Today's Message Index:
----------------------
1. 02:34 AM - Re: 12v supply to stabilize avionics ()
2. 09:36 AM - Re: Re: 12v supply to stabilize avionics (Robert L. Nuckolls, III)
3. 09:39 AM - Re: 12v supply to stabilize avionics (Robert L. Nuckolls, III)
4. 09:46 AM - Re: Lamar SuperSwitch (Robert L. Nuckolls, III)
5. 11:28 AM - Re: Garmin GPS antenna (az_gila)
6. 11:31 AM - Re: 12v supply to stabilize avionics (C Smith)
7. 01:04 PM - Re: 12v supply to stabilize avionics (Robert L. Nuckolls, III)
8. 03:08 PM - Re: 12v supply to stabilize avionics (C Smith)
9. 04:03 PM - Re: 12v supply to stabilize avionics (Robert L. Nuckolls, III)
10. 04:29 PM - Re: Cigarette Lighter Alternatives -> EmPower ARINC 628, Power (Eric M. Jones)
11. 04:40 PM - Re: radar altimeter (Eric M. Jones)
12. 04:51 PM - Off Topic--Eastwood Powdercoat Gun (Eric M. Jones)
13. 08:48 PM - HID landing lights (cnpeters)
Message 1
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| Subject: | Re: 12v supply to stabilize avionics |
That is a hard to believe price for that power supply.
What about weight?
What if it fails?
Why not as suggested use a capacitor and diode?
How about turn the avionics off during start with a avionics master switch?
How about a more efficient starter (NL skytec), bigger starter wire and stronger
battery?
Good luck but sounds like more complication than necessary. Of course the aeroelectric
way is more complication and weight, always good.
George
>Subject: AeroElectric-List: 12v supply to stabilize avionics
>From: "bob mackey" <n103md@yahoo.com>
>
>I am purchasing a 12V power supply that takes
>6-24V input and gives 12V out at up to 14 A continuous.
>It's a 95% efficient switcher with a quiescent current
>around 10mA. We need to buy ten of them to get a
>better price (about $55).
---------------------------------
Ahhh...imagining that irresistible "new car" smell?
Check outnew cars at Yahoo! Autos.
Message 2
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| Subject: | Re: 12v supply to stabilize avionics |
At 02:32 AM 4/28/2007 -0700, you wrote:
>That is a hard to believe price for that power supply.
Agreed
>
>What about weight?
Devices like this don't need to be "heavy". With
some of the new high frequency, boost-buck topology
supplies available, this device could weigh under
a pound.
>
>What if it fails?
Single points of failure for lots of things
running downstream is a consideration.
>
>Why not as suggested use a capacitor and diode?
The ability of a capacitor to support a load is
bounded by the relationship . . .
A V
---- = -----
F S
This says Amps per Farad equals Volts per Second.
Assuming "brownout" is defined a duration that a
battery is under 9 volts, the time is rather short
. . . on the order of 200 milliseconds or so. See:
Here's a battery trace on an engine with a PM
starter who's inrush drags the battery down to
7.5 volts. In 200 milliseconds, the engine speed
is up high enough to allow battery to rise to
9 volts or more. Note that "cranking" is happening
at about 10 volts. We can see that the engine starts
on the third cylinder compression after a total
cranking duration of 500 milliseconds.
So assume you have a capacitor charged to battery
voltage (12.5 according to our trace) minus a diode
drop so we're going to start out at about 11.7 volts.
Assume a brownout protected load of 1A. We want to
limit the voltage sag to 1.7 volts for 500 mS plus
headroom - lets say 1 second. One of those auto
super audio system monster caps is readily
available in 1 Farad sizes. 1 Farad will drop 1
volt per second with our 1 A load. A 1 Farad
capacitor would support about 1.7 amps for
1 second to keep the sag under 1.7 volts.
If you have lighter loads, then the capacitor
can get smaller. Assume a couple of solid state
electro-whizzies at perhaps .2A each for total
of 0.4A. A 1.7 volt sag over one second at
0.4A calls for about 250,000 microfarads.
We're talking pretty BIG hunks of hardware here.
There are other considerations about connecting
large capacitors across a battery fed bus . . . big
inrush currents. When you purchase one of those
1F capacitors (about 3" diameter, 10" long)
the installation instructions suggest charging
the capacitor through a resistor before connecting
it directly to the battery.
Now, if one chooses to diode isolate an e-bus,
then the diode is already in place. But the
pre-start interval where lots of things are
already powered up puts a load on the battery
that may have you starting out at less than
12.5 volts hypothesized above. Further,
the trace shows BATTERY voltage. There
are small but perhaps significant drops elsewhere
to consider.
Obviously, one can stir the design goals.
Perhaps you can live with a half second brown
out buffer. The size of the capacitor goes down
by half.
Hmmmm . . . perhaps the diode isolated
capacitor is not very practical for loads of
more than 100 mA or so.
Okay, you could put the stabilizing supply
in series with the e-bus isolation diode. This
leaves you with the e-bus alternate feed path
to back up a possible failure of the stabilization
supply. But I'd want to do more study about the
potential for other problems should the e-bus
alternate feed switch get closed during normal
operations . . . you don't want to close a loop
that causes the stabilization supply to attempt
to charge the battery with the battery's own
output.
A stabilization supply is going to be lighter
and smaller than a monster capacitor that will
never have the sag-mitigation capabilities of
the stabilization supply. How about a small,
SVLA battery that would support the e-bus during
cranking. A 2 a.h. battery connected to one of
the e-bus fuses and controlled from a switch
on the panel would be a stone-simple means for
providing e-bus support during start-up brownout
offers a low risk means by which one avoids
disappointing results from more complex approaches.
How about a battery pak of 8 d-size alkaline
cells that are relay connected to an e-bus fuse
when you hit the starter button. Alkalines have
VERY long self lives, they're only needed a few
seconds per flight cycle. The eliminate any
need to worry about charging or extraordinary
maintenance. You would throw a new d-pak in on
condition . . . i.e. the first time it failed
to cover the brown out. Sound's pretty
attractive to me. It puts nothing in series
with your e-bus loads and loss of performance
does not impact any flight condition.
The point of this dissertation is not so much
to champion or trash any given approach. It's
intended to be an illumination of the duties that
engineers have to fully understand the statics and
dynamics of their ideas as they impact design
goals. It's not intended to discourage experimentation.
It would be a good thing if 10 folks got together
and tried the brown-out protection scheme being
proposed. My role here is only to shine the
light around and help identify things lurking
out there in the dark that one needs to be
watchful for during the experiment. But finally,
how ever the experiment comes out, publish your
findings here on the List. Letting folks know
what does not work is more valuable some times
that limiting your postings to things that
do work.
The 'complexity' arises not so much from amount
or kinds of hardware used but from a need to
identify, study and understand the system dynamics
as it affects design goals. I'm working a problem
now that arose from a hip-shot decision of a tiny
detail of a major system change that has cost us
about $100K a year for the last six years dealing
with the fallout. It took six years for the
pressure gauge to reach a point that someone of
authority says we need to do something about it . . .
which leaves others wailing about the $200K and
6-10 months it's going to take to certify a fix
that should never have been needed in the first
place.
>
>How about turn the avionics off during start with a avionics master switch?
If the issue is simply that some electro-whizzies
reboot due to the brownout event, why turn them off?
>
>How about a more efficient starter (NL skytec),
There is no study I'm aware of that shows any
starter to be more "efficient" than another starter.
Such claims are made but unsupported in the 4-color
brochures for all the popular products offered.
In fact, efficiency of a starter (h.p. out for watts
consumed) is the last of our concerns for optimizing
system functionality. It's how fast the engine gets
started. If I could trade a 50% loss of absolute
efficiency for a 50% drop in cranking time, I'd do
it in a heartbeat.
The starter feature under discussion here is locked-
rotor current or inrush. It's a given that for starters
of about the same size, the series wound starter will
have lower inrush currents than a PM starter. This
is a hard fact that drove B&C's decision to say with
their original philosophy. While others (most notably
the automotive industry) were rapidly embracing PM
starters for lower cost, we knew that aviation was not
so much driven by absolute cost as it was by performance
delivered for cost.
Until someone is ready to fund an apples for apples
comparison of the various starters and quantify their
relative performance numbers, the gold-plated,
bright shining claims to market superiority of any
electrical feature are to be taken with a grain
of sand. Pontiac has touted a "new wider look" since
I was a kid. If they were really meeting their marketing
claims claims, you'd need a wide load permit by now
just to drive one.
> bigger starter wire and stronger battery?
Certainly worth considering . . . but that
inrush can be 1000 amps! Remember folks, we're
talking about techniques to mitigate an event
that lasts for less than one second per flight cycle.
The obvious, low cost, maximum efficiency, minimum
risk, minimum weight approach is to develop
a operating procedure work-around and leave the
hardware alone.
Every other approach offers a requirement to
deduce, understand, consider and then fit every
new system integration problem into the design
goals for the airplane. There can be a lot more
to the task than plug-play-and-pretend that
we've done a good thing. Man! when I think of all
those whippy new products I could have brought
to market with the $600K that went down the
tubes . . .
>
>Good luck but sounds like more complication than necessary.
Agreed.
> Of course the aeroelectric way is more complication and weight, always good.
Please describe any modification you would make to any
suggestion in the 'Connection that would reduce
weight and/or complexity. Describe also what features
of the design goals for that suggestion one
should be willing to give up in exchange for
the perceived reduction in weight or complexity.
If your claim is accurate, then a substantiation
dissertation of underlying simple-ideas would be
much appreciated.
Bob . . .
Message 3
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| Subject: | Re: 12v supply to stabilize avionics |
At 02:09 PM 4/27/2007 -0700, you wrote:
>
>
>I am purchasing a 12V power supply that takes
>6-24V input and gives 12V out at up to 14 A continuous.
>It's a 95% efficient switcher with a quiescent current
>around 10mA. We need to buy ten of them to get a
>better price (about $55).
>
>Why do I want one? Why might you want one?
Put me down on the list to buy one should this
deal move forward. I'd like to have one to play
with on the drive stand this summer.
>I have a 1-battery airplane and don't want to rewire the
>whole thing. The GPS and radios reboot if they are on when
>I start the engine. During cranking, the bus voltage drops
>to around 10 V, and the avionics brown out. I want that
>problem to go away, and also want to keep the radio working
>for a while if the alternator shuts down and the battery drains
>below 10V.
Actually, your battery probably spends a few milliseconds
at voltages below 8 volts . . . Actual cranking, i.e. energy
delivered to the engine for starting does happen at about
10 volts but there's that gawd-awful inrush before cranking
actually beings that is the real dragon to slay.
>So, the solution I am trying is a switching power supply that
>converts anything between 6 and 24 V in to a stabilized 12V out.
>with 95% efficiency, the lost power is minimal. We would like to
>buy 10 units for about $55 each (+ s/h). We've accounted for
>four units, so there will be six more available. Who wants one?
ME!
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 4
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| Subject: | Re: Lamar SuperSwitch |
At 04:59 AM 4/27/2007 -0700, you wrote:
>
>I just saw an AD for the SuperSwitch from Lamar in Southern Aviator:
>http://www.southern-aviator.com/editorial/articledetail.lasso?-token.key=14206&-token.src=index&-nothing
>
>And an AD in
>Trade-A-Plane: http://trade-a-plane.aero/unprotected/dispads/0000774727.pdf
>
>I tried to locate more info on this at the www.lamartech.com web site, but
>can't seem to access their site right now.
>
>My question is has anyone looked into this product yet or obtained more
>info on it at Sun N Fun? I would think less weight, and no moving parts
>is a good thing? If the price is right, why wouldn't one use the SuperSwitch?
>
>Thanks for your inputs here.
Haven't been able to stir up any data on this product.
Their server seems to be hooked to the 'net but the
directory is not public access and their portal
file is either missing or hosed.
I'll give them a call Monday and see if they'll sample
one to Hawker-Beech. I'll do a white paper on it for
the boss and then let you folks know all about what I
discover.
These kinds of products are the wave of the future. Whether
or not they offer a return on investment for what MUST be
a higher cost depends on application, design goals and
marketplace where the product is intended to perform. ASSUMING
you've designed a failure tolerant system and KNOW how to
maximize its performance to upstaged your personal
starring role in a dark-n-stormy-night story, then
embracing this technology might not offer much of an
ROI. Let's see if I can get one and find out more.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 5
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| Subject: | Re: Garmin GPS antenna |
Jim Weir at RST has some GPS antennae and details on the drive...
http://www.rst-engr.com/rst/catalog/gps_antenna.html
gil in Tucon :)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=109727#109727
Message 6
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| Subject: | 12v supply to stabilize avionics |
Interesting thread, my 182 with a g1000 doesn't even blink during a
start-up. It's a 24volt system though. I wonder if there are fat caps in the
avionics modules that prevent any reaction to the starting load. Startups
are performed with one pfd, one com, and the rest of the avionics energized
(bus 1).
CS
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Saturday, April 28, 2007 1:39 PM
Subject: Re: AeroElectric-List: 12v supply to stabilize avionics
--> <nuckollsr@cox.net>
At 02:09 PM 4/27/2007 -0700, you wrote:
>--> <n103md@yahoo.com>
>
>
>I am purchasing a 12V power supply that takes 6-24V input and gives 12V
>out at up to 14 A continuous.
>It's a 95% efficient switcher with a quiescent current around 10mA. We
>need to buy ten of them to get a better price (about $55).
>
>Why do I want one? Why might you want one?
Put me down on the list to buy one should this
deal move forward. I'd like to have one to play
with on the drive stand this summer.
>I have a 1-battery airplane and don't want to rewire the whole thing.
>The GPS and radios reboot if they are on when I start the engine.
>During cranking, the bus voltage drops to around 10 V, and the avionics
>brown out. I want that problem to go away, and also want to keep the
>radio working for a while if the alternator shuts down and the battery
>drains below 10V.
Actually, your battery probably spends a few milliseconds
at voltages below 8 volts . . . Actual cranking, i.e. energy
delivered to the engine for starting does happen at about
10 volts but there's that gawd-awful inrush before cranking
actually beings that is the real dragon to slay.
>So, the solution I am trying is a switching power supply that converts
>anything between 6 and 24 V in to a stabilized 12V out.
>with 95% efficiency, the lost power is minimal. We would like to buy 10
>units for about $55 each (+ s/h). We've accounted for four units, so
>there will be six more available. Who wants one?
ME!
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 7
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| Subject: | 12v supply to stabilize avionics |
At 02:30 PM 4/28/2007 -0400, you wrote:
><pilot4profit@sbcglobal.net>
>
>Interesting thread, my 182 with a g1000 doesn't even blink during a
>start-up. It's a 24volt system though. I wonder if there are fat caps in the
>avionics modules that prevent any reaction to the starting load. Startups
>are performed with one pfd, one com, and the rest of the avionics energized
>(bus 1).
>CS
Probably not. It takes more than the simple diode-capacitor
ploy to fool an appliance into ignoring a startup-brownout.
Your appliances were no doubt qualified under
DO-160 recommendations by folks who took those recommendations
to heart and crafted products designed to live in the real
world of airplanes.
The absence problems manifested by other products being discussed
in this thread is a testament to their professional responsibility
an skills as engineers.
Bob . . .
Message 8
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| Subject: | 12v supply to stabilize avionics |
--> <nuckollsr@cox.net>
Probably not. It takes more than the simple diode-capacitor
ploy to fool an appliance into ignoring a startup-brownout.
Your appliances were no doubt qualified under
DO-160 recommendations by folks who took those recommendations
to heart and crafted products designed to live in the real
world of airplanes.
The absence problems manifested by other products being discussed
in this thread is a testament to their professional responsibility
an skills as engineers.
Bob . . .
Certainly I didn't mean to suggest something that simple, but do you mean to
say that there is no other source of current other than the battery bus? I
guess what I'm getting at is would a fat cap be employed as a component of a
more sophisticated sub-system between the bus and the avionics circuitry, at
a module level or avionics bus level?
Or would something like Lion batteries be the chosen component, again, not
as a standalone thing, but as the choice component to be the current
reservoir in an engineered sub-system to keep the avionics alive.
CS
Message 9
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| Subject: | 12v supply to stabilize avionics |
At 06:07 PM 4/28/2007 -0400, you wrote:
><pilot4profit@sbcglobal.net>
>
>
>--> <nuckollsr@cox.net>
>
>
> Probably not. It takes more than the simple diode-capacitor
> ploy to fool an appliance into ignoring a startup-brownout.
> Your appliances were no doubt qualified under
> DO-160 recommendations by folks who took those recommendations
> to heart and crafted products designed to live in the real
> world of airplanes.
>
> The absence problems manifested by other products being discussed
> in this thread is a testament to their professional responsibility
> an skills as engineers.
>
>
> Bob . . .
>
>Certainly I didn't mean to suggest something that simple, but do you mean to
>say that there is no other source of current other than the battery bus? I
>guess what I'm getting at is would a fat cap be employed as a component of a
>more sophisticated sub-system between the bus and the avionics circuitry, at
>a module level or avionics bus level?
>Or would something like Lion batteries be the chosen component, again, not
>as a standalone thing, but as the choice component to be the current
>reservoir in an engineered sub-system to keep the avionics alive.
. . . or the power supply within the product has the
same wide input range cited in the topic that
started this thread. Nowadays, it's not a big
deal to tailor input power conditioning to
cover ALL expected inputs. On a 14v device a
design goal might be for normal operation over
the DO-160 11 to 16 volt suggested range,
useable if somewhat degraded down to 9 volts
and orderly behavior for start-up brownouts.
I seriously doubt that anyone finds it useful
to go for a diode-cap or internal battery unless
a swift footed power supply is just impossible
or impractical.
Bob. . .
Message 10
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| Subject: | Re: Cigarette Lighter Alternatives -> EmPower ARINC |
628, Power
I suppose if you wanted a standard, the "cigar lighter" jacks are as standard as
it gets. Adapters to other connectors from cigar lighters are also readily
available. Better quality lighter connectors are available from marine supply
houses. Marinco makes them (horrible website, but lots of distributors).
USB is often used to power small devices. It has the advantage of inherent current
control and talks to a computer if required. BUt it is still simple for the
homebuilder.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=109760#109760
Message 11
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| Subject: | Re: radar altimeter |
I've been looking at a "short range radar altimeter" too.
But along the way I ran into the Mattel Hotwheels Radar Gun. $25 or so. I kid you not. This thing is a functional doppler radar gun (not detector!) that will measure the speed of Hotwheels, or real objects like dogs and bicycles. Amazing piece of technology see: http://www.edparadis.com/radar/
A little work might make a nifty radar altimeter.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=109761#109761
Message 12
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| Subject: | Off Topic--Eastwood Powdercoat Gun |
If you ever have to paint something that will fit into an oven, buy the Eastwood
Powdercoat system. What an absolute JOY to use.
This is one tool that I used and immediately emailed a "thank you" to the makers.
The Eastwood system is an electrostatic powercoat. You simply shoot a bit of smoke-like
powder, watch it magically coat the parts. Then pop the parts into a
375 degF toaster oven for 20 minutes. ASTONISHING. No other word can describe
it.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=109762#109762
Message 13
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| Subject: | HID landing lights |
I'm looking at rolling my own Xenon HID landing/taxi lights for an RV-9A, and
have a question regarding noise and one on the type of reflector (or projector).
Most of the commercial aircraft applications use the D1 type HID system, with
the igniter built into the bulb base, separate from the voltage regulating
ballast. D2 systems, which are easier to find (auto OEM), have the 25,000 volt
generating igniter in the ballast, and thus a special shielded cable to the bulb.
Has anyone tried the D2 type bulb/system and checked for noise, assuming
no antennae in the wingtips?
To anyone that rolled their own HID lights, what reflector/lens did you use? I
am interested in a wide angle for taxiing (at least 35 degrees) and a narrow for
landing (eg 12 degrees). I know a lens can change the dispersion given the
same reflector. Thoughts?
--------
Carl Peters
RV-9A wings
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=109788#109788
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