Today's Message Index:
----------------------
1. 04:16 AM - Re: Battery Contactor (Robert L. Nuckolls, III)
2. 05:22 AM - Re: Microair CS experiment update (Mark Phillips)
3. 05:27 AM - Re: Run away alternator scenario (Vince Ackerman)
4. 07:19 AM - Re: Run away alternator scenario (Robert L. Nuckolls, III)
5. 07:27 AM - Re: Microair CS experiment update (Robert L. Nuckolls, III)
6. 07:42 AM - Re: Microair CS experiment update (David Chalmers)
7. 08:08 AM - BS-1 bond studs disappearing fast (Robert L. Nuckolls, III)
8. 08:14 AM - Re: Microair CS experiment update (Richard@riley.net)
9. 08:15 AM - Re: Fuse Holders (Robert L. Nuckolls, III)
10. 08:29 AM - Re: Dual Alts (Robert L. Nuckolls, III)
11. 08:53 AM - Re: Ground loop ... (Robert L. Nuckolls, III)
12. 08:57 AM - FW: Fuse Holders (David Swartzendruber)
13. 09:02 AM - Loadmeter Troubleshooting (Ross Mickey)
14. 09:02 AM - Re: AMP / Cannon Connectors (Robert L. Nuckolls, III)
15. 09:05 AM - Re: AMP / Cannon Connectors (Robert L. Nuckolls, III)
16. 09:18 AM - Re: Fastons (Robert L. Nuckolls, III)
17. 10:57 AM - Re: Ground Loop (MikeM)
18. 02:24 PM - Re: Inductive current measuring device .... (Robinson, Chad)
19. 03:41 PM - Re: AMP / Cannon Connectors (David Schaefer)
20. 03:50 PM - Re: Microair CS experiment update (Chris Byrne)
21. 04:00 PM - Fuse Holders (Kingsley Hurst)
22. 07:28 PM - Re: AMP / Cannon Connectors (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Battery Contactor |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 04:22 PM 10/29/2003 -0700, you wrote:
>--> AeroElectric-List message posted by: Larry <larry@grrok.com>
>
>How can I verify that the battery contactors have closed in a dual battery
>system, Figure Z-30. It is easy to verify that the contactor coils are
>energized but system voltage will be established as soon as the one of the
>two battery contactors close. This condition can be detected during
>preflight by switching: Main Battery, Both, Aux Battery but I think there
>has to be a more elegant method.
The best way is to have a switched voltmeter that can read
each battery bus. If you had one battery and an e-bus, putting
the voltmeter on the e-bus is sufficient. With two batteries,
using the voltmeter to read battery busses is a good way to
see that the contactors are closed. One could put lv warning
sensors on the battery busses too . . . but these would need
some switching so that they're drawing current only when the
alternator is working. If the alternator is off line, then
you're either parked or in a battery only ops mode where
you'd NOT want to have the lights flashing at you. Perhaps
reversed sense lvwarn circuit with no flasher would be cool.
Have the light come on ABOVE 13.0 volts and make them green
lamps that might be labeled MAIN BAT, AUX BAT.
There are a number of options you could consider. Most builders
aren't worrying about it. It's easy to pre-flight by turning on
one battery at a time. After you're airborne, there is a slight
chance of contactor failure but it doesn't represent a hazard
to flight and is easily spotted at next pre-flight. If it were
my airplane, I think I'd consider the pre-flight testing to
be sufficient.
Bob . . .
Message 2
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| Subject: | Re: Microair CS experiment update |
--> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
Microair has asked me to send the radio back to the factory for repair- can
anyone who's gone through this recommend the best way to ship? Their return
information mentions airmail and UPS or FedEx.
Thanks - Mark in TN
Mark Phillips wrote:
> --> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
>
> Bob-
> I received the replacement processor from Ian at Microair one week from
> his offering to send it- pretty good from Oz to TN it would seem! I was
> able to borrow the proper removal tool and replacement was simple (talk
> about clever packaging!!). Unfortunately, it was not the problem and
> the radio behaves the same as before. I have e-mailed Microair
> requesting further guidance and will let y'all know what happens...
>
> Mark
>
> At 07:44 AM 10/24/2003 -0500, you wrote:
> >Yessir- here's the reply from Oz:
> >
> >"G,day mark,
> >Sorry you are having radio problems,I have just returned from 2 weeks
> >leave,hence the delay in reply.It seems from your description you may
> have a
> >microprocessor problem.Do you think you could replace it if i sent one
> to
> >you.It is a plug in device.
> >Regards Ian.G." (Ian Games)
> >
> Interesting! Owner maintained radios. What will they think of
> next.
>
> I am encouraged that Microair has taken this tiny leap
> into crafting a cooperative and more useful relationship
> with their customers.
>
> Let us
> know how the great Microair experiment plays out . . .
>
> Bob . . .
>
Message 3
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| Subject: | Re: Run away alternator scenario |
--> AeroElectric-List message posted by: Vince Ackerman <vack@mac.com>
Trying to get my meager brain around a few things.... if the battery
contactor failed and disconnected the battery while the alternator was
running, what would be the consequences/ indications? If there was a
normal load (radios, strobes, etc) it would still provide power to the
busses or would it behave differently?
Vince Ackerman
On Oct 28, 2003, at 19:50, Robert L. Nuckolls, III wrote:
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <bob.nuckolls@cox.net>
>
>
>>
>> ...................SKIP...............We've got an external voltage
>> regulator
>> powered via a 5 amp field supply breaker. However, virtually all light
>> aircraft then power the field breaker from the battery side of the
>> 'B' lead
>> fuse/breaker (typically 40 to 60 amps rating).
>> If this main breaker/fuse opens, the VR senses low voltage and
>> maximizes
>> alternator field current in the impossible attempt to restore 13.8 to
>> 14.5
>> volts on
>> the disconnected buss. The result is 100+ volts at the alternator B
>> terminal
>> and sometimes severe alternator damage involving the faults
>> mentioned. In my
>> opinion, the field supply breaker should be powered from the
>> alternator side
>> of the main breaker. Regards, Mike>>
>
> This has circulated around the lists for years. The scenario
> is true IF you open the b-lead breaker without also shutting
> off the field . . . and this can be REALLY important for the
> majority of certified airplanes where the b-lead breaker is
> designed to nuisance trip (see chapter 17 of the 'Connection).
>
> Modern OBAM aircraft designs provide sufficient headroom in b-lead
> protection to prevent the dreaded condition cited. So, the only
> time we expect b-lead protection to open is when shorted diodes
> or some other serious malady has befallen the alternator in which
> case, the thing needs to be worked on anyhow. The design goal is
> to protect the AIRPLANE from the alternator, not protect the
> alternator from itself. By eliminating the probability of nuisance
> tripping the b-lead protection, concerns cited in this anecdote
> are alleviated.
>
> Bob . . .
>
>
> _-
> =======================================================================
> _-
> =======================================================================
> _-
> =======================================================================
> _-
> =======================================================================
> >
>
>
Message 4
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| Subject: | Re: Run away alternator scenario |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 05:27 AM 10/30/2003 -0800, you wrote:
>--> AeroElectric-List message posted by: Vince Ackerman <vack@mac.com>
>
>Trying to get my meager brain around a few things.... if the battery
>contactor failed and disconnected the battery while the alternator was
>running, what would be the consequences/ indications? If there was a
>normal load (radios, strobes, etc) it would still provide power to the
>busses or would it behave differently?
Assuming that you have active notification of low voltage
like I would have in my airplane, you'll have a light flashing
at you within seconds of the failure.
Bob . . .
Message 5
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| Subject: | Re: Microair CS experiment update |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:17 AM 10/30/2003 -0600, you wrote:
>--> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
>
>Microair has asked me to send the radio back to the factory for repair- can
>anyone who's gone through this recommend the best way to ship? Their return
>information mentions airmail and UPS or FedEx.
I recommend airmail parcel post where you can get a
2# package there in 6-10 days. You can
also buy insurance a parcel post package. Total
cost of shipping and insurance about $26.00
( See http://ircalc.usps.gov ) You'll need
to fill out customs form PS Form 2976-A cause
the radio is over $400 in value.
They will return the radio to you at their
expense and probably by air mail as well.
Bob . . .
Message 6
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| Subject: | Microair CS experiment update |
--> AeroElectric-List message posted by: "David Chalmers" <David@ChalmersFamily.com>
I just returned my Microair 760 for repair. Sent it airmail and it got there very
quickly. I got the radio back 10 days after I sent it.
-----Original Message-----
From: Mark Phillips [mailto:ripsteel@edge.net]
Subject: Re: AeroElectric-List: Microair CS experiment update
--> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
Microair has asked me to send the radio back to the factory for repair- can
anyone who's gone through this recommend the best way to ship? Their return
information mentions airmail and UPS or FedEx.
Thanks - Mark in TN
Mark Phillips wrote:
> --> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
>
> Bob-
> I received the replacement processor from Ian at Microair one week from
> his offering to send it- pretty good from Oz to TN it would seem! I was
> able to borrow the proper removal tool and replacement was simple (talk
> about clever packaging!!). Unfortunately, it was not the problem and
> the radio behaves the same as before. I have e-mailed Microair
> requesting further guidance and will let y'all know what happens...
>
> Mark
>
> At 07:44 AM 10/24/2003 -0500, you wrote:
> >Yessir- here's the reply from Oz:
> >
> >"G,day mark,
> >Sorry you are having radio problems,I have just returned from 2 weeks
> >leave,hence the delay in reply.It seems from your description you may
> have a
> >microprocessor problem.Do you think you could replace it if i sent one
> to
> >you.It is a plug in device.
> >Regards Ian.G." (Ian Games)
> >
> Interesting! Owner maintained radios. What will they think of
> next.
>
> I am encouraged that Microair has taken this tiny leap
> into crafting a cooperative and more useful relationship
> with their customers.
>
> Let us
> know how the great Microair experiment plays out . . .
>
> Bob . . .
>
Message 7
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| Subject: | BS-1 bond studs disappearing fast |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
We had about 800+ of the BS-1 bond studs a couple of months
ago . . . we're down to less than 100. I'm in no big hurry
to get rid of them but I thought I would let list-readers
get first dibs on what's left. I have no source for more.
Bob . . .
--------------------------------------------
( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
--------------------------------------------
Message 8
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| Subject: | Re: Microair CS experiment update |
--> AeroElectric-List message posted by: Richard@Riley.net
I sent mine USPS Airmail, it came back the same way. Total turnaround was
8 days. I was VERY impressed.
At 07:17 AM 10/30/03 -0600, you wrote:
>--> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
>
>Microair has asked me to send the radio back to the factory for repair- can
>anyone who's gone through this recommend the best way to ship? Their return
>information mentions airmail and UPS or FedEx.
>
>Thanks - Mark in TN
>
>Mark Phillips wrote:
>
> > --> AeroElectric-List message posted by: Mark Phillips <ripsteel@edge.net>
> >
> > Bob-
> > I received the replacement processor from Ian at Microair one week from
> > his offering to send it- pretty good from Oz to TN it would seem! I was
> > able to borrow the proper removal tool and replacement was simple (talk
> > about clever packaging!!). Unfortunately, it was not the problem and
> > the radio behaves the same as before. I have e-mailed Microair
> > requesting further guidance and will let y'all know what happens...
> >
> > Mark
> >
> > At 07:44 AM 10/24/2003 -0500, you wrote:
> > >Yessir- here's the reply from Oz:
> > >
> > >"G,day mark,
> > >Sorry you are having radio problems,I have just returned from 2 weeks
> > >leave,hence the delay in reply.It seems from your description you may
> > have a
> > >microprocessor problem.Do you think you could replace it if i sent one
> > to
> > >you.It is a plug in device.
> > >Regards Ian.G." (Ian Games)
> > >
> > Interesting! Owner maintained radios. What will they think of
> > next.
> >
> > I am encouraged that Microair has taken this tiny leap
> > into crafting a cooperative and more useful relationship
> > with their customers.
> >
> > Let us
> > know how the great Microair experiment plays out . . .
> >
> > Bob . . .
> >
>
>
Message 9
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:34 AM 10/30/2003 +1000, you wrote:
>--> AeroElectric-List message posted by: "Kingsley Hurst"
><khurst@taroom.qld.gov.au>
>
>
>Do not archive
>
>Re fuse holders at http://www.bussauto.com/pdf/rta.pdf
>
>Bob N.
>
>Thank you for your reply and for passing this info on to B&C. Hope they
>oblige. Could have knocked me over with a feather when you said you
>hadn't heard of them!!
>
>Dave and William
Not being in the parts business, I don't track new
product developments as tightly as I used to. Talked to
B&C about these fuseblocks. Tim noticed and pointed out
that the output terminals are not supplied with the fuseblock.
One needs to acquire Delphi Pack-Con Series III terminals
which are, no doubt, crimped on. This means special tools
too. Soooooo . . . it's B&C's decision not to add these critters
to their catalog.
Bob . . .
Message 10
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:39 PM 10/29/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Jim Butcher" <europa@triton.net>
>
>Bob,
>
>I'm building a europa with Rotax 914. The plan is to use Z-13 with a SD20
>for one alternator and the Rotax alt for the other. Will two alternators
>work together to charge the battery? Neither one has the capacity to keep
>up, but the two together do.
>
>Thanks
I presume that since you know that two outputs added together
will carry your loads, you have done a rudimentary load analysis.
Is your SD-20 going to run from the vacuum pump pad on the 914?
If I recall correctly, this pad is pretty slow compared to a
Lyc or Continental. You won't get 20A out of it unless you're
going to direct drive from the crankshaft at the back. I've seen
some installations that do this. In this case, you'll get 40A
from the SD-20 and the Rotax's built in alternator can be your
standby power source.
Can you share more of your design intentions and along with
details of your load analysis?
Bob . . .
Message 11
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| Subject: | Re: Ground loop ... |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:19 AM 10/28/2003 +0100, you wrote:
>--> AeroElectric-List message posted by: "Michel RIAZUELO"
><mt.riazuelo@wanadoo.fr>
>
>Hi all,
>
>I have heard about "ground loop". Who can tell me more or indicate where
>are the things I have to read ?
>
>I am thinking about the wiring of my MCR SPORTSTER.
>
>I will have a ground block under the seats and a mini battery bus (fuse
>holder) for the trim and flaps (and can be later for the heating seats!!).
>I would have also a ground block on the firewall (engine side) and finally
>the principal bus, the essential bus and the main ground block behind of
>instrument panel.
>
>For information, MCR SPORTSTER is a composite carbon epoxy aircraft and
>the tank is located between the firewall and the instrument panel.
>
>
>Do I risk problems with this ground blocks layout ?
I didn't get to this for a couple of days . . . you've had
several replies, all of which contain some facts and a few
of which have poorly explained or erroneous information.
Do you have a copy of the AeroElectric Connection? There's
a chapter on grounding and another on system noise issues
that would be good starting points for understanding
how it all works.
The short answer is a single point ground block on the firewall.
An example of a product can be seen at:
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?26X358218
Many builders have fabricated their own ground blocks. If
you choose to do so, consider brass studs made from brass
screws where the heads are soldered to the back side of
the buss-plate. Then use locknuts to insure mechanical
integrity of the joints. Minimum recommended diameter of
stud would be 8-32 thread (US) or 4mm in any other thread
standard.
Since your airplane is composite, a min 5/16 brass stud
(8.5mm) should tie grounds aft and forward of firewall
together. Crankcase ground strap and battery (-) wires
go right to this bolt. All other accessories get their
own, independent ground wires to studs on either front
or backside of the firewall.
Bob . . .
Message 12
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--> AeroElectric-List message posted by: "David Swartzendruber" <dswartzendruber@earthlink.net>
Charlie,
If you look at the Bussman info, the fuseholders are made in sections;
the two end sections and center sections. These snap or interlock
together somehow to make whatever size of fuseholder is needed. I would
think that the individual sections would be available to buy and stock
so that a builder could specify and purchase whatever configuration they
wanted. If B&C doesn't want to do this, I'll research it and find a way
of doing it.
The output terminals are the one disadvantage of this fuseholder. They
are crimped onto the wire that feeds the electrical load and then
inserted into the fuseblock. The blade of the fuse inserts directly
into this terminal. I say it's a disadvantage because it will require a
crimping tool that most builders won't have. If I do this, I'll make
terminals available bare, or already crimped onto a length of
MIL-W-22759/16 wire. The other disadvantage of the output terminal is
that it appears that 16AWG is the smallest size wire that is
accommodated. If this is true, we could probably get around it by
stripping the smaller wire twice as far and doubling it over.
Well, I just looked at my inbox before sending this message and saw
Bob's report that B&C is not going to add this to their catalogue. I'll
begin to look into it myself.
Dave Swartzendruber
Wichita
>
> Dave,
> I noted that they say they can supply other sizes as a special order.
I
> want 2 of these, BUT without a split bus. I would like a 12 fuse unit
and
> a 16 fuse unit (both with single bus). I don't see a listing for
output
> terminals of 18-22 AWG listed. Are they available? Let me know if
this is
> possible? Could you get a photo of the connector for these blocks?
> Charlie Kuss
Message 13
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| Subject: | Loadmeter Troubleshooting |
--> AeroElectric-List message posted by: "Ross Mickey" <rmickey@ix.netcom.com>
Bob,
I installed one of your Voltmeter/Loadmeters in my RV6A. I started the
engine for the first time this week and the voltmeer works fine. The
Loadmeter, however, does not move no matter how many electrical goodies I
turn on.
Can you give me some direction in trobleshooting?
Ross Mickey
N9PT
Inspection on Nov 6th
Message 14
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| Subject: | Re: AMP / Cannon Connectors |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:08 PM 10/28/2003 -0800, you wrote:
>--> AeroElectric-List message posted by: "David Schaefer"
><dschaefer1@kc.rr.com>
>
>Bob .. this may be more of a philosophical question vs. a 'best
>electrical practices' question. I've always been taught not to 'break'
>a wire if it can be avoided i.e. a solid wire was better than two
>pieces.
>
>However, now that I've got miles of wire strung out I'm becoming
>enamored with cannon connectors both bulkhead and in-line to make my
>life easier and make the airplane more serviceable when I'm on my back
>under the panel! When I look at 'production' planes from 747's to
>F-16's I see gaggles of cannon-type plugs and they seem to have workable
>electronics.
>
>What are the plusses and minuses of using these connectors? Breaking
>wires? I've got access to good gold-plated pins etc.
Plusses are convenience of installation and maintenance.
Minuses are cost of installation and ownership with
reduced reliability. Use connectors where they're
really going to help out over the next ten years
of owning and maintaining your airplane. Just 'cause
AT Category airplanes are full of connectors doesn't
make a direct translation to being a good idea for
your project. Consider the trade-offs, make a decision
and drive ahead. Whatever you decide to do will probably
have no serious consequences one way or the other.
My connector of first choice is the D-sub with machined
pins. This selection is based on commonality with many
products that use d-subs and availability of low cost tools
and pins. If you need other form factors, consider the
Amp plastic circular connectors
http://dkc3.digikey.com/pdf/T033/0220-0221.pdf
in Series II uses same pins as d-sub, Series I uses
heavier pins that can be installed with the low-cost
b-crimp tool from B&C.
Bob . . .
Message 15
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| Subject: | AMP / Cannon Connectors |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 09:23 AM 10/29/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Jim Stone" <jrstone@insightbb.com>
>
>Peter, do you have a part number?
>Jim
I would avoid Deutsch . . . I've had enough problems with
their connectors and relays over the years to write them
of my list of preferred components for new design.
If you need a metal connector MS3470 series devices
or more modern Mil-C-38999 connectors. These are getting
pretty pricey . . . let's talk about it before you go
out to buy something.
Bob . . .
Message 16
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:56 AM 10/28/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>Bob (et al),
>
>I've read your various epistles on Fastons and I fully agree. My experience
>is that the Faston to quick-fit connections are superior in many ways to
>most other fastening methods.
>
>I do a lot of design with Fastons and Mosfets that invariably leads to the
>issue of how much current a female Faston and the mating pcb "quick-fit"
>terminal is rated for. Info is hard to come by.
>
>My presumption is -- if Fastons are sold in AWG 10 sizes-- then it is only
>reasonable that the proper quick-fit terminal should be assumed to carry the
>rated AWG 10 ampacity. (Which depends more on the wire insulation melting
>point than anything else.)
Actually, 10AWG is good up to 30A . . . I don't think I'd load
a fast-on that heavily. The fuse-blocks are rated for up to 30A
per slot but there are few places where we need more than 10A continuous
with short intervals of 15-18A (pitot heaters). For long service
life, I de-rate fast-ons to 10A continuous, 20A short term surge
irrespective of wire size. In a nice, clean low stress environment
they're probably okay for 30A but given that we don't NEED to load
them that heavy, I'll suggest it's a good design philosophy to
de-rate as I've cited above.
One concern for performance at high currents are the
side forces induced by fat wires like 10AWG. All the "magic"
in a fast-on joint happens in the very low area, high pressure
grooves. Any force that deflects the terminal perpendicular
to the face of the fast-on tab can only act to reduce effectiveness
of that interface.
Bob . . .
Message 17
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--> AeroElectric-List message posted by: MikeM <mladejov@ced.utah.edu>
> From: Michel RIAZUELO
>
> I think (I hope!) I have understood the philosophy of "single
> not ground"and I will try to respect it !
That's "Single POINT Ground"
> I think too that the layout I plan and dscribe in my first
> message, is near the "radial grounds" concept you describe.
> I am lucky!
In the case of an airframe where the alternator/engine is in the
front, the battery is in the back, and the cabin is in the
middle, I would describe the power grounds as a "backbone",
where the backbone is the aircraft, or a conductor capable of
carrying the starter cranking current...
If the battery and alternator are near the engine, then things
get way easier. You will have a Radial ground system where the
center is the minus lead of the battery, but the all of the
spokes are really short.
> Please, allow me two questions:
>
> (1) I will use a MED 80 for the monitoring of my ROTAX 912 (
> http://www.bwavio.com/manuali/man_med_80_usa.pdf ). It collect
> informations from probes on the engine (witch certainly have
> engine-ground) and have its own electrical feed. If I have
> well understand, I have to wire the MED 80 ground up to engine
> ground and keep its frame isolated with the instrument panel.
> Am I right ?
If you can do that, by all means. If not, then all of the
avionics can be concentrated in another region of the same panel
area where the MED80 is mounted and you can still have a "single
point ground" for the avionics as long as nothing related to the
audio grounds anywhere else.
> (2) I will use the diagram recommended by Bob for the
> ignition blocks and the starter commands with 2 swithes S700
> 2-5. The two "put to ground "wires, killers of ignition will
> be shielded. Should they be connected only to the "engine
> ground" or also to the ` instrument panel ground " (as ROTAX
> said) and might have a "ground loop" ?
You are very perceptive. The magnetos are defacto grounded by
being bolted to the engine. To prevent a mag from sparking, the
P-lead must be shorted to the magneto case using a magneto
switch. You have at least four options:
1. Unshielded P-lead wires, with common side of OFF-L-R-BOTH
switch grounded to panel. This relies on the fact that the panel
is connected to the airframe, then to the firewall, then via a
ground strap across the engine mount to the engine cradle, then
to the engine, and finally through the engine to the mag case.
This is a very bad idea, because when the engine is running, the
P-leads have very high risetime pulses of hundreds of volts on
them, which radiate like an antenna into radios (at radio
frequencies), or can capacitively couple into nearby audio
wiring.
2. Shielded, insulated-sleeve coaxial wires with the P-lead on
the center conductor, and the shield grounded to the mag case at
the engine end, and the shield connected only to the common side
of the mag switch (no jumper to the panel).
3. Same as above, but add a "safety" jumper from the com side of
the mag switch to the panel.
4. Install two feedthru style coaxial rfi low-pass filters in
the firewall. Use shielded wire between the mag and the filter.
Then you dont have to shield the P-leads on the panel side of
the firewall, and then it doesn't matter if you ground the
common side of the Mag switch to the panel. The low-pass filters
block the high-rise time high amplitude pulses from appearing on
the panel side of the firewall. My 1958 Piper Pacer has these.
From a radio/audio noise (single point ground) standpoint, 2 is
the preferred method. Some will say that 3 (with jumper)
is needed for "safety" (redundant shorting path back to the
mag). However, if the shield in 2 breaks, the worst that will
happen is that you will have a "hot mag" until you fix it.
Since the return path from panel to mag is so circuitous, I
question the "added safety" argument.
If the jumper in 3 is installed, then you have connected the
panel to the engine block via the shields of the two P-leads.
This maybe a good thing for your engine instruments, but may be
a bad thing for your radio/audio systems. I have to do this in
my Skylane, because the ground jumper is mandated by an AD.
Mike Mladejovsky
Skylane '1MM
Pacer '00Z
Message 18
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| Subject: | Inductive current measuring device .... |
--> AeroElectric-List message posted by: "Robinson, Chad" <crobinson@rfgonline.com>
Jim Sower wrote:
>
> Now THAT could be a solution. It takes a lot of panel space, but that might
> be negotiable. I checked the specs for the AMP25 and AMP200 and figured
> they would need some supporting circuitry. I was hoping I could maybe
> connect it to the meter I have after removing the shunt and get the accuracy
> I need (vaguely accurate, charge and discharge magnitudes). Guess not. The
> CS50P would "plug and play" and I could open up the panel hole to accept it.
> Thanks a million for the heads up ... Jim S.
Jim, I hate to be a party pooper, but if you'll tolerate my playing devil's advocate
for a moment, consider ALL of the aspects (drawbacks too) before you go
forward.
This thing weighs half a pound, and costs $70 or so. That's not terrible in an
industrial situation, but compared to a $25 shunt that weighs a quarter as much,
it's not as great of a deal.
This unit's is more accurate than most - about a third of an amp max error at 50A.
You still have a resistor here to convert that 50mA to voltage for the meter
(the same way the shunt would have done).
Finally, you need to equip this thing with a bipolar power supply. Their handbook
mentions the PT78NR112, which will certainly do this, but it's again added
complexity. You could also use the "Output proportional to sensed current" example
schematic on page 7 of their handbook, but it's still additional components,
and you lose half the device's accuracy in that case.
Ampsense's handbook at:
http://www.ampsense.com/HANDBOOK%203.pdf
addresses many of these details if you're still interested. These may still fit
your bill and I hope I haven't "killed the dream" but the sensors do take some
care to use.
Regards,
Chad
Message 19
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| Subject: | AMP / Cannon Connectors |
--> AeroElectric-List message posted by: "David Schaefer" <dschaefer1@kc.rr.com>
Thanks for the info. I'm actually using the AMP plugs with gold pins
you pointed out. Is there any 'electrical' loss, noise etc. inserted
when breaking a wire with one of these connectors and quality pins?
David
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Subject: Re: AeroElectric-List: AMP / Cannon Connectors
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
At 08:08 PM 10/28/2003 -0800, you wrote:
>--> AeroElectric-List message posted by: "David Schaefer"
><dschaefer1@kc.rr.com>
>
>Bob .. this may be more of a philosophical question vs. a 'best
>electrical practices' question. I've always been taught not to 'break'
>a wire if it can be avoided i.e. a solid wire was better than two
>pieces.
>
>However, now that I've got miles of wire strung out I'm becoming
>enamored with cannon connectors both bulkhead and in-line to make my
>life easier and make the airplane more serviceable when I'm on my back
>under the panel! When I look at 'production' planes from 747's to
>F-16's I see gaggles of cannon-type plugs and they seem to have
workable
>electronics.
>
>What are the plusses and minuses of using these connectors? Breaking
>wires? I've got access to good gold-plated pins etc.
Plusses are convenience of installation and maintenance.
Minuses are cost of installation and ownership with
reduced reliability. Use connectors where they're
really going to help out over the next ten years
of owning and maintaining your airplane. Just 'cause
AT Category airplanes are full of connectors doesn't
make a direct translation to being a good idea for
your project. Consider the trade-offs, make a decision
and drive ahead. Whatever you decide to do will probably
have no serious consequences one way or the other.
My connector of first choice is the D-sub with machined
pins. This selection is based on commonality with many
products that use d-subs and availability of low cost tools
and pins. If you need other form factors, consider the
Amp plastic circular connectors
http://dkc3.digikey.com/pdf/T033/0220-0221.pdf
in Series II uses same pins as d-sub, Series I uses
heavier pins that can be installed with the low-cost
b-crimp tool from B&C.
Bob . . .
==
==
==
==
Message 20
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| Subject: | Re: Microair CS experiment update |
--> AeroElectric-List message posted by: "Chris Byrne" <jcbyrne@ozemail.com.au>
Mark
If your sending it to Australia, send it Via the post. Its light and wont
cost much. I sent a package about the same size (slightly lighter) to the
States 18mths ago, it took about 4 days and cost about $6.00 US.
Call it radio for repairs on the customs sticker and mark the value way down
(its not worth much U/S) and then it wont attract the attention of the
customs duty man on the way in.
Send it VIA UPS or FedEx and it will cost a fortune for them to handle it
and clear it through customs etc.
My last package that was mistakenly sent FEDEX cost me $60.00 freight and
another $30 to be put through customs then they added the actual duty.
(all for about 2lbs in a padded envelope)
Chris Byrne
Sydney
Message 21
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--> AeroElectric-List message posted by: "Kingsley Hurst" <hurstkr@growzone.com.au>
Do not archive
Re fuse holders at http://www.bussauto.com/pdf/rta.pdf
Bob N.
Thank you for your reply and for passing this info on to B&C. Hope they
oblige. Could have knocked me over with a feather when you said you
hadn't heard of them!!
Dave and William
I agree we should wait to see what B&C does. I have to order other
items from them in the near future so it would be more convenient for me
if the fuse blocks will be available through them.
However if this does not eventuate Dave, I certainly would appreciate
the insurance of having you as a stand-by if you don't mind. Thank you
too for posting the cost of these items as I was unaware or this aspect
before.
Cheers
Kingsley Hurst
Europa Builder in Oz
Message 22
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| Subject: | AMP / Cannon Connectors |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 05:45 PM 10/30/2003 -0800, you wrote:
>--> AeroElectric-List message posted by: "David Schaefer"
><dschaefer1@kc.rr.com>
>
>Thanks for the info. I'm actually using the AMP plugs with gold pins
>you pointed out. Is there any 'electrical' loss, noise etc. inserted
>when breaking a wire with one of these connectors and quality pins?
>
>David
Unfortunately, there is no such thing as a 0-ohms joint (except
in the superconducting world) and worse yet, every cut and paste
in a circuit path can open "cracks" where the wedges of environmental
mischief are driven in. This doesn't mean we can't do very, VERY
good joints taking care in selection of materials and techniques
for installation. Fortunately, the typical wire-to-wire interface
through a good connector is measured in the hand-full of milliohms
which are almost never significant in terms of system performance.
The risks are totally bounded by effects of time-in service
and your ability and willingness to learn how to do it right the
first time and every time.
I would guess that Beechjet has perhaps thousands of pin-socket interfaces
that pass through hundreds of connectors. Many of these airplanes
are 20+ years old with connectors that have never been de-mated
for any reason. In spite of the fact that it "rains" inside one
of these machines every time it descends from altitude, the vast
majority of joints have maintained operational integrity for
a satisfyingly long time. They're all gold plated with gas-tight
crimps.
Bob . . .
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