = V^2 / 2000 > > If we do the algebra we get: > > V = sqrt (200 * 2000) or 632V.... > > That could be for what I know, but I thought we worked on 50 ohms by fiat. I have a musty, ancient xponder service manual I eBayd cheap for maybe giggles. To measure power, they had you kludge a commercial voltage detector together with a special diode, IN23B. Then you observed reply pulse trains on any whatever scope and counted P-P volts by graticule divisions. Volts squared, divided by 50 (into a dummy 50-ohm load) and thems peak watts. So only 100V P-P would work out to 200W. Thats the purists approach, and funny that around 1990, I had my xponder check done by a crotchety old-timer. Hed ramp check also Mode C by observing similarly kludged, detected xponder output on what looked like his Dads old scope -- on wheels. For his selected altitude test points per Part 43, he had sketched the bit pattern on little index cards. Head cocked skyward to use his bifocals, holding said card up to the scope with round display. Pump vacuum at the plane, then run to the scope to check. He had to work fast, as permissible leak-down in the static sys at higher alts can cause up to multiple bits to flip Grey-code style (he seemed to rely on an observed time lag). Who needs very expensive equipment, when all you need are FAA-approved index cards? Worked for him and me, a priceless observance of an actual FAR Part 145 repair facility at work, worth every penny for the log entry. Purists impress me.... Had the temptation to hit the IDENT button whilst he was straining through bifocals, but dared not! How 50-ohm impedance became the norm, where impedance of the atmosphere is etched in stone by a higher power, and a 1/4-wave straight element is natural at 37, well I beg off. Perhaps cuz it all works, or perhaps you know.... 75 works for video hi-def TV with 2-way for nefarious purpose. The history of the decibel may be similar whimsy? Not the convenient, additive/subtractive nondimensional math, but Dr. Bell didn't get recognized as did Watt, Ohm, etc., and his employer allegedly thought dividing by 10 (deci) was more practical. Purists like me write "dB,"not "db." :D It's like in very current cell phone technology, where despite awesome cleverness to me at least, nobody's been memorialized for nuthin'. :x Fred F. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=46993#46993 ________________________________ Message 8 _____________________________________ Time: 07:37:20 PM PST US From: "Bret Smith" Subject: AeroElectric-List: Capacitor for Z-13/8 Where can I purchase the capacitor (20-50KuFd) called out in Z13/8? I cannot find it on the B&C site and wondered if the automotive variety would work? TIA Bret Smith RV-9A (91314) Mineral Bluff, GA www.FlightInnovations.com