Today's Message Index:
----------------------
1. 07:21 AM - Re: Transponder antennas (Robert L. Nuckolls, III)
2. 08:00 AM - Re: Transponder antennas (Harley)
3. 08:33 AM - Incandescent lamps in Wig-Wag systems (Robert L. Nuckolls, III)
4. 09:07 AM - RAC RP3 LED Indicators (Bill S)
5. 09:25 AM - Re: Incandescent lamps in Wig-Wag systems (David Lloyd)
6. 09:32 AM - Altitude Encoder Pin Outs (Jerald Folkerts)
7. 10:19 AM - Re: RAC RP3 LED Indicators (Robert L. Nuckolls, III)
8. 10:39 AM - Re: Incandescent lamps in Wig-Wag systems (Robert L. Nuckolls, III)
9. 11:33 AM - Re: Incandescent lamps in Wig-Wag systems (Robert L. Nuckolls, III)
10. 11:39 AM - Portable Bench Test Battery (Robert L. Nuckolls, III)
11. 11:43 AM - Portable Bench Test Battery (Robert L. Nuckolls, III)
12. 02:05 PM - Z16 voltage concern (Les Goldner)
13. 07:26 PM - Re: Z16 voltage concern (Robert L. Nuckolls, III)
14. 11:45 PM - Re: Z16 voltage concern (Jay Hyde)
Message 1
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Subject: | Re: Transponder antennas |
At 01:37 PM 10/25/2011, you wrote:
Since there is functionally no difference between the two antennas,
sure, you can have the "RST" unit, Bob...I'll use the TED antenna (it
looks more professional!)...and fabricate a new ground plane plate for it.
Actually, the pictures will suffice.
Now you've got me wondering. If it was not from RST, then I have no
idea where else I would have got that aluminum antenna from...it was
on a shelf at my hangar with the parts that I did get from RST that I
didn't use (nav antenna and some BNC connectors and cable)...and the
octagon ground plane was with it. BTW...now that I've had it in my
hand, the grommet is fiber, not rubber.
Yeah, that makes sense. It needs to be mechanically
rigid.
I'll send the ground plane along with it...where do you want me to send them?
Here's two pictures of the front and back of it that I just took a
few minutes ago (I assembled it...the small parts all came in a small
plastic bag...the ground plane was separate):
I published a similar configuration in the 'Connection way
back when. It would be interesting to know who made it.
In any case, the pictures are great. I'll probably add them
to the photo album on the website.
What do you plan to do with it?
I would have photographed it and then put it into the collection
of curiosities . . . but I have plenty of those laying around!
Bob . . .
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Subject: | Re: Transponder antennas |
> Since there is functionally no difference between the two
> antennas, sure, you can have the "RST" unit, Bob...I'll use the
> TED antenna (it looks more professional!)...and fabricate a new
> ground plane plate for it.
>
> Actually, the pictures will suffice.
Well, then...if anyone else here wants it, just drop me a line.
Just pay for the postage...I am talking about the one in the
pictures, not the TED unit, which I will be using.
Harley
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Subject: | Incandescent lamps in Wig-Wag systems |
A few weeks ago I was called to task for some
demonstrably sloppy data gathering when we were
discussing inrush limiting on incandescent lamps
used in wig-wag recognition systems. The plot I'd
published at:
http://www.aeroelectric.com/Pictures/Curves/Wig_Wag_Currents.jpg
. . . was properly identified as somewhat 'fuzzy' and
not properly supportive of some estimates of the cold
start inrush values. I ran across my little po' boy's
solid state switch yesterday so I drug it to the bench
and set up the following experiment:
http://aeroelectric.com/Pictures/Schematics/Test_Set-Up_Picture.jpg
http://aeroelectric.com/Pictures/Schematics/Test_Set-Up_Schematic.jpg
I ran some data plots with a 1 ohm resistor-load in place
of the lamp. Here we observe the expected current flow
plotted at scan speeds that will display 3-4 wig-wag cycles.
http://www.aeroelectric.com/Pictures/Curves/1-OHM_250mS.jpg
Then I zoomed in on an exemplar ON transition . . .
http://www.aeroelectric.com/Pictures/Curves/1-OHM_50uS.jpg
. . . and we see that the 'probe' connection is a tad
bit over-damped as indicated by the rounding at the upper
corner of the rise.
I then replaced the load resistor with a 55w halogen
head lamp bulb and produced this plot of wig-wag
currents:
http://www.aeroelectric.com/Pictures/Curves/55W%20WIGWAG.jpg
Here we see the effects of lamp temperature on the inrush
and running currents. At turn on, the lamp was cool enough
to produce about a 9A spike. The measured current just
before turn-off was on the order of 5A.
Inrush current from a cold start is determined by total
loop resistance of the wiring, battery source impedance,
and lamp cold resistance. The lamp has a measured cold
resistance of 145 milliohms. If driven by a zero-ohms
source at 12v, the theoretical inrush would be
12/.134 = 83 amps. The slow sweep peek at a cold start
in this test setup yielded the following trace:
http://www.aeroelectric.com/Pictures/Curves/55W_COLD-START_1mS.jpg
Here we see a measured inrush on the order of 42 amps.
This suggests that wiring and battery resistances added
another 140 milliohms or so to the loop resistance.
Zooming in for a closer peek at the cold start . . .
http://www.aeroelectric.com/Pictures/Curves/1-OHM_50uS.jpg
we see the same 42A displayed value for peak current.
Further, there is still more rounding of the plot as
compared with the almost purely resistive plot cited
above.
Exploration of lamp behavior during turn-on could not
be conducted with a mechanical switch or relay. Contact
bounce during turn-on would badly contaminate the data.
The solid state switch driven by a function generator
suffers no such shortcomings.
The closer look confirms that my original suppositions
for inrush on the trashy trace were correct. The earlier
plot was made with longer wires than for this experiment
hence we saw a 32A cold start inrush as opposed to 42A
in this case. It also confirms that the dynamics for rate of
rise and peak currents are limited by system wiring
(resistance and inductance) and there were no erroneous
observations limited by oscilloscope sample rates.
This experiment supports my original assertions that
turn-on transitions during wig-wag operations are a small
fraction (about 25%) of the initial cold-start value.
Bob . . .
Message 4
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Subject: | RAC RP3 LED Indicators |
Can two or more rp3 indicators be paralleled to one POS 5 or
POS12 position sensor? Thanks Doc
Message 5
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Subject: | Re: Incandescent lamps in Wig-Wag systems |
Bob,
Your further investigation of the halogen 55W inrush current is enlightening
and hints at why the early failures.
I am ignorant concerning "modern" filaments used in these brighter lamps.
A start-up of 42 amps seems high for a design that nominally floats at 4 - 5
amps. I am wondering what that inrush thump does to a captured spring
round, mechanical filament. There must a some mechanical jolting going on
for those few msecs.
When I observed the filament under a 6X magnifier, the filament windings
appeared to have little spacing between turns. You could observe some
spacing but, it was the same or less than the diameter of the filament wire.
Possibly they have an alloy now that does not expand much from heat and
magnetics of a huge initial inrush of current.
David
___________________________________________________________
----- Original Message -----
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Wednesday, October 26, 2011 8:30 AM
Subject: AeroElectric-List: Incandescent lamps in Wig-Wag systems
> <nuckolls.bob@aeroelectric.com>
>
> A few weeks ago I was called to task for some
> demonstrably sloppy data gathering when we were
> discussing inrush limiting on incandescent lamps
> used in wig-wag recognition systems. The plot I'd
> published at:
>
> http://www.aeroelectric.com/Pictures/Curves/Wig_Wag_Currents.jpg
>
> . . . was properly identified as somewhat 'fuzzy' and
> not properly supportive of some estimates of the cold
> start inrush values. I ran across my little po' boy's
> solid state switch yesterday so I drug it to the bench
> and set up the following experiment:
>
> http://aeroelectric.com/Pictures/Schematics/Test_Set-Up_Picture.jpg
>
> http://aeroelectric.com/Pictures/Schematics/Test_Set-Up_Schematic.jpg
>
> I ran some data plots with a 1 ohm resistor-load in place
> of the lamp. Here we observe the expected current flow
> plotted at scan speeds that will display 3-4 wig-wag cycles.
>
> http://www.aeroelectric.com/Pictures/Curves/1-OHM_250mS.jpg
>
> Then I zoomed in on an exemplar ON transition . . .
>
> http://www.aeroelectric.com/Pictures/Curves/1-OHM_50uS.jpg
>
> . . . and we see that the 'probe' connection is a tad
> bit over-damped as indicated by the rounding at the upper
> corner of the rise.
>
> I then replaced the load resistor with a 55w halogen
> head lamp bulb and produced this plot of wig-wag
> currents:
>
> http://www.aeroelectric.com/Pictures/Curves/55W%20WIGWAG.jpg
>
> Here we see the effects of lamp temperature on the inrush
> and running currents. At turn on, the lamp was cool enough
> to produce about a 9A spike. The measured current just
> before turn-off was on the order of 5A.
>
> Inrush current from a cold start is determined by total
> loop resistance of the wiring, battery source impedance,
> and lamp cold resistance. The lamp has a measured cold
> resistance of 145 milliohms. If driven by a zero-ohms
> source at 12v, the theoretical inrush would be
> 12/.134 = 83 amps. The slow sweep peek at a cold start
> in this test setup yielded the following trace:
>
> http://www.aeroelectric.com/Pictures/Curves/55W_COLD-START_1mS.jpg
>
> Here we see a measured inrush on the order of 42 amps.
> This suggests that wiring and battery resistances added
> another 140 milliohms or so to the loop resistance.
>
> Zooming in for a closer peek at the cold start . . .
>
> http://www.aeroelectric.com/Pictures/Curves/1-OHM_50uS.jpg
>
> we see the same 42A displayed value for peak current.
> Further, there is still more rounding of the plot as
> compared with the almost purely resistive plot cited
> above.
>
> Exploration of lamp behavior during turn-on could not
> be conducted with a mechanical switch or relay. Contact
> bounce during turn-on would badly contaminate the data.
> The solid state switch driven by a function generator
> suffers no such shortcomings.
>
> The closer look confirms that my original suppositions
> for inrush on the trashy trace were correct. The earlier
> plot was made with longer wires than for this experiment
> hence we saw a 32A cold start inrush as opposed to 42A
> in this case. It also confirms that the dynamics for rate of
> rise and peak currents are limited by system wiring
> (resistance and inductance) and there were no erroneous
> observations limited by oscilloscope sample rates.
>
> This experiment supports my original assertions that
> turn-on transitions during wig-wag operations are a small
> fraction (about 25%) of the initial cold-start value.
>
>
> Bob . . .
>
>
>
Message 6
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Subject: | Altitude Encoder Pin Outs |
I recently purchased a used II Morrow Apollo Altitude Encoder, model
#428-2003. I haven't been able to find a diagram/description of the 15 pin
connector on the back. Does anyone have a description, or are these
standard pinouts?
Thanks,
Jerry Folkerts
SR #093
www.mykitlog.com/jfolkerts/
Message 7
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Subject: | Re: RAC RP3 LED Indicators |
At 11:04 AM 10/26/2011, you wrote:
> Can two or more rp3 indicators be paralleled to one POS
> 5 or POS12 position sensor? Thanks Doc
Not enough data to offer considered advice.
Do these indicators have built in resistors?
If so, they're designed to work on some voltage
higher than the threshold voltage of the LED.
In this case, they can probably be paralleled.
If no internal resistors, then they're current
operated devices and need to be wired in series.
Bob . . .
Message 8
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Subject: | Re: Incandescent lamps in Wig-Wag systems |
At 11:22 AM 10/26/2011, you wrote:
>
>Bob,
>Your further investigation of the halogen 55W inrush current is
>enlightening and hints at why the early failures.
>I am ignorant concerning "modern" filaments used in these brighter lamps.
I'm not sure there's much difference in modern vs.
legacy tungsten filaments. Both lamps us the same
material. The major differences are the surrounding
gasses within the glass envelope that permit operation
at higher temperatures.
>A start-up of 42 amps seems high for a design that nominally floats
>at 4 - 5 amps. I am wondering what that inrush thump does to a
>captured spring round, mechanical filament. There must a some
>mechanical jolting going on for those few msecs.
If you wired your landing light system with say,
10AWG wire, you could get more than a 10X increase
of inrush vs. running current. Yes, the thermal stresses
during cold-start turn on are impressive. Power
dissipated in the exemplar filament at cold start . . .
W = R x I^2
.145 x 42 x 42 is 255 watts
if you wired with short runs of fat wire
that produced an 82A inrush we get
.145 x 82 x 82 = 974 watts.
Of course this tapers off rapidly. Referring
to the 'fuzzy' plot
http://www.aeroelectric.com/Pictures/Curves/Wig_Wag_Currents.jpg
We see that it takes about 100 milliseconds
for the max inrush value to fall to normal
operating levels. But for the first 20 milliseconds
or so, that little chunk of tungsten is being
bullied rather severely.
>When I observed the filament under a 6X magnifier, the filament
>windings appeared to have little spacing between turns. You could
>observe some spacing but, it was the same or less than the diameter
>of the filament wire.
>
>Possibly they have an alloy now that does not expand much from heat
>and magnetics of a huge initial inrush of current.
I think it's mostly a rate of temperature rise combined
with the manner in which conductors burn in two.
If you hang a length of wire out in space and hit
it with a current expected to burn it in two, it
will open up close to the center of the span.
This is because resistance goes up with temperature
and material at the center of the span gets energy
pumped into it both locally and from both sides. I.e.
temperature AND resistance goes up fastest in the
middle thus making it the most likely point to reach
destructive temperatures.
Evaporation of filament material causes localized
increase in resistance. This aggravates the rate
of rise for temperature during the inrush transient
and causes failure to happen in the filament's weakest
location.
I believe there are two forces at work in the failure
of lamps. Vibration while cold and d-temp/d-seconds
rate during inrush. Keep-warm offers some mitigation
of both effects . . . inrush limiting can only
mitigate turn-on transients.
Bob . . .
Message 9
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Subject: | Re: Incandescent lamps in Wig-Wag systems |
<nuckolls.bob@aeroelectric.com>
At 11:22 AM 10/26/2011, you wrote:
>
>A start-up of 42 amps seems high for a design that nominally floats
>at 4 - 5 amps. I am wondering what that inrush thump does to a
>captured spring round, mechanical filament. There must a some
>mechanical jolting going on for those few msecs.
I went back and got this plot
http://www.aeroelectric.com/Pictures/Curves/55W_COLD-START_25mS.jpg
This shows that current draw for lamp under examination
in this test configuration goes from 44A down to 10A in
about 37 mS. It probably takes another 150-200 mS to
settle out on the steady state current measured at 5.2 amps.
Bob . . .
Message 10
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Subject: | Portable Bench Test Battery |
As I was putting the morning's experiment tools away
it occurred to me that many of you might find value
in this tool.
If you're pulling a battery out of your airplane because
it no longer meets design goals for battery-only operations,
it may well have lots of life in a work-bench based role.
See:
http://aeroelectric.com/Pictures/Tools/Test_Equipment/Bench-Test_Battery.jpg
This particular battery was brand new about 10 years ago
and placed into service as an instrumentation battery
for stuff I was doing at Beech.
Haven't cap-checked it lately but it still load tests
at over 300 Amps for 15 seconds. Here you see how I bonded
a breaker-switch on the top along with a 3/4" spaced
banana jack set with JB-Weld. A handle was added by running
three strands of 2" wide glass-reenforced strapping tape
from side to side . . . bunching it up in the 'grip' area
and wrapping with tape.
This tool has seen service in many situations where I
needed some 12-Volt snort with considerable load handling
ability and/or capacity. Your choice of connectors and switch
are optional as well as size of protection. If you use a
generic switch, stick an in-line fuse holder in the wiring.
You can select a plug in fuse from 3 to 30 amps . . .
appropriate to the task at hand.
Bob . . .
Message 11
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Subject: | Portable Bench Test Battery |
See:
http://aeroelectric.com/Pictures/Tools/Test_Equipment/Bench-Test_Battery.jpg
This particular battery was brand new about 10 years ago
and placed into service as an instrumentation battery
for stuff I was doing at Beech.
Haven't cap-checked it lately but it still load tests
at over 300 Amps for 15 seconds.
Oh yeah, forgot to mention. This battery has been used
to start numerous cars given the exposed jumper-cable-
friendly posts.
When not in use, it sets on a Battery Tender.
Bob . . .
Message 12
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Subject: | Z16 voltage concern |
Robert,
I used your Z16 drawing in my Rotax 912 powered Zenith aircraft when I built
it three yours ago. It works great except for a low voltage problem from the
get-go whenever the main power distribution bus is on without turning on the
endurance bus.
With the main bus only, I get about 12.5 volts on instruments attached to
the endurance bus. With both buses set to "on" I get about 13.5 volts
coming to these instruments. Of course this varies somewhat depending on
whether the motor is on, with RPM, and with the state of battery charge, but
the difference remains depending upon whether the endurance bus is on or
off. Some of my instruments are sensitive to voltage so I have to leave the
endurance buss on at all times. I have changes batteries and the Rotax
voltage regulator but this situation remains.
Is this normal or is there a problem that needs to be addressed? If there is
a problem, can you suggest a fix?
Thank you for your help,
Les
Message 13
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Subject: | Re: Z16 voltage concern |
At 03:59 PM 10/26/2011, you wrote:
Robert,
I used your Z16 drawing in my Rotax 912 powered Zenith aircraft when
I built it three yours ago. It works great except for a low voltage
problem from the get-go whenever the main power distribution bus is
on without turning on the endurance bus.
With the main bus only, I get about 12.5 volts on instruments
attached to the endurance bus. With both buses set to "on" I get
about 13.5 volts coming to these instruments. Of course this varies
somewhat depending on whether the motor is on, with RPM, and with the
state of battery charge, but the difference remains depending upon
whether the endurance bus is on or off. Some of my instruments are
sensitive to voltage so I have to leave the endurance buss on at all
times. I have changes batteries and the Rotax voltage regulator but
this situation remains.
Is this normal or is there a problem that needs to be addressed? If
there is a problem, can you suggest a fix?
Thank you for your help,
Have you conducted a load analysis? What's the
expected load on the alternator with everything
turned on? Does your engine have the external
belt driven alternator . . . or just the built
in? Since you referenced Z16, I presume it's
the built in alternator.
The built-in alternator is good for about 18A total. If
the battery is not fully charged, it can soak up
a large proportion of that 18A.
You need to put a good charger/maintainer on the
battery and make sure it is topped off. Start
the engine and turn off every accessory with
a switch.
You can't get full output out of the alternator
except at cruise:
Emacs!
This data plot is a real 'hedge' on reality. First
a 5% tolerance. Next good at 20C. Finally, output
at these loads may be as low as 13.5 volts. In other
words, high enough to keep you from discharging
the battery but not enough to charge it either.
Hence, that excursion above 20A is a bit
of whimsy seldom realized in real world utility.
In your case, we first need to see if the alternator
WILL charge a battery at 14.2 or a tad better if
all the system loads are minimized if not OFF>
Bob . . .
Message 14
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Subject: | Z16 voltage concern |
Hello Les,
The problem comes from the diode between the Main Bus and the Endurance bus;
the forward voltage drop across this diode leaves you with the lower voltage
at the Endurance bus. When you put the alternate feed on to the Endurance
bus you 'boost' boost the voltage because there is no diode in the alternate
path. If you use a Schottkey diode instead of a normal diode between the
Main and Endurance bus the Endurance bus voltage will be better as the
forward voltage drop across a Schottkey is less than that of a normal diode,
but you will always have a slightly lower voltage on the Endurance bus.
Jay
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Les
Goldner
Sent: 26 October 2011 10:59 PM
Subject: AeroElectric-List: Z16 voltage concern
Robert,
I used your Z16 drawing in my Rotax 912 powered Zenith aircraft when I built
it three yours ago. It works great except for a low voltage problem from the
get-go whenever the main power distribution bus is on without turning on the
endurance bus.
With the main bus only, I get about 12.5 volts on instruments attached to
the endurance bus. With both buses set to "on" I get about 13.5 volts
coming to these instruments. Of course this varies somewhat depending on
whether the motor is on, with RPM, and with the state of battery charge, but
the difference remains depending upon whether the endurance bus is on or
off. Some of my instruments are sensitive to voltage so I have to leave the
endurance buss on at all times. I have changes batteries and the Rotax
voltage regulator but this situation remains.
Is this normal or is there a problem that needs to be addressed? If there is
a problem, can you suggest a fix?
Thank you for your help,
Les
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