Today's Message Index:
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1. 06:16 AM - Electronics International MVP-50 Display (Angier M. Ames)
2. 06:16 AM - Electronics International MVP-50 Display (Angier M. Ames)
3. 06:51 AM - Re: Electronics International MVP-50 Display (Robert L. Nuckolls, III)
4. 07:14 AM - Bi-Directional Zener vs. Diode and Zener in Series for Coil Suppression (mikeeasley)
5. 08:18 AM - Bi-Directional Zener vs. Diode and Zener in Series for Coil Suppression (Robert L. Nuckolls, III)
6. 05:10 PM - Re: XeVision HIDs (Speedy11@aol.com)
7. 05:44 PM - Re: Control Stick/Flap Switches (Speedy11@aol.com)
8. 06:14 PM - Re: Bell and Whistles (Speedy11@aol.com)
9. 07:25 PM - Re: XeVision HIDs (XeVision)
Message 1
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| Subject: | Electronics International MVP-50 Display |
I'm currently struggling with a display issue. The MVP-50 has a
photocell which dims the display under low light conditions. With the
unit installed in the panel and audio fed to an unswitched input on
the PS Engineering PMA4000 audio panel, there is a distinct hum in the
headset when the display is fully dimmed. The hum gradually fades to
nothing with normal daylight conditions. The display can be set to dim
automatically or manually through an external dimmer pot and I hear
the same result either way. I called the folks at EI in Oregon and
with the phone held near the speaker in the cockpit, they were able to
hear the hum!
The initial suspect was a ground loop problem but this was ruled out
because when I removed the display and powered it up on the bench and
connected my headset directly to the audio output, I was able to
reproduce the same hum. Unfortunately, I don't have a scope to see
what I hear.
EI requested that I return the unit since they were convinced the
problem was internal to the display.
Now here's the weird part. Their techs were not able to duplicate what
I heard AND what they heard over the phone.
They say the display is operating normally and I got it back
yesterday. My first action was to set it back up on the bench and Low
and Behold, the hum is still there when the display is dimmed.
Any suggestions here would be most helpful since I'm beginning to
think that electrons behave differently on the west coast vs the east
coast!
Angier Ames
N4ZQ
Message 2
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| Subject: | Electronics International MVP-50 Display |
I'm currently struggling with a display issue. The MVP-50 has a
photocell which dims the display under low light conditions. With the
unit installed in the panel and audio fed to an unswitched input on
the PS Engineering PMA4000 audio panel, there is a distinct hum in the
headset when the display is fully dimmed. The hum gradually fades to
nothing with normal daylight conditions. The display can be set to dim
automatically or manually through an external dimmer pot and I hear
the same result either way. I called the folks at EI in Oregon and
with the phone held near the speaker in the cockpit, they were able to
hear the hum!
The initial suspect was a ground loop problem but this was ruled out
because when I removed the display and powered it up on the bench and
connected my headset directly to the audio output, I was able to
reproduce the same hum. Unfortunately, I don't have a scope to see
what I hear.
EI requested that I return the unit since they were convinced the
problem was internal to the display.
Now here's the weird part. Their techs were not able to duplicate what
I heard AND what they heard over the phone.
They say the display is operating normally and I got it back
yesterday. My first action was to set it back up on the bench and Low
and Behold, the hum is still there when the display is dimmed.
Any suggestions here would be most helpful since I'm beginning to
think that electrons behave differently on the west coast vs the east
coast!
Angier Ames
N4ZQ
Message 3
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| Subject: | Re: Electronics International MVP-50 Display |
At 08:11 AM 10/15/2009, you wrote:
>
<snip>
>Any suggestions here would be most helpful since I'm beginning to
>think that electrons behave differently on the west coast vs the east
>coast!
Until you identify the propagation mode, a solution
is not easy to deduce. It seems most likely that
the noise is conducted on the 14v supply lines.
Try operating either or both devices from separate
12v sources (preferably batteries) and see what
combination, if any eliminates the noise.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 4
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| Subject: | Bi-Directional Zener vs. Diode and Zener in Series |
for Coil Suppression
In the SnapJack literature, Eric shows the comparative merits of various forms
of coil suppression. One option is the diode and zener in series. Eric list
this option as "second best", showing the downside of having to get the polarity
right. I think I can overcome that!
I ran this question by the engineer at Kilovac Tyco, specifiying the Tyco LEV100
contactor in a 24-28V electrical system and his response was:
Use a 1N5406 or equivalent for the blocking diode, and a 1.5KE39A voltage suppressor
diode or equivalent for the clamping diode. Connect them common anode, and
connect the cathode of the blocking diode to the +24 Vdc line of the coil,
the cathode of the TVS diode to the coil return. Common clamping for a 28Vdc aircraft
system is -42V maximum, and most contactors rated to MIL-Specs have coil
suppression using a diode+zener diode combo. Bi-directional zeners are not
generally used due to concerns of higher overvoltages expected during lightning
strikes. The failure mode, you have to assume is the worst thing, which is a
short, but as I mentioned, this suppression method is pretty robust, and common
for this type of application. This will also give the best performance for
the contacts.
So is anyone willing to explain why the diode-zener diode is more robust than the
bi-directional zener (SnapJack) method?
I understand that you have the ability to control the ratings of each diode which
might be preferable to a bi-directional diode where you don't.
Mike Easley
Colorado Springs
Message 5
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| Subject: | Bi-Directional Zener vs. Diode and Zener in Series |
for Coil Suppression
>
>So is anyone willing to explain why the diode-zener diode is more
>robust than the bi-directional zener (SnapJack) method?
Not sure why "robustness" is being questioned. If one
is addressing lightning issues (like we do on TC aircraft)
then it's a WHOLE NEW BALLGAME. It's not uncommon to select
transient management devices rated to stand off 600V tranisents
with a 100 ohm source impedance (6A short circuit). An that's
for INDIRECT effects of lightning. If your electrowhizzie's
wiring is at risk for direct strike . . . well.
Lightning strikes and load dumps are NOT spikes. These
are high-energy over-voltage events that are managed
with something much more than a sprinkling of diodes or
Transorbs of appropriate "ratings".
>
>I understand that you have the ability to control the ratings of
>each diode which might be preferable to a bi-directional diode where you don't.
I think I explained that electrical stresses placed on
the coil suppression device are limited in voltage to
ordinary levels experienced on the airplane's electrical
system. It's limited in current based on demands of
the energized relay or contactor coil. Total energy
is a time dependent function measured in ten of
milliseconds.
The short answer is that you're worrying about breaking
the handle on your sledge hammer while using it to
squash ants.
The "ratings" of all commonly used devices far exceed
the electrical stresses the device is expect to
accommodate. I.e., electrical ROBUSTNESS so tiny a
a concern, I find it more useful to select devices for
their mechanical ROBUSTNESS.
Please review the documents offered on aeroelectric.com that
speak to "spikes". 99.9% of what is considered common
knowledge about the existence and risks of "spikes"
is urban legend elevated to what ever level of concerns
will sell more/better prophylactics against electrical
gremlins and goblins.
I spent a lot of get-yer-hands-dirty time looking at the best
and the worst of electrical system events on aircraft.
There's a REASON that spike suppression in the Z-figures
is limited to a very few components using very simple
devices.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 6
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| Subject: | Re: XeVision HIDs |
Dan,
Please accept my apology. I thought XeVision was part of Lopresti. It
was the LoPresti booth that I was referring to at SnF. Perhaps they marketed
their own lights.
Sorry for the mistake. Let me reiterate that, from my study of various
lighting systems, the XeVision product appears to be an excellent product.
I looked up the Precise Flight bulb after I emailed - it is Osram. I will
likely change to a different color temperature when I change the power
supply to 70W, but I will stay with the quality brands you recommended.
Stan Sutterfield
Do not archive
Stan, my name is Dan (Male).
Your comment is rather "interesting" in light of the fact that we have
NEVER had
a booth at Sun N Fun, in fact we (nor I or any employee) have never even
attended
Sun N Fun. So I am not sure how we could have been rude to you or anyone
else at "our booth".
Precise Fight uses Osram (Sylvania) brand D1S HID bulbs for their 35 watt
applications.
This bulb is made in Germany.
Dan
Message 7
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| Subject: | Re: Control Stick/Flap Switches |
A good point, Carlos. I'd forgotten about that option.
Stan Sutterfield
Do not archive
You can put a flap switch on the control stick and install an airspeed
relay
like this
http://www.aircraftextras.com/RelaySpeedCont1.htm
Message 8
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| Subject: | Re: Bell and Whistles |
Bob,
Are you also opposed to the flap positioning systems that are available to
set flaps to preselected positions? And opposed to the trim speed
adjustment devices that change the trim speed at a chosen airspeed?
Similar devices aren't used on certificated aircraft?
Stan Sutterfield
I would caution folks about urges
to add "bells and whistles" to their projects
"just because we can".
Message 9
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| Subject: | Re: XeVision HIDs |
Accepted,
Lopresti does market HID. It is called "Boom Beam"
Very unlikely 70 or 75 watt HID will ever be offered to the Aviation Public or
light aircraft by XeVision or anyone else. A 600 watt incandescent equivalent
light output is WAY "over the top" for light aircraft. 50 watt HID is about
equal to 450 watt incandescent. 35 watt HID about the same lumens as 200 watt
incan.
Optimal color temp for HID is 4000-5500 Kelvin. As the 4200K bulbs (as you have)
age from new they color shift towards 5000K. This takes 50-100 hours burn time
to occur.
What is wrong with the color output you have ???
Dan
[quote="Speedy11(at)aol.com"]
Dan,
Please accept my apology. I thought XeVision was part of Lopresti. It was the
LoPresti booth that I was referring to at SnF. Perhaps they marketed their
own lights.
Sorry for the mistake. Let me reiterate that, from my study of various lighting
systems, the XeVision product appears to be an excellent product.
I looked up the Precise Flight bulb after I emailed - it is Osram. I will likely
change to a different color temperature when I change the power supply to
70W, but I will stay with the quality brands you recommended.
Stan Sutterfield
Do not archive
>
>
--------
LED still has a long way to go to compete with HID as a landing light. This is
true in terms of total lumens and reach (distance).
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=268161#268161
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