Today's Message Index:
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1. 01:56 PM - Re: Analyze This (Peter Pengilly)
2. 03:29 PM - Re: Voltage/Current Measurement & Logging (Robert L. Nuckolls, III)
3. 08:15 PM - Northstar M-3 GPS internal battery (Kelly McMullen)
Message 1
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| Subject: | Re: Analyze This |
Its not me who needs the answers ...
On 08/02/2014 18:50, Jeff Luckey wrote:
> Peter,
>
> Thanks for taking the time to review the drawing. I really appreciate
> the insightful comments.
>
> My responses are mixed-in with you questions.
>
> Thx again,
>
> -Jeff
>
> ------------------------------------------------------------------------
> *From:* Peter Pengilly <peter@sportingaero.com>
> *To:* aeroelectric-list@matronics.com
> *Sent:* Saturday, February 8, 2014 1:08 AM
> *Subject:* Re: AeroElectric-List: Analyze This
>
> Jeff,
>
> I would like a little explanation of the basic operation. I'm assuming
> both master switches on all the time, both batteries are the same,
> throw one battery away each year.
>
> Yes - both masters on for normal ops. In addition,
> at start-up by turning-on each master individually and
> watching the power indicators & volt meter you can
> confirm that isolation diodes are functioning properly.
>
>
> If alternator fails no simple load shedding is available, pilot must
> select items individually (or have a check-list of what to switch
> off). You're now wasting 2 amps (1 or each battery contactor).
>
> See comment re load shedding below. My master
> relays draw 200 mA each.
>
>
> Think about the information you want the 2 shunts to provide, will the
> do that, is there a better (simpler) way? As you already have the
> power indicators, I would put the shunt in the alternator to bus feed.
> Agree with comment about fusing (or current limiting) feed to batt B.
> I thought a current limiter was better placed in the alternator output?
>
> I'm using a zero-center ammeter. With the shunt in
> its current location it provides info on the health of
> the battery charging system when everything is
> working properly.
>
> When the alternator fails, it automatically becomes
> a load meter to aid the pilot in load-shedding. Exactly
> the info you want, exactly when you need it.
>
> There are fuses in alternator output leads.
> An over-voltage protection module will prevent alternator
> run-away.
>
> With the shunt in the alternator output, in the case that the
> alternator fails, you get no information about system load and
> that's when you need it the most in order to do
> effective load-shedding.
>
>
> I'm unsure what the 'K-...' means
>
> 'K' is an industry standard abbreviation for relay/contactor
>
>
> 2 batteries will provide way more than 45 minutes operation on battery
> power, even with a very full panel and no load shedding. Therefore
> system grossly exceeds design goal resulting in more cost/weight than
> required. Where does 45 minutes come from? FAR-23 requires 30 minutes,
> alternatively assume half or full fuel endurance.
>
> That would depend upon battery selection and system load.
> I did not provide any info on this for my airplane.
> 45 minutes is my personal preference.
>
>
> No simple load shedding appears available - meets goal 2 (but perhaps
> goal 1 & 2 are actually, survive any failure for 45 minutes with no
> pilot interaction)
>
>
> I prefer to be in control of load-shedding based upon the
> situation. I don't like the idea of having it predetermined
> by what is wired to an E-buss.
>
> If I'm day VFR I may want to turn-off lots of things. If
> I'm preparing for an Instrument approach, I may decide
> not to turn-off anything.
>
>
> System seems more complex/costly than a 2 bus system would be. Seems
> that goals 1 & 2 are weighted much more highly than the others?
>
> Perhaps simplicity/complexity is in the eye of the beholder.
> I think a single buss is simpler than multiple busses with
> inter-connection/bypass relays.
>
> The buss-isolation diode units cost ~$20 each. I'm willing
> to spend the extra $40.
>
>
> Its your airplane, build the system that meets your needs.
>
> Regards, Peter
>
>
> On 02/02/2014 23:38, Jeff Luckey wrote:
>> Listers,
>>
>> Attached find a schematic (some people call them ladder diagrams) of
>> a design for the electrical system for my RV-7A. Below is a list of
>> design goals, pros and cons. Please take a look and provide
>> engineering feedback.
>>
>> TIA
>>
>>
>> Electrical Systems Design Goals:
>> 1. fault tolerant - able to tolerate failure of any single component
>> and fly for 45 min.
>> 2. easy to operate
>> 3. no avionics brown-out on engine start
>> 4. easy to repair
>> 5. comprised of standard, readily-available components
>> 6. cost effective
>>
>>
>> Pros:
>> 1. simplified operation - only 2 master switches
>> 2. simplified design - single buss
>> 3. no brown-out on engine start
>> 4. automatic fail-over - no pilot interaction required; avionics
>> won't reset
>> In the event a battery system suffers a failure, either an open
>> circuit or a ground fault, the faulty
>> system simply stops providing power to the buss and the remaining
>> good system continues to
>> provide electricity without interruption.
>>
>> Cons:
>> 1. buss-isolation power diodes may require heat sinks
>> 2. some energy wasted as heat thru power diodes
>>
>>
>
>
> *
>
>
> *
Message 2
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| Subject: | Re: Voltage/Current Measurement & Logging |
At 06:08 PM 2/9/2014, you wrote:
>very cool
>
>On Feb 9, 2014, at 4:50 PM, Eric Page wrote:
>
>>Bob & Listers,
>>
>>There's been some talk on here in recent weeks about measuring and
>>logging voltage and current in aircraft buses for diagnostic
>>purposes. I came across a crowd-funding campaign for an
>>interesting device that looks like it might be just the ticket for
>>this kind of measurement, so I thought I'd pass it along:
>>
>><https://www.dragoninnovation.com/projects/34-mooshimeter>https://www.dragoninnovation.com/projects/34-mooshimeter
>>
>>Eric
There's been an explosion in recent years for
low cost data acquisition products. I bought
my first computer driven measuring tool back
in '99 and used it to gather 8, 12-bit
channels of data at 1000 samples per second.
The thing ran off the parallel printer port
of my laptop. It cost me about $100 and
I used it substitute for a multi-killobuck
instrumentation package on a jog I was
doing at Beech.
The thing had NO graphical user interface,
I had to plot data with autocad and analyze
data with programs I wrote.
You can see the critter hanging off the back
of my laptop in this article . . .
http://tinyurl.com/kjuhl67
The price of hardware has continued to fall
while the utility of user interfaces has
grown. I ordered two of these guys a couple
weeks ago.
http://tinyurl.com/m68rbdl
The hardware is simple and easily adapted to
the task of characterizing current draw of
strobes that like to burn switches. But the
major driver for buying this was the GUI that
appears to be quite capable.
We're all going to learn more about this
product with some hands-on gathering of
data off List-member airplanes.
Bob . . .
Message 3
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| Subject: | Northstar M-3 GPS internal battery |
Does anyone have a part number and source for this battery?
Thanks,
Kelly
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