Today's Message Index:
----------------------
1. 06:51 AM - Re: Re: Heavy E-Bus & Fuseable Link (Robert L. Nuckolls, III)
2. 07:14 AM - Re: Re: questions about "filter" capacitors (Robert L. Nuckolls, III)
3. 10:31 AM - Re: CD ROM Question (Dave VanLanen)
4. 12:08 PM - Report on the Harbor Freight 42292 battery charger (Robert L. Nuckolls, III)
5. 12:17 PM - Re: Re: CD ROM Question (Robert L. Nuckolls, III)
6. 12:20 PM - Report on the Harbor Freight 42292 battery charger (WITH CORRECTIONS) (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Heavy E-Bus & Fuseable Link |
At 02:55 PM 6/6/2008 -0700, you wrote:
><hammer408@comcast.net>
>
>Bob:
>
>Im installing a Heavy E-Bus architecture, per Z-32.
>Currently my E-Bus load is around 13amps...architecture is:
>18g F-link at E-Bus---14 awg---S704-1 relay---14 awg---10amp fuse at Battery
>Bus.
>
>According to B & C, fuseable links are for low power, 10 amps or less.....so
>should I eliminate the fuseable link and directly wire my 14 g wire to #10
>stud on E-Bus
>OR wire to a 10 or 15 amp fuse on the E-bus - and increase the Battery Bus
>Fuse from 10 amp to 15 amp?
>
>What I'm carring on my E-Bus is basically my Avionic's Panel: 340 audio, 430
>nav/com gps,330 Transponder and 106 Indicator - Amp draw is approx:7 amps,
>but in TRANSMIT Mode, I'm pulling an extra 6 AMPs for a total of about 13
>amps.
>
>Any suggestions appreciated, or should I wire per Z-32, since the extra 6
>Amp in transmit mode is interminent and will only spike to 13 or so amps
>periodically.
FUSIBLE LINKS are recommended ONLY for those places
where shown in the Z-figures and there are no fusible
links in Z-32. Use a 15A fuse for your Z-32 e-bus
alternate feed path. I don't know where B&C got that
10A number. The fuse blocks are factory rated for up to
30A in any given fuse slot . . . My personal design
criteria de-rates them to 15A which is large enough
for 99% of situations. For larger loads I would consider
a FUSIBLE LINK or other form of robust current limiter.
Bob . . .
Message 2
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| Subject: | Re: questions about "filter" capacitors |
At 01:29 PM 6/6/2008 -0700, you wrote:
>
>
>rampil wrote:
> > 22 mFd is what the factory decrees, so that is what a responsible
> builder should used unless there is strong evidence to the contrary.
>
>
>Understood. The 22000 uFd cap is installed and will certainly remain on
>the 914 per Rotax schematics. Rather than wanting to fix what isn't
>broken I'm simply trying to understand where these "magic" numbers come from.
In this particular case, I'll bet that somebody when to
the parts store, bought something that "looks like it will
work" and installed it. When nobody complained about noise
after that, what ever value was in place (22KuF) was called
"golden". It may have been that the 1KuF/Amp rule-of-thumb
was applied. We'll never know.
>rampil wrote:
> > The value of the cap is determined by estimating the resistance of the
> driven system and then the desired tau (time constant) which will give
> the desired degree of smoothing to the DC output. If you don't put a cap
> in, your systems will get rectified AC as the supply waveform, not the
> desired DC.
>
>
>Makes sense, Ira. Thanks. Somewhere there exists an "allowable ripple"
>spec and, given the expected/typical loads on a system, the cap is sized
>accordingly to satisfy the spec.
If we were talking about General Motors or Honda, yeah,
there might be a house spec for maximum allowable noise
to meet corporate design goals. There might even be an
IEEE or SAE spec but there's no practical way of knowing if
Rotax has a spec or consulted anyone else's documents.
Rotax's regulators are supplied by Ducati and since these
folks are in the vehicular electrics business, their
recommendations may well have been the outcome of well
considered conditions. But Rotax probably wouldn't be
aware of it.
In the US aerospace industry, there are generally accepted
recommendations embodied in RTCA DO-160 and Mil-Std-704.
Go to my website and do a site search on "DO-160" and
then another search on "mid-std-704". These two searches
will produce a number of hits on what these documents
are and how they help us.
>Would it be practical for us to estimate the system resistance alongside
>the power budget to derive an educated guess for how big the B-lead cap
>should be? Seems like a science project with little return on investment
>(time/effort), but perhaps it will provide a reasonable ballpark #?
It's a bit beyond 'estimating' . . . the range of
bus impedances can be large depending on size and
condition of battery, numbers of accessories and any
associated internal capacitors, etc.
>Alternatively, is there any harm in simply hooking things up WITHOUT a
>B-lead cap and measuring how "noisy" the bus is before I stick a filter
>cap in the system? This is more of a build-test-fix approach but at least
>I would have data to substantiate the size (and weight and cost) of the
>cap chosen.
ABSOLUTELY! But this has already been done. See:
http://www.aeroelectric.com/Pictures/Curves/SD-8_Noise_Data.pdf
Here I loaded the SD-8 to 10.5 amps and applied
the 1KuF/A rule-of-thumb. Bus noise from the SD-8 was
quite nominal in comparison with the 1.5 v pk-pk
noise that we're told is acceptable under Mil-Std-704
design goals.
But this was one measurement on equipment that I
had access to at the time. The repeatable
experiment is what validates all recipes for success
and any data you can collect and add to our collective
knowledge would no only be appropriate but most
welcome. I've not had an opportunity to 'scope
a Rotax 912 installation.
Bob . . .
Message 3
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| Subject: | Re: CD ROM Question |
I found them. Thank you Bob.
Two additional questions:
- What are .SHX files, and what software is needed to access them?
- Are there any .PDF versions of the wirebook examples contained in
http://www.aeroelectric.com/PPS/ACAD_Wirebook_Samples ? (I attempted to
use the wirebook.exe file, but nothing seems to happen).
Thanks...
Do Not Archive
-----------------------------------------------
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net>
Subject: Re: CD ROM Question
<http://www.matronics.com/searching/getmsg_script.cgi?INDEX=73159197?KEYS=cd
_rom?LISTNAME=AeroElectric?HITNUMBER=1?SERIAL=1015301720?SHOWBUTTONS=NO>
>I downloaded the CD ROM from the AeroElectric website, but I am unable to
>open the various drawings. I was told that the CD ROM should also contain
>.PDF copies of the drawings, but I cannot find them. Am I missing
>something? Does the purchased version contain more than the downloadable
>version? I am trying to find examples of wirebooks and wire labeling
examples.
The .dwg files are opened with AutoCAD or one of its
compatible brothers like TurboCAD V7 or higher.
The downloadable CD is the same as the purchased one
which is the same as the website itself. CAD drawings
are found at:
http://www.aeroelectric.com/PPS/ACAD_Architecture_Dwgs/
the .pdf versions are at:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/
and both directories cited above are mirrored on the
CD
Bob . . .
Message 4
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| Subject: | Report on the Harbor Freight 42292 battery charger |
A short time ago I picked up a version of this device
from Harbor Freight.
http://aeroelectric.com/Pictures/Battery_Chargers/HF_Chargers/42292.gif
Hooked it up to a partially discharged battery yesterday
morning with a data acquisition system to plot its performance.
At .47A load its output voltage is 11.62 volts. At .67A it
drops to 8.33 volts. So with a delta-V of 5.07 and delta-I
of 0.2 the output impedance calculates to 5.07/.2 = 25
ohms. If it were not voltage limited, it would be classified
as a "trickle charger". By adding simple voltage limiting,
it's not capable of damaging a battery but also not capable
of topping off a discharged battery. However, it is entirely
suitable for keeping a charged battery from discharging itself
in long term storage.
If I were choosing sides for HF el-cheeso battery chargers
also suitable for long term storage, it would have to
be the 93258.
http://aeroelectric.com/Pictures/Battery_Chargers/HF_Chargers/HF93258_1.jpg
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 5
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| Subject: | Re: CD ROM Question |
At 12:25 PM 6/7/2008 -0500, you wrote:
>I found them. Thank you Bob.
>
>Two additional questions:
>- What are .SHX files, and what software is needed to access them?
Those are font shape files. Of no use to you unless you plan to open,
edit, print and save the .dwg files in an AutoCAD-like application.
>- Are there any .PDF versions of the wirebook examples contained in
>http://www.aeroelectric.com/PPS/ACAD_Wirebook_Samples
No, the samples are wirebooks-in-progress that were taken
from a client's project years ago. Again, intended to be
starting points for someone interested in saving a lot
of time in to crafting their own wirebooks in a CAD program.
> ? (I attempted to
>use the wirebook.exe file, but nothing seems to happen).
It may not have been obvious but that is a self-extracting
.zip file. After you exercised the file, about a dozen new
files were deposited in the same directory. This too
is a sampling of .dwg files of use only to an individual
with CAD editing capabilities.
Bob . . .
Message 6
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| Subject: | Report on the Harbor Freight 42292 battery charger |
(WITH CORRECTIONS)
At 02:01 PM 6/7/2008 -0500, you wrote:
<nuckolls.bob@cox.net>
A short time ago I picked up a version of this device
from Harbor Freight.
http://aeroelectric.com/Pictures/Battery_Chargers/HF_Chargers/42292.gif
Hooked it up to a partially discharged battery yesterday
morning with a data acquisition system to plot its performance.
At .47A load its output voltage is 11.62 volts. At .67A it
drops to 8.33 volts. So with a delta-V of 5.07 and delta-I
of 0.2 the output impedance calculates to 5.07/.2 = 25
ohms. It is votlage limited to about 13.4 volts of output.
If it were NOT voltage limited, it would be classified
as a "trickle charger". By adding simple voltage limiting,
it's not capable of damaging a battery but also not capable
of topping off a discharged battery. However, it is entirely
suited to keeping a charged battery from discharging itself
in long term storage.
If I were choosing sides for HF el-cheeso battery chargers
also suitable for long term storage, it would have to
be the 93258.
http://aeroelectric.com/Pictures/Battery_Chargers/HF_Chargers/HF93258_1.jpg
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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