---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 11/12/04: 18 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:21 AM - RV 8 roll Trio roll servo install (luckymacy@comcast.net (lucky)) 2. 06:45 AM - Re: Grounding (William Yamokoski) 3. 07:15 AM - Re: Grounding (Robert L. Nuckolls, III) 4. 07:20 AM - Re: Strobe Ground Circuit Question (Robert L. Nuckolls, III) 5. 07:55 AM - Re: 406 Mhz GPS ELT (Eric M. Jones) 6. 08:05 AM - ELT Access () 7. 08:12 AM - Re: Grounding (William Yamokoski) 8. 09:18 AM - Re: Re: 406 Mhz GPS ELT (SportAV8R@aol.com) 9. 09:33 AM - Re: Re: 406 Mhz GPS ELT (Brian Lloyd) 10. 09:58 AM - Re: Re: 406 Mhz GPS ELT (Richard Riley) 11. 10:44 AM - Re: Re: 406 Mhz GPS ELT (Brian Lloyd) 12. 01:46 PM - Re: Strobe power supply grounding (Mickey Coggins) 13. 06:00 PM - Re: Keep warm circuit for Landing/Taxi lights (D Fritz) 14. 07:09 PM - Re: Keep warm circuit for Landing/Taxi lights (glaesers) 15. 07:29 PM - Re: Re: 406 Mhz GPS ELT (Gregory Young) 16. 07:55 PM - 406 Mhz GPS ELT cost issues (Jim Stone) 17. 08:23 PM - Re: Re: Keep warm circuit for Landing/Taxi lights (Richard E. Tasker) 18. 11:04 PM - 914 second alternator? (Ronald J. Parigoris) ________________________________ Message 1 _____________________________________ Time: 03:21:43 AM PST US From: luckymacy@comcast.net (lucky) Subject: AeroElectric-List: RV 8 roll Trio roll servo install 0.01 RCVD_DOUBLE_IP_LOOSE Received: by and from look like IP addresses --> AeroElectric-List message posted by: luckymacy@comcast.net (lucky) you guys with the tru track servos have it made. Seems the Trio/Air Nav roll servo's possible arm orientations and sheer overall size won't allow for installation in there. The only place I see it will fit without modifying the floor panels is up front of the spar on the right side. Anyone else able to fit the Trio servo where Larry but his Try Track servo? > --> AeroElectric-List message posted by: "Larry Bowen" > > Mickey, > > Here is a pic of the strobe power pak. > > http://bowenaero.com/mt3/archives/2003/01/ap_servo_strobe.html > > - > Larry Bowen > Larry@BowenAero.com > http://BowenAero.com > > > > -----Original Message----- > > From: Mickey Coggins [mailto:mick-matronics@rv8.ch] > > Sent: Thursday, November 11, 2004 2:22 PM > > To: aeroelectric-list@matronics.com > > Subject: RE: AeroElectric-List: Strobe power supply grounding > > > > --> AeroElectric-List message posted by: Mickey Coggins > > --> > > > > Hi Larry, > > > > That's good info. I searched for 'strobe' on your site but > > didn't find anything. Can you tell me where you mounted your > > strobe power supply, and where you put your "central" ground? > > > > Best regards, > > Mickey > > > > At 20:02 11-11-04, Larry Bowen wrote: > > -----Start of Original Message----- > > >--> AeroElectric-List message posted by: "Larry Bowen" > > >--> > > > > > >I have the same power supply. I followed the directions and > > have no noise. > > >That's all I can offer. > > > > > >- > > >Larry Bowen, RV-8 23.5 hrs. > > >Larry@BowenAero.com > > >http://BowenAero.com > > > > > > > > >> -----Original Message----- > > >> From: Mickey Coggins [mailto:mick-matronics@rv8.ch] > > >> Sent: Thursday, November 11, 2004 9:31 AM > > >> To: aeroelectric-list@matronics.com > > >> Subject: AeroElectric-List: Strobe power supply grounding > > >> > > >> --> AeroElectric-List message posted by: Mickey Coggins > > >> --> > > >> > > >> I'm installing a Nova Electronics Superpak 906 strobe > > power supply in > > >> my RV, and the installation instructions say, with emphasis: > > >> > > >> Note: The power supply baseplate must be connected to > > chassis ground > > >> (GND) to reduce radio interference. > > >> > > >> Since there is also a ground wire with the power wire, wouldn't it > > >> actually cause *more* noise to do this, since the device would be > > >> grounded in two different places? > > >> > > >> Seems to me like it would it be better to electrically isolate the > > >> baseplate, and run a ground wire from it back to the > > airplane common > > >> ground. Am I missing something here? > > >> > > >> Thanks for your advice. > > >> > > -----End of Original Message----- > > > > -- > > Mickey Coggins > > http://www.rv8.ch/ > > #82007 QB Wings/Fuselage > > > > > > ========= > > ========= > > Matronics Forums. > > ========= > > http://www.matronics.com/FAQ/AeroElectric-List.htm > > ========= > > > > > > > > > > > > > > > > > > ________________________________ Message 2 _____________________________________ Time: 06:45:03 AM PST US From: "William Yamokoski" Subject: Re: AeroElectric-List: Grounding --> AeroElectric-List message posted by: "William Yamokoski" Hi Folks, In my Glastar, I have two batteries about 10' aft of the firewall. I have each separately connected to the firewall ground stud, the other side of which connects to the engine via a grounding strap. Other than weight reduction, is there any advantage to moving those battery (-) fat wire ground points off the common ground stud and further aft, to the cage itself. I can't think of any electrical advantage, but that's why I ask the experts. Thanks for any input. Bill Yamokoski, N4970Y 415 hrs on the EggenSoob still getting intermittent reports that my radio is unreadable, still wondering why ________________________________ Message 3 _____________________________________ Time: 07:15:09 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Grounding --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:44 AM 11/12/2004 -0500, you wrote: >--> AeroElectric-List message posted by: "William Yamokoski" > > >Hi Folks, > In my Glastar, I have two batteries about 10' aft of the firewall. I > have each separately connected to the firewall ground stud, the other > side of which connects to the engine via a grounding strap. Other than > weight reduction, is there any advantage to moving those battery (-) fat > wire ground points off the common ground stud and further aft, to the > cage itself. I can't think of any electrical advantage, but that's why > I ask the experts. No, what you have is the best from an electrical perspective. > Thanks for any input. >Bill Yamokoski, N4970Y >415 hrs on the EggenSoob >still getting intermittent reports that my radio is unreadable, still >wondering why I'm assuming you've checked antenna SWR. What kind of antenna and were installed. Intermittent complaints can be associated with "holes" in radiation pattern for the antenna. See: http://www.aeroelectric.com/Pictures/Antenna_Pattern.gif A pilot trying to talk on this antenna might get a lot of otherwise unexplainable complaints. Does your radio have a "sidetone" . . . can you hear yourself and do you always hear yourself well in the headsets? Next time ask about "unreadable" Do they mean strong signal but distorted audio or weak signal -AND- audio? Bob . . . ________________________________ Message 4 _____________________________________ Time: 07:20:47 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Strobe Ground Circuit Question --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 09:21 AM 11/12/2004 +1000, you wrote: >--> AeroElectric-List message posted by: "Kingsley Hurst" > > >Bob et al > >I have a Kuntzleman Strobe and in reading the 'Noise Trouble Shooting >Guide' supplied with the kit, it says QUOTE "The ground path is very, >very important. The strobe circuit draws high current through the >ground circuit." END QUOTE > >Since I have always understood the current is the same in both the feed >and ground circuits, could someone please enlighten me as to what is >meant by the 'high current through the ground circuit'. I don't have >the unit completely installed yet so don't have any noise problems, just >trying to understand ! They're simply quoting Kirchoff's law that says for every electron going into the system, there'a a companion electron exiting the system . . . I.e. same current in both supply and ground return lines. What you quoted from the instruction manual is a lousy attempt to explain something . . . I wonder if the writer really understands what he's trying to write about. For the composite airplane, you'll need both power and ground return lines to the strobe. Take your (-) power lead from strobe to on of the mounting bolts for the case then come off that same bolt with the ground lead to your single point ground. Run ground and plus leads together for as far as practical before they separate to route to switch and ground stud. If you have a noise problem after doing this, then a filter AT the STROBE supply is called for . . . let's cross that bridge as we come to it. Bob . . . ________________________________ Message 5 _____________________________________ Time: 07:55:34 AM PST US From: "Eric M. Jones" Subject: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: "Eric M. Jones" The reality of the 121.5/243 ELT system is that they will begin to degrade in 2006 (the Russians aren't launching anymore of these satellites). The old system is OFFLINE Feb 2009. Does anyone have a clear description of what is required in OBAM aircraft as far as 406 MHz Emergency Locator Thingies (or whatever)? My guess is not much. There are many more nautical 406 MHz locators. The ACR GlobalFix 406 EPIRB http://store.yahoo.com/landfallnav/globalfix.html can be bought for under $850 in quantity of one. It is possibly to internet together a Buyer's Club to purchase a pallet of these if they are suitable for OBAM aircraft use. Let's see what the price might be and any technical issues before proceeding. Regards, Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge MA 01550-2705 Phone (508) 764-2072 Email: emjones@charter.net ________________________________ Message 6 _____________________________________ Time: 08:05:24 AM PST US From: Subject: AeroElectric-List: ELT Access --> AeroElectric-List message posted by: AeroElectric-List message previously posted by: GMC <> 11/12/2004 Hello George, Thanks for your question. Now for a round about answer. I have a very low regard for the investment to return benefit ratio of our presently required ELT's. I felt that they were unwisely forced upon us by the US Congress in a knee jerk reaction to the loss of one of their members in a plane crash in Alaska. So as I was building my airplane I wanted minimal ELT impact. I had my professionally built instrument panel built with no remote ELT control panel. After I purchased my ELT, which included a remote control panel, and got ready to install the ELT without the control panel, I decided to find out if this would be acceptable to the FAA. My research generated a whole bunch of hearsay, gossip, rumor, speculation, opinions, beliefs, etc. indicating that the remote control panel was required, but I could not nail down the specifics of that requirement. So I made a last minute install of the control panel in a manner that was acceptable to me, but I wasn't entirely happy because the remote panel installation was not part of my overall design concept. Came the time of my very first test flight and I could not fly because every time I keyed my number one VHF communication radio the ELT was activated. I was able to shut down the ELT with the remote panel switch and taxi back to my hangar. I disconnected the ELT and flew without it (this is legal) for that flight. Before my second flight I moved the ELT antenna a bit further away from the number one VHF communication antenna and rotated the ELT antenna ninety degrees. This solved that inadvertant ELT activation problem. Several weeks later I was returning to the airport and using my number two VHF communication radio for the very first time (it had been off to Garmin for repair). My ELT was activated when I made my very first transmission on tower frequency. This was very disruptive, but I was able to shut my ELT down very quickly with the remote panel switch. This particular activation scenario has never happened again. When I performed my first annual inspection of the ELT (required by FAR Sec 91.207 (d)) I found the remote switch to be pretty useful. One of our local Lancair 360 builders had inadvertant ELT activiation that he attributed to VHF communication wiring being in proximity to some ELT wiring. His remote ELT control switch was useful in shutting down his ELT. So I am a convert -- if one must have an ELT then the current regulatory requirement (I believe that requirement exists even though I have not yet seen it with my own eyes) for pilot access and control from the cockpit is a good thing. I hope this answers your question. OC PS: I am not philosophically opposed to an ELT that would justify the return on the investment. I think that a compatible (with our 12 volt airplanes), practical, affordable, 406 Mhz ELT, preferably with GPS location capability, would be a great thing. If it exists, I can't find it. PPS: In anticipation of a forced landing (crash) and survival situation (been there, done that) one should always have with them a portable handheld VHF radio with fresh / unused batteries (don't depend upon old rechargeable batteries). Some may find great comfort in also carrying a 406 Mhz EPIRB. See <> ________________________________ Message 7 _____________________________________ Time: 08:12:14 AM PST US From: "William Yamokoski" Subject: Re: AeroElectric-List: Grounding --> AeroElectric-List message posted by: "William Yamokoski" > >Hi Folks, > I can't think of any electrical advantage, but that's why > I ask the experts. No, what you have is the best from an electrical perspective. Thanks very much. I'm assuming you've checked antenna SWR. That was one of the first things checked a couple of years ago What kind of antenna and were installed. Intermittent complaints can be associated with "holes" in radiation pattern for the antenna. See: http://www.aeroelectric.com/Pictures/Antenna_Pattern.gif A pilot trying to talk on this antenna might get a lot of otherwise unexplainable complaints. I have a copper strip dipole mounted in the vertical stabilizer. The strip is not exactly vertical....it pretty much parallels the slope of the leading edge of the vertical stabilizer Does your radio have a "sidetone" . . . can you hear yourself and do you always hear yourself well in the headsets? MicroAir 760. It does have a sidetone, which I have turned down to the point where I can hear myself consistently and well in the headsets. At the factory setting there was a strong "echo" effect in the headsets. This went away when I turned the sidetone down a bit. Next time ask about "unreadable" Do they mean strong signal but distorted audio or weak signal -AND- audio? The signal is strong but distorted Would there be much point in trying a different antenna? Thanks for all the help Bill Yamokoski ________________________________ Message 8 _____________________________________ Time: 09:18:32 AM PST US From: SportAV8R@aol.com Subject: Re: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: SportAV8R@aol.com Eric_ we'd probably want to work out an impact-activation feature for the ELT (rather than water immersion or manual "on" only, right? -Bill B ________________________________ Message 9 _____________________________________ Time: 09:33:14 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: Brian Lloyd On Nov 12, 2004, at 11:57 AM, Eric M. Jones wrote: > --> AeroElectric-List message posted by: "Eric M. Jones" > > > The reality of the 121.5/243 ELT system is that they will begin to > degrade > in 2006 (the Russians aren't launching anymore of these satellites). > The old > system is OFFLINE Feb 2009. > > Does anyone have a clear description of what is required in OBAM > aircraft as > far as 406 MHz Emergency Locator Thingies (or whatever)? The real problem is not whether a 406MHz EPIRB would be suitable and would help people to find you should you go down. That they do very well and certainly meet the spirit of the law. The problem is whether or not they meet the letter of the law which, as we know, has nothing to do with actually getting the job done. The 121.5MHz/243MHz ELT which does such a poor job of helping people find you meets the letter of the law and makes FAA types happy whether or not it actually performs the desired function. I don't know whether any of the very fine and inexpensive 406MHz EPIRBs available from various sources for somewhat reasonable prices also would. Guessing from experience with the FAA I would have to guess that they do not since they cost way too little to have the FAA certification surcharge built into their price. So, if it doesn't cost wildly too much, it probably does not have FAA approval. And, yes, I am jaded. Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________ Message 10 ____________________________________ Time: 09:58:46 AM PST US From: Richard Riley Subject: Re: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: Richard Riley At 09:32 AM 11/12/04, you wrote: >The 121.5MHz/243MHz ELT which does such a poor job of helping people >find you meets the letter of the law and makes FAA types happy whether >or not it actually performs the desired function. I don't know whether >any of the very fine and inexpensive 406MHz EPIRBs available from >various sources for somewhat reasonable prices also would. Guessing >from experience with the FAA I would have to guess that they do not >since they cost way too little to have the FAA certification surcharge >built into their price. So, you buy an inexpensive 406 MHz EPIRB with built in GPS, and two cheap 121.5 ELT's off EBAY. Put new batteries in on of the ELT and mount it in the airplane. Salvage the impact switch from the second, hack it into the manual "on" switch of the EPIRB. Tuck it in a box that just happens to be the right size to hold it. ________________________________ Message 11 ____________________________________ Time: 10:44:07 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: Brian Lloyd On Nov 12, 2004, at 1:57 PM, Richard Riley wrote: > --> AeroElectric-List message posted by: Richard Riley > > > At 09:32 AM 11/12/04, you wrote: >> The 121.5MHz/243MHz ELT which does such a poor job of helping people >> find you meets the letter of the law and makes FAA types happy whether >> or not it actually performs the desired function. I don't know >> whether >> any of the very fine and inexpensive 406MHz EPIRBs available from >> various sources for somewhat reasonable prices also would. Guessing >> from experience with the FAA I would have to guess that they do not >> since they cost way too little to have the FAA certification surcharge >> built into their price. > > So, you buy an inexpensive 406 MHz EPIRB with built in GPS, and two > cheap > 121.5 ELT's off EBAY. > > Put new batteries in on of the ELT and mount it in the airplane. > Salvage > the impact switch from the second, hack it into the manual "on" switch > of > the EPIRB. Tuck it in a box that just happens to be the right size > to > hold it. That seems like quite a sensible approach! OTOH, I would tend to want to disable the "operational" ELT to keep it from generating false alerts. The remote control switch on the panel that has positions "off/arm/on" might prove to be useful for that purpose. Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 There is a time to laud one's country and a time to protest. A good citizen is prepared to do either as the need arises. ________________________________ Message 12 ____________________________________ Time: 01:46:58 PM PST US From: Mickey Coggins Subject: Re: AeroElectric-List: Strobe power supply grounding --> AeroElectric-List message posted by: Mickey Coggins Thanks a lot for the clarification. I'm just starting my wiring, and it is coming along well, mainly thanks to all I've learned from your book and the list. I'm really enjoying it. Best regards, Mickey -- Mickey Coggins http://www.rv8.ch/ #82007 QB Wings/Fuselage ________________________________ Message 13 ____________________________________ Time: 06:00:48 PM PST US DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; b=YyVgDmZaNVrvg7P+8Pp4siUvND57e4ryYX3qO6RN37/8v1Wk7b0IKw9eHjzGr2qny2XuLdILrm/boVJWQuEZiYWhLgYRRRCWmmJDPjHAV2Oq5+FqhMxH6EDQQvxQiRmjH5o4ao7mNLmXDfcH0eKz86ZWiRotADQnNNN9FyCuj5s= ; From: D Fritz Subject: Re: AeroElectric-List: Keep warm circuit for Landing/Taxi lights --> AeroElectric-List message posted by: D Fritz Quick question about Halogens: How well do they survive in a wig-wag setup? is the constant on and off a problem for these bulbs? On a related note, has anyone looked at using clear UltraBrite LEDs as recognition lights? Do these do well with a wig-wag setup? This site is marketing a "taxi" light combined with a strobe that may prove interesting in recognition: https://ssl.perfora.net/gs-air.com/sess/utn;jsessionid=1541956839198eb/shopdata/index.shopscript Dan Fritz --------------------------------- ________________________________ Message 14 ____________________________________ Time: 07:09:36 PM PST US From: "glaesers" Subject: AeroElectric-List: Re: Keep warm circuit for Landing/Taxi lights clamav-milter version 0.80j on pop-7.dnv.wideopenwest.com --> AeroElectric-List message posted by: "glaesers" What the heck, lets get a bit technical (I'm an Aero Engr - so you may have to take it slow ;-) You seem to have selected thermistors rated for about twice the amperage for the light. Based on that, for a 75W bulb I'd use the KC022L. Now since it won't be operating at I-max, the resistance won't be the min value (.02 ohms). So for argument's sake, lets use .03 ohms. That means a voltage drop of .39 (I used 13V for all calculations). 3% doesn't seem so bad. Regarding the inrush current - As the thermistor rated current goes up the initial resistance goes down (some dumb law of physics no doubt). The KC022L's resistance (0.7 ohms) is less than half the bulb's (about 2 ohms). So the bigger the bulb the higher the initial current. How much initial resistance is enough? I guess anything is better than nothing. I'm thinking that limiting the inrush current is as much about being kind to the whole electrical system as it is about bulb life - am I out in left field on that? Anyway, they're cheap enough to try. It's wierd to think of something getting hot and going down in resistance - kind of like nichrome wire in an inverse universe! Thanks for your help, Dennis ------------------------ There are particulars like how much you want to limit the current and how much reduction in current you can accept (there will be some). If you don't want to get too technical: For a 35W lamp--use Digikey KC004L, for a 50W use a KC003L. Remember that these get hot and are supposed to get hot. Don't try to cool them off!--in fact they should be protected from cooling. Regards, Eric M. Jones www.PerihelionDesign.com --------------------------- ________________________________ Message 15 ____________________________________ Time: 07:29:49 PM PST US From: "Gregory Young" Subject: RE: AeroElectric-List: RE: 406 Mhz GPS ELT --> AeroElectric-List message posted by: "Gregory Young" Seems like it would make sense to certify an impact sensor that could activate the locator of your choice. Then the low volume switch would be the only piece subject to aviation prices and the locator could take advantage of the economies of scale and technical improvements that non-aviation markets enjoy. But no, that would never work. Never mind... Greg > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On > Behalf Of SportAV8R@aol.com > Sent: Friday, November 12, 2004 11:18 AM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: RE: 406 Mhz GPS ELT > > --> AeroElectric-List message posted by: SportAV8R@aol.com > > Eric_ we'd probably want to work out an impact-activation > feature for the ELT (rather than water immersion or manual > "on" only, right? > > -Bill B ________________________________ Message 16 ____________________________________ Time: 07:55:40 PM PST US From: "Jim Stone" Subject: AeroElectric-List: 406 Mhz GPS ELT cost issues --> AeroElectric-List message posted by: "Jim Stone" As both a pilot and boater in Florida, I suggest that anyone interested in acquiring a 406 MHz ELT or EPIRB pay special attention to the cost of replacing the battery. I have carried a Litton Marine 406 MHz portable EPIRB for the last 8 years, and had the "joy" of getting a replacement battery. At $600 installed, it was a shock even to my certified airplane parts budget. The new ones will obviously be less expensive, but my queries to vendors a Oshkosh and boat shows indicated most dealers haven't the foggiest what the battery replacement procedure or cost will be. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Bruce Gray Subject: RE: AeroElectric-List: 406 Mhz GPS ELT --> AeroElectric-List message posted by: "Bruce Gray" --> Try http://www.artex.net/3_freq_beacons.html, bring your wallet. Bruce www.glasair.org -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of bakerocb@cox.net Subject: AeroElectric-List: 406 Mhz GPS ELT --> AeroElectric-List message posted by: AeroElectric-List message previously posted by: Mickey Coggins < ... For my money, if I wanted an ELT that REALLY > works, I'd go for the GPS aided location option as well. > This ELT broadcasts your exact location which has a lot better > resolution than satellite based locator system.>> 11/1/2004 Hello Mickey, I don't think that a practical, affordable, GPS reporting, TSO-C126 approved, 406 Mhz ELT compatible with a 12 volt airplane exists. I'd love to be proved wrong. Let us know what you find. You can start your search here <> and move on to the various manufacturers listed. Be very precise / meticulous in your search -- you are entering a swamp with many diverting alligators. Realize that you are looking for an ELT, not just a beacon. OC ________________________________ Message 17 ____________________________________ Time: 08:23:22 PM PST US From: "Richard E. Tasker" Subject: Re: AeroElectric-List: Re: Keep warm circuit for Landing/Taxi lights --> AeroElectric-List message posted by: "Richard E. Tasker" Actually, if you look at the specific data sheet for these parts: Using 75W @ 13V gives us 5.77A - which is close enough to 50% of the 12A rating. Looking at the data sheet, one finds that the resistance at this current is 0.06 ohms which gives us a voltage drop of 0.35 V. So, your 3% calculation is not far off - although I have no idea what you did to get your numbers. Remember, E=I*R, I=E/R, R=E/I :-) . Actually, based on the vendors data sheet, I would probably choose the next lower size that is rated for 8A max. Using this one, the starting resistance is 1.3 ohms vs 0.7 ohms for the 12A device. The resistance at the operating current is essentially the same so the voltage drop would be the same. As far as your further comments about the 0.7 ohms adding to the bulb's resistance, you are correct that it adds, but your value for the bulb's resistance at start is way off. Your estimate of two ohms is basically correct when the bulb is operating (R=13V/5.77A=2.25ohms). However, before the bulb warms up, its resistance is less than 0.5 ohm (probably much less but I do not have a milliohmeter to measure it accurately). That means that you are reducing the inrush current by a factor of (0.7 + 0.5) /0.5 or almost 2.5 times - probably more if we knew the actual start resistance. So we are limiting the inrush current to approximately: I = 13V / 1.2 ohms = 10.8A Much better than: I = 13V / 0.5 ohms = 26A! Or, if you use the next lower rated limiter you can limit the current to: I = 13V / (1.3 + 0.7) ohms = 6.5A Not much more than the steady state current of 5.77A. The reason for using current limiters is, as you suggested, as much to be gentle on your electrical system (not to good to use a 15A switch to turn on a bulb with a 26A surge, but fine for a 10.8A surge) as to increase the life of your bulb by limiting the shock of turning it on. Dick Tasker glaesers wrote: >--> AeroElectric-List message posted by: "glaesers" > >What the heck, lets get a bit technical (I'm an Aero Engr - so you may have >to take it slow ;-) > >You seem to have selected thermistors rated for about twice the amperage for >the light. >Based on that, for a 75W bulb I'd use the KC022L. Now since it won't be >operating at I-max, the resistance won't be the min value (.02 ohms). So >for argument's sake, lets use .03 ohms. That means a voltage drop of .39 (I >used 13V for all calculations). 3% doesn't seem so bad. > >Regarding the inrush current - As the thermistor rated current goes up the >initial resistance goes down (some dumb law of physics no doubt). The >KC022L's resistance (0.7 ohms) is less than half the bulb's (about 2 ohms). >So the bigger the bulb the higher the initial current. How much initial >resistance is enough? I guess anything is better than nothing. > >I'm thinking that limiting the inrush current is as much about being kind to >the whole electrical system as it is about bulb life - am I out in left >field on that? Anyway, they're cheap enough to try. > >It's wierd to think of something getting hot and going down in resistance - >kind of like nichrome wire in an inverse universe! > >Thanks for your help, > > Dennis > >------------------------ >There are particulars like how much you want to limit the current and how >much reduction in current you can accept (there will be some). > >If you don't want to get too technical: For a 35W lamp--use Digikey KC004L, >for a 50W use a KC003L. >Remember that these get hot and are supposed to get hot. Don't try to cool >them off!--in fact they should be protected from cooling. > >Regards, >Eric M. Jones >www.PerihelionDesign.com >--------------------------- > > > > ________________________________ Message 18 ____________________________________ Time: 11:04:43 PM PST US From: "Ronald J. Parigoris" Subject: AeroElectric-List: 914 second alternator? --> AeroElectric-List message posted by: "Ronald J. Parigoris" I was looking through aircraft spruce tonight and saw a 8 amp permanent magnet alternator. http://www.aircraftspruce.com/catalog/eppages/sdaltreg.php Would this work on a vacuum pad on a rotax 914 and put out rated amps? If I were to run second fuel pump from this and a 2 amp strobe power supply, what sort of battery would be needed? Could you get away with no battery? If not any other ideas? This is for a Europa XS. Thx. Ron Parigoris