Today's Message Index:
----------------------
1. 05:36 AM - Re: Alternator output (Robert L. Nuckolls, III)
2. 06:08 AM - Re: Re: Multimeter problem (Robert L. Nuckolls, III)
3. 06:29 AM - Re: Regulator output (Doerr, Ray R [NTK])
4. 07:01 AM - Re: Alternator output (Vern W.)
5. 09:04 AM - ICOM PTT ()
6. 09:36 AM - ICOM PTT ()
7. 09:46 AM - Re: Re: Multimeter problem (Paul Wilson)
8. 12:17 PM - Re: AeroElectric-List Digest: 33 Msgs - 07/06/05 (joelrhaynes@AOL.COM)
9. 01:37 PM - Battery Isolation. (BobsV35B@AOL.COM)
10. 07:04 PM - Re: Battery Isolation. (Robert L. Nuckolls, III)
11. 10:27 PM - Re: alternator testing (Doug Gray)
Message 1
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| Subject: | Alternator output |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 01:46 PM 7/7/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: "RV Builder (Michael Sausen)"
><rvbuilder@sausen.net>
>
>I believe B&C sells a regulator specifically to keep the backup alternator
>offline until the bus voltage drops below a specific point. This is
>probably what you want. Someone else can chime in with the part specifics.
This is the SB-1 regulator crafted for certified installations
similar to Z-12 where both alternators share a common main bus.
This is not recommended for new design but that doesn't mean
it won't work. But it was intended for UPGRADING a certified
ship where the standby alternator was added to an existing
architecture that was difficult to change.
ANY adjustable regulator can be set up for autoswitching.
Run both altenrnators all the time. Set the standby regulator
for 1 volt or so BELOW the normal bus voltage. When the main
alternator comes up, the standby regulator simply relaxes
believing that it has control of the bus and that the bus
voltage is presently too high . . . the standby alternator
shuts down.
If the main alternator quits, the bus voltage sags and the
standby alternator comes on line to pick up whatever slack
it is capable of handling. The low voltage warning circuitry
in the regulator was not useful so we converted it to a
"alternator active" detection circuit. When the main alternator
goes down and the standby switches automatically, we wanted
a light to indicate the event.
Nothing magic or very special and easy to accomplish with
generic hardware if Figure Z-12 rings your chimes. This mode
of operation MIHGT work with an SD-8 . . . it would have to
be tested. The SD-8's regulator does not operate with
the same precision as the wound-field alternators.
Bob . . .
Message 2
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| Subject: | Re: Multimeter problem |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 04:15 PM 7/7/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: Paul Wilson <pwilson@climber.org>
>
>Thanks Eric,
> I had been using the bad meter and was trying to figure why the batt
>always read low suspected it needed charging. Yes it was a distraction. I
>am off this issue and will find a better meter to use in the shop and call
>the question resolved. The GB meter is one I leave at home for messing with
>AA powered gadgets. It only cost around $10 compared to the RS ones which
>were much more expensive.
> BTW I did try Chad's suggestion and the numbers were all over the place
>because the meters wont read amps that are accurate enough.
>
> Hey guys, suggest a cost effective meter that I can rely on.
I have a half dozen multimeters of various manufacture and
yes, some are from Radio Shack. Two are from Fluke with one
of them being over 30 years old. The to Flukes agree with
each other to 2 parts per thousand (0.2%), all others agree
with the Flukes to within 5 parts per thousand (0.5%). One
of the el-cheeso instruments came from Sears with Craftsman's
brand on it for $19.95 . . . it agreed to 0.3%
I used to give away a multimeter as part of the door prizes
for my weekend seminars. I purchased a dozen devices from my
supplier for under $5 each and they all tracked the Flukes
to better than 1.0%.
Modern technology offers the ability to craft a lot 0f accuracy
into a measurement system to the extent that price of the
instrument is driven more by mechanical features (ruggedness)
and marketing (Fluke buys full page ads in journals circulated
world wide).
If one desires off-the-shelf, no doubts assurances of quality
and accuracy, anything with John Fluke's name on it can be
relied upon to meet advertised performance for decades of
reasonable use (I dropped a Fluke from a tower once . . .
it didn't survive).
However, it's not useful to sniff at anything less just
because it doesn't have a brand or history to support it.
When I buy a new instrument, I check it against the Flukes
and make note of it's shortfall should it be more than
1.0% in error. There are some excellent buys out there
but you have to "trust but verify".
I was saddened when they outlawed mercury cells. The RM
series cells at room temperature were VERY accurate
sources of 1.345 volts that could be used to check voltmeters.
Nowadays, you can buy an off-the-shelf, precision
voltage reference factory trimmed to better than 1 part
in 4000 for an accuracy of 0.025% for a few dollars and
build your own voltmeter checker.
There is no value in making simultaneous battery readings
with these modern instruments. All have input impedances of
10 megohms or more and variability of independent versus
simultaneous readings is down in the nanovolt region.
Finally, the voltmeter is a rough check of battery capacity
due to a number of variables. It anyone has concerns about
whether a battery is fully charged. Put a 14.2 volt power
supply on it and wait until recharge current drops below
0.2A or so (Concord uses 0.5A). Then you KNOW the battery
is topped off. Similarly, keeping a battery stored on
a talented maintainer is another sure bet for knowing that
the battery is charged to it's FULL CAPACITY, whatever
it happens to be. This does not mean that the battery is
still capable of factory-new capacity, that's a different
test.
The short answer to the question is check at sears for
a little blister-packed multimeter like the one you see
illustrated in:
http://www.aeroelectric.com/articles/LowOhmsAdapter_3.pdf
I found this particular device to be a very good value
at $20. If you know someone with a Fluke or other laboratory
grade instrument, it wouldn't hurt to check any multimeter
you have against it. But most manufacturers only offer
1.0% accuracy with a handful going to 0.5% or below. Just
because the critter displays 4 digits should not imply
accuracy that may not be there.
Bob . . .
Message 3
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| Subject: | Regulator output |
--> AeroElectric-List message posted by: "Doerr, Ray R [NTK]" <Ray.R.Doerr@mail.sprint.com>
Could you not also run with the Essential Buss Bypass switch on.
This would allow the current to flow through the switch and not the
diode, whereby eliminating the voltage drop across the diode. The down
side with this is that if you don't get an early indication that your
alternator failed, you would have used up some of your reverse battery
power while the master was still on. On the plus side, there is no
voltage drop on the essential bus and no high current via the diode.
The diode would simply ensure that if the master is off and the
essential bus bypass is no, then current will not flow from the
essential buss to the main buss.
Thank You
Ray Doerr
-----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: Regulator output
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
At 11:56 AM 7/7/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: Charlie Brame
<chasb@satx.rr.com>
>
>Bob, et. al.,
>
>The electrical system in my RV-6A is configured very close to Bob's
>Z-13, All Electric on a Budget. I have a B&C alternator and a Ford
>equivalent regulator which is adjustable and bench set to 13.8 volts.
>With the main contactor off and using the essential bus only, I show
>about 13.5 volts at the bus. However, when using the normal system with
>the essential bus powered through a diode, the essential bus only shows
>12.8 volts. This is understandable considering the loss through the
>contactor and the diode.
>
>My avionics and my gyros (ADI and DG) are connected via the essential
>bus and I wonder if a higher voltage would improve both radio and gyro
>perfomance somewhat.
>
>My question is: should I up the regulator voltage in order to get close
>to 13.8 volts at the essential bus when using the main or normal
system?
>This would result in 14+ volts on the main bus, but that shouldn't
>adversely affect anything, IMHO.
No. When the alternator is running, it's set for 13.8 plus which
puts
13.0 plus on the e-bus. When when the alternator stops, you move the
e-bus feed directly to the battery which delivers it's capacity over
the range of 12.5 down to about 11.0 volts.
Assuming you've chosen instruments that are designed to operate
over the range of battery supply voltages, then I'll suggest that
an alternator-ON operating voltage of 13.0 to 13.8 is superior
to the still satisfactory alternator-OFF operating voltage of
11.0 to 12.5.
The diode drop is, therefore insignificant. Further, the energy
dissipation
differences between the various technologies are also insignificant
while the alternator is operating because you have a 500+ watt,
unlimited duration energy source supplying all the BTUs. When you're
down to battery-only ops, then energy expenditure needs to be
considered
more closely . . . This is why you seldom see a diode of any kind
downstream of a battery feed in my drawings.
Bob . . .
Message 4
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| Subject: | Re: Alternator output |
--> AeroElectric-List message posted by: "Vern W." <vernw@ev1.net>
I'd like to ask a simple follow-up question here, Bob.
In a scenario of Z13/8 with only the one main battery existing in the
system, if (for example) a lug breaks on the battery and it's taken out of
the system, will the main alternator continue to power the system? Or
without the battery in the system, would there be a voltage runaway and the
main alternator would have to be taken offline? ... (If that were the case,
then the SD8 would have no chance of coming alive by itself).
If the main alternator WOULD continue to power the system within the
proper voltage range (due to it's regulator controlling the voltage?), and
the SD8 is then switched on, would the SD8 come alive using the voltage from
the main alternator as the exciter? And then would the SD8 continue to power
the system on it's own without a battery in the system?
What I'm trying to get straight in my head is the various failure
scenarios possible and how the "surviving" components are expected to react.
Vern
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
Subject: AeroElectric-List: Alternator output
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
>
> At 10:53 AM 7/7/2005 -0700, you wrote:
>
> So my all electric IFR plane (no mech fuel pump) will have main alt and
> an SD-8 for backup.
>
> My question is around failure detection.
>
> It seems to me NOT to be a good idea to rely on voltage reduction to
> detect an alternator failure, because it may take a while for the volts
> to dip if at all.
>
> Absolutely not true. Batteries charge, and alternators are set
> down. A low voltage light set for 13.0 volts comes on in seconds
> after
> the alternator quits.
>
> A much better way would appear to be to use the Dynon engine management
> system to measure current from the alternator and to set an alarm below
> the minimum day VFR loads...This alarm would send an audio tone thru my
> headset...
>
> This method should work fine if I only had one alternator...with the
> SD-8 I have 2 and the current may not drop that low because the min day
> VFR could be a s low as 7 to 8 amps, depending on voltage the Main alt
> may only be generating a couple of amps and a failure difficult to
> detect.
>
> An alternative would be not to run the SD-8 unless I had to...I.e keep
> it switched off...if the main alt dies or trips on OV I get a low
> current alarm...Then bang on the SD-8 and start load managing.
>
> That's the recommended operating procedure. SD-8
> stays off until after you get a low-volts light
> to show that main alternator is off. Then turn
> SD-8 ON, Main battery master OFF. Continue in en route
> endurance mode until airport in sight. Close battery
> master contactor to bring main bus up to use any
> equipment you like for approach to landing.
>
> Bob . . .
>
>
Message 5
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--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: Charlie Brame
<chasb@satx.rr.com>
<<I can't speak to the ICOM IC-A4. I have an ICOM IC-A23 which I also use
as a comm backup. With my headset plugged into the A23, the side button
PTT works as advertised - i.e., it transmits with a good side tone. I
can also plug in a separate PTT switch which works just as well. My
headset adapter is an ICOM product, but the separate PTT switch is an
off brand item. Charlie>>
7/8/2005
Hello Charlie Brame, Does the off brand PTT switch that you use have the
normal standard sized (larger) PTT switch plug or the small 3.5mm size plug?
Each switch would get plugged into the headset adapter in a different place
/ manner.
Thanks, OC
PS: One of the more aggravating aspects of trying to sort through what
should be a rather simple problem is that some of ICOM's PTT switches are
identified as being used with only certain of their radio models when I
think that there is really only one ICOM 3.5mm PTT switch for use with all
of their radios when using a headset adapter.
Message 6
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--> AeroElectric-List message posted by: <bakerocb@cox.net>
AeroElectric-List message previously posted by: Charlie England
<ceengland@bellsouth.net>
<<My reply was rather poorly worded. I should have said that mine actually
works fine in both xmit & rcv using the headset adaptor & the builtin
PTT. I assumed that you had no 2nd radio to test with, & the led is a
pretty strong indicator that the button is doing what it claims to do.
Consider the extra design/circuit work involved in making it light under
both conditions of transmit & no-transmit.>>
from another post:
<<....skip....RE:operation while charging issues, if the radio would be
damaged by external charge
voltage due to operating on 9.6 V, the battery would also be damaged rather
quickly from the same overvoltage. It is so simple to design this feature
into the radio that it never occurred to me to question the rep's word about
it.
I was shocked & disgusted when I discovered that he lied about it & that I
couldn't use ship's power, even with a purpose built adapter, to both keep
the
battery topped off & operate the radio. (Ahh well... rants about ICOM's
?integrity?
are best left for another post.) Good luck with your testing, Charlie>>
7/8/2005
Hello Charlie England, I don't know why one would assume that the 9.6 volt
battery would be damaged when exposed to a DC charging source of greater
than 9.6 volts. I am under the impression that to charge a battery one must
apply more than its nominal voltage output. And the ICOM charger that I have
says it puts out 12 volts DC. The ICOM IC-A4 manual says 12-16 charging
volts is OK.
Obviously there is some voltage level above which the battery would be
damaged just as there some applied voltage level above 9.6 volts by which
the radio itself would be damaged if turned on or transmitted from. ICOM
apparently is sensitive to the issue of damage to their radios from too high
a voltage source applied through the battery charging port so they mislead
you in their manuals to stop you from operating and possibly damaging your
radio while charging.
But I don't know why they would mislead us about the non functioning of the
IC-A4 on set transmitter button while the headset adapter is installed if
the button and the radio works OK just like Charlie Brame says it does for
the IC-A23.
ICOM Tech Support, do you wish to comment?
OC
Message 7
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| Subject: | Re: Multimeter problem |
--> AeroElectric-List message posted by: Paul Wilson <pwilson@climber.org>
Bob, Sorry to belabor this issue, but two more questions please:
I just want a meter that tells me the battery status. Then I can put on the
charger as needed. I thought that the table published in the Battery tender
flyer was good enough. It says a fully changed batt (after a 12 hr rest)
would have 12.6-12.8v and one with 12.2-12.4v would be charged at 50-75%
based on the chemistry of the battery. Thus that 3+% is a big deal to me
and my meters showed a spread of more than 1% and therefore I am being
misled about my battery condition.
I suspect my newest ~$10 GB meter is accurate, but I would like to know.
1) Bob can you make available the gadget to test the meter discussed in
your link below?
I hate to throw away a meter/s until I know how they test. I have zero
confidence that I can build your gadget. lots easier to test the MM than to
drive to town and use the battery guys Fluke.
Related question to bolster my confidence.
2) Am I correct that the Schumacher WM1562A charger/maintainer meets the
criteria for a properly charging these RG batteries?
I like your method of just putting a smart charger on the batt an then one
knows it is charged fully.
Thanks for your wisdom, Paul
=====================
At 07:07 AM 7/8/2005, you wrote:
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
><nuckollsr@cox.net>
>
>At 04:15 PM 7/7/2005 -0600, you wrote:
>
> >--> AeroElectric-List message posted by: Paul Wilson <pwilson@climber.org>
> >
> >Thanks Eric,
> > I had been using the bad meter and was trying to figure why the batt
> >always read low suspected it needed charging. Yes it was a distraction. I
> >am off this issue and will find a better meter to use in the shop and call
> >the question resolved. The GB meter is one I leave at home for messing with
> >AA powered gadgets. It only cost around $10 compared to the RS ones which
> >were much more expensive.
> > BTW I did try Chad's suggestion and the numbers were all over the place
> >because the meters wont read amps that are accurate enough.
> >
> > Hey guys, suggest a cost effective meter that I can rely on.
>
>
> I have a half dozen multimeters of various manufacture and
> yes, some are from Radio Shack. Two are from Fluke with one
> of them being over 30 years old. The to Flukes agree with
> each other to 2 parts per thousand (0.2%), all others agree
> with the Flukes to within 5 parts per thousand (0.5%). One
> of the el-cheeso instruments came from Sears with Craftsman's
> brand on it for $19.95 . . . it agreed to 0.3%
>
> I used to give away a multimeter as part of the door prizes
> for my weekend seminars. I purchased a dozen devices from my
> supplier for under $5 each and they all tracked the Flukes
> to better than 1.0%.
>
> Modern technology offers the ability to craft a lot 0f accuracy
> into a measurement system to the extent that price of the
> instrument is driven more by mechanical features (ruggedness)
> and marketing (Fluke buys full page ads in journals circulated
> world wide).
>
> If one desires off-the-shelf, no doubts assurances of quality
> and accuracy, anything with John Fluke's name on it can be
> relied upon to meet advertised performance for decades of
> reasonable use (I dropped a Fluke from a tower once . . .
> it didn't survive).
>
> However, it's not useful to sniff at anything less just
> because it doesn't have a brand or history to support it.
> When I buy a new instrument, I check it against the Flukes
> and make note of it's shortfall should it be more than
> 1.0% in error. There are some excellent buys out there
> but you have to "trust but verify".
>
> I was saddened when they outlawed mercury cells. The RM
> series cells at room temperature were VERY accurate
> sources of 1.345 volts that could be used to check voltmeters.
> Nowadays, you can buy an off-the-shelf, precision
> voltage reference factory trimmed to better than 1 part
> in 4000 for an accuracy of 0.025% for a few dollars and
> build your own voltmeter checker.
>
> There is no value in making simultaneous battery readings
> with these modern instruments. All have input impedances of
> 10 megohms or more and variability of independent versus
> simultaneous readings is down in the nanovolt region.
>
> Finally, the voltmeter is a rough check of battery capacity
> due to a number of variables. It anyone has concerns about
> whether a battery is fully charged. Put a 14.2 volt power
> supply on it and wait until recharge current drops below
> 0.2A or so (Concord uses 0.5A). Then you KNOW the battery
> is topped off. Similarly, keeping a battery stored on
> a talented maintainer is another sure bet for knowing that
> the battery is charged to it's FULL CAPACITY, whatever
> it happens to be. This does not mean that the battery is
> still capable of factory-new capacity, that's a different
> test.
>
> The short answer to the question is check at sears for
> a little blister-packed multimeter like the one you see
> illustrated in:
>
>http://www.aeroelectric.com/articles/LowOhmsAdapter_3.pdf
>
> I found this particular device to be a very good value
> at $20. If you know someone with a Fluke or other laboratory
> grade instrument, it wouldn't hurt to check any multimeter
> you have against it. But most manufacturers only offer
> 1.0% accuracy with a handful going to 0.5% or below. Just
> because the critter displays 4 digits should not imply
> accuracy that may not be there.
>
>
> Bob . . .
>
>
Message 8
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| Subject: | Re: AeroElectric-List Digest: 33 Msgs - 07/06/05 |
--> AeroElectric-List message posted by: joelrhaynes@aol.com
I have an IC-A22 that works just fine with a large plug headset adapter and a
non-Icom PTT switch used as you suggest.
Joel Haynes
Bozeman, MT
RV-7a canopy
bakerocb@cox.net wrote:
>--> AeroElectric-List message posted by: <bakerocb@cox.net>
>
>7/6/2005
>
>Hello Experts, I have an ICOM IC-A4 hand held radio that I carry in my
>airplane as a communications back up. I also have the ICOM OPC-752 Headset
>Adapter cable accessory, but I do not have the separate ICOM 3.5 mm diameter
>PTT switch accessory for keying the transmitter while using the radio with
>that adapter and a headset. The manual says that the transmitter keying
>button on the side of the radio will not work when the headset adapter is
>plugged in.
>
>According to a diagram in the ICOM IC-A4 manual the ICOM PTT switch simply
>connects the tip of the microphone plug to the shank of the microphone plug
>in order to key the IC-A4 transmitter.
>
>My question is: Can I instead use my standard push-to-talk switch, with the
>larger diameter sized microphone receptacle and plug such as David Clark and
>Telex sell, in line with the microphone plug from the headset to the OPC-752
>Adapter to key the IC-A4 transmitter?
>
>ICOM refuses to answer this question for me by saying they won't comment on
>any one else's equipment. Thanks.
>
>OC
>
>PS: I suppose that there is no substitute for an actual trial test, but I
>haven't been able to get two people and another radio together to run such a
>test.
>
Message 9
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| Subject: | Battery Isolation. |
--> AeroElectric-List message posted by: BobsV35B@aol.com
Would Anyone On The AeroElectric-List care to comment on this dissertation?
Happy Skies,
Old Bob
"Fred,
The make-before-break switch and two-switch approaches would work, but a
third possibility, which intrigues me the most, is to use no switches at all.
I
suspect that the backup/redundancy capability you are looking for could be
accomplished automatically by the appropriate use of isolation diodes.
Consider this approach:
- Alternator output is connected to main bus and battery #1 as usual.
- Main bus also charges battery #2 through an isolation diode which
prevents battery #2 from discharging onto main bus.
- Battery #2 and main bus both feed power to an essential power bus
through isolation diodes, so that the essential power bus is powered by
whichever of those two have the higher voltage.
Under normal circumstances, the essential power bus is powered from the main
bus (alternator and Battery #1). If the main bus voltage drops below the
voltage of Battery #2, then the essential power bus is powered by Battery #2.
Hook essential items (#1 gps/nav/com, audio panel, transponder, electric
gyros, cockpit lighting, etc.) to essential power bus. Hook everything else
(especially anything with a motor or heating element) to main bus.
Look ma, no switches!
Whatcha think?
Best...Mike
P.S. I'd probably use 100-amp silicon rectifiers for the isolation
diodes. They should be heat-sinked, since they could dissipate up to 70
watts of heat at their maximum 100-amp current capacity.
At 03:17 AM 7/8/2005, Fred Scott, Jr wrote:
How can two batteries be selected so as to switch from BATT1 to BATT2
without losing voltage (for a few milliseconds) to the load as the selection occurs?
>
Some of our Beech aircraft (P-Barons, 58TC, etc.) have Alternate
Battery busses..these come alive only with MASTER OFF and AVIONICS OFF.
Turning power OFF, even for an instant, and then back ON will re-boot most
electronic devices.
>
If you are switching to an alternate buss, that=B9s the wrong time to be
rebooting anything.
>
To explain. Let=B9s say we add a second ship=B9s battery, for backup. One of my
thoughts would be to have a [ Batt1<--> Batt2 ] selector that can ONLY be
physically released to detents as BATT1 or BATT2, yet must slide through and
maintain an electrical BOTH ON (internally, not as a detent, and only as the
selection occurs) as the Battery source is selected from 1 to 2 or vice versa.
When the new position is achieved, the switch would then disconnect
>from the previous source.
>
Is this nuts? Anyone in the electrical world know how to do this? Are such=20
selectors available? ..... or:.. How to insert a non-interrupt delay of some
sort? My KLN-94 has that internally. One assumes: for the purpose of
avoiding re-boots.
>--
>Fred W. Scott, Jr. _fscott@bundoranfarm.com_
(http://b3.mail.yahoo.com/ym/beechowners.com/Compose?
Tofscott@bundoranfarm.com&YY2888&orderdown&sortdate&pos0)
>BUNDORAN FARM please visit us at... _http://www.bundoranfarm.com_
(http://www.bundoranfarm.com/)
>1801 Bundoran Drive
>North Garden, VA 22959
>
>Office 434-295-4188 ; fax 977-2552
>Home 434-293-9221 ; fax 963-4888
Michael D. Busch, A&P/IA
SAVVY AVIATOR, INC.
URL: _http://www.savvyaviator.com/_ (http://www.savvyaviator.com/)
Email: _mike.busch@savvyaviator.com_
(http://b3.mail.yahoo.com/ym/beechowners.com/Compose?Tomike.busch@savvyaviator.com&YY2888&orderdown&sortdate&pos0)
Message 10
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| Subject: | Re: Battery Isolation. |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
Not sure I deduce the rational but the core seems to be
avoid having any glitches cause the pilot to do
anything . . . but I wonder if the writer would be fond
of moving map displays, engine analyzers and any number
of goodies on the panel that require much more NON-PILOTING
thought and attention than it takes to observe a low voltage
warning light and flip a few switches.
Interesting thing about this thinking is that the writer
may be putting a lot of effort into mitigating workload
for an event that may NEVER happen while plenty of
other electro-whizzies guaranteed to be distractions
are also a part of his "complete" design.
If it's not a 'sin' to expect a pilot to operate
engine, flight and nav-aid controls as a normal course
of aviating from A -> B then it seems that the effort
to eliminate one or two switches that may never have to
be operated under duress is not a good return on investment
of design time.
Without seeing schematics of what's being proposed, I
cannot comment on the how well the system being described
meets the writer's design goals. The more interesting
question might be to deduce exactly what the design goals
are.
Bob . . .
At 04:36 PM 7/8/2005 -0400, you wrote:
>--> AeroElectric-List message posted by: BobsV35B@aol.com
>
>Would Anyone On The AeroElectric-List care to comment on this dissertation?
>
>Happy Skies,
>
>Old Bob
>
>"Fred,
>
>The make-before-break switch and two-switch approaches would work, but a
>third possibility, which intrigues me the most, is to use no switches at
>all. I
>suspect that the backup/redundancy capability you are looking for could be
>accomplished automatically by the appropriate use of isolation diodes.
>Consider this approach:
>
>- Alternator output is connected to main bus and battery #1 as usual.
>
>- Main bus also charges battery #2 through an isolation diode which
>prevents battery #2 from discharging onto main bus.
>
>- Battery #2 and main bus both feed power to an essential power bus
>through isolation diodes, so that the essential power bus is powered by
>whichever of those two have the higher voltage.
>
>Under normal circumstances, the essential power bus is powered from the main
>bus (alternator and Battery #1). If the main bus voltage drops below the
>voltage of Battery #2, then the essential power bus is powered by Battery #2.
>
>Hook essential items (#1 gps/nav/com, audio panel, transponder, electric
>gyros, cockpit lighting, etc.) to essential power bus. Hook everything else
>(especially anything with a motor or heating element) to main bus.
>
>Look ma, no switches!
>
>Whatcha think?
>
>Best...Mike
>
>P.S. I'd probably use 100-amp silicon rectifiers for the isolation
>diodes. They should be heat-sinked, since they could dissipate up to 70
>watts of heat at their maximum 100-amp current capacity.
>
>At 03:17 AM 7/8/2005, Fred Scott, Jr wrote:
>How can two batteries be selected so as to switch from BATT1 to BATT2
>without losing voltage (for a few milliseconds) to the load as the
>selection occurs?
> >
>Some of our Beech aircraft (P-Barons, 58TC, etc.) have Alternate
>Battery busses..these come alive only with MASTER OFF and AVIONICS OFF.
>Turning power OFF, even for an instant, and then back ON will re-boot most
>electronic devices.
> >
>If you are switching to an alternate buss, that=B9s the wrong time to be
>rebooting anything.
> >
>To explain. Let=B9s say we add a second ship=B9s battery, for backup. One
>of my
>thoughts would be to have a [ Batt1<--> Batt2 ] selector that can ONLY be
>physically released to detents as BATT1 or BATT2, yet must slide through and
>maintain an electrical BOTH ON (internally, not as a detent, and only as the
>selection occurs) as the Battery source is selected from 1 to 2 or vice
>versa.
>When the new position is achieved, the switch would then disconnect
> >from the previous source.
> >
>Is this nuts? Anyone in the electrical world know how to do this? Are such
>selectors available? ..... or:.. How to insert a non-interrupt delay of some
>sort? My KLN-94 has that internally. One assumes: for the purpose of
>avoiding re-boots.
Message 11
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| Subject: | Re: alternator testing |
--> AeroElectric-List message posted by: Doug Gray <dgra1233@bigpond.net.au>
Bob,
Re: http://www.aeroelectric.com/articles/Alternators/Alternator_Test.pdf
The paper suggests (to me anyway) that the alternator field plus regulator current
load alone
exceeds 2 Amps. I am a little surprised that this is so high and I had not factored
it in to my
load analysis.
Is this a typical load, and if so for what sized alternator?
How does this current vary with alternator load?
Is the rating of an Alternator inclusive of this load? That is, does an alternater
rating of say 30
Amps mean the Alternator 'system' can suppply 30Amps or only 28Amps if we assume
the regulator and
field are drawing 2 Amps.
Doug Gray
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