---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 11/24/04: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:49 AM - Re: starter contactor unnecessary? (Ronnie Brown) 2. 05:18 AM - Re: Private Pilot (Robert L. Nuckolls, III) 3. 05:20 AM - Re: starter contactor unnecessary? (Robert L. Nuckolls, III) 4. 05:31 AM - Re: starter contactor unnecessary? (Robert L. Nuckolls, III) 5. 05:57 AM - Re: Private Pilot (Bobby Hester) 6. 06:32 AM - Re: Re: PowerSchottky (echristley@nc.rr.com) 7. 07:28 AM - Re: PowerSchottky (Glaeser, Dennis A) 8. 07:53 AM - Re: PowerSchottky (Paul Messinger) 9. 08:47 AM - Re: Re: PowerSchottky//various Vdrops (Paul Messinger) 10. 09:19 AM - Re: Re: PowerSchottky//uses (Paul Messinger) 11. 09:38 AM - (Ron Triano) 12. 03:31 PM - Re: PowerSchottky (Robert L. Nuckolls, III) 13. 05:27 PM - Re: PowerSchottky (glaesers) ________________________________ Message 1 _____________________________________ Time: 04:49:21 AM PST US From: "Ronnie Brown" Subject: Re: AeroElectric-List: starter contactor unnecessary? --> AeroElectric-List message posted by: "Ronnie Brown" --> AeroElectric-List message posted by: "thomas a. sargent" > I talked to a fellow at SkyTec about wiring up my starter (149-12LSX). > He told me that since I intend not to have an ignition key switch, I can > dispense with my starter contactor. Apparently the SkyTec starter has a > contactor solenoid built into it which also engages the drive gear. My > start push button is stout enough to handle the current (about 1 amp I > think) that the solenoid requires to engage. Key switches evidently are > a little too light to handle the load directly, so in those cases he > recommends the starter contactor. I wired my SkyTec (IO360 Lycoming) directly from the ACS Ignition Switch - but I had to replace the 2 amp circuit breaker with a 5 amp. I have 150 hours and a like number of starts without any problem. The AD required surge suppression diode is installed. I had not heard of the current problem on the starter switch. Ronnie Brown Velocity ________________________________ Message 2 _____________________________________ Time: 05:18:11 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Private Pilot --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 02:04 AM 11/24/2004 -0600, you wrote: >--> AeroElectric-List message posted by: "Tom Brusehaver" > > >There is an article in the current Private Pilot magazine, >well kind of a question about avionics master stitches. The >author of the article not only says it is a good idea, he >even suggests putting in a relay. > >I tried to straighten him out, but he believes, or won't >consider any other position. Pretty weird. Deeply held beliefs trump simple-ideas any day. Bob . . . ________________________________ Message 3 _____________________________________ Time: 05:20:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: starter contactor unnecessary? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 11:44 PM 11/23/2004 -0700, you wrote: >--> AeroElectric-List message posted by: "thomas a. sargent" > > >I talked to a fellow at Skytec about wiring up my starter (149-12LSX). >He told me that since I intend not to have an ignition key switch, I can >dispense with my starter contactor. Apparently the Skytec starter has a >contactor solenoid built into it which also engages the drive gear. My >start push button is stout enough to handle the current (about 1 amp I >think) that the solenoid requires to engage. Key switches evidently are >a little too light to handle the load directly, so in those cases he >recommends the starter contactor. > >Eliminating a part always sounds like a good idea. But, I don't recall >anyone mentioning this configuration on the list before. Is everybody >using a key switch, or is there some downside to this approach that he >didn't tell me? I can only guess but there's a lot he didn't tell you because he doesn't know . . . See: http://aeroelectric.com/articles/strtctr.pdf Bob . . . ________________________________ Message 4 _____________________________________ Time: 05:31:04 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: starter contactor unnecessary? --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 07:48 AM 11/24/2004 -0500, you wrote: >--> AeroElectric-List message posted by: "Ronnie Brown" > > >--> AeroElectric-List message posted by: "thomas a. sargent" > > > > I talked to a fellow at SkyTec about wiring up my starter (149-12LSX). > > He told me that since I intend not to have an ignition key switch, I can > > dispense with my starter contactor. Apparently the SkyTec starter has a > > contactor solenoid built into it which also engages the drive gear. My > > start push button is stout enough to handle the current (about 1 amp I > > think) that the solenoid requires to engage. Key switches evidently are > > a little too light to handle the load directly, so in those cases he > > recommends the starter contactor. > >I wired my SkyTec (IO360 Lycoming) directly from the ACS Ignition Switch - >but I had to replace the 2 amp circuit breaker with a 5 amp. I have 150 >hours and a like number of starts without any problem. The AD required >surge suppression diode is installed. I had not heard of the current >problem on the starter switch. The AD on starter control contacts of the ACS key-switch is bogus. See: http://aeroelectric.com/articles/spikecatcher.pdf The ACS keyswitch uses the same start switch technology as for automobiles and is severely abused when modern starters with integral solenoids are substituted for the Prestolite pigs with external contactors. It's just a matter of time. Suggest you move the diode from across the switch contacts to make it parallel the solenoid coil . . . or better yet, install an external contactor with integral spike catcher diode as illustrated in virtually every Z-figure and offered by B&C and others. Bob . . . ________________________________ Message 5 _____________________________________ Time: 05:57:08 AM PST US From: "Bobby Hester" Subject: Re: AeroElectric-List: Private Pilot --> AeroElectric-List message posted by: "Bobby Hester" It would be really neat if Bob Nuckolls would send in an artical for next month explaining why he sees no reason for one. At least a letter from the readers artical. > -----Original Message----- > From: "Tom Brusehaver" > To: "aeroelectric-list@matronics.com" > Date: Wed, 24 Nov 2004 02:04 (CDT) > Subject: AeroElectric-List: Private Pilot > > --> AeroElectric-List message posted by: "Tom Brusehaver" > > > There is an article in the current Private Pilot magazine, > well kind of a question about avionics master stitches. The > author of the article not only says it is a good idea, he > even suggests putting in a relay. > > I tried to straighten him out, but he believes, or won't > consider any other position. Pretty weird. > > > > > > > ------- Surfing the web from Hopkinsville, KY RV7A web site: http://www.geocities.com/hester-hoptown/RVSite ________________________________ Message 6 _____________________________________ Time: 06:32:47 AM PST US From: echristley@nc.rr.com Subject: Re: AeroElectric-List: Re: PowerSchottky --> AeroElectric-List message posted by: echristley@nc.rr.com ----- Original Message ----- From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: PowerSchottky > > agonizing over a few tenths of a volt difference is like chrome > plating one's prop > spinner for more speed. s. > > Bob . . . > You can get a speed increase from chroming the spinner!?! COOL, DUDE!! Oh, sorry... We now return you to your regularly scheduled thread...and do not archive. ________________________________ Message 7 _____________________________________ Time: 07:28:35 AM PST US From: "Glaeser, Dennis A" Subject: AeroElectric-List: Re: PowerSchottky 0.13 DRUGS_PAIN Refers to a pain relief drug --> AeroElectric-List message posted by: "Glaeser, Dennis A" --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > >>There's no reason to run any accessory through diodes during battery-only operations >> Bob . . . For a dual battery, ECM engine architecture, where the Endurance Bus and the ECM power (ignition) need to be able to be powered by either battery via separate switches (no SPOF), does this mean that those separate feeds do not need & should not have diodes? Normally you would select only one feed at a time, but I thought it was 'safer' to run the feeds through diodes to keep each side isolated - in case you turned on both switches and one side had a serious short (or something) that could 'kill' both sides. But the 'cure' has undesirable side effects also (the electric version of Vioxx). If the only problem is no alternator, I would think switching both on would be fine - you're just putting the batteries in parallel. Even if you switched on both ECM feeds with the alternator running, you are just running a parallel circuit. I didn't have diodes on these feeds initially - sounds like my 'plan-for-failure education' may have wandered off course on this a bit...? Dennis Glaeser ________________________________ Message 8 _____________________________________ Time: 07:53:58 AM PST US From: "Paul Messinger" Subject: Re: AeroElectric-List: PowerSchottky --> AeroElectric-List message posted by: "Paul Messinger" Embedded comments ----- Original Message ----- From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: PowerSchottky > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > At 07:35 AM 11/23/2004 -0800, you wrote: > >--> AeroElectric-List message posted by: "Paul Messinger" > > > >Bob you sort of missed Eric's main point. > > > ??? Eric cited a 50% de-rating of a device's spec-sheet rating > based on mis-interpretation of an operating characteristic. > You seem to be talking about a technique for driving > down the already low Vf by under-cooling the device . . . > different discussion. Agree with your above but Erid was mostly interested in a very low forward V drop. Both his original post also cited this and a telecon with Eric confirmed this. The way to get very low voltage drop is to use a hi current diode and derate it a lot. 160 amp diode in 20 amp circuit for example. > >Also its not isolated so there is the need for special mounting. > > Yup . . . one of several reasons for choosing the lowly bridge > rectifier . . . As long as you can stand the V drop its a good inexpensive solution. The V drop becomes more important in electrically dependent applications where getting as much power out of the battery is important. My point is there are easy to use very low drop devices out there, not to suggest that they need to be used blindly as a replacement for the "diode bridge". > > >Even 15 V units are used in 12V battery applications but they have extra > >external protection from any noise spikes. > > Yeah, but if the system sees a load dump transient, it's positive . . . > meaning that it drives any system power steering diodes into > conduction. It's the reverse voltage transient that puts the > diode at risk. It depends on where the voltage spike occurs and how much energy it has. The ones I have documentated are reverse V spikes (to potential diode applications) that can damage low reverse rated diodes. Damaging spikes can come from places other than the "load dump" case. Transorbs solve that concern. Paul > > Bob . . . > > ________________________________ Message 9 _____________________________________ Time: 08:47:45 AM PST US From: "Paul Messinger" Subject: Re: AeroElectric-List: Re: PowerSchottky//various Vdrops --> AeroElectric-List message posted by: "Paul Messinger" Embedded comments ----- Original Message ----- From: "glaesers" Subject: AeroElectric-List: Re: PowerSchottky > --> AeroElectric-List message posted by: "glaesers" > > Do we really need devices rated for 160A for our applications - or is it > that those devices are the ones with the really low Vf? They are rather > pricey! I'm willing to live with a somewhat higher loss across the diode > for a better price. I wonder about "penny wise and pound foolish". Your concern is extremely common but if you have spent 50K on your aircraft what is another $50 IF you really need the lower V drop. Only you can decide. And yes the only way to get really low V drops is with the use of a very high current device used in a low current application. But consider your specific case. The IR 160CMQ045 for example is two diodes in one package that I use as a way to supply power from two battery busses to one load. Thus I think in your case you would only need 2 of these for 4 of your applications and that is $15 per diode and its a non insulated bolt on and bolt to terminal package. For a lower cost and somewhat higher V drop consider the ST 12045TV at under $20 and get two independent diodes in an isolated bolt on package. Either of the above and there are several others that do not need ANY mechanical insulation as your 50HQ device and the above are in the $10 -$15 per diode with no mounting issues. > > If you only need one - for the Primary bus to Endurance bus, it's not so > bad. But I'm looking at 5 (+2 for the dual feeds for ECM power, and +2 for > dual alternate feeds from the Main & Aux hot busses to the Endurance Bus). > If I use regular diodes I can get them all for the price of one of those > Schottkys - but with about a volt loss. Only you can decide how much V drop you can allow. To get all the power out of the battery you will be discharging the battery to around 11V at the terminal. If your equipment can work at 10V or slightly lower then use the low cost diode bridge. If you need 10V minimum I would consider using the ST part with a V drop of 0.6V at 10 amps and the IR160 device has a Vdrop max of 0.4v at 10 amps. The diode bridge has a 0.9v drop at 10 amps. All of the above parts have two usable diodes if you are using two sources of power to one load. The diode bridge costs $3 to $8 depending on brand based on Digikey or Mouser Current pricing NOT what is in printed catalog as its not current anymore. The ST part costs under $10 per diode and each diode is independent. The IR part costs under $15 per diode but the diodes are connected at the output. So the magic question is what is the minimum voltage your end module needs. Not all that much difference at 10 amps, best case is a 0.4 drop and worst case is 0.9v drop for a savings of 0.5V. It can be important to have the extra 0.5V available but surely not in all cases. Personally I do like the ST part but it was not available when I was doing my design many years ago. Bottom line is designing the power distribution system so when the battery V drops to 11V the essential equipment will still work. Paul ________________________________ Message 10 ____________________________________ Time: 09:19:56 AM PST US From: "Paul Messinger" Subject: Re: AeroElectric-List: Re: PowerSchottky//uses --> AeroElectric-List message posted by: "Paul Messinger" For my part, I was only addressing the type of diode not the basic design of your electrical system. There are good reasons for different designs and the types of fault protection one worries about. I feel its very important to have as little to deal with (cockpit load) after any failure as possible(Ideally no pilot action needed at all). If a failure results in battery only ops then the best thing to do is head to the nearest airport that you can safely land at. I know of some who promote keeping on flying as the analysis says the batteries will last. But what if they do not? Given that the batteries may not be fully charged and you are likely discharging them above the 20 hour rate. The amp hour rating of the battery at above rate will result in lower usable AH and can be as low as 1/2 what you might expect, so flight duration can be far less than what is calculated on paper. The loss of an alternator is the simple case. Loss of an essential engine electrical component is far more critical. (Hince Dual mags.) So we really need dual electrical systems for electrically dependent (IE no mags) engines. Further both systems need to be on at the same time, or an automatic fault detection system needs to take action to switch to the backup system, in the case of landing and departing, as there likely is no time for pilot detection and switching. In this case dual systems and diodes may be used in essential equipment feeds. The emphasis is on MAY as designs vary. As for crosstrapping. Where you have dual batteries and dual ign systems the issue is does the crosstrapping (IE allowing either battery power either ign system) really improve reliability. It does on paper but not by nearly as much as one might think. Consider the likelihood of even a single failure in any single flight. If its likely that two failures can happen in a single flight I would not fly at all. :-) Protecting against more than one failure per flight increases the possibly of a failure simply due to the additional complexity of the crosstrapping components. Not to mention the weight of the additional parts and the potential of the pilot's mishandling the more complex system. In my aerospace experience we avoided crosstrapping wherever possible due to in some cases to a reliability analysis that shower a net reduction in reliability. Two parallel independent strings was the best solution in many cases. Paul ----- Original Message ----- From: "Glaeser, Dennis A" Subject: AeroElectric-List: Re: PowerSchottky > --> AeroElectric-List message posted by: "Glaeser, Dennis A" > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > 40431.iAO4VbT05041@matronics.com> > > > >>There's no reason to run any accessory through diodes during > battery-only operations > > >> Bob . . . > > For a dual battery, ECM engine architecture, where the Endurance Bus and the > ECM power (ignition) need to be able to be powered by either battery via > separate switches (no SPOF), does this mean that those separate feeds do not > need & should not have diodes? Normally you would select only one feed at a > time, but I thought it was 'safer' to run the feeds through diodes to keep > each side isolated - in case you turned on both switches and one side had a > serious short (or something) that could 'kill' both sides. But the 'cure' > has undesirable side effects also (the electric version of Vioxx). > If the only problem is no alternator, I would think switching both on would > be fine - you're just putting the batteries in parallel. Even if you > switched on both ECM feeds with the alternator running, you are just running > a parallel circuit. > I didn't have diodes on these feeds initially - sounds like my > 'plan-for-failure education' may have wandered off course on this a bit...? > > Dennis Glaeser > > ________________________________ Message 11 ____________________________________ Time: 09:38:18 AM PST US From: "Ron Triano" Subject: AeroElectric-List: 1.16 MISSING_SUBJECT Missing Subject: header 0.26 UPPERCASE_25_50 message body is 25-50% uppercase --> AeroElectric-List message posted by: "Ron Triano" NEXGEN BUILDERS RON TRIANO PROJECT SUPERINTENDENT SIERRA VISTA TOWNHOUSES ________________________________ Message 12 ____________________________________ Time: 03:31:37 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: PowerSchottky --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 07:49 AM 11/24/2004 -0800, you wrote: >--> AeroElectric-List message posted by: "Paul Messinger" > >Embedded comments > >----- Original Message ----- >From: "Robert L. Nuckolls, III" >To: >Subject: Re: AeroElectric-List: PowerSchottky > > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > > > At 07:35 AM 11/23/2004 -0800, you wrote: > > >--> AeroElectric-List message posted by: "Paul Messinger" > > > > > > >Bob you sort of missed Eric's main point. > > > > > > ??? Eric cited a 50% de-rating of a device's spec-sheet rating > > based on mis-interpretation of an operating characteristic. > > You seem to be talking about a technique for driving > > down the already low Vf by under-cooling the device . . . > > different discussion. > >Agree with your above but Erid was mostly interested in a very low forward V >drop. Both his original post also cited this and a telecon with Eric >confirmed this. The way to get very low voltage drop is to use a hi current >diode and derate it a lot. 160 amp diode in 20 amp circuit for example. > > > >Also its not isolated so there is the need for special mounting. > > > > Yup . . . one of several reasons for choosing the lowly bridge > > rectifier . . . > >As long as you can stand the V drop its a good inexpensive solution. The V >drop becomes more important in electrically dependent applications where >getting as much power out of the battery is important. Why do we have ANY diodes in series with battery powered equipment? Seems that the best design doesn't need to consider electrically efficient diodes for battery-only operations. >My point is there are easy to use very low drop devices out there, not to >suggest that they need to be used blindly as a replacement for the "diode >bridge". > > > > > >Even 15 V units are used in 12V battery applications but they have extra > > >external protection from any noise spikes. > > > > Yeah, but if the system sees a load dump transient, it's positive . . . > > meaning that it drives any system power steering diodes into > > conduction. It's the reverse voltage transient that puts the > > diode at risk. > >It depends on where the voltage spike occurs and how much energy it has. The >ones I have documentated are reverse V spikes (to potential diode >applications) that can damage low reverse rated diodes. Damaging spikes can >come from places other than the "load dump" case. Transorbs solve that >concern. Sure . . . which reminds me. Did your studies size the energy signature of alternator load dumps sufficiently to select a Transorb to trap them? Bob . . . ________________________________ Message 13 ____________________________________ Time: 05:27:26 PM PST US From: "glaesers" Subject: AeroElectric-List: Re: PowerSchottky --> AeroElectric-List message posted by: "glaesers" Embedded comments: --> AeroElectric-List message posted by: "Paul Messinger" >> Do we really need devices rated for 160A for our applications - or is it >> that those devices are the ones with the really low Vf? They are rather >> pricey! I'm willing to live with a somewhat higher loss across the diode >> for a better price. >I wonder about "penny wise and pound foolish". Your concern is extremely >common but if you have spent 50K on your aircraft what is another $50 IF you >really need the lower V drop. Only you can decide. I agree - and I don't 'need' an extremely low V drop. But if there is something out there that is a significant improvement over the 'lowly bridge rectifier' (to quote Bob), for nearly the same price, why not use it? I'm just looking for the most bang for the buck. >And yes the only way to get really low V drops is with the use of a very >high current device used in a low current application. It seemed that way, but wasn't sure if there was something else I was missing. Thanks for clarifying. >But consider your specific case. The IR 160CMQ045 for example is two diodes >in one package that I use as a way to supply power from two battery busses >to one load. Thus I think in your case you would only need 2 of these for 4 >of your applications and that is $15 per diode and its a non insulated bolt >on and bolt to terminal package. For a lower cost and somewhat higher V drop >consider the ST 12045TV at under $20 and get two independent diodes in an >isolated bolt on package. I was going to ask about that and forgot! It looked like they could be used that way, but I wasn't sure. That doubles their bang! The ST device looks good too! That's the problem. Many choices exist, but it is rather difficult to find them - at least for folks like me who don't deal with this stuff all the time. That's why this forum is so great. I've seen more diode choices, and where to find them, in the past couple of days on this list than I would have found in a month of Sundays on my own. Thanks for your help! Dennis Glaeser