Today's Message Index:
----------------------
1. 07:20 AM - Relays (Robert L. Nuckolls, III)
2. 11:18 AM - Battery Charger as Ground Power (Craig Winkelmann)
3. 11:26 AM - Re: Battery Charger as Ground Power (woxofswa)
4. 11:44 AM - Re: GPU - 24V System - Crowbar Needed (woxofswa)
5. 12:23 PM - Re: Re: GPU - 24V System - Crowbar Needed (George, Neal E Capt USAF ACC 605 TES/DOA)
6. 12:24 PM - Comm & Nav audio with SPA 400 (Gilles Thesee)
7. 01:09 PM - Re: Comm & Nav audio with SPA 400 (Patrick Hildebrand)
8. 01:12 PM - Re: Comm & Nav audio with SPA 400 (Patrick Hildebrand)
9. 02:00 PM - Re: Battery Charger as Ground Power (Robert L. Nuckolls, III)
10. 02:22 PM - Re: Re: GPU - 24V System - Crowbar Needed (Robert L. Nuckolls, III)
11. 03:11 PM - Re: Re: Ground Power (Walter Fellows)
12. 03:33 PM - Re: Battery Charger as Ground Power (Matt Dralle)
13. 05:11 PM - Re: Re: GPU - 24V System - Crowbar Needed (Ed Holyoke)
14. 05:55 PM - Ground Power Receptacle? ()
15. 06:43 PM - Re: Re: Battery Charger as Ground Power (David L.)
16. 07:16 PM - Re: Battery Charger as Ground Power (Craig Winkelmann)
17. 07:47 PM - Wonky Ammeter Redux (Kevin Jones)
18. 08:42 PM - Re: Re: Battery Charger as Ground Power (Robert L. Nuckolls, III)
19. 08:44 PM - Re: Re: Battery Charger as Ground Power (Robert L. Nuckolls, III)
Message 1
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Subject: Re: relays
Bcc: nuckolls.bob@aeroelectric.com
At 11:06 AM 5/10/2009 +0100, you wrote:
>Hi Bob,
>
>
>I m really struggling to understand how to wire a relay. Whilst I
>understand in principle the wiring, I m struggling to get it to work
>and no amount of reading schematics is sinking into my head!
>
>
>This is what I understand about the relay so far;
>
>Pin 30 is power in
>
>Pin 87 goes to the item to be powered - (let s say fuel pump)
>
>Pin 86 goes to ground
>
>Pin 85 is to the switch.
The numbers you're referring to are artifacts of a European
terminal identification system commonly used in automobiles
and probably other vehicles for decades. It's not uncommon
today to find off-the-shelf relays with terminal markings
molded into the housings that conform to this convention.
The numbering convention is illustrated in the drawing
cited below.
Think of the relay as a big, fat, remotely operated push-
button. Continuity through the push-button in the "relaxed"
state is through terminals 30 and 87a. Power can go either
way through these contacts.
The push-button is remotely operated by a magnetic motor
with coil terminals 85 and 86. It doesn't matter how
you apply 12v to this coil . . . terminal 85 OR 86
can be (+).
When you apply power to the coil, the "push-button"
contacts move to break continuity between 30/87a
and make contact between 30/87. This state is maintained
until you remove power from the coil.
>
>
>At the moment this switch is wired directly to the unit and for me
>that is easy to understand. The fuel pump 12v + is wired to the
>switch on the panel and then into the bus, fuel pump 12v is to
>airframe ground. Press the switch and it works. But put a relay
>in the midst of this and nothing happens apart from frying my brain!
Relays are used to shorten the distance you might
need to run "fat wires" and/or to add functionality.
For example, the switch needed to control the relay
is a simple single-pole, single-throw device but the
relay effects a single-pole, double-throw functionality.
>Is pin 30 the power supply from the bus that would normally go to
>the switch ? I m struggling to understand how to wire the switch
>into this circuit. Whilst this might sound elementary to you Bob,
>I just cannot get my head around it !!
>
>I need an verbatim explanation on how to wire the pump to the bus,
>the switch and the relay. Once I see it in practical terms, i.e.
>this wire goes to this, this wire goes to that, I m sure the penny
>will drop, just as it has on all other problems I ve hit!
There's a drawing on my website at . . .
http://www.aeroelectric.com/PPS/Engine/Fuel/Fuel_Pump.pdf
. . . that describes one way to implement the
wiring you've asked about. Of course, the 10A fuse
and 18AWG wires may need to be resized for your
specific fuel pump . . .
I will invite you to join us on the AeroElectric List
to continue this and similar discussions. It's useful to
share the information with as many folks as possible.
A further benefit can be realized with membership on
the list. There are lots of technically capable folks
on the list who can offer suggestions too. You can
join at . . .
http://www.matronics.com/subscribe/
Ask your question again on the List. I check the List
several times a day and attempt to be responsive as time
will allow. Further, there are 1800 or so subscribers
that include many technically capable teachers. This
is the best venue for assisting you in your studies.
Bob . . .
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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Subject: | Battery Charger as Ground Power |
Bob:
I've been reading some posts on ground power and noted that some people are using
a battery charger as a ground power unit. From what I remember about the output
voltage of almost all battery chargers, there is a significant potential
to overvoltage the aircraft isn't there? The voltage from most chargers is not
filtered and is not as clean as you'd want for powering avionics, etc.
Am I right,
Craig
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243567#243567
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Subject: | Re: Battery Charger as Ground Power |
I'm no expert, but I think you are right.
I think a 12.5 volt "maintainer" would make much more sense. They can be had
at Harbor Freight for $5
For ground tests and assembly, I plan on using a cheapo lawn tractor battery with
a maintainer hooked up to it. The battery would then serve as a sink if there
is a problem with the maintainer.
--------
Myron Nelson
Mesa, AZ
Emp completed, legacy build fuse in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243569#243569
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Subject: | Re: GPU - 24V System - Crowbar Needed |
Can I ask a neophyte question in the quest for further light and knowledge?
Why is a contactor, and/or switch needed for ground power?
It seems to me that the very act of plugging in the plug could serve as "activating"
the power, and pulling the plug out would deactivate it.
What am I missing?
--------
Myron Nelson
Mesa, AZ
Emp completed, legacy build fuse in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243572#243572
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Subject: | Re: GPU - 24V System - Crowbar Needed |
Myron -
Switching the ground power connection allows the pilot full control of the
circuit. Over-voltage warning enhancements provide the opportunity to
monitor and verify that the lineboy has indeed plugged in 12v instead of 24v
- before you light up the internal circuits.
Neal
==================
Can I ask a neophyte question in the quest for further light and knowledge?
Why is a contactor, and/or switch needed for ground power?
It seems to me that the very act of plugging in the plug could serve as
"activating" the power, and pulling the plug out would deactivate it.
What am I missing?
--------
Myron Nelson
Mesa, AZ
Emp completed, legacy build fuse in progress
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Subject: | Comm & Nav audio with SPA 400 |
Hi all,
A buddy is trying to install a KX 155 with a Sigtronics SPA 400 in a two
seater.
He is trying to devise a way to hook up the Nav audio output.
Any suggestions as to how to mix or hook up Comm AND Nav audio ?
Thanks in advance
Best regards,
--
Gilles
http://contrails.free.fr
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Subject: | Comm & Nav audio with SPA 400 |
Usually, there is a audio input or "aux" input for the coms. This is
designed to mix the audio for a variety of devices.
You could try hooking pins 10 and L of connector A1 (Nav high and low) to
Pins H and F of connector A2 (Aux high and low in). This would mix the Nav
audio output into the comm audio input.
Probably accomplish what you need to mix the audio prior to the SAP400.
Patrick
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Gilles
Thesee
Sent: May 11, 2009 1:20 PM
Subject: AeroElectric-List: Comm & Nav audio with SPA 400
<Gilles.Thesee@ac-grenoble.fr>
Hi all,
A buddy is trying to install a KX 155 with a Sigtronics SPA 400 in a two
seater.
He is trying to devise a way to hook up the Nav audio output.
Any suggestions as to how to mix or hook up Comm AND Nav audio ?
Thanks in advance
Best regards,
--
Gilles
http://contrails.free.fr
Message 8
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Subject: | Comm & Nav audio with SPA 400 |
Usually, there is a audio input or "aux" input for the coms. This is
designed to mix the audio for a variety of devices.
You could try hooking pins 10 and L of connector A1 (Nav high and low) to
Pins H and F of connector A2 (Aux high and low in). This would mix the Nav
audio output into the comm audio input.
This would probably accomplish what you need to mix the audio prior to the
SAP400.
Patrick
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Gilles
Thesee
Sent: May 11, 2009 1:20 PM
Subject: AeroElectric-List: Comm & Nav audio with SPA 400
<Gilles.Thesee@ac-grenoble.fr>
Hi all,
A buddy is trying to install a KX 155 with a Sigtronics SPA 400 in a two
seater.
He is trying to devise a way to hook up the Nav audio output.
Any suggestions as to how to mix or hook up Comm AND Nav audio ?
Thanks in advance
Best regards,
--
Gilles
http://contrails.free.fr
Message 9
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Subject: | Re: Battery Charger as Ground Power |
At 01:11 PM 5/11/2009, you wrote:
><capav8r@gmail.com>
>
>Bob:
>
>I've been reading some posts on ground power and noted that some
>people are using a battery charger as a ground power unit. From
>what I remember about the output voltage of almost all battery
>chargers, there is a significant potential to overvoltage the
>aircraft isn't there? The voltage from most chargers is not
>filtered and is not as clean as you'd want for powering avionics, etc.
"Battery Charger" is non-qualified. Technically, any
source of energy that is capable of reversing current
flow into a battery is a 'charger'.
The quality of output power from chargers can be all
over the map. The very first charger I owned was a
6v Tungar rectifier electro-whizzy.
Emacs!
The output quality of this thing would have been
REALLY noisy, ZERO voltage regulation, hideously
inefficient, but entirely suited to keeping my '41
Pontiac straight-6 ready to start on a cold morning.
By the way, anyone interested in exploring/reliving
some of the history of lead-acid battery technology,
feel free to download this item. (Caution 9+ MB)
http://tinyurl.com/owad89
45 years later and at the other end of the spectrum,
we can purchase light, relatively inexpensive, high
quality switch-mode power supplies that will serve as
both ground power supplies for system operations but
battery chargers as well.
Unfortunately, devices tailored to serve as "smart"
chargers (quick recharge, indefinite storage) probably
don't make good ground power supplies because their
internal battery-pampering software gets confused when
the "battery" being maintained keeps changing terminal
voltage and load.
A few years ago, we made a great buy on a quantity
of Samlex 1223 power supplies.
http://www.universal-radio.com/catalog/hamps/2423.html
We offered these as "alternator simulators" with the
suggestion that they could be used to make the ship's
systems believe that a 23A alternator was running.
This would allow the ship's battery to be charged
and ship's systems of up to 20A draw (about anything
but pitot heat) to be tested in the shop.
The short answer is that not all battery chargers
are suited for use as ground power supplies perhaps
due to their particular noise/voltage-regulation
characteristics. However, you can hook any charger
across a battery and give it a try. Make sure you
know how it behaves in the long term (watch bus
voltage) and know it's specific limits. With
a modicum of due-diligence, the experiment offers
minimal risk to system components.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 10
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Subject: | Re: GPU - 24V System - Crowbar Needed |
At 01:38 PM 5/11/2009, you wrote:
>
>Can I ask a neophyte question in the quest for further light and knowledge?
>
>Why is a contactor, and/or switch needed for ground power?
The implementation of ground power connectors
published on my website and discussed on the forums
grew out of the following design goals:
(1) protection from 28 volt ground power being applied
to a 14v airplane.
(2) pilot control of ground power from the left seat.
(3) reverse polarity protection.
(4) convenience of an industry-common connection to
the aircraft relatively free of hazard to ground
crew from spinning props.
Twice in my experience, I've had 28v connected to my
14v airplane. In one case, the line-boy caught the error
and flipped the switch before I could even react. In the
other case he couldn't hear me over the roar of the
ground power cart engine and he had his back to me
watching the gages on the cart. I had to unbuckle,
slide over, open r.h. cabin door and yell at him while
stuff in the airplane suffered.
>It seems to me that the very act of plugging in the plug could serve
>as "activating" the power, and pulling the plug out would deactivate it.
Making and breaking a high current load during
mate/de-mate operations is hard on the connector.
But if you plan to exercise absolute and personal
control over how and under what conditions external
sources of power get hooked to your airplane, then
it might be as simple a task as hooking up the
jumper cables.
But standing in a stream of wet, wind-driven snow
this winter, I got a pair of jumper cables reversed
to my son's van . . . didn't hurt anything but it
sure COULD have. The degree of risk you're willing
to shoulder is up to you.
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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Subject: | Re: Ground Power |
Thanks for the post, your installation is nicely documented.
On Sat, May 9, 2009 at 6:21 PM, Matt Dralle <dralle@matronics.com> wrote:
> At 05:42 PM 5/9/2009 Saturday, you wrote:
> >
> >I am bumping this after a search.
> >
> >I am in the process of putting together a ground power receptacle for my
> RV10.
> >
> >I have ordered a piper receptacle from A. Spruce, and the crowbar and
> contactor from BandC.
> >
> >My primary goals are:
> >
> >1. To be able to come up to a dead airplane, start it from ground power,
> and go fly.
> >
> >2. To be able to charge a dead or weak battery without having to remove
> access panels.
> >
> >3. to be able to provide power during construction/testing with a cheapo
> spare battery. I don't want to buy my ship's battery until the day before
> my first start.
> >
> >I don't necessarily need to be able to switch the ground power on or off.
> I'm okay with the act of putting the plug in as switching it on. However,
> I would like the circuit to die once I pulled the plug out if that makes
> sense.
> >
> >Does the Aero'lectric diagram meet my needs or do I need changes?
> >
> >Anyone have pictures of an installation, preferably in an RV10?
> >
> >--------
> >Myron Nelson
> >Mesa, AZ
> >Emp completed, legacy build fuse in progress
>
>
> Hi Myron,
>
> Attached are some pictures of my GPU power installation in the RV-8. Works
> great and allows me to charge the battery, run the avionics, or start the
> engine. I also included the backbone wiring schematic. I'm using the
> Vertical Power VP-200 electrical system, but the GPU wiring should be fairly
> common. The GPU wiring is shown in the lower right hand side of the
> diagram. I haven't updated the diagram yet, but you might need to add a
> connection between the Sense input on the GPU plug through a Normally Open
> push button to the EBus (and through a small fuse or polyfuse). What I
> found was that the late-model chargers won't turn on their output unless
> they see about 4-5 volts. So, they won't pull the GPU relay down when you
> plug the GPU plug in. The button allows you to pull the relay in and make
> the charger think there is voltage. The only catch is that your aircraft
> battery has to have enough juice to pull the relay down.
>
> Let me know if you've have any questions.
>
> Matt Dralle
> RV-8 #82880 N998RV
> Laying Carpet Out in CAD...
>
>
Message 12
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Subject: | Re: Battery Charger as Ground Power |
At 01:58 PM 5/11/2009 Monday, you wrote:
>At 01:11 PM 5/11/2009, you wrote:
>>
>>Bob:
>>
>>I've been reading some posts on ground power and noted that some people are using
a battery charger as a ground power unit. From what I remember about the
output voltage of almost all battery chargers, there is a significant potential
to overvoltage the aircraft isn't there? The voltage from most chargers is
not filtered and is not as clean as you'd want for powering avionics, etc.
>
> Unfortunately, devices tailored to serve as "smart"
> chargers (quick recharge, indefinite storage) probably
> don't make good ground power supplies because their
> internal battery-pampering software gets confused when
> the "battery" being maintained keeps changing terminal
> voltage and load.
>
> A few years ago, we made a great buy on a quantity
> of Samlex 1223 power supplies.
>
> Bob . . .
I've got one of these Black and Decker BC40EB units that has adjustable charge
output limits in addition to a 110amp starter booster. I'm plugging it into my
GPU plug and use it to run the avionics, charge the battery, and I'm hoping
eventually to jump start the engine when the battery is on the low side. The
only downside seems to be that the unit has to see 4-5volts on the "battery" before
it will turn on its output. This means that it won't flip the GPU relay
and you have to have an external switch to do that.
Bob, does this seem like a good charger/GPU product for aircraft systems?
http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID=17925
Matt Dralle
RV-8 #82880 N998RV
Carpet CAD Drawings...
(1200+ Hours Build Time...)
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Subject: | Re: GPU - 24V System - Crowbar Needed |
Besides keeping the wrong voltage from hitting your battery and buss, a
ground power contactor keeps the fat wire running to the receptacle from
being hot all the time and being a potential shorting hazard.
Pax,
Ed Holyoke
woxofswa wrote:
>
> Can I ask a neophyte question in the quest for further light and knowledge?
>
> Why is a contactor, and/or switch needed for ground power?
>
> It seems to me that the very act of plugging in the plug could serve as "activating"
the power, and pulling the plug out would deactivate it.
>
> What am I missing?
>
> --------
> Myron Nelson
> Mesa, AZ
> Emp completed, legacy build fuse in progress
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=243572#243572
>
>
>
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Subject: | Ground Power Receptacle? |
5/11/2009
Hello Ian, You wrote:
1) "Having spent the last couple of weeks needing to repeatedly recharge my
RV-9A battery,........"
What is abnormal about either your system or your mode of operation that
causes this repeat problem? If there is a fundamental fault in either of
those two areas maybe a fault correction approach rather than an external
charging receptacle band-aid should be considered.
2) "......I can say that an external charging receptacle would have made my
life a lot easier."
Realize that external charging receptacles can come in two different
flavors:
A) A simple low amperage connection system going directly to the battery
that is suitable for connecting a 120 volt input, low amperage output
battery charger / maintainer for just the purpose of recharging /
maintaining the battery.
B) A more elaborate high amperage system that would facilitate cranking the
engine as well as recharging the battery with maybe some additional features
such as reverse voltage protection.
3) "Can anyone tell me the best receptacle to use, that would be the most
standard?"
You would have to decide whether you wanted an A or a B solution in order to
answer the "best" question.
If an A solution satisfies your needs then there are dozens of choices -- it
only requires two wires with some simplistic polarity protection. I have
operated for several years now with just two wires coming directly from my
battery up to the cockpit area. One wire is terminated with a female, fully
insulated, Faston type connector, the other wire is terminated with a male,
fully insulated, Faston type connector. The wires are just tucked out of the
way when not in use. See:
http://www.terminaltown.com/Pages/Page9.html
My battery charger clip ons have been modified with the appropriate stub
wires and Faston type connectors added. One benefit of this system is that I
can connect it up and then attach a volt meter to the charger clips. It
tells me what the battery voltage is. Then I can plug in the charger and
monitor the charging voltage -- very handy.
If only a B solution will satisfy you then look to Bob Nuckoll's published
material on this subject. The most commonly found receptacle and plug
arrangement found at FBO's is the three prong. See here:
http://www.aircraftspruce.com/catalog/elpages/extpowerrect.php
The next most commonly found is the Piper receptacle and plug arrangement.**
See here:
http://www.aircraftspruce.com/catalog/elpages/piperplugsock.php
BUT there is a major "gotcha" that you must be aware of if you have a 12
volt aircraft electrical system and you install one of the above
receptacles -- some ground power carts with the above plugs will only put
out 24 volts. If you zap your 12 volt system with 24 volts you will suffer
damage.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
**PS: There is also a single center post receptacle and plug system similar
in apprearance to the Piper system, but not compatible, that is found on
some Beechcraft airplanes. Very unlikely to find a ground power cart with a
plug compatible with this odd ball receptacle.
========================================================
Time: 12:24:10 PM PST US
Subject: AeroElectric-List: Ground Power Receptacle?
From: Ian <ixb@videotron.ca>
Having spent the last couple of weeks needing to repeatedly recharge my
RV-9A battery, I can say that an external charging receptacle would have
made my life a lot easier.
Can anyone tell me the best receptacle to use, that would be the most
standard? Can you also suggest a good source?
While not planning to fly away on an almost dead battery, I do envisage
moments when it would be useful to start from ground power, and then do
some charging direct from the alternator. I'd imagine that flying
locally would be fairly safe while the battery is being topped up, as
long as your whole panel doesn't shut down if you lose battery.
Ian Brown
Bromont
Quebec
Message 15
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Subject: | Re: Battery Charger as Ground Power |
The little, cheap Harbor Freight "maintainers" work quite well. I have used several.
One key point however, ...many of them come set a tad too high in their
fixed "float" voltage, to my thinking. I have seen them as high as 13.9 v.
The good news, is they can be adjusted to the float voltage that you want. The
little controller box should have a back lid that is lightly glued in place.
Carefully work a very narrow blade screw driver or other tough, but thin device
into the glued seam and work it until the back pops off. Inside is a small
circuit board and potentiometer. It may have a spot of RTV on it. Work this
loose. Turning the pot CW lowers to float voltage. I like about 13.2 v. Others
may want a slightly different setting. I usually locate where the pot slotted
screw adjust hole is located next to the little case and drill a 3/16 hole.
That way, it can be adjusted from the outside. The little unit is quite stable
after you get the setting where you want it. David
---- woxofswa <woxof@aol.com> wrote:
============
I'm no expert, but I think you are right.
I think a 12.5 volt "maintainer" would make much more sense. They can be had
at Harbor Freight for $5
For ground tests and assembly, I plan on using a cheapo lawn tractor battery with
a maintainer hooked up to it. The battery would then serve as a sink if there
is a problem with the maintainer.
--------
Myron Nelson
Mesa, AZ
Emp completed, legacy build fuse in progress
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243569#243569
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Subject: | Re: Battery Charger as Ground Power |
Bob:
Thanks, BUT some GPUs bypass the battery because they are not meant to be a port
for charging the battery. In these cases, whatever comes out of the charger
goes on the main bus. I suspect the right thing is to see how conditioned and
stable the output voltage is prior to plugging the unit into a plane full of
expensive avionics.
Craig
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243643#243643
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Subject: | Wonky Ammeter Redux |
Hello Folks,
I have a problem that is very similar to the Aeroelectric Connection
issue of the same subject from 2001. I've got a Vans -40,0+40 ammeter
(load meter) connected to a 40mV @40A shunt wired exactly (minus the
fuselinks) as Figure Z-13 in the Connection. I also have a 10mV shunt
wired to read the aux SD-8 alternator loads. The signal wires from the
two shunts are controlled by a switch on the panel. Main is wired to
show negative, aux is positive ammeter deflection. The following is my
scenario:
1. Ground operation with engine off; power supplied to main alternator
feed through a radio shack 13.8V 3A supply.
2. Ammeter power is on the E-Bus, with alternate feed switch off.
3. Power supply is providing ~3A and I measure 3.8mV across the shunt.
Shunt voltage to ground is 13.08V.
4. Instrument reads ~3.5mV at the sense wire connections
5. Instrument power voltage is ~12.2 volts
6. Ammeter shows full-scale discharge (negative). If I turn power
supply off, this doesn't change???
If I switch on the E-Bus alternate feed, the ammeter returns to zero.
Instrument voltage increases to 12.6V.
If I power the alternate alternator feed, ammeter shows slight positive
deflection, but nothing near the 35% deflection expected.
I first started running this problem down after seeing large ammeter
deflections with the strobe on without any load applied to the shunt.
How robust are the Vans ammeters and should I invest in a new one or
re-wire the system? Why would opening the E-Bus alternate path cause a
change in ammeter reading? Do I need to feed the ammeter with the same
voltage as the shunt?
Many thanks.
KJ
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Subject: | Re: Battery Charger as Ground Power |
>I think a 12.5 volt "maintainer" would make much more sense. They
>can be had at Harbor Freight for $5
>
>For ground tests and assembly, I plan on using a cheapo lawn tractor
>battery with a maintainer hooked up to it. The battery would then
>serve as a sink if there is a problem with the maintainer.
Actually, the ideal maintainer voltage is just
above 100-200 millivolts the battery's open circuit
voltage 24 hours or so after taking it off the charger.
Lead-Acid batteries, this is 13.1 to 13.2 volts.
The idea is that you want to hold the battery at or
just above it's own chemistry voltage . . . thus
any and all tendencies to self-discharge are supported
by the external energy source. I.e. self-discharge
currents do not tax the chemistry. See:
http://www.aeroelectric.com/Pictures/Curves/Battery_Tender_Recharge.pdf
http://www.aeroelectric.com/Pictures/Curves/Ideal_Recharge_Protocol.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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Subject: | Re: Battery Charger as Ground Power |
At 09:13 PM 5/11/2009, you wrote:
><capav8r@gmail.com>
>
>Bob:
>
>Thanks, BUT some GPUs bypass the battery because they are not meant
>to be a port for charging the battery. In these cases, whatever
>comes out of the charger goes on the main bus. I suspect the right
>thing is to see how conditioned and stable the output voltage is
>prior to plugging the unit into a plane full of expensive avionics.
It's the system integrator's task to decide whether
or not the battery is on line during ground power
connection. I've heard the stories for both cases
for BIG airplanes with BIG batteries and BIG ground
power carts.
For our purposes and considering relative sizes
of our hardware, it's best to have a battery on
line during ground power ops . . . especially
if the power quality of the power source has not
been fully qualified to the task.
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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