Today's Message Index:
----------------------
1. 04:34 AM - Re: Switch problem (Robert L. Nuckolls, III)
2. 06:07 AM - Re: Switch problem (George, Neal E Capt USAF ACC 605 TES/TBM)
3. 09:56 AM - Relay coils and diodes (Ralph E. Capen)
4. 10:52 AM - ELT Mounting Bracket (JohnInReno)
5. 11:47 AM - Re: ELT Mounting Bracket (Bret Smith)
6. 12:30 PM - Re: ELT Mounting Bracket (John Morgensen)
7. 12:34 PM - Re: ELT Mounting Bracket (JohnInReno)
8. 01:02 PM - Re: Switch problem (Robert L. Nuckolls, III)
9. 03:17 PM - Re: Relay coils and diodes (Robert L. Nuckolls, III)
10. 03:32 PM - Re: ELT Mounting Bracket (Ron Quillin)
11. 04:20 PM - Re: Switch problem (Vernon Little)
12. 10:37 PM - Re: Switch problem (Gary Lineberry)
Message 1
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Subject: | Re: Switch problem |
At 02:10 PM 9/4/2008 -0700, you wrote:
>Interestingly I have had almost the same problem. With a little over 200
>hours on the aircraft my Whelen strobe system stopped working. It did not
>open the 10A fuse, but when switched on the strobes would flash for about
>10 seconds and then stop. I was thinking that it was a problem with the
>Whelen unit but it is in a very difficult place to get to in my RV8 (under
>the floor) so I haven t yet gone to the effort to take up the floor to
>check it out. I looked at the fuse block and things looked good. Until I
>read this thread I didn t think about looking at the switch&..my mistake.
Not a mistake . . . just an unhappy discovery that
one ingredient in your system's recipe for success may
not be performing as-advertised.
> When I examined the switch today I discovered that the blue insulation
> on the Fast-On connectors had darkened considerably, indicating that they
> have been getting hot. They are still firmly attached to the wire but it
> appears there is an internal problem in the switch that is causing
> excessive heat.
A logical deduction.
>It is the B&C 1-3 switch referenced in this discussion. I have just
>ordered a few of the Honeywell switches from Digi-Key and will replace it
>with one of those.
I'd really like to put my hands on the overheated switch
for teardown, documentation and analysis.
>I don t know what the actual current draw on the circuit is, but I have a
>10A fuse that has not opened, so I would think that the B&C switch should
>handle it. On the other hand, it appears that there is some other factor
>afoot here in the strobe circuit that the 1-3 does not like. We ll see
>how the Honeywell switch handles it.
Agreed. There are valuable experiments to conduct
for the purpose of clearer understanding. It's
interesting to see how the act of bringing one
event to forums like these triggers a cascade of
recollection and consideration of similar events.
Situations that might have been pushed aside as isolated
events for individuals but raise flags of common
concerns for the group when the knowledge is pooled
together.
The strobe supply is unique among loads on the bus.
For those of you who are interested, take a peek at:
http://www.aeroelectric.com/Pictures/Curves/Strobe_Supply_Current.pdf
This is the current plot on a small strobe system I
was able to document some years ago. We were investigating
the effectiveness of various filter techniques for
the purpose of reducing the whining noise that some
strobes put out onto the bus.
The bottom two plots of this figure show the unfiltered
supply current draw of the system at two different
sample rates. Of particular interest is the fast rate
plot (second one up). Here we can clearly see the
modulation of on-current that is indicative of the
audio rate switching of the high voltage power
supply.
The third plot was measured after a 10KuF capacitor
was placed across the strobe supply leads. Note that
the switching noise is for all practical purposes
gone. The fourth plot is with one of the now discontinued
audio noise filters from Radio Shack. It too proved to
be an effective suppressor of the audio rate noise
but note the little spike at the onset of current
draw.
This is a GREAT illustration of the potential for
unintended consequences of an otherwise good thing.
This spike is a ringing at the resonant frequency of
the filter's inductor and capacitor. While the
combination of components DID relieve us of the
audio rate noise, it produces a new stimulus that
might now be perceived as a once-per-flash "tick"
at some other place in the system.
Clearly, this experiment suggests that the stand-alone
capacitor is effective and offers the least
risk for unintended byproducts of an otherwise
effective solution.
Now the problem before us is one of discovering the
energy signature that offends a switch that should
be sufficient to the task based on its ratings.
Neal, are you following this thread? We were discussing
an experiment to deduce the suitability of smaller gage
shielded wire when used as the connection between strobe
supply and the flash-tubes. Any chance you could get your
hands on a 'scope with digital data recording features
like a Tek TDS2012? These new gee-whizz scopes plot
.jpg screen shots AND ascii sample plots to a thumbdrive.
REALLY slick. If you could get the current plots from
your system the same time you do the flash intensity
experiments, it might lend some insight as to why the
switches that control the strobes are barfing.
If push came to shove, I could mail you my 'scope for
a few days to get the measurements. Let's talk about
this.
Another interesting piece of data from the plots
I cited above. Note that the POWER required to run
this little feller was 1.3 a-s per cycle x 14 volts
or 18 watts. THIS is the number that drives your
load analysis for the purpose of sizing batteries
and alternators. Note that it is smaller than the
value derived by simply multiplying bus votlage by
peak current draw of 2.7 amps (38 watts).
Bob . . .
Message 2
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Neal, are you following this thread?
I'm trying. The water's deep and I'm short.
Any chance you could get your hands on a 'scope with digital
data recording features like a Tek TDS2012?
Maybe. I'll ask around and see what I can find.
neal
Message 3
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Subject: | Relay coils and diodes |
My experience - shared for mine and other's education and offering of opinion.
This past weekend, I was working on the wiring of my flap position sensor for my
two-speed elevator trim circuit. The two-speed trim circuit essentially switches
a low speed set matronics governor for a high speed set one via a pair of
4PDT relays whenever the flaps come off the upstop.
As I was testing the detector switch - I got 'bit' by something that felt like
house current (done that too!). Not knowing what was going on, I repeated the
test...with identical results.
OK, break out some of Bob's literary work - read-up and put in some diodes across
the power terminals of the coil.
Re-reading made me think that in my case, the diodes may be even more important...in
Bob's writings (Paraphrased) "the absence of the diode presents the opening
switch with the spike"; in my case, I have a couple of things wired up within
the master switch... I'm thinking that in my case the master switch would
'see' the spike...along with anything else that is left on when I turn off the
master.
I know that the 'real' airplane stuff should be able to live in this environment
and should not produce this environment either - however in the OBAM world,
I can put in non tso'd trim servos and indicators (of which I have had a couple
of them mysteriously blow one of their indicator lights) which are pretty good
gear as far as I'm concerned - they just haven't spent the money and gone through
the certification process.
Got the diodes and will be putting them in this weekend. Is it possible that I'm
allowing a spike to wander around my electrical system by turning off the master
with some of these relays energized?
Your thoughts please,
Ralph Capen
Message 4
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Subject: | ELT Mounting Bracket |
Why does the mount for the Ameri-King ELT have a "wedge" under the rearward end
so that the radio is tilted 20 up in the back?
John Morgensen
RV-9A fuselage
Grumman AA1B-150
--------
RV-9A - Fuselage
Grumman AA1B-150 (RV-Trainer) Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 2780#202780
Message 5
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Subject: | ELT Mounting Bracket |
It doesn't. Loosen the strap and slide the unit forward until it sits flat,
then re-fasten the strap.
Bret Smith
RV-9A N16BL
Blue Ridge, Ga
www.FlightInnovations.com
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
JohnInReno
Sent: Friday, September 05, 2008 1:51 PM
Subject: AeroElectric-List: ELT Mounting Bracket
--> <john@morgensen.com>
Why does the mount for the Ameri-King ELT have a "wedge" under the rearward
end so that the radio is tilted 20 up in the back?
John Morgensen
RV-9A fuselage
Grumman AA1B-150
--------
RV-9A - Fuselage
Grumman AA1B-150 (RV-Trainer) Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 2780#202780
Message 6
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Subject: | Re: ELT Mounting Bracket |
I should have included pictures the first time. This is the Ameri-King
451 406 ELT and the very first ELT that I have ever dealt with. There
is a lip around the tray that completely surrounds the radio. The only
way to move it forward would be to have the radio sit on the forward
lip. See the attached pictures.
Bret Smith wrote:
>
> It doesn't. Loosen the strap and slide the unit forward until it sits flat,
> then re-fasten the strap.
>
>
> Why does the mount for the Ameri-King ELT have a "wedge" under the rearward
> end so that the radio is tilted 20 up in the back?
>
>
> --------
> RV-9A - Fuselage
> Grumman AA1B-150 (RV-Trainer) Flying
>
>
>
Message 7
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Subject: | Re: ELT Mounting Bracket |
I should have included pictures the first time. This is the Ameri-King 451 406
ELT and the very first ELT that I have ever dealt with. There is a lip around
the tray that completely surrounds the radio. The only way to move it forward
would be to have the radio sit on the forward lip. See the attached pictures.
JohnInReno wrote:
> Why does the mount for the Ameri-King ELT have a "wedge" under the rearward end
so that the radio is tilted 20 up in the back?
>
> John Morgensen
> RV-9A fuselage
> Grumman AA1B-150
--------
RV-9A - Fuselage
Grumman AA1B-150 (RV-Trainer) Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p 2794#202794
Attachments:
http://forums.matronics.com//files/img_1581_medium_117.jpg
http://forums.matronics.com//files/img_1580_medium_151.jpg
http://forums.matronics.com//files/img_1579_medium_580.jpg
Message 8
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At 08:02 AM 9/5/2008 -0500, you wrote:
>TES/TBM" <Neal.George@Hurlburt.AF.MIL>
>
>
> Neal, are you following this thread?
>
>I'm trying. The water's deep and I'm short.
>
> Any chance you could get your hands on a 'scope with digital
>data recording features like a Tek TDS2012?
>
>Maybe. I'll ask around and see what I can find.
Thanks!
Bob . . .
Message 9
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Subject: | Re: Relay coils and diodes |
At 12:54 PM 9/5/2008 -0400, you wrote:
><recapen@earthlink.net>
>
>My experience - shared for mine and other's education and offering of opinion.
>
>This past weekend, I was working on the wiring of my flap position sensor
>for my two-speed elevator trim circuit. The two-speed trim circuit
>essentially switches a low speed set matronics governor for a high speed
>set one via a pair of 4PDT relays whenever the flaps come off the upstop.
>
>As I was testing the detector switch - I got 'bit' by something that felt
>like house current (done that too!). Not knowing what was going on, I
>repeated the test...with identical results.
Yeah, been there, done that. In my case I got the
fingers across the contacts of a cub-scout electric
buzzer project that operated from 3 volts (two flashlight
cells). The field collapse from the small buzzer
solenoid coil was sufficient to give ME a buzz which
caused me to drop the project thus damaging it.
Unfortunately it was not my project and my schoolmate was
pretty unhappy about it. Neither of us understood what
happened or why . . . but he got a personal demonstration
of the effect a few days later. Even after my Navy veteran
electrician father explained it to us, we didn't really
understand.
>OK, break out some of Bob's literary work - read-up and put in some diodes
>across the power terminals of the coil.
>
>Re-reading made me think that in my case, the diodes may be even more
>important...in Bob's writings (Paraphrased) "the absence of the diode
>presents the opening switch with the spike"; in my case, I have a couple
>of things wired up within the master switch... I'm thinking that in my
>case the master switch would 'see' the spike...along with anything else
>that is left on when I turn off the master.
>
>I know that the 'real' airplane stuff should be able to live in this
>environment and should not produce this environment either - however in
>the OBAM world, I can put in non tso'd trim servos and indicators (of
>which I have had a couple of them mysteriously blow one of their indicator
>lights) which are pretty good gear as far as I'm concerned - they just
>haven't spent the money and gone through the certification process.
>
>Got the diodes and will be putting them in this weekend. Is it possible
>that I'm allowing a spike to wander around my electrical system by turning
>off the master with some of these relays energized?
No. First, while the voltages generated by magnetic
field collapse on a relay or contactor can be pretty
spectacular, the ENERGY they contain is small. Given
that the voltage is proportional to rate-of-magnetic
decay, it stands to reason that maximum rate occurs at
minimum current or widest opening of contacts on the
controlling switch. This is a long winded way of stating
that the source impedance of the relay coil as an energy
storage device is big . . . too big to propagate significant
pulses of "spike" energy out onto the bus.
Most accessories have some amount of capacitance right
across the power input leads as filters. This capacitance
alone is a huge energy sink to inductively stored spikes.
Risks to anything other than the controlling switch due
to magnetic field collapse has been greatly exaggerated
and poorly understood.
There is no reason to be concerned beyond the effects
on the controlling device . . . even if the diodes are
not present.
Bob . . .
Message 10
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Subject: | Re: ELT Mounting Bracket |
At 10:50 9/5/2008, you wrote:
>Why does the mount for the Ameri-King ELT have a "wedge" under the
>rearward end so that the radio is tilted 20 up in the back?
Mount for a helo?
They're at an angle...
Ron Q.
Message 11
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I checked the switch that I installed as a replacement for the one that I
fried about 100 hours ago. No sign of external damage or discoloration on
the new switch.
My failed switch was installed in 2005, purchased somewhat earlier. I had
two switches that had loose rivets, so I'm wondering if there was a QC
problem with the Carling switches made about that time. It would be
interesting to see the date codes on the failed switches.
My failed switch says C0344 Mexico. My guess was this is a date code (44th
week in 2003?). The one Bob analysed says 9936 Mexico on it.
Vern
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: September 5, 2008 9:08 AM
Subject: RE: AeroElectric-List: Switch problem
--> <nuckolls.bob@cox.net>
At 08:02 AM 9/5/2008 -0500, you wrote:
>--> 605
>TES/TBM" <Neal.George@Hurlburt.AF.MIL>
>
>
> Neal, are you following this thread?
>
>I'm trying. The water's deep and I'm short.
>
> Any chance you could get your hands on a 'scope with digital
>data recording features like a Tek TDS2012?
>
>Maybe. I'll ask around and see what I can find.
Thanks!
Bob . . .
Message 12
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Subject: | RE: Switch problem |
Bob:
Thank you for your analysis. I would have been happy to send you the
offending switch, but I have already dismantled it in order to satisfy
my
curiosity. The only real visual sign was some arc pitting on the
contact
surfaces. I believe that over time this pitting caused a high
resistance
that did two things. First, there was a voltage drop across this
resistance
which in series with the strobe unit caused the unit to stop working
because
of reduced voltage. When that happened I shut the circuit off and did
not
use it anymore. Second, the resistance at the pitted contacts generated
enough heat to discolor the blue insulation on the Fast-On connectors,
but I
caught it before any further heat damage occurred. The switch
components
looked normal except for the pitting. Nothing anywhere near the fried
specimen you referenced earlier. I temporarily installed a new 1-3
switch
today and ran the system for =BD hour and noticed no heat increase on
the
fasteners. But I wouldn=92t expect that until many switch actuations
and
subsequent pitting of the contacts. I will put the Honeywell switch in
when
it arrives and keep an eye on it. If it shows any signs of impending
failure I will research a Mil-Spec switch that might be a good
replacement.
Gary Lineberry
RV8 N18BL
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