Today's Message Index:
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1. 04:55 AM - Converting to externally reg alternator (Bob Verwey)
2. 06:07 AM - Re: Converting to externally reg alternator (Robert L. Nuckolls, III)
3. 06:59 AM - Re: Re: Looking for suggestions (Dan Billingsley)
4. 09:14 AM - Re: Re: Looking for suggestions (Robert L. Nuckolls, III)
5. 09:19 AM - Re: Re: Looking for suggestions (Robert L. Nuckolls, III)
6. 04:58 PM - Regarding Capacitor Filters (Eric M. Jones)
7. 07:26 PM - Re: Re: Looking for suggestions (Dan Billingsley)
8. 09:10 PM - Re: Looking for suggestions (user9253)
Message 1
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| Subject: | Converting to externally reg alternator |
Is the alternator in picture "externally regulated"?
Bob Verwey
Safari ZU-AJF
On 02/04/2012, Bob Verwey <bob.verwey@gmail.com> wrote:
> Does the crowbar module not offer enough protection? With a VFR day
> only, electronic ignition setup, minimal elctrogizmos, does not the
> reserve battery power give a safe reserve?
>
> Bob Verwey
>
>
> On 02/04/2012, ROGER & JEAN CURTIS <mrspudandcompany@verizon.net> wrote:
>> Consider the fact that if automobile regulators had a lower failure rate
>> if
>> they were externally regulated, auto makers would use them. The fact is
>> that
>> BRAND NEW (not rebuilt) Nippon Denso alternators seem to have a
>> nearly-zero
>> failure rate.
>>
>> Then make your decision. I have had several builders send me their
>> external
>> regulators for examination. This cemented my opinion permanently.
>>
>>
>> Eric,
>>
>> I believe that perhaps Bob does agree with you, in that the
>> internally regulated alternator has "nearly-zero" but NOT ZERO failure.
>> Apparently there have been some cases of catastrophic over voltage with
>> no
>> way to shut it down, when in the air. Have you found this to be the case
>> with the externally regulated alternators? With the external regulator,
>> when you shut off power to the regulator it positively shuts down the
>> alternator.
>>
>> I personally feel that the risk is very low with the
>> internal regulation, but also wonder why TC aircraft have continued to
>> use
>> external regulation.
>>
>> Roger
>>
>>
>>
>
Message 2
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| Subject: | Re: Converting to externally reg alternator |
At 06:52 AM 4/16/2012, you wrote:
>Is the alternator in picture "externally regulated"?
>
>Bob Verwey
>Safari ZU-AJF
The parts list for spares lists a regulator
so I would guess that the regulator is internal
to the machine.
Bob . . .
Message 3
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| Subject: | Re: Looking for suggestions |
=0A=0A=0A=0A=0A>________________________________=0A> =0A>=0A>=0A>- I real
ly doubt that the coax ground=0A>- to the airframe is the culprit here .
. .=0A>- unless for some strange, as yet undiscovered=0A>- reason it is
the ONLY ground for that radio=0A>- or cluster of black boxes.=0A>=0A>
- Do all of your box-grounds go to the=0A>- common power bus -If you
were asking do all the box-grounds go to a common ground bus? Yes I have a
ground bus on the firewall that passes through to engine compartment. ALL g
rounds for anything electrical on either side of the firewall was sent to t
his ground bus. Even sent a braided wire to the engine block.=0A>and all sh
ield and=0A>- signal grounds connect to their respective=0A>- LO or GND
pins on the boxes? This I will need to check again, but my initial answer
is I'm fairly certain. The other thing I have discovered in my system yeste
rday...I went to the airport in the morning only to find the new battery de
ad. I charged it and came back later in the day and it was good to go. I ch
ecked both-buses-with everything off and found the Master bus was showi
ng 24mV being pulled. The E-bus was 0 volts. Didn't have time to trace the
-========================
=========== =0A>=0A>
Message 4
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| Subject: | Re: Looking for suggestions |
At 11:52 PM 4/15/2012, you wrote:
I am trying to understand why a ground loop causes problems with
audio noise. To me, a ground loop means that the negative side of
the electrical system is connected to ground at two or more
points. Current has two possible parallel paths: either through the
negative wire or through the airframe. If any voltage is dropped
between the two points where the negative wire is grounded, then the
current going to one load will affect the voltage and thus the
current gong to the other load.
Close. This isn't about dual paths in the same system,
it's about SHARED paths in two systems where a strong
antagonist (alternator, strobe, motor) induces noisy
current into a path SHARED by a potential victim (audio
system, small signal instrumentation, etc).
The ideal electrical system would be grounded at only one point; thus
no current whatsoever would flow through the airframe. That is
difficult to accomplish since avionics are internally grounded to their cases.
Yes. The design goal is to insure that ALL
potential victims in a constellation of
appliances have no shared ground paths with
potential antagonists.
Example: Grounding the headsets and/or microphones
locally causes tiny audio signals to be carried on
an airframe path shared with currents flowing into
or out of alternators, etc.
This is why the avionics ground was crafted.
http://tinyurl.com/7hvmat6
The idea is to CLUSTER all grounds for potential
victims together on the panel before taking a
jumper to power ground on the airframe or at the
fire wall.
General rules for avoiding ground loops is
illustrated in the Z-figures:
http://tinyurl.com/6m3bk8k
http://tinyurl.com/7fnbhqn
http://tinyurl.com/6w87rvb
Bob . . .
Message 5
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| Subject: | Re: Looking for suggestions |
The other thing I have discovered in my system yesterday...I went to
the airport in the morning only to find the new battery dead. I
charged it and came back later in the day and it was good to go. I
checked both buses with everything off and found the Master bus was
showing 24mV being pulled. The E-bus was 0 volts. Didn't have time to
trace the culprit load.
Not sure that a tiny voltage on the bus is significant.
With everything turned OFF, disconnect a battery lead and
put your multimeter in SERIES with that battery lead and
measure CURRENT. If you have a battery bus, there may
be some device like a clock or a device needing memory
support voltage connected to it. A few milliamps of
constant drain is not a big deal . . . as long as you
KNOW and AGREE to the use of that energy. But for most
airplanes, this current will for all practical purposes
be ZERO.
Refresh my memory: What's your radio/audio system
look like?
Bob . . .
Message 6
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| Subject: | Regarding Capacitor Filters |
I have watched the conversation regarding the big capacitor for filtering the generator/alternator/dynamo/etc.
and want to make a few comments:
1) Usually a capacitor doesn't get charged to a higher voltage that was applied.
But this is not true in all cases. Capacitors can and do "space charge" (all
by themselves) to extremely high voltages. Really big, efficient, very high ESR
(Equivalent Series Resistance--usually high voltage) caps are stored and shipped
with a shorting strap for this reason. And yes, this doesn't have much to
do with OUR situation. ...but just sayin'....don't learn stuff that ain't true.
2) Capacitors are almost always used with a "bleeder" resistor that guarantees
that any retained charge will be dissipated in a short time after the power is
removed. A capacitor is really a battery that should be disconnected or discharged
if you are going to crash your airplane. You can calculate this (Google
"capacitor bleed resistor calculator") but for general purposes a 200 ohm 2W resistor
across the capacitor terminals will lower 15V to 5V in 5 seconds for a
22000 uF cap). Should you add one? Consider that the resistor improves the filtering
all by itself and only add 75 mA to the load. So YES!
2) An electrolytic capacitor can be subjected to any number of insults. Some of
these can easily be prevented. Lets look at a typical part: A CDE Capacitor about
the size of a D-cell battery: SLPX223M025H5P330 X 40 mm. 25 Vdc (32 Vdc Surge)
High applied voltages damage the foil plates. These plates are self-healing usually,
but they steadily degrade. Use a parallel Zener with a Vz below the withstand
V of the capacitor for a longer, happier life.
Temperature. Keep the cap far away from major heat sources (easy). Keep the cap
from extreme cold (harder). Watch those environmental specs. Capacitor actually
perform better HOT, but have shorter lifetimes. At -40C cold (brrrrrr) the
capacitance is about 1/10 of what it is when hotbut they warm up fast.
Common Electrolytic caps have a limited lifetimein this example 3000 hours. So
you should perhaps replace it with at engine TBO, or if permanency is what you
want, choose a different part.
For filtering, a capacitor is only part of the answer. Any decent filter uses a
resistor (R), an inductor (L), in addition to a capacitor (C). These are called
RLC filters, and usually have a small ceramic cap and a Zener too. Standard
automotive filters are made like this and work fine in 14.5V aircraft applications.
See: http://www.jmkfilters.com/autofilterssc1.htm
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=371002#371002
Message 7
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| Subject: | Re: Looking for suggestions |
=0A=0A=0A=0A=0A>________________________________=0A> =0A>=0A>The other thin
g I have discovered in my system yesterday...I went to the airport in the m
orning only to find the new battery dead. I charged it and came back later
in the day and it was good to go. I checked both buses with everything off
and found the Master bus was showing 24mV being pulled. The E-bus was 0 vol
ts. Didn't have time to trace the culprit load.=0A>=0A>=0A>- Not sure th
at a tiny voltage on the bus is significant.=0A>- With everything turned
OFF, disconnect a battery lead and=0A>- put your multimeter in SERIES w
ith that battery lead and=0A>- measure CURRENT. If you have a battery bu
s, there may=0A>- be some device like a clock or a device needing memory
=0A>- support voltage connected to it. A few milliamps of=0A>- consta
nt drain is not a big deal . . . as long as you=0A>- KNOW and AGREE to t
he use of that energy. But for most=0A>- airplanes, this current will fo
r all practical purposes=0A>- be ZERO.=0A>=0A>- Refresh my memory: Wh
at's your radio/audio system=0A>- look like?=0A>PM1000=0A>Garmin SL-40
=0A>I also took a shortcut doing pinouts between avionics with a commercial
junction box made by-http://www.approachfaststack.com/hubs.html- I use
d the Pro-X.=0A>It was quite a time saver, they have good reviews and they
were quite-thorough. If interested I have a connection schematic from the
m.=0A>Dan-=0A>=0A>- Bob . . . =0A>=0A>-=0A>=0A>=0A>=0A>=0A>
Message 8
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| Subject: | Re: Looking for suggestions |
Bob,
Since noise can be caused by two or more circuits sharing the same conductor, would
it help to use a larger conductor? Have any experiments been done comparing
noise with various wire sizes?
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=371015#371015
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