AeroElectric-List Digest Archive

Sat 09/15/07


Total Messages Posted: 8



Today's Message Index:
----------------------
 
     1. 06:46 AM - Re: Design Questions (Ken)
     2. 07:16 AM - Re: Design Questions (Robert L. Nuckolls, III)
     3. 08:39 AM - Re: switch suitability? (Chris Johnston)
     4. 10:17 AM - Re: switch suitability? (Robert L. Nuckolls, III)
     5. 11:07 AM - Re: switch suitability? (Ken)
     6. 11:48 AM - Re: switch suitability? (Chris Johnston)
     7. 12:30 PM - Re: Rotax electrical switches (Robert L. Nuckolls, III)
     8. 01:24 PM - Re: switch suitability? (Chris Johnston)
 
 
 


Message 1


  • INDEX
  • Back to Main INDEX
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 06:46:33 AM PST US
    From: Ken <klehman@albedo.net>
    Subject: Re: Design Questions
    MTBehnke wrote: > >I have a few questions as I'm trying to work through my electrical design. I've looked through the Aeroelectric book and other sources, but can't seem to find answers to the following: > >1. Is there some design guidelines for minimum fuse sizes to avoid nuisance trips? I've seen a couple of people mention keeping current below 80% of the fuse size. I also saw one recommendation on keeping below 50% for radios based on transmitting current draw. > > Rule one is to size the fuse to protect the wire. ie an 18awg wire gets a 10 amp fuse, 22 awg gets 5 amps etc. Or use the manufacturers recommendation. Some things like landing lights draw momentary high current while the filament is heating up which can be a consideration but in practice refer to rule one and all should be fine. Some motors and solenoids may draw considerable extra current while starting but again you fuse to protect the wire from overheating in case the motor shorts or seizes. In extreme cases you'd use a circuit breaker or slow blow fuse but I think that is rare for us here. I guess I do have a few fuses smaller than rule one would suggest but only because awg22 wire is the smallest that I purchased or because the wire was oversized to keep the voltage drop low. Since wire and fuses only come in fixed sizes you generally will have adequate margin without any conscious effort. A single failed fuse or circuit should not be any cause for great concern anyway with a good design. >2. I have the Creativair strobe power supply. I noticed that the strobe kit came with 22 ga. shielded wire to go from the power supply to the strobes. The installation instructions give Joules per flash, but nothing about voltage, current, etc. I don't have any way to validate whether 22 ga. is okay, especially as it's round trip distances. Should I just assume it's fine? > > I'd assume it is fine. Strobes run on several hundred volts and short bursts of current so it is intermittant duty (the wire does not continuously conduct current). >3. This may be overly nit-picky, but do you generally use 12 or 14 volts when calculating loads? For example, I have the Duckworks 100W landing light. Using 12V gives 8.3A versus 7.2A using 14V. On top of that, a 5% drop of 12V is 0.6V compared to 0.7V for 14V. I'm not sure if this would result in any different wire or fuse sizes. > I use 14 volts but if it is close enough to make a difference I would just upsize the wire anyway in most cases. Ken > >Thanks, > >-------- >Mike Behnke >RV-9A Fuselage >Andover, MN > > >Read this topic online here: > >http://forums.matronics.com/viewtopic.php?p=134314#134314 > > > >


    Message 2


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 07:16:49 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Design Questions
    At 07:37 PM 9/13/2007 -0700, you wrote: > >I have a few questions as I'm trying to work through my electrical >design. I've looked through the Aeroelectric book and other sources, but >can't seem to find answers to the following: > >1. Is there some design guidelines for minimum fuse sizes to avoid >nuisance trips? I've seen a couple of people mention keeping current >below 80% of the fuse size. I also saw one recommendation on keeping >below 50% for radios based on transmitting current draw. Ken has already offered some good response to this. I would only add that any advise you get for de-rating fuses is not based on any real science. Every fuse is designed to carry 100% of it's rated value indefinitely. See: http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATC_Specs.pdf In some cases (for VERY robust fuses called current limiters) they'll carry twice their rated current. See: http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf You see, the manufacturer has already de-rated the product. Bob . . .


    Message 3


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 08:39:20 AM PST US
    Subject: switch suitability?
    From: "Chris Johnston" <CJohnston@popsound.com>
    hey all - i've spent the morning perusing the archives about switch electrical ratings, and have read the PDF by Bob on switch ratings, but i'm feeling like i'm not getting any hard and fast rules about this stuff. in most of the posts about electrical ratings, someone invariably says "don't loose any sleep over switch ratings". i'm losing sleep over my switch ratings. :) i'm considering using some super neato (and also very high quality) switches, but the ratings are: 30 volts DC or 125 volts AC, 2.0A res., 0.5A ind. that's the only info given about them. are these switches appropriate (safe) for use for all the things you'd find in a "technically advanced" aircraft? i'm talking things like pitot heat, trim motors, flap motors, exterior lighting etc? also, what about in the place of tying electrical busses together? i'm considering having an alternate battery feed to the E-buss, and i suspect that with a fairly heavily loaded E-buss such as the one i'm considering, these switches would be inadequate? for reference, the E-buss on my ship has the EFIS, AHRS, one NAV, one COM, autopilot, trim, and flaps. i'd hate to put a relay in this spot (up the parts count, etc) that is so critical. i'm not (yet) asking a public critique of my electrical design, which i'm comfortable with, just worrying about the switches i'm thinking of going with. any help would be greatly appreciated! thanks cj


    Message 4


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 10:17:30 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: switch suitability?
    At 08:37 AM 9/15/2007 -0700, you wrote: >hey all - > >i've spent the morning perusing the archives about switch electrical >ratings, and have read the PDF by Bob on switch ratings, but i'm feeling >like i'm not getting any hard and fast rules about this stuff. in most of >the posts about electrical ratings, someone invariably says "don't loose >any sleep over switch ratings". i'm losing sleep over my switch >ratings. :) i'm considering using some super neato (and also very high >quality) switches, but the ratings are: > >30 volts DC or 125 volts AC, 2.0A res., 0.5A ind. These are generally too small for anything practical in the DC power distribution system. These will require relays to boost the capability of the higher current draw applications. Switches best suited to the task will be rated at 7A or better. They will also be easy to acquire from more than one source. >that's the only info given about them. are these switches appropriate >(safe) for use for all the things you'd find in a "technically advanced" >aircraft? i'm talking things like pitot heat, trim motors, flap motors, >exterior lighting etc? > >also, what about in the place of tying electrical busses together? i'm >considering having an alternate battery feed to the E-buss, and i suspect >that with a fairly heavily loaded E-buss such as the one i'm considering, >these switches would be inadequate? for reference, the E-buss on my ship >has the EFIS, AHRS, one NAV, one COM, autopilot, trim, and flaps. i'd >hate to put a relay in this spot (up the parts count, etc) that is so critical. Suggest you begin with one of the architectures published and then define what failure mode is not being addressed by the diagram as published. Read the chapter on System Reliability. You have too many and the wrong things on the e-bus. Bob . . . ---------------------------------------- ( "Physics is like sex: sure, it may ) ( give some practical results, but ) ( that's not why we do it." ) ( ) ( Richard P. Feynman ) ----------------------------------------


    Message 5


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 11:07:08 AM PST US
    From: Ken <klehman@albedo.net>
    Subject: Re: switch suitability?
    Just in case it helps Chris -the ratings you quote are 2 amps resistive load (steady current with no turn on surges) or 0.5 amp inductive (higher momentary turn on surges of current) so these are small switches. Other issues are connections to switches and how many diferent types you wish to use. 1/4" wide tab connections for push on AMP PIDG connectors are very convenient. Solder connections will drive you crazy. Screw terminals are somewhere in between ;) Ken Chris Johnston wrote: >hey all - > >i've spent the morning perusing the archives about switch electrical ratings, and have read the PDF by Bob on switch ratings, but i'm feeling like i'm not getting any hard and fast rules about this stuff. in most of the posts about electrical ratings, someone invariably says "don't loose any sleep over switch ratings". i'm losing sleep over my switch ratings. :) i'm considering using some super neato (and also very high quality) switches, but the ratings are: > >30 volts DC or 125 volts AC, 2.0A res., 0.5A ind. > >that's the only info given about them. are these switches appropriate (safe) for use for all the things you'd find in a "technically advanced" aircraft? i'm talking things like pitot heat, trim motors, flap motors, exterior lighting etc? > >also, what about in the place of tying electrical busses together? i'm considering having an alternate battery feed to the E-buss, and i suspect that with a fairly heavily loaded E-buss such as the one i'm considering, these switches would be inadequate? for reference, the E-buss on my ship has the EFIS, AHRS, one NAV, one COM, autopilot, trim, and flaps. i'd hate to put a relay in this spot (up the parts count, etc) that is so critical. > >i'm not (yet) asking a public critique of my electrical design, which i'm comfortable with, just worrying about the switches i'm thinking of going with. any help would be greatly appreciated! > >thanks >cj > >


    Message 6


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 11:48:18 AM PST US
    Subject: switch suitability?
    From: "Chris Johnston" <CJohnston@popsound.com>
    -----Original Message----- From: owner-aeroelectric-list-server@matronics.com on behalf of Robert L. Nuckolls, III Sent: Sat 9/15/2007 11:15 AM Subject: RE: AeroElectric-List: switch suitability? <nuckolls.bob@cox.net> At 08:37 AM 9/15/2007 -0700, you wrote: >hey all - > >i've spent the morning perusing the archives about switch electrical >ratings, and have read the PDF by Bob on switch ratings, but i'm feeling >like i'm not getting any hard and fast rules about this stuff. in most of >the posts about electrical ratings, someone invariably says "don't loose >any sleep over switch ratings". i'm losing sleep over my switch >ratings. :) i'm considering using some super neato (and also very high >quality) switches, but the ratings are: > >30 volts DC or 125 volts AC, 2.0A res., 0.5A ind. These are generally too small for anything practical in the DC power distribution system. These will require relays to boost the capability of the higher current draw applications. Switches best suited to the task will be rated at 7A or better. They will also be easy to acquire from more than one source. >that's the only info given about them. are these switches appropriate >(safe) for use for all the things you'd find in a "technically advanced" >aircraft? i'm talking things like pitot heat, trim motors, flap motors, >exterior lighting etc? > >also, what about in the place of tying electrical busses together? i'm >considering having an alternate battery feed to the E-buss, and i suspect >that with a fairly heavily loaded E-buss such as the one i'm considering, >these switches would be inadequate? for reference, the E-buss on my ship >has the EFIS, AHRS, one NAV, one COM, autopilot, trim, and flaps. i'd >hate to put a relay in this spot (up the parts count, etc) that is so critical. Suggest you begin with one of the architectures published and then define what failure mode is not being addressed by the diagram as published. Read the chapter on System Reliability. You have too many and the wrong things on the e-bus. Bob . . . ---------------------------------------- ( "Physics is like sex: sure, it may ) ( give some practical results, but ) ( that's not why we do it." ) ( ) ( Richard P. Feynman ) ----------------------------------------


    Message 7


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 12:30:18 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: Rotax electrical switches
    At 10:40 AM 8/28/2007 -0700, you wrote: >I am building my Zenith 701/Rotax 912 electrical system following >Aeroelectric s Z16 diagram because I trust that Bob Nuckolls knows a hell >of a lot more about aircraft electrical systems than I do. I don t even >know enough to fully understand the use of the two switches in the >diagram. I would appreciate if Bob or someone who understands this diagram >can tell me how to use switch S1 (the double poll double throw switch) and >the switch attached to the endurance buss. I also need to understand what >type of switch this second one is. It looks like a single poll on-off type >but I m not certain because it has a ^ symbol in it. That's an error in the symbol. The mid positioned ^ symbol says theres a center-off position. Not so in this case. The e-bus alternate feed switch is an S700-1-3. SPDT ON-ON or equal. I've updated the diagram at: http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z16M.pdf S1 does have three positions. It mimics the functionality of the famous "split-rocker" master switch widely used on single engine TC aircraft for decades. It's a DP3P, ON-ON-ON device. A double pole, progressive transfer switch. Bottom is ALL OFF. Moving up to the mid position adds the BATTERY only. Top position is BATTERY+ALTERNATOR. This is called out as the S700-2-10 switch or equal. The e-bus alternate feed switch is used to power e-bus loads only in case of alternator failure. Turn e-bus alternate feed switch ON. Turn master switch OFF. Continue battery-only until airport in sight whereupon you can turn the master switch back up to BATTERY only if there are things on the main bus useful for approach to landing. See chapter 17 for more detailed explanation of the endurance bus architecture and operating philosophy. Bob . . . ---------------------------------------- ( "Problems are the price of progress. ) ( Don't bring me anything but trouble. ) ( Good news weakens me." ) ( -Charles F. Kettering- ) ----------------------------------------


    Message 8


  • INDEX
  • Back to Main INDEX
  • PREVIOUS
  • Skip to PREVIOUS Message
  • NEXT
  • Skip to NEXT Message
  • LIST
  • Reply to LIST Regarding this Message
  • SENDER
  • Reply to SENDER Regarding this Message
    Time: 01:24:52 PM PST US
    Subject: switch suitability?
    From: "Chris Johnston" <CJohnston@popsound.com>
    Thanks for the reply Bob, and i really appreciate the insight from someone who knows more about this stuff than me. i've been studying the connection for awhile now, and with my proposed architecture i don't mean to pretend i'm more knowledgable than i am. i am learning new stuff daily, so be patient! your reply that i have too many and the wrong things is curious to me. the aircraft has no "conventional" instruments, so the EFIS and AHRS are essential. In my application, the AHARS includes a GPS receiver, (GADAHARS) so i've got the GPS without the draw of a big panel mounted Garmin style unit. the NAV/COM (SL30) isn't too spendy in terms of power (as long as i don't feel the need to transmit in a long winded fashion!) and gets me quite a bit in terms of navigational ability. The autopilot is possibly excessive, but as you say in the chapter on electrical system reliability, it's got an off switch, and if i don't need it, it can be turned off. The flaps and trim could be considered excessive, but my my thinking, they're only as "electrically spendy" as you want them to be (use sparingly), and in a fast slippery aircraft, my personal opinion is that these items are essential. with my proposed 28Ah main battery and the 17Ah aux battery, the E-bus should keep the electrons flowing for quite awhile right? The reason i'm trying to sort out an alternate feed to the E-bus from a second battery is that from what i understand, there is an issue with the EFIS screens rebooting while you're cranking to start the engine. as i type this, i'm thinking that it's possible that this is a mythical problem that i just took for granted to be real. i'll have to investigate that one... but the before start procedure would be to turn on the EFIS, then do the pre-flight, and by the time i'm ready to hop in and start the engine, the EFIS is booted up and ready to go. also, this way i have the engine gauges during engine start. the last piece of the puzzle has to do with starter kickback caused by the lightspeed ignition if the voltage it's getting drops too low during engine cranking. this was a motivator for having a second battery in the aircraft, and an alternate feed to the ignition. the ignition, by the way, would be on the always hot aux battery, or the always hot main battery (switchable) for the reasons that you state in the connection. just to be clear, i'm not one of these guys who has tons of flight experience. i'm a new pilot with an instrument rating, and for my mission, it is important to me that i have every advantage if i have an emergency in the cockpit. in the event of a charging malfunction, i'd be landing as soon as it was reasonably safe to do so, even if i had the electrical endurance to continue much farther. i'm not talking about shouting "MAYDAY!" and setting it down in a field, but i would choose to land at the first airport that i saw. i'm kinda funny that way. thanks for all your help and insight... please set me straight if necessary! cj -----Original Message----- From: owner-aeroelectric-list-server@matronics.com on behalf of Robert L. Nuckolls, III Sent: Sat 9/15/2007 11:15 AM Subject: RE: AeroElectric-List: switch suitability? <nuckolls.bob@cox.net> At 08:37 AM 9/15/2007 -0700, you wrote: >hey all - > >i've spent the morning perusing the archives about switch electrical >ratings, and have read the PDF by Bob on switch ratings, but i'm feeling >like i'm not getting any hard and fast rules about this stuff. in most of >the posts about electrical ratings, someone invariably says "don't loose >any sleep over switch ratings". i'm losing sleep over my switch >ratings. :) i'm considering using some super neato (and also very high >quality) switches, but the ratings are: > >30 volts DC or 125 volts AC, 2.0A res., 0.5A ind. These are generally too small for anything practical in the DC power distribution system. These will require relays to boost the capability of the higher current draw applications. Switches best suited to the task will be rated at 7A or better. They will also be easy to acquire from more than one source. >that's the only info given about them. are these switches appropriate >(safe) for use for all the things you'd find in a "technically advanced" >aircraft? i'm talking things like pitot heat, trim motors, flap motors, >exterior lighting etc? > >also, what about in the place of tying electrical busses together? i'm >considering having an alternate battery feed to the E-buss, and i suspect >that with a fairly heavily loaded E-buss such as the one i'm considering, >these switches would be inadequate? for reference, the E-buss on my ship >has the EFIS, AHRS, one NAV, one COM, autopilot, trim, and flaps. i'd >hate to put a relay in this spot (up the parts count, etc) that is so critical. Suggest you begin with one of the architectures published and then define what failure mode is not being addressed by the diagram as published. Read the chapter on System Reliability. You have too many and the wrong things on the e-bus. Bob . . . ---------------------------------------- ( "Physics is like sex: sure, it may ) ( give some practical results, but ) ( that's not why we do it." ) ( ) ( Richard P. Feynman ) ----------------------------------------




    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
  • 7-Day List Browse
  •   http://www.matronics.com/browse/aeroelectric-list
  • Browse AeroElectric-List 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.

    -- Please support this service by making your Contribution today! --