Today's Message Index:
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1. 08:49 AM - AEC 9009 Audio Iso Amp for sale (Jared Yates)
2. 10:25 AM - Re: Tips for Building a Wiring Harness (Bill Watson)
3. 05:38 PM - Re: Re: Non-aero app: 120/240 AC through 24vdc switch? (Robert L. Nuckolls, III)
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Subject: | AEC 9009 Audio Iso Amp for sale |
I built this little circuit to Bob's specs here:
http://www.aeroelectric.com/Catalog/AEC/9009/
and it worked great for 250 hours. I've recently replaced it with an audio
panel due to some other equipment upgrades.
This circuit allows you to consolidate up to 5 channels of audio into a
single audio output, which can then be fed into an intercom's auxiliary
input. In my case I used it for left entertainment, right entertainment,
VHF nav ident, and Dynon audio. The volume of each channel is adjusted by
replacing the resistors.
Asking $40 shipped (cost of materials), please reply directly if you are
interested.
Thanks,
Jared
Message 2
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Subject: | Re: Tips for Building a Wiring Harness |
A bit OT but I think many builders could benefit from the following
approach (pun) if they understood what it does.
My 'harness' was done with the Approach Fast Stack
<http://www.approachfaststack.com/> hub and cables. The panel includes
(3) GRT HX EFISs, G430w, G327 Trpdx, PS Audio box, Garmin SL30, and a
Trutrak AP (all vintage 2009-10). I ordered the components directly and
through various channels (including Fast Stack I recall) but in every
case I did not order any kind of harness for any of them.
Instead I supplied the Approach folks with my list of equipment. They
asked a few questions and came back to me with their standard Pro Hub
and a list of the customized cables required for the panel and the
desired functionality. Truth be told, I didn't fully understand which
connections were required for which functions, which were redundant,
which were unnecessary. I certainly didn't have what I needed to plan
all the connections between certified products like the Garmins and
experimental products like the GRTs. Challenges included the fact that
Garmin primarily supports their dealer network and GRT documentation
always lagged a bit behind delivery of functionality.
But the folks at Approach fully understood what connections were
required and did things that took me a year or more to fully understand
how complete a job they did. And all I had to do was to mount their hub
under the panel, plug in the cables, and wire a handful of power and
ground pigtails to my electrical system. The hub is a hardware-only
device that looks like a collection of D-Sub connectors. There's a
cable from each panel component to the hub with no direct component to
component connections. Upgrading or replacing a component generally just
involves getting a new cable from Fast Stack.
And perhaps most valuable of all, the entire 'harness' is fully
documented for your installation.
Any of you that have installed a full IFR panel with full Nav, RNAV, and
a 2 axis AP functions know that it takes awhile to learn your way around
the many capabilities. The good part is that I found every single
necessary connection and option had been wired up correctly and reliably
through the Fast Stack hub and cables. I just wish it could have pushed
all the necessary buttons at the right time.
Doing a DIY panel still involves a lot of planning wiring, labeling and
documentation. Using Fast Stack still qualifies as a DIY panel with all
the satisfaction and $$$ savings that can be realized.... and a whole
lot less headache pain. Looking back after 6 years of flying my panel,
I would do it the same way if I did it again.
Sorry for hitch-hiking on this thread.
Bill "back to paying a bunch of bills and doing paperwork" Watson
On 8/25/2017 11:14 PM, Art Zemon wrote:
> Folks,
>
> I have all but two of the components for my instrument panel in-hand
> so it's time to start building the wiring harness. Other than obvious
> stuff, like draw it out on paper before starting to solder and crimp,
> do you have any tips or suggestions for how to construct this complex
> piece of wire and connectors?
>
> Thanks,
> -- Art Z.
>
> --
> https://CheerfulCurmudgeon.com/
>
> /"If I am not for myself, who is for me? And if I am only for myself,
> what am I? And if not now, when?" Hillel/
---
This email has been checked for viruses by Avast antivirus software.
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Message 3
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
At 12:00 PM 8/26/2017, you wrote:
>
>Bob,
>Here's the schematic, and late breaking...the ballast mfgr engineer
>informed me that the max inrush for the ballast is 101 A. Combined
>with the Pwr Supply's 40A inrush, rough duty for a 5A switch.
>
>Thanks for looking at this,
>John
>
Okay, let's talk about 'inrush' currents.
Emacs!
Here's a simple model of an inrush-energy study that will
suffice for this discussion. In reality, the model is
much more complex with features (inductances and capacitances)
combined with dynamics of the power source and timing . . .
if you close a switch at the exact instant the AC voltage
is at its peak, then MAXIMUM inrush currents can be expected.
On the other hand, if you can somehow close the switch while
the incoming voltage is zero . . . then inrush effects on
the switch will be . . . uh . . . almost zero.
I show two resistances, Rs which is the source resistance.
This component sets the maximum current that can flow if a
dead short is placed across the source. It also set the
requirements for 'interrupt current ratings' on circuit
breakers and fuses.
Then I've show a load resistance Rl which is controlled
by the configuration of your products input components,
in this case . . . a combined ballast and power supply.
The ballast mfgr has quoted a rather impressive inrush
current number . . . which is only partly significant.
Consider a range CAPACITORS sized from picofarads
to farads. The exact instant that your switch contacts
close, the inrush current will be V(applied)/Rs+Rl and
may very well be on the order of 100 amps . . . which
says NOTHING about the size of the capacitor, only that
V is applied over the total resitance for some period of
time after contact closure.
If C is picofarads, the DURATION of the inrush event is
very short, perhaps measured in picoseconds. If C is
Farads (like some of those capacitors favored by
installers of mobile gray-matter mashers) then the
duration of inrush event is orders of magnitude more
severe.
The ability of a switch to manage that event has roots
in contact mass, spring rates of closing forces and
velocity of the moving contact mass as it crashes into it's
stationary mate.
Contact bounce is an inevitable feature of ALL mechanical
switches. Further, the severity of bounce is only loosely
related to the switches pedigree. Here's a study I did
on a system with mil-spec, sealed relays that were GOING
to stick irrespective of how well the device was
built.
http://tinyurl.com/pstsggm
As you can see in this article, the sticking
wasn't even a high energy event. The relays were being
used in a situation well inside their catalog ratings . . .
but a combination of capacitance and PROPAGATION delay
down and back over a crude coaxial feed line stacked
up to offer the 'perfect low energy relay welder'.
The 100A inrush value offered by your supplier simply
acknowledges that there is some capacitive component
across the input to their product . . . but no help
for how large it might be.
Obviously, the COMBINATION of that inrush energy event
and contact bounce on your switch of choice has produced
a condition prone to sticking.
What kind of switch are we talking about? How long does
it take to produce a failure event? Have you been able to
duplicate the sticking even in a laboratory environment?
Are there a lot of fielded devices that may need
upgrading? One sure bet for fixing the problem and staying
with your existing switch is to add some electronics behind
the panel . . . perhaps a solid state relay with ZERO CROSSING
detection that reduces inrush to a minimum.
http://tinyurl.com/y7rst4a6
http://tinyurl.com/y8g8zyj9
Another possibility is to change the switch. Just a
difference in brand for the same physical switch
can make a big difference. Adding to Rl in the
inrush loop, either inrush limiter or perhaps just
a 3 ohm, 5 watt resistor (1A running current across
three ohms is 3 volts drop, 3W dissipated . . . but
a reduction in inrush MAGNITUDE by a factor of 3
or more . . . with an insignificant change in
over all performance.
Making the elegant decision demands more data. Perhaps
'scope traces on the inrush event. A study of bounce
characteristics of the switch. Better data on exactly
what the inputs to your loads look like will help.
But it seems likely that a change in brand/style
of switch is the shortest path and perhaps even
doable as a field retrofit. The elegant equation
demands a lot more 'numbers'
Bob . . .
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