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 |
|
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 |
|
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 |
|
Subject: | switch suitability? |
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 |
|
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 |
|
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 |
|
Subject: | switch suitability? |
-----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 |
|
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 |
|
Subject: | switch suitability? |
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
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! --
|