AeroElectric-List Digest Archive

Sat 02/27/10


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 08:57 AM - Re: Z-12 Architecture - Parallel Master Contactors (user9253)
     2. 12:46 PM - Re: Circuit protection - Amps (Carlos Trigo)
     3. 04:14 PM - SD-8 self excite capacitor (Tom Barter)
     4. 09:16 PM - Re: SD-8 self excite capacitor (Robert L. Nuckolls, III)
     5. 09:16 PM - Re: Re: Clearing some away some fog and fuzzy logic . . . (Robert L. Nuckolls, III)
     6. 09:38 PM - Re: Z13/20 (Robert L. Nuckolls, III)
 
 
 


Message 1


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    Time: 08:57:48 AM PST US
    Subject: Re: Z-12 Architecture - Parallel Master Contactors
    From: "user9253" <fran4sew@banyanol.com>
    Re: A second parallel battery contactor in lieu of an E-Bus. The cost of the E-Bus and diode and switch and relay are relatively inexpensive and weigh less than a second contactor and associated heavy wire. When I am faced with a decision, I ask myself, "What is best in the long run?" Your proposal is feasible for a backup in case of contactor failure in Z-12 (two alternators). I do not see any safety issues. You have double the chance of leaving the master switch on. :-) Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=288501#288501


    Message 2


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    Time: 12:46:07 PM PST US
    From: "Carlos Trigo" <trigo@mail.telepac.pt>
    Subject: Circuit protection - Amps
    Thanks Ralph I did the same as you and kept the old units (which I'll probably have to toss when my bird will hit the weighing scales ... :-(), so I am maintaining the same protection. Carlos > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list- > server@matronics.com] On Behalf Of Ralph E. Capen > Sent: sexta-feira, 26 de Fevereiro de 2010 15:58 > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Circuit protection - Amps > > <recapen@earthlink.net> > > The fuse is supposed to protect the wire. Shouldn't be an issue. You can > downsize the fuse based on expected draw and any unexpected draw will pop the > fuse. > > I had similar Whelens which I replaced with LED units...kept the same fuse as I am > carrying one of the old units (with both lenses) as a backup in case of hangar rash > at a destination....I can easily swap out to my backup and the wiring is already set- > up. > > > My .02 > > Ralph > > > -----Original Message----- > >From: Carlos Trigo <trigo@mail.telepac.pt> > >Sent: Feb 26, 2010 10:01 AM > >To: aeroelectric-list@matronics.com > >Subject: AeroElectric-List: Circuit protection - Amps > > > >I had Whelen Nav lights in my RV-9A, in a circuit protected by a 7Amp PTC. > > > >I replaced those by new LED nav lights, which draw about 0.5A, and should > >need a protection device not bigger than 1A. > > > > > >If I leave the circuit with the same 7A protection, what are the > >implications? > > > > > >Carlos >


    Message 3


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    Time: 04:14:39 PM PST US
    From: "Tom Barter" <kesleyelectric@iowatelecom.net>
    Subject: SD-8 self excite capacitor
    Bob, The SD-8 that I recently purchased was supplied with a 10K mfd capacitor. The self excite mod in the 'Connection calls for a 20-50K mfd. I seem to remember reading that the capacitor rating was not that critical. With the addition of the resistors and bridge rectifier, will the supplied capacitor be satisfactory for the SD-8 to self excite? Tom Barter Kesley, IA Avid Magnum


    Message 4


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    Time: 09:16:05 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: SD-8 self excite capacitor
    At 06:09 PM 2/27/2010, you wrote: >Bob, > >The SD-8 that I recently purchased was supplied with a 10K mfd >capacitor. The self excite mod in the 'Connection calls for a >20-50K mfd. I seem to remember reading that the capacitor rating >was not that critical. With the addition of the resistors and >bridge rectifier, will the supplied capacitor be satisfactory for >the SD-8 to self excite? Yes. Bob . . .


    Message 5


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    Time: 09:16:06 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Clearing some away some fog and fuzzy logic
    . . . At 10:43 AM 2/26/2010, you wrote: > >The main issue in this debate seems to be whether to use fuses or >circuit breakers. Like many decisions in life, there is more than >one way to accomplish a goal. One way may have certain advantages >over the other way, and visa-versa. Many times the decision boils >down to a matter of personal preference; and I believe that is the case here. It's always a personal preference but it's not always a matter of 'let's take out a 5A breaker and put in a 5A fuse'. There are even instances where two 5A breakers can exhibit SIGNIFICANT differences. It's not even a debate about which is better or preferred but a reminder that what ever device is being considered, confident compliance with design goals may goe far beyond current ratings. Some people might argue that fuses will blow quicker than circuit breakers will trip, thus offering better protection. Although technically true, I do not think the time difference is significant. It's not necessarily better but it IS different. The time-to-trip dynamics for the full gamut of protective devices is huge . . . if you're just protecting the wire to gear down indicator LEDS, the differences may not be significant. But as soon as the load offers high inrush or transient characteristics like incandescent landing lights, pump motors, pitot heaters, confident application of the chosen device demands understanding. One way to avoid nuisance blowing of fuses is to use a larger size. For instance, an avionics manufacturer might recommend using a 1 amp fuse. If you use a 3 amp fuse instead, there will be a lot less chance of it blowing. I counsel rejection of the off-hand up-sizing just to hedge one's bets. The prudent designer doesn't wager, he strives for the sure thing. >Quote from Bob, > > "discussed, researched, and demonstrated not to be true." > End Quote >I am taking Bob's side here. The technician is basing his statement >on rumors. Bob has done experiments with expensive lab >equipment. I trust his work. Even if the technician is correct >(which I doubt), I would rather ruin an alternator than have an >over-voltage condition ruin thousands of dollars worth of avionics. It's not about gathering followers into the camp of any particular individual. We're not running for office. It's about the physics of simple-ideas, about lessons-learned, about failure-tolerant design based on logic. > Although the technician is highly critical of Bob's > recommendations, I do not take his statements as being a personal attack. I guess you've not been hanging around this List very long my friend. The "technician" in another life claims much in the way of qualifications for his opinion . . . including engineering degrees. He was asked to leave the List some years back simply because he proved incapable or unwilling to comport with list decorum. See: http://www.aeroelectric.com/articles/gmcjetpilot.html But since ALL our writings have been archived for the future, I continue to be asked about certain of his assertions years later. What was that we read about 'sins of the fathers'? > Still, he was expressing his opinions as fact and pooh-poohing > Bob's, which is not a nice thing to do. If I say something that > others disagree with, it is OK to tell me, as long as it is done > diplomatically. LOL I quite agree as do the vast majority of the List members. This particular circumstance may well bubble up to the surface for years to come . . . Bob . . .


    Message 6


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    Time: 09:38:33 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Z13/20
    >I don't have much experience analyzing schematics but when I look at >Z-13/20, I guess I just don't see what the issue is. Can someone >please educate me? It's clumsy . . . my associates would call it a kluge. Z-12 shows a well considered integration of the SD20 into a legacy system with an e-bus added. I'm working on a drawing that explores another approach to tying the SD-20 and a main alternator onto two batteries. Build a 13/20 if you wish. It will function as advertised. I pulled the drawing because I'm not proud of it and I'd prefer not to be associated with the system when and if it is used. Bob . . .




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