---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 05/09/08: 14 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:03 AM - Re: PMA-6000 intercom 28V install (Etienne Phillips) 2. 04:08 AM - Re: PMA-6000 intercom 28V install (RALPH HOOVER) 3. 06:15 AM - Re: PMA-6000 intercom 28V install (sam@fr8dog.net) 4. 06:39 AM - Z13/8, max. E-bus and self-excitation (Camillo) 5. 08:26 AM - Re: Z13/8, max. E-bus and self-excitation (Robert L. Nuckolls, III) 6. 08:46 AM - Re: Z-19 Item Clarification (Allen Fulmer) 7. 08:59 AM - Re: Z-19 Item Clarification (Mark Sletten) 8. 09:47 AM - Re: Re: Z-19 Item Clarification (Scott R. Shook) 9. 09:59 AM - Re: Re: Z-19 Item Clarification (Allen Fulmer) 10. 10:53 AM - Re: Z13/8, max. E-bus and self-excitation (Camillo) 11. 10:54 AM - Re: Re: Z-19 Item Clarification (Harley) 12. 12:25 PM - Re: Re: Z13/8, max. E-bus and self-excitation (Matt Prather) 13. 03:17 PM - Re: Z-19 Item Clarification (Ken) 14. 10:47 PM - Re: PMA-6000 intercom 28V install (Etienne Phillips) ________________________________ Message 1 _____________________________________ Time: 12:03:18 AM PST US Subject: Re: AeroElectric-List: PMA-6000 intercom 28V install From: Etienne Phillips Here's my suggestion... (Hello for the first time everybody, by the way): What about using a DC-DC converter? Using a resistor, the extra energy provided by the 28V is simply dissipated as heat... Using a DC- DC converter, the voltage is usually dropped using a tiny switching- type power supply. Doing the Maths: Worst case is that the 15W resistor is being driven to the limit of 15W Using P=I^2 * R yields a current draw by the intercom of 1A There is a fair variety of 14V switching voltage regulators (or DC-DC converters), eg: PT78ST114 from Texas Instruments (spec sheet: http:// www.ti.com/lit/gpn/pt78st114 ) this one has a 90%+ efficiency, and is a single component with 3 legs: In, Out and Ground... In connects to 28V, Out connects to the intercom power in, and the intercom's ground, the voltage regulator's ground and panel ground connect together. It's also advised to put a smoothing cap on either side, so I guess the total component count is actually 3 parts. No heat, no power wastage, and ripple- and spike-free power for the intercom... Disadvantage: black box between power and intercom that could fail. Risk: Highly unlikely, these things have all sorts of built in protection against heat, short-circuit, open circuit, over-current draw, etc... Anyway, it's just an intercom ;-) What do you guys think? Etienne On 08 May 2008, at 12:59 PM, RALPH HOOVER wrote: > Ben, > Sounds like about 12 w or so of extra heat localized near the > regulator (probably not a switcher with this note) I would follow > PS Engineering=92s recommendation. Because some have ignored the > advice and not installed the resistor and it worked doesn=92t > mitigate the long term effects of additional heat. Most things > electronic work better and last longer if kept cool. > > Ralph Hoover > > > From: owner-aeroelectric-list-server@matronics.com [mailto:owner- > aeroelectric-list-server@matronics.com] On Behalf Of Ben Westfall > Sent: Wednesday, May 07, 2008 11:24 PM > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: PMA-6000 intercom 28V install > > PS Engineering=92s PMA-6000 intercom has the following note: > > =93To reduce the amount of heat dissipated in the audio selector > panel, when used in a 28 > Volt aircraft, it is required that the 15-Ohm, 15-Watt dropping > resistor (p/n 701-015-1501) be in- > stalled in series with the power input.=94 > > The install manual goes on to say =93failure to do so will generate > unnecessary heat inside the unit and may void PS Engineering=92s > warranty=94. Does anyone have experience installing one of these > units in a 28V environment? Is the dropping resistor really > required? The only reason I ask is the local radio shops don=92t > seem to know much about it which makes me wonder if they ever used > them. They all say they can order one but nobody has one in stock. > > -Ben Westfall > > > http://www.matronics.com/contribution > > ________________________________ Message 2 _____________________________________ Time: 04:08:43 AM PST US From: "RALPH HOOVER" Subject: RE: AeroElectric-List: PMA-6000 intercom 28V install Etienne, I suspect that PS engineering is using an analog regulator for noise concerns (cost can figure in as well). Use care inserting a switcher without properly considering the noise concern. A switcher would certainly allow for a wide input voltage range without a lot of heat. Not a show stopper but a design challenge to address. This is just my take I have no knowledge of PS Engineering's design or the process and decisions they have taken to arrive at their design. I have used a switcher for my ANR power supply I'll soon find out if I have any issues! Ralph & Laura Hoover RV7A N527LR _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Etienne Phillips Sent: Friday, May 09, 2008 2:58 AM Subject: Re: AeroElectric-List: PMA-6000 intercom 28V install Here's my suggestion... (Hello for the first time everybody, by the way): What about using a DC-DC converter? Using a resistor, the extra energy provided by the 28V is simply dissipated as heat... Using a DC-DC converter, the voltage is usually dropped using a tiny switching-type power supply. Doing the Maths: Worst case is that the 15W resistor is being driven to the limit of 15W Using P=I^2 * R yields a current draw by the intercom of 1A There is a fair variety of 14V switching voltage regulators (or DC-DC converters), eg: PT78ST114 from Texas Instruments (spec sheet: http://www.ti.com/lit/gpn/pt78st114 ) this one has a 90%+ efficiency, and is a single component with 3 legs: In, Out and Ground... In connects to 28V, Out connects to the intercom power in, and the intercom's ground, the voltage regulator's ground and panel ground connect together. It's also advised to put a smoothing cap on either side, so I guess the total component count is actually 3 parts. No heat, no power wastage, and ripple- and spike-free power for the intercom... Disadvantage: black box between power and intercom that could fail. Risk: Highly unlikely, these things have all sorts of built in protection against heat, short-circuit, open circuit, over-current draw, etc... Anyway, it's just an intercom ;-) What do you guys think? Etienne On 08 May 2008, at 12:59 PM, RALPH HOOVER wrote: Ben, Sounds like about 12 w or so of extra heat localized near the regulator (probably not a switcher with this note) I would follow PS Engineering's recommendation. Because some have ignored the advice and not installed the resistor and it worked doesn't mitigate the long term effects of additional heat. Most things electronic work better and last longer if kept cool. Ralph Hoover _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ben Westfall Sent: Wednesday, May 07, 2008 11:24 PM Subject: AeroElectric-List: PMA-6000 intercom 28V install PS Engineering's PMA-6000 intercom has the following note: "To reduce the amount of heat dissipated in the audio selector panel, when used in a 28 Volt aircraft, it is required that the 15-Ohm, 15-Watt dropping resistor (p/n 701-015-1501) be in- stalled in series with the power input." The install manual goes on to say "failure to do so will generate unnecessary heat inside the unit and may void PS Engineering's warranty". Does anyone have experience installing one of these units in a 28V environment? Is the dropping resistor really required? The only reason I ask is the local radio shops don't seem to know much about it which makes me wonder if they ever used them. They all say they can order one but nobody has one in stock. -Ben Westfall http://www.matronics.com/contribution ________________________________ Message 3 _____________________________________ Time: 06:15:17 AM PST US From: "sam@fr8dog.net" Subject: Re: AeroElectric-List: PMA-6000 intercom 28V install Hi Etienne, I'm not installing an intercom,but I do have the need to reduce bus voltage to a stable 4.8 to 5.0 volts for instrumentation at times. But I was wondering why you chose the PT78ST114S,isn't that 13.9 volt max out? Wouldn't the PT78ST05S work for 5.0v out? Or am I reading the chart incorrectly? Thanks, Sam Marlow ---- Etienne Phillips wrote: ============ Here's my suggestion... (Hello for the first time everybody, by the way): What about using a DC-DC converter? Using a resistor, the extra energy provided by the 28V is simply dissipated as heat... Using a DC- DC converter, the voltage is usually dropped using a tiny switching- type power supply. Doing the Maths: Worst case is that the 15W resistor is being driven to the limit of 15W Using P=I^2 * R yields a current draw by the intercom of 1A There is a fair variety of 14V switching voltage regulators (or DC-DC converters), eg: PT78ST114 from Texas Instruments (spec sheet: http:// www.ti.com/lit/gpn/pt78st114 ) this one has a 90%+ efficiency, and is a single component with 3 legs: In, Out and Ground... In connects to 28V, Out connects to the intercom power in, and the intercom's ground, the voltage regulator's ground and panel ground connect together. It's also advised to put a smoothing cap on either side, so I guess the total component count is actually 3 parts. No heat, no power wastage, and ripple- and spike-free power for the intercom... Disadvantage: black box between power and intercom that could fail. Risk: Highly unlikely, these things have all sorts of built in protection against heat, short-circuit, open circuit, over-current draw, etc... Anyway, it's just an intercom ;-) What do you guys think? Etienne On 08 May 2008, at 12:59 PM, RALPH HOOVER wrote: > Ben, > Sounds like about 12 w or so of extra heat localized near the > regulator (probably not a switcher with this note) I would follow > PS Engineerings recommendation. Because some have ignored the > advice and not installed the resistor and it worked doesnt > mitigate the long term effects of additional heat. Most things > electronic work better and last longer if kept cool. > > Ralph Hoover > > > From: owner-aeroelectric-list-server@matronics.com [mailto:owner- > aeroelectric-list-server@matronics.com] On Behalf Of Ben Westfall > Sent: Wednesday, May 07, 2008 11:24 PM > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: PMA-6000 intercom 28V install > > PS Engineerings PMA-6000 intercom has the following note: > > To reduce the amount of heat dissipated in the audio selector > panel, when used in a 28 > Volt aircraft, it is required that the 15-Ohm, 15-Watt dropping > resistor (p/n 701-015-1501) be in- > stalled in series with the power input. > > The install manual goes on to say failure to do so will generate > unnecessary heat inside the unit and may void PS Engineerings > warranty. Does anyone have experience installing one of these > units in a 28V environment? Is the dropping resistor really > required? The only reason I ask is the local radio shops dont > seem to know much about it which makes me wonder if they ever used > them. They all say they can order one but nobody has one in stock. > > -Ben Westfall > > > http://www.matronics.com/contribution > > ________________________________ Message 4 _____________________________________ Time: 06:39:01 AM PST US Subject: AeroElectric-List: Z13/8, max. E-bus and self-excitation From: "Camillo" Hi. I read all the book, surfed the forum and still have a couple of questions. 1) Is there any reason why I cannot put almost every load on E-bus and then switch what's not necessary off via breakers? I mean, if battery contactor fails, I could not use all loads on main bus. If main alternator/battery contactor fails, I can select what I need to remain under 8/10 amp. 2) Is Z25 self excitation mode utility needed in case of a battery short? Thank-you. Camillo RV9A Read this topic online here: http://forums.matronics.com/viewtopic.php?p=182144#182144 ________________________________ Message 5 _____________________________________ Time: 08:26:58 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Z13/8, max. E-bus and self-excitation At 06:35 AM 5/9/2008 -0700, you wrote: > >Hi. I read all the book, surfed the forum and still have a couple of >questions. > >1) Is there any reason why I cannot put almost every load on E-bus and >then switch what's not necessary off via breakers? I mean, if battery >contactor fails, I could not use all loads on main bus. If main >alternator/battery contactor fails, I can select what I need to remain >under 8/10 amp. Sure . . . you can do that. Why would you want to? The point of the e-bus is to maximize utilization of a limited resource of energy (battery) during alternator out operations with a minimum of pilot work load (minimum risk of doing something undesirable under stressful conditions) and dual feedpaths for power. Obviously, there are countless combinations of architecture, bus loading and "plans-b" one could craft for their project. All combinations would function as designed. The questions to be asked and answered is what benefits are derived by departing from a repeatable experiment where design goals have been debated and refined for over a decade? In other words, what shortcoming do you perceive in Z13/8 as published. What design goals do you have that are not addressed by Z13/8? Perhaps Z12 is a better fit for you. >2) Is Z25 self excitation mode utility needed in case of a battery short? No, in case the battery is not available . . . I.e. disconnected. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 6 _____________________________________ Time: 08:46:02 AM PST US From: "Allen Fulmer" Subject: RE: AeroElectric-List: Z-19 Item Clarification Thanks Ken, If your panel contains EFIS display units, are they on when your "master switch" is turned on? Keeping them off until the engine is started is my desire. I think BobN says it is not an issue with modern day electronics but I seem to remember that GRT (at least) recommends that you not expose the display units to the potential voltage drop during engine start. (Actually, I seriously doubt starting the Subaru with it's geared starter is going to create much of a drop but . . ..) Allen >>>-----Original Message----- >>>From: owner-aeroelectric-list-server@matronics.com >>>[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Ken >>>Sent: Thursday, May 08, 2008 9:33 PM >>>To: aeroelectric-list@matronics.com >>>Subject: Re: AeroElectric-List: Z-19 Item Clarification >>> >>> >>> >>>Allen >>> >>>My EIS comes on any time the master switch is on so it is on before >>>startup. However I elected not to provide any other power >>>source for it >>>so it does go dead if I turn off the master switch. >>> >>>The warning light flashes for everything outside of spec >>>which means you >>>can cancel them one at a time to confirm they are working. However I >>>normally just start the engine which removes all the >>>warnings except low >>>coolant pressure. >>> >>>At shutdown the warnings come back on for low voltage and low oil >>>pressure which can again be canceled one at a time as you suggest. >>>However if the oil pressure indicated normal at any time while the >>>engine was running, it is very unlikely that the low >>>pressure warning >>>will not work from the EIS. You can also set the low oil pressure >>>warning such that it will come on at slow idle just before >>>shutdown (if >>>the oil is up to temperature). In my case I also wired a >>>small light to >>>the low pressure switch that was already installed in my >>>stock engine. >>>The engine is my own conversion and I run a modified Z-14 >>>architecture >>>with two small alternators and two very small 8AH batteries. >>>The system >>>actually weighs less than many single alternator single battery >>>installations. >>>Ken >>> >>> >>>Allen Fulmer wrote: >>> >>>> >>>> Thanks Ken, >>>> >>>> One of the reasons for turning on the EIS before starting >>>the engine is to >>>> make sure the oil pressure sensor DOES work like it is >>>supposed to. But you >>>> make a good point. Maybe the light could be checked when >>>shutting DOWN the >>>> engine before the EIS is turned OFF? Thoughts? >>>> >>>> Allen >>>> >>>>>>> -----Original Message----- >>>>>>> From: owner-aeroelectric-list-server@matronics.com >>>>>>> [mailto:owner-aeroelectric-list-server@matronics.com]On >>>Behalf Of Ken >>>>>>> Sent: Thursday, May 08, 2008 4:03 PM >>>>>>> To: aeroelectric-list@matronics.com >>>>>>> Subject: Re: AeroElectric-List: Z-19 Item Clarification >>>>>>> >>>>>>> >>> >>>>>>> >>>>>>> FWIW you might consider that you simply don't have the >>>oil pressure >>>>>>> issues that air cooled engines have with single grade oil. I >>>>>>> run 5W50 >>>>>>> synthetic and I pretty much ignore the oil pressure just >>>>>>> like most car >>>>>>> drivers. If it doesn't come up or if it goes out of limits, >>>>>>> the EIS will >>>>>>> bring it to my attention. The chances of a secondary failure >>>>>>> where the >>>>>>> EIS would be helpful, at the same time as an alternator >>>>>>> failure, have >>>>>>> got to to be very small. Keeping it simple has advantages. >>>>>>> Do you really >>>>>>> care if the EIS works after an alternator failure? Will it >>>>>>> help you fly >>>>>>> the airplane or just be a distraction? >>>>>>> Ken >>>>>>> >>>>>>> Allen Fulmer wrote: >>>>>>>> snip >>>>>>>> 4. One of the things I am wrestling with is how to >>>power the engine >>>>>>>> instruments (GRT EIS4000 in my case; AFS3500 EMS in yours) >>>>>>> so ONLY it comes >>>>>>>> on when the Engine Bus Master Switch is placed in either >>>>>>> ON position. (To >>>>>>>> check oil pressure light working and to see the oil >>>>>>> pressure come up when >>>>>>>> engine starts.) That may require an Avionics Switch/Relay >>>>>>> since the starter >>>>>>>> requires/prefers to have both Battery Contactors >>>>>>> energized. Still thinking >>>>>>>> about that issue. >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>> >>>> >>>> >>>> >>>> >>> >>> >>> >>> ________________________________ Message 7 _____________________________________ Time: 08:59:05 AM PST US Subject: AeroElectric-List: Re: Z-19 Item Clarification From: "Mark Sletten" sshook(at)cox.net wrote: > For my Z19/Egg Hybrid wiring, I used all of Jan's recommendations for supplying electrical power to the engine ECU, prop, and fuel pumps.-- Ok, I'll be the first to bite... why run power to all critical engine components thru a single point of failure, specifically the four-pole switch? While you have redundant sources feeding redundant poles on the feed side of the switch, the failure of a single pole on the feed side of the switch (bad connection, poor crimp, broken wire, etc.) results in engine shut down. Additionally, you have both fuel pumps feeding off a single pole on the switch. This seems like a single-point of failure added to a single-point of failure. If this one pole of the switch fails you lose both fuel pumps. In my mind, the whole point of redundant power supplies is to avoid single points of failure. Regards, -------- Mark Sletten Legacy FG N828LM http://www.legacyfgbuilder.com Read this topic online here: http://forums.matronics.com/viewtopic.php?p=182183#182183 ________________________________ Message 8 _____________________________________ Time: 09:47:50 AM PST US From: "Scott R. Shook" Subject: RE: AeroElectric-List: Re: Z-19 Item Clarification I hear what you are saying with the 4P3T switch. I just don't see any other alternatives to switching bus power while still staying within the recommendations/requirements of Eggenfellner. Certainly, if someone has a suggestion or recommendation for me - I am always ready to hear it. Eventually, all roads in our redundant electrical systems lead to a single point of failure - the power wire for the component we are powering. That will always be a single point of failure as I do not know of many components that have independent, redundant power sources. Scott R. Shook RV-7A (Building) N696JS (Reserved) -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Mark Sletten Sent: Friday, 09 May, 2008 08:56 Subject: AeroElectric-List: Re: Z-19 Item Clarification sshook(at)cox.net wrote: > For my Z19/Egg Hybrid wiring, I used all of Jan's recommendations for supplying electrical power to the engine ECU, prop, and fuel pumps.-- Ok, I'll be the first to bite... why run power to all critical engine components thru a single point of failure, specifically the four-pole switch? While you have redundant sources feeding redundant poles on the feed side of the switch, the failure of a single pole on the feed side of the switch (bad connection, poor crimp, broken wire, etc.) results in engine shut down. Additionally, you have both fuel pumps feeding off a single pole on the switch. This seems like a single-point of failure added to a single-point of failure. If this one pole of the switch fails you lose both fuel pumps. In my mind, the whole point of redundant power supplies is to avoid single points of failure. Regards, -------- Mark Sletten Legacy FG N828LM http://www.legacyfgbuilder.com Read this topic online here: http://forums.matronics.com/viewtopic.php?p=182183#182183 ________________________________ Message 9 _____________________________________ Time: 09:59:18 AM PST US From: "Allen Fulmer" Subject: RE: AeroElectric-List: Re: Z-19 Item Clarification Mark and all interested in the Z19/Eggenfellner Subaru electrical system design discussion: See if this link works to the thread titled: "Diode verses Switches 101" http://forums.matronics.com/viewtopic.php?p=169493#169493 Allen Fulmer >>>-----Original Message----- >>>From: owner-aeroelectric-list-server@matronics.com >>>[mailto:owner-aeroelectric-list-server@matronics.com]On >>>Behalf Of Mark >>>Sletten >>>Sent: Friday, May 09, 2008 10:56 AM >>>To: aeroelectric-list@matronics.com >>>Subject: AeroElectric-List: Re: Z-19 Item Clarification >>> >>> >>> >>> >>> >>>sshook(at)cox.net wrote: >>>> For my Z19/Egg Hybrid wiring, I used all of Jan's >>>recommendations for supplying electrical power to the engine >>>ECU, prop, and fuel pumps.-- >>> >>> >>>Ok, I'll be the first to bite... why run power to all >>>critical engine components thru a single point of failure, >>>specifically the four-pole switch? While you have redundant >>>sources feeding redundant poles on the feed side of the >>>switch, the failure of a single pole on the feed side of the >>>switch (bad connection, poor crimp, broken wire, etc.) >>>results in engine shut down. >>> >>>Additionally, you have both fuel pumps feeding off a single >>>pole on the switch. This seems like a single-point of >>>failure added to a single-point of failure. If this one pole >>>of the switch fails you lose both fuel pumps. >>> >>>In my mind, the whole point of redundant power supplies is >>>to avoid single points of failure. >>> >>>Regards, >>> >>>-------- >>>Mark Sletten >>>Legacy FG N828LM >>>http://www.legacyfgbuilder.com >>> >>> >>> >>> >>>Read this topic online here: >>> >>>http://forums.matronics.com/viewtopic.php?p=182183#182183 >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> ________________________________ Message 10 ____________________________________ Time: 10:53:15 AM PST US Subject: AeroElectric-List: Re: Z13/8, max. E-bus and self-excitation From: "Camillo" > Sure . . . you can do that. Why would you want to? > The point of the e-bus is to maximize utilization of a > limited resource of energy (battery) during alternator > out operations with a minimum of pilot work load (minimum > risk of doing something undesirable under stressful > conditions) and dual feedpaths for power. Among the others instruments, I'm planning a Dynon D10A, a GPS and an ADI, all with internal batteries and I would like to disconnect them from airplane power to lower aux. alternator load in case of primary alternator failure. But, I still would be able to use plane power for them, if necessary. I understand the pilot work stress came from switching each one off separately, but I plan to mark the three said breakers in yellow in the CB panel and to make a remind above the main alt. warning light (i.e.: in case of failure, switch off bks. x,y,z). In addition, I'm planning to do IFR and I would not like to have NAV/COMM off (for a mayday or a radar assistance to home). So, if I have to keep at least this things on the E-bus, I thought it would be better to have all on it. > Obviously, there are countless combinations of architecture, > bus loading and "plans-b" one could craft for their > project. All combinations would function as designed. > The questions to be asked and answered is what > benefits are derived by departing from a repeatable > experiment where design goals have been debated and > refined for over a decade? > In other words, what shortcoming do you perceive in Z13/8 > as published. What design goals do you have that are not > addressed by Z13/8? Perhaps Z12 is a better fit for > you. I chose Z13/8 because I understood that in Z12 SD-20 would not work without a battery and adding a second battery would have not been a great idea, since an RV9 is not a Boeing (actually, the idea was to pass to Z-14, since the step would have been short...the Boeing relates to this). So, I thaught SD8, even if less powerful, would have been a better choice in terms of safety (cost and weight). Also, I can't say if Z12 could be adapted to receive SD-8. If yes, I anyway doubt it would be good choice: the battery contactor will take 1 amp. off!. In such event, will it work with SB-1 (great capability having it...) or shall it be activated manually as per Z13/8? At the end of this, I may guess options are: - Z13/8 as I said; - Z12 (L40 + SD20) with Z35 to supply power to secondary alternator. > No, in case the battery is not available . . . I.e. disconnected. Sorry...I may need a fourth reading of the book here. If battery is shorted I would have no alternative than using analogic instrument and internally powered electronics one. Isn't it? Thank-you again. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=182216#182216 ________________________________ Message 11 ____________________________________ Time: 10:54:57 AM PST US From: Harley Subject: Re: AeroElectric-List: Re: Z-19 Item Clarification >>I do not know of many components that have independent, redundant power sources.<< The P-Mag for one...electrically, anyway Harley ------------------------------------------------------------------------ Scott R. Shook wrote: > > I hear what you are saying with the 4P3T switch. I just don't see any other > alternatives to switching bus power while still staying within the > recommendations/requirements of Eggenfellner. > > Certainly, if someone has a suggestion or recommendation for me - I am > always ready to hear it. > > Eventually, all roads in our redundant electrical systems lead to a single > point of failure - the power wire for the component we are powering. That > will always be a single point of failure as I do not know of many components > that have independent, redundant power sources. > > > Scott R. Shook > RV-7A (Building) > N696JS (Reserved) > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Mark > Sletten > Sent: Friday, 09 May, 2008 08:56 > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: Re: Z-19 Item Clarification > > > > > sshook(at)cox.net wrote: > >> For my Z19/Egg Hybrid wiring, I used all of Jan's recommendations for >> > supplying electrical power to the engine ECU, prop, and fuel pumps.-- > > > Ok, I'll be the first to bite... why run power to all critical engine > components thru a single point of failure, specifically the four-pole > switch? While you have redundant sources feeding redundant poles on the feed > side of the switch, the failure of a single pole on the feed side of the > switch (bad connection, poor crimp, broken wire, etc.) results in engine > shut down. > > Additionally, you have both fuel pumps feeding off a single pole on the > switch. This seems like a single-point of failure added to a single-point of > failure. If this one pole of the switch fails you lose both fuel pumps. > > In my mind, the whole point of redundant power supplies is to avoid single > points of failure. > > Regards, > > -------- > Mark Sletten > Legacy FG N828LM > http://www.legacyfgbuilder.com > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=182183#182183 > > > > ------------------------------------------------------------------------ > > > Agelesswings certifies that no virus is in this incoming message. > Checked by AVG. > ________________________________ Message 12 ____________________________________ Time: 12:25:23 PM PST US Subject: Re: AeroElectric-List: Re: Z13/8, max. E-bus and self-excitation From: "Matt Prather" > > > snip > Among the others instruments, I'm planning a Dynon D10A, a GPS and an ADI, > all with internal batteries and I would like to disconnect them from > airplane power to lower aux. alternator load in case of primary alternator > failure. But, I still would be able to use plane power for them, if > necessary. I wonder how much power these items will draw when the main bus voltage drops after an alternator failure. It might be slick if they'd switch to internal battery if the bus voltage drops down to ~12V.. Not terribly difficult to accomplish. Regards, Matt- ________________________________ Message 13 ____________________________________ Time: 03:17:07 PM PST US From: Ken Subject: Re: AeroElectric-List: Z-19 Item Clarification Hello Allen No I do not have an EFIS, just a six pack of conventional flight instruments on my bird. Computers make wonderful monitoring tools though and my Grand Rapids EIS (engine instruments only) is always powered during start up. It does not reboot as far as I know but it wouldn't matter anyway as it comes up pretty much instantly when turned on. It has survived several hundred startups so far ;) Thanks to the crowbar overvoltage module, it has also survived a voltage regulator failure that drove the voltage up. Ken Allen Fulmer wrote: > > Thanks Ken, > > If your panel contains EFIS display units, are they on when your "master > switch" is turned on? Keeping them off until the engine is started is my > desire. I think BobN says it is not an issue with modern day electronics > but I seem to remember that GRT (at least) recommends that you not expose > the display units to the potential voltage drop during engine start. > (Actually, I seriously doubt starting the Subaru with it's geared starter is > going to create much of a drop but . . ..) > > Allen > ________________________________ Message 14 ____________________________________ Time: 10:47:22 PM PST US From: Etienne Phillips Subject: Re: AeroElectric-List: PMA-6000 intercom 28V install On 09 May 2008, at 3:10 PM, sam@fr8dog.net wrote: > Hi Etienne, > I'm not installing an intercom,but I do have the need to reduce bus > voltage to a stable 4.8 to 5.0 volts for instrumentation at times. > But I was wondering why you chose the PT78ST114S,isn't that 13.9 > volt max out? Wouldn't the PT78ST05S work for 5.0v out? Or am I > reading the chart incorrectly? > Thanks, > Sam Marlow Hi Sam I suggested that one, because I presumed that the intercom (as per the topic ;-) ) would run very comfortably on 14V. If you need 5V, then I'd suggest a PT78ST105V, assuming your entire bus doesn't require more than 1.5A, and as per Ralf Hoover's comment, make sure that your instruments can handle having a switch-mode supply up stream. The reason I like this family of switchers though is because they have a fairly high internal frequency of 650kHz, which can be filtered out quite easily using the smoothing caps. However, there is still a chance of that noise getting through into the instrument, so some testing is probably in order... Hope that helps :-) Etienne P.S. For my last response, I made a mistake with the part number - it should read PT78ST114V, and not PT78ST114S - S is for surface mount, and V is for vertical mount! ------------------------------------------------------------------------------------- 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.