---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 12/01/11: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:48 AM - EFIS brownout capacitor (user9253) 2. 06:59 AM - Re: EFIS brownout capacitor (Robert L. Nuckolls, III) 3. 09:41 AM - Re: EFIS brownout capacitor (user9253) 4. 09:43 AM - Knobs and Dials (Etienne Phillips) 5. 09:44 AM - Re: EFIS brownout capacitor (user9253) 6. 10:01 AM - Re: Knobs and Dials (Jeff Luckey) 7. 12:08 PM - Re: Re: EFIS brownout capacitor (Robert L. Nuckolls, III) 8. 01:19 PM - Re: 1 Wire vs. 3Wwire alternators (cdnch701builder) 9. 02:37 PM - Re: Re: EFIS brownout capacitor (Robert L. Nuckolls, III) 10. 06:22 PM - Re: 1 Wire vs. 3Wwire alternators (Robert L. Nuckolls, III) 11. 09:34 PM - Re: Knobs and Dials (Etienne Phillips) ________________________________ Message 1 _____________________________________ Time: 12:48:06 AM PST US Subject: AeroElectric-List: EFIS brownout capacitor From: "user9253" Bob and all, Is it feasible to provide brownout protection for an EFIS during engine cranking with a large electrolytic capacitor? A capacitor would not have to be replaced periodically and it might not weigh as much as a backup battery. Each brand of EFIS might have a different supply voltage requirement. But for this discussion, let's assume that 9 volts are required to prevent the EFIS from rebooting. How long is the battery voltage below 9 volts when starting the engine? The starter will draw the most current when it is first energized. Once the starter is rotating, back EMF will reduce the current draw. So for the first several milliseconds, the battery voltage will be at the lowest. If a large capacitor could support the EFIS voltage for one second, would that be long enough? If an EFIS draws 1 amp, what size capacitor would be required? Some EFISs have dedicated terminals for a backup battery. I assume that those EFISs have an internal diode to prevent discharge of the backup battery into the aircraft electrical system. Otherwise an external diode is needed. Could a capacitor provide brownout protection? Or would it have to be so large as to make it impractical? Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=359987#359987 ________________________________ Message 2 _____________________________________ Time: 06:59:33 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: EFIS brownout capacitor At 02:44 AM 12/1/2011, you wrote: Bob and all, Is it feasible to provide brownout protection for an EFIS during engine cranking with a large electrolytic capacitor? A capacitor would not have to be replaced periodically and it might not weigh as much as a backup battery. Each brand of EFIS might have a different supply voltage requirement. But for this discussion, let's assume that 9 volts are required to prevent the EFIS from rebooting. How long is the battery voltage below 9 volts when starting the engine? The starter will draw the most current when it is first energized. Once the starter is rotating, back EMF will reduce the current draw. So for the first several milliseconds, the battery voltage will be at the lowest. If a large capacitor could support the EFIS voltage for one second, would that be long enough? Probably. It might even be as short as 250 milliseconds. See: http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1_2.gif http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1.jpg http://www.aeroelectric.com/Pictures/Curves/95_GMC_Safari_3.gif http://www.aeroelectric.com/Pictures/Curves/95_GMC_Safari_1.gif The traces above were taken from the two vehicles we were driving at the time. The Saturn has a PM starter motor, the Safari has a wound field. The larger depression of battery voltage in the Saturn trace can be partially attributed to the the greater inrush current for the PM motor. If an EFIS draws 1 amp, what size capacitor would be required? Some EFISs have dedicated terminals for a backup battery. I assume that those EFISs have an internal diode to prevent discharge of the backup battery into the aircraft electrical system. Otherwise an external diode is needed. Could a capacitor provide brownout protection? Or would it have to be so large as to make it impractical? It's been done. Consider that the rate of change across a capacitor is defined by V/S = A/F 1 Amp of charge (or discharge) on a 1 Farad capacitor produces a voltage change rate of 1 Volt per Second. Of course, few devices draw a constant current as the voltage varies so this relationship has a practical limitation that falls apart for more than short durations. Of course, that's what we're talking about. Of the top of our head, we could estimate that a capacitor charged to .7 volts below battery voltage (12.5 - .7) = 11.8 volts. The goal is to limit voltage drop to 2.8 volts over a .25 second interval So, V/S = A/F (V/S)F = A F = AS/V = .25/2.8 = .09 Farads There's an RC vs. V calculator at http://www.bowdenshobbycircuits.info/rc.htm which can be used to do the same math. In this case, plug in some essentially constant current combination, say 100 volts and 0.1K ohms (1A). Then plug in time of 250mS and voltage change of 2.8 volts. The tool calculates 88029.7978 microFarads or 0.088F. Unfortunately, fat-caps don't come in the range of incremental sizes as their smaller cousins. Also, 16V ratings is in the realm of high voltage for a super-cap. Here's a device that would fit our hypothetical: http://search.digikey.com/us/en/products/BZ12GA124ZAB/478-6281-ND/2506257 It's a 120 milliFarad device described in this data sheet: http://www.avx.com/docs/Catalogs/bestcap.pdf This exercise suggests to the practicality of using more 'active' forms of bus voltage regulation. If I were writing specs for a modern EFIS system where design goals called for improved immunity to starter brownout, I'd call for the switchmode power supply output to be stable down to 7 or 8 volts. Of course, input currents to the supply would double during the brownout interval but it's a short duration. Bottom line is that its a lower cost of ownership to design brown out protection into a device than to paste it on outside. I proposed a scheme to a customer some years back where we explored the addition of a 3 volt, DC to DC converter to be switched in as a bus voltage booster during cranking times. The customer tried it in the lab with positive results . . . don't know if it ever went into production. A 3v, 1A supply is an ittty-bitty critter compared to a super-cap. Bob . . . ________________________________ Message 3 _____________________________________ Time: 09:41:09 AM PST US Subject: AeroElectric-List: Re: EFIS brownout capacitor From: "user9253" Bob, Thank you very much for taking the time to reply. Digikey has some other large capacitors that are not as expensive: $16 http://search.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=ECE-T1EP104FA $12 http://search.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=ECE-T1CP104FA One of these capacitors might be a viable alternative to replacing an expensive internal backup battery for someone who only needs brownout protection and not a longer backup time. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=360010#360010 ________________________________ Message 4 _____________________________________ Time: 09:43:06 AM PST US Subject: AeroElectric-List: Knobs and Dials From: Etienne Phillips Hi All Not strictly aero-electric, but vaguely related... I'm desperately looking for 2 knob assemblies for a 4mm shaft >From this catalogue http://docs-europe.electrocomponents.com/webdocs/002a/0900766b8002a402.pdfthe parts numbers for the assembly are S210 004 - Black knob C210 Black 5 cap D211 or D218 figure dial I've tried RS Components, Mouser, Digikey, Mantech, Selco (who make them, have a $50 minimum charge, but don't have the figure dials), and a horde of others without success. If I had one already, I'd consider making a mould and casting a new one! Thanks, in desperation... Etienne ________________________________ Message 5 _____________________________________ Time: 09:44:04 AM PST US Subject: AeroElectric-List: Re: EFIS brownout capacitor From: "user9253" When the master switch is turned on, would the inrush current to a 0.1F capacitor be a problem? Thanks, Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=360011#360011 ________________________________ Message 6 _____________________________________ Time: 10:01:10 AM PST US From: "Jeff Luckey" Subject: RE: AeroElectric-List: Knobs and Dials Just off the top of my head - Could you get a more standard/easier-to-find knob for a 1/8 inch shaft (isn't that about 3 mm?) and drill it out? _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Etienne Phillips Sent: Thursday, December 01, 2011 09:40 Subject: AeroElectric-List: Knobs and Dials Hi All Not strictly aero-electric, but vaguely related... I'm desperately looking for 2 knob assemblies for a 4mm shaft >From this catalogue http://docs-europe.electrocomponents.com/webdocs/002a/0900766b8002a402.pdf the parts numbers for the assembly are S210 004 - Black knob C210 Black 5 cap D211 or D218 figure dial I've tried RS Components, Mouser, Digikey, Mantech, Selco (who make them, have a $50 minimum charge, but don't have the figure dials), and a horde of others without success. If I had one already, I'd consider making a mould and casting a new one! Thanks, in desperation... Etienne ________________________________ Message 7 _____________________________________ Time: 12:08:18 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: EFIS brownout capacitor At 11:41 AM 12/1/2011, you wrote: > >When the master switch is turned on, would the inrush current to a >0.1F capacitor be a problem? >Thanks, Joe Good question. If the cap is fed with say, 4' of 22AWG (16 mOhm/ft) then there is potential for a 150+ Amp inrush. You might want to consider some ballasting resistance or perhaps an inrush limiter sized to your operating loads. Bob . . . ________________________________ Message 8 _____________________________________ Time: 01:19:36 PM PST US From: cdnch701builder Subject: Re: AeroElectric-List: 1 Wire vs. 3Wwire alternators Thanks bob... I have a 3 wire internally regulated alternator... that I would like to convert to external regulator! Is there any info online somewhere that provides instructions to do the conversion? I have been searching and I cannot find! Ron :--)> :--)> :--)> At 11:43 AM 11/22/2011, you wrote: :--)>:--)> :--)>:--)> I need some help here with alternators! What is the difference :--)>:--)> between a 1 wire and a 3 wire :--)>:--)> system? :--)>:--)> :--)> I'm not sure there's a uniform convention for :--)> 1 versus 2 versus 3 wire alternators. The :--)> 1-wire alternators I see for boats, RVs and :--)> utility vehicles have regulators built in. They :--)> have ONE b-lead that connects to the system and :--)> they automatically shut down internally when :--)> the alterantor is not turning. :--)> :--)>:--)> Can a 1 wire setup be shut down with a switch as per over voltage protection :--)>:--)> :--)> No :--)> :--)>:--)> ... or does it have :--)>:--)> to be a 3 wire? :--)>:--)> :--)> :--)> It certainly needs to have more than one wire, the :--)> second of which offers absolute control over field :--)> excitation. Check out B&C or Plane Power. They've :--)> provided for satisfaction of the legacy philosophy for :--)> putting alternators on airplanes. :--)> :--)> :--)> Bob . . . :--)> :--)> http://www.matronics.com/Navigator?AeroElectric-List ________________________________ Message 9 _____________________________________ Time: 02:37:26 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: EFIS brownout capacitor At 01:35 PM 12/1/2011, you wrote: > After some sifting through the gray matter archives, I retrieved the core principals behind an active 'bus booster' that I crafted some years back. Making this technology work for brown-out protection would look something like this: http://aeroelectric.com/Pictures/Schematics/Royer_Oscillator_Bus-Booster.pdf I've used this style power oscillator in dozens of products. It's designed around a saturable core transformer that operates in the 1000-4000 Hz range. These are usually tape-wound toroidal cores. This particular implementation uses 'upside down PNP' power transistors with grounded collectors. The assembly staff really liked that . . . no insulating washers and grease! This would be a DC-DC power supply that produces say 3.5 volts for a 12 volt input. The instant the starter contactor is energized, battery voltage applied to the protected device is boosted to about 16.0 volts. When the starter inrush hits, battery voltage drops to say 9 volts with a proportional drop in boost level to about 2.4 volts which is added to the 9 volts for a 'protected' output of 11.4 or so. When the starter is de-energized, the oscillator is unpowered, boosting is replaced by normal bus power through the upper, diode-isolated input. To handle a 1A load, output power would be under 5 watts. This is a really small oscillator. Bob . . . ________________________________ Message 10 ____________________________________ Time: 06:22:41 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 1 Wire vs. 3Wwire alternators At 03:13 PM 12/1/2011, you wrote: > >Thanks bob... > >I have a 3 wire internally regulated alternator... that I would like >to convert to external >regulator! > >Is there any info online somewhere that provides instructions to do >the conversion? I have >been searching and I cannot find! It varies from one brand and model to the next. An alternator repair shop could open it up and easily identify the means by which the internal regulator could be by-passed. I've seen some articles but don't recall now where . . . Sorry. Perhaps somebody here on the List will recall some exemplar articles. Bob . . . ________________________________ Message 11 ____________________________________ Time: 09:34:09 PM PST US From: Etienne Phillips Subject: Re: AeroElectric-List: Knobs and Dials On 01 Dec 2011, at 7:58 PM, Jeff Luckey wrote: > Just off the top of my head ' > > Could you get a more standard/easier-to-find knob for a 1/8 inch shaft (isn=92t that about 3 mm?) and drill it out? > > > Hi Jeff That is definitely an option, along with using a spacer sleeve to get the shaft size to 6mm. However, the 21mm knob diameter and the figure dials seem to be what makes this combination particularly hard to find. Thanks for the input though :) Etienne ------------------------------------------------------------------------------------- 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.