---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 07/07/08: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:38 AM - Fuse Sizing (Jeff Page) 2. 07:22 AM - Re: Nippondenso alternator question (Paul) 3. 08:11 AM - Flight Test Architecture (lee.logan@gulfstream.com) 4. 10:46 AM - Re: power to handheld gps. (Larry L. Tompkins, P.E.) 5. 01:11 PM - power to handheld gps (bob noffs) 6. 07:15 PM - Re: power to handheld gps. (Joe) ________________________________ Message 1 _____________________________________ Time: 06:38:18 AM PST US From: Jeff Page Subject: AeroElectric-List: Fuse Sizing I just looked through Chapter 10 and didn't find any guidance on selecting the size of a fuse. I am quite sure that a 10A fuse is designed to blow at, or barely above, 10A and thus would be unsuitable for protecting a circuit with an actual current flow of 10A. In my case, I have a landing light circuit totalling 9.2A. Mostly it is 4.6A to each bulb, but there are some common wires at the switch that carry both loads. Looking at Bob's Wire Size Selection chart with 10C Rise (which makes wire selection incredibly easy, compared to the graphs in 43-13-1B), I could use 18 gauge wire in the wings and 14 gauge wire where both currents are common. I can't use a double pole switch to wire each light independently with separate fuses, because I am already using a double pole switch to give me off, on or wig wag. So I need a single circuit with a single fuse. The fuse needs to be sufficient for the total current. This also means upgrading the 18 gauge wire in the wings to 14 gauge, to avoid having a fuse too big for the wire. So my gut feel is to use the 35C Rise part of the table to pick a current rating for the fuse, which would give me 15A fuse for 14 gauge wire. Correct ? Also, the calculations quite clearly include the return to ground part of the current when calculating wire losses due to resistance. What equivalent resistance value would be typical of the frame of aluminum aircraft when used for the ground return ? Thanks for your advice, Jeff Page Dream Aircraft Tundra #10 ________________________________ Message 2 _____________________________________ Time: 07:22:27 AM PST US From: "Paul" Subject: Re: AeroElectric-List: Nippondenso alternator question Depends on the specific ND alternator. The ones I have experience with have a switch (internal to the regulator) that provides a ground at the "L" terminal where (in automobiles) an "Idiot Light" is connected across the "L" to the"IG" and indicates the alternator is getting power to the "IG terminal but the Alternator's "B" lead Voltage is not high enough to charge the battery. The ground is removed (and the light goes out) when the alternator starts supplying power. There are apparently some ND alternators that use the "L" terminal to power the internal regulator and in that case the "L" must have a specific light connected to provide starting voltage. In that case the light is powered by the regulator current before the power from the "B" lead takes over and the light goes out indicating the alternator is working properly. I have never seen that type of ND alternator but there are a few people on other groups who state the Light is required or the alternator will not provide power. If your alternator requires a light it should be the light specified in the original application. This provides the proper current to the regulator. The only ND alternators I have data for shows the "L" terminal as a simple switch to ground and personal testing shows the alternator can be turned on and off while running with no connection to the "L" lead (simply switching power to the "IG" connection. Turning the alternator off under power is not recommended as that causes an alternator "load dump" which may damage the alternator if its disconnected under higher amp charging current. Hasent happened to me up to a tested 40 amp load dump but still to be avoided except when the alternator regulator fails high "B" terminal voltage. The addition of a transorb of sufficient power will shunt the load dump and protect the alternator but that is a different topic. ND alternators come in many versions of internal regulators, some sense the charging voltage thru the IG terminal to accurately charge the battery based on the battery terminal voltage not the "B: lead voltage. Thus as originally designed for auto use, the "B" lead is hard wired directly to the battery. The IGN switch is turned on before starting and the "idiot light" is powered by the "IG" power input and the regulator internal ground. There is no requirement for the "L" terminal to be connected to anything (at least with the ND alternators I have evaluated). If there is a connection it must limit the current as the internal ground switch may require external current limiting. In an aircraft application generally there is no need for any connection to the "L" terminal as the alternator wiring and its current generation is monitored in a different method. Be sure your design provides a connection to the battery before starting the engine. Sorry but perhaps the supplier of the alternator can tell you. If you purchased the add on alternator as a specific Kit for your engine. In any event If the light is required you must install the proper one. Do not connect the "L" terminal to any thing else other than the proper bulb. Not an LED as if a light is required the LED with limiting resistor will not pass enough current and clearly nothing else. If the light is not required (my personal experience its not) then there is no need if you have other ways to tell if the alternator is functioning properly like current monitor or bus voltage. The ND alternator generally requires approx 1500 alternator RPM to start generation. In an automobile this is generally around the just above idle rpm of the engine and again in an auto the idiot light can turn on at slow idle and go out just above that rpm. Paul ----- Original Message ----- From: "darinh" Sent: Sunday, July 06, 2008 10:35 PM Subject: AeroElectric-List: Nippondenso alternator question > > This is my last question...at least for tonight. I have a Rotax 914 and > the onboard generator is not enough so I added a optional 40 amp > nippondenso alternator. It has the alt. output and a plug labeled "L" and > "IG". I assume the "IG" is the field circuit and the "L" is obviously the > lamp circuit. > > The question is this: I have been told that the alt. must have the > indicator lamp installed for it to charge the battery. I don't really > want to add another "idiot" light to my panel as I already had two for the > turbo control unit and one for my GRT EIS. Can I run it through the EIS > light or will this screw it up? If I have to have a light, I may just > mount it behind the panel. Lastly, I was told this light cannot be an > LED...is this also correct? > > -------- > Darin Hawkes > Series 7 (Final Assembly) > 914 Turbo > Kaysville, Utah > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=191541#191541 > > ________________________________ Message 3 _____________________________________ Time: 08:11:06 AM PST US Subject: AeroElectric-List: Flight Test Architecture From: lee.logan@gulfstream.com Good information, Bob, thanks for taking the time to answer my questions about electrical system performance. Good point too, that Z-13/8 with a big battery back-up is really designed to get you to destination, not just back on the ground safely. As I said, "...I would already be headed for good weather/divert/home base/whatever if the SD-8 let go" too, but that is clearly situationally dependant (the "whatever" clause). You also said you think a voltmeter indicating SD-8 performance would be useful. Are there any schematics/parts recommendations available for that? I'd prefer to have the voltmeter on my EDM-900C do double duty depending upon which alternator were supplying power to the system, but don't know if that is possible or not. Thanks again for the recommendations. Lee... ________________________________ Message 4 _____________________________________ Time: 10:46:24 AM PST US From: "Larry L. Tompkins, P.E." Subject: Re: AeroElectric-List: power to handheld gps. Bob: My experience is the smallest connectors are ones used in RC aircraft and car models. They are sort of a mini Molex connector. I was able to obtain then at a local hobby shop. Hope this helps. Larry Tompkins ________________________________ Message 5 _____________________________________ Time: 01:11:44 PM PST US From: "bob noffs" Subject: AeroElectric-List: power to handheld gps thanks to all who offered good solutions to my power outlet question. i finally settled on a power jack assembly similar to what you find on the business end of a 12 volt transformer used to power just about you name it! my new dilemma is now the gps. the large screen on the airmap 2000 which is great for viewing also makes the unit about the size of a 2 car garage. i now am having second thoughts about where to mount it! but when i decide , i know how to get power to it! bob noffs ________________________________ Message 6 _____________________________________ Time: 07:15:17 PM PST US From: "Joe" Subject: Re: AeroElectric-List: power to handheld gps. Bob Noffs, Here are some Radio Shack parts that might work for you: Size N Coaxial DC Power Plug (2-Pack) $2.99 Model: 274-1573 Catalog #: 274-1573 http://www.radioshack.com/product/index.jsp?productId=2102488&cp=&sr= 1&origkw=dc+plug&kw=dc+plug&parentPage=search Size N Panel-Mount Coaxial DC Power Jack $2.99 Model: 274-1576 Catalog #: 274-1576 http://www.radioshack.com/product/index.jsp?productId=2102489&cp=&sr= 1&origkw=dc+jack&kw=dc+jack&parentPage=search Joe ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.