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Panel lighting questions

 
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dean.psiropoulos(at)veriz
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PostPosted: Sun Feb 12, 2006 10:33 pm    Post subject: Panel lighting questions Reply with quote

Trying to resolve some nagging instrument lighting control issues here:

1) MAC (?Ray Allen?) trim servo position INDICATOR(LED bar graph type). The
MAC drawings show a white wire (used for dimming control) connected to the
INPUT side of the aircraft's dimmer pot (the side of the pot connected to
+12 volts). Is this diagram correct and do I have to connect this wire to
the input side of the dimmer control? Or can I connect it to the OUTPUT
side of a B&C solid state dimmer? The connection drawing also shows
separate power and ground connections to the indicator so I'm not sure if
the dimming action needs a variable resistance to ground or a variable input
voltage!? Also...anyone know how much current these draw at full intensity?

2)Mid Content Instruments MD200-306 VOR/ILS indicator internal light
dimming. Thanks for giving me the scoop on the connections here. NOW.....I
need to know how much current the internal lighting needs at maximum
brightness. Anybody know the answer to this one? Can't seem to locate an
answer in the manual I have. I need to know this so I can determine the
current capacity of the dimming control circuit.

3) Electronic International FL-2CA fuel gauge (capacitive fuel sensing with
display of 2 tanks at once) has both LEDs (which form an analog bar graph to
show fuel levels in both tanks simultaneously) and an LCD digital readout
(which can be switched between each tank to give a digital indication of
fuel remaining). The instructions show a connection to the dimming control
that allows varying the intensity of the LED bar graph lights. The LCD
backlight shows only a +12 volt connection with no dimming capability. For
those of you that have one of these gauges, could a dimmer be connected to
the LCD backlight 12 volt input to provide a dimming of the LCD backlight?
Is dimming the LCD backlight worth-wile or even needed at all? Or..have you
just connect the +12 volts and lived with the LCD backlight being on all the
time? Also for the LED bar graphs that are dimmable...does anyone know if
that takes a variable voltage input (ala B&C dimmer controller)or do I need
a variable resistance to ground?

4)For dimming control on the EZ Pilot and AFS AOA indicators, a momentary
push button switch is used that temporarily grounds one pin on the
connector. Is there a way to control these two instruments with an
potentiometer style instrument panel dimmer control or do we have to use the
buttons? Is such precise dimming control of these instruments worth-wile or
even needed at all?

5)Non related to panel lights but related to Lightspeed Plasma II+
electronic ignition. I got this one because it uses the aircraft style key
switch to turn it on and off. I didn't find any key switch depicted or
specified in the manual. I'm using the STD aircraft A510 key switch that
grounds the P leads to shutoff the mags (I have one mag on the left side).
Is this the correct switch or do I need a car style that makes a connection
to enable the electronic ignition? I would also like to install an
annunciator light that will turn on when I have the ignition turned on at
the key switch and turn off when the key is off...anyone done this or know
how to accomplish it? Thanks much.

Dean Psiropoulos
RV-6A N197DM
Autocad-21 drawings so far


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schamber(at)glasgow-ky.co
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PostPosted: Mon Feb 13, 2006 3:38 am    Post subject: Panel lighting questions Reply with quote

Dean wrote:
Quote:
Trying to resolve some nagging instrument lighting control issues here:

3) Electronic International FL-2CA fuel gauge (capacitive fuel sensing
with
display of 2 tanks at once) has both LEDs (which form an analog bar graph
to
show fuel levels in both tanks simultaneously) and an LCD digital readout
(which can be switched between each tank to give a digital indication of
fuel remaining). The instructions show a connection to the dimming
control
that allows varying the intensity of the LED bar graph lights. The LCD
backlight shows only a +12 volt connection with no dimming capability.
For
those of you that have one of these gauges, could a dimmer be connected to
the LCD backlight 12 volt input to provide a dimming of the LCD backlight?
Is dimming the LCD backlight worth-wile or even needed at all? Or..have
you
just connect the +12 volts and lived with the LCD backlight being on all
the
time? Also for the LED bar graphs that are dimmable...does anyone know if
that takes a variable voltage input (ala B&C dimmer controller)or do I
need
a variable resistance to ground?

Dean,

I can't help with the other issues, but the EI gage, I can. The LEDs are
dimmed with 12 vdc applied at the specified pin (unless they have changed
something) and at max brightness with no voltage. If you don't connect the
backlight to keep it on all the time, you will wish you did.

Sam Chambers
Long-EZ N775AM
Glasgow, KY


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Bill Denton



Joined: 10 Jan 2006
Posts: 97
Location: Chicago, IL USA

PostPosted: Mon Feb 13, 2006 5:30 am    Post subject: Panel lighting questions Reply with quote

You posted:

"1) MAC (?Ray Allen?) trim servo position INDICATOR(LED bar graph type).
The
MAC drawings show a white wire (used for dimming control) connected to the
INPUT side of the aircraft's dimmer pot (the side of the pot connected to
+12 volts). Is this diagram correct and do I have to connect this wire to
the input side of the dimmer control? Or can I connect it to the OUTPUT
side of a B&C solid state dimmer? The connection drawing also shows
separate power and ground connections to the indicator so I'm not sure if
the dimming action needs a variable resistance to ground or a variable input
voltage!? Also...anyone know how much current these draw at full
intensity?"
The Ray Allen indicators do not have "variable" lighting; they simply have a
full intensity state and a dimmed state. Applying a voltage to the white
wire causes the LED's to dim; removing that voltage causes them to operate
with full intensity.

You would not want to put them on the "output" side of a dimmer.

The rationale for connecting the white wire to the "input" side of the
dimmer is that you would normally not have a voltage there unless the panel
lights were turned on, either via the NAV light switch or a separate PANEL
light switch.

So, with the panel lights OFF, no voltage would be applied to either the
"input" side of the dimmer switch, nor to the white wire connected there,
and the LED's would operate with full brightness. Turning the panel lights
ON would apply a voltage to the "input" side of the dimmer switch, and to
the white wire connected there, which would dim the LED's.

Hope this is helpful...

--


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gregcampbellusa(at)gmail.
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PostPosted: Mon Feb 13, 2006 6:57 am    Post subject: Panel lighting questions Reply with quote

I'll take a shot at Question #1)

The white wire is a "logic input" to control a dimmer built into the LED
trim indicator.

The two "logic states" are "FULL Brightness" and "HALF Brightness",
controlled by
the voltage supplied to the white wire as a "command" to the built in
dimmer.


If you don't apply any voltage to the white wire, (or if you don't bother
connecting it),
then you are commanding FULL Brightness whenever the trim display is powered
up.

If you apply anything from 12v down to some "threshold voltage"
(which can be determined), then the display will be at "HALF Brightness".

If you apply some voltage, but less than the "threshold voltage",
then the display will again be at "FULL brightness".
(Essentially treating it the same as applying no voltage to it.)


So the simplest thing is to hook the white wire up to the INPUT side of your
panel lights
dimmer. If you've turned on the panel lights - then the trim display will
sense 12v on
the white wire and go to HALF Brightness and stay there regardless of how
low
you turn the panel lights.

However, if you hook the white wire to the OUTPUT side of your dimmer - then
the
trim indicator will probably go to HALF Brightness when you turn your panel
lights ON,
but it may go back up to FULL Brightness when you turn your panel lights way
down low.
This would happen if the OUTPUT voltage from the panel dimmer is below the
switching threshold of the trim indicator's "dimmer input" circuit.

It won't hurt anything to try - it's just a logic input. You might be able
to "get away"
with hooking the white wire up to the OUTPUT side. It will add a miniscule
load
to the dimmer's load - and worst case you'll see your trim indicators get
brighter
when you turn the panel dimmer all the way down low.
Maybe you see that as a feature, not a bug Wink
A reminder that you have the panel lights turned down low.




A FEW OTHER NOTES:

The MAC / Ray Allen trim indicators rely on a simple 5K potentiometer inside
the servo.

The three colored wires coming out of a Servo are connected to the three
terminals of the pot.
You can figure out which is which by using an Ohmmeter across them. Two
wires
will have a 5,000 ohm resistance regardless of the position of the servo.
The other wire
is the "tap" - and the readings from the "tap" to each "end" should add up
to 5,000 Ohms.

In normal use, the indicator applies some "reference voltage" (probably 5v
regulated)
across the ends of the potentiometer, and the tap returns a voltage
proportional to the servo's position.


The 5K potentiometer inside the servo will handle 12v applied across the
"ends" of the pot
regardless of the position of the servo arm. However, if you have the servo
arm at one
end or the other - the resistance from the tap to that end of the
potentiometer can be fairly low.
Inadvertently applying 12v across the tap and that end could smoke the
potentiometer
inside the servo. I can't think of any good reason to be applying 12v to
the servo
potentiometer lines - but it's something to keep in mind.

Similarly, you shouldn't apply 12v to the Trim Indicator wires (other than
the red & black).
To do so could smoke a diode inside the RP2 indicator, or possibly damage
the RP3 indicator.
See this link for more details:
www.RayAllenCompany.com/RACmedia/instructionsT2andT3.pdf



Another comment is the availability of the "needle type" RP2 trim
indicators.
See: www.AircraftSpruce.com/catalog/elpages/racindicators.php
I find the green LED from the (RP3) trim indicator gives some strong
reflections in the cockpit
that turn up on the windshield at night. And sometimes I have to shade the
LED indicator
with my hand to read it in direct sunlight. (Mine is a few years old
though.)
So. you might want to consider the analog RP2 meter version of the trim
indicator.
I'm not sure if it has a built in light - but for $75 I'm hoping it does.

Hope it helps,
Greg


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jschroeder(at)perigee.net
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PostPosted: Mon Feb 13, 2006 8:49 am    Post subject: Panel lighting questions Reply with quote

Dean -

Answer is yes. That is the way they dim the led's in that indicator. If
you have the input to your dimmer switched, you can take the dimmer input
to the same pole on the switch or from its connection to the input side of
the dimmer.

John
On Mon, 13 Feb 2006 01:24:43 -0500, DEAN PSIROPOULOS
<dean.psiropoulos(at)verizon.net> wrote:

Quote:
1) MAC (?Ray Allen?) trim servo position INDICATOR(LED bar graph type).
The
MAC drawings show a white wire (used for dimming control) connected to
the
INPUT side of the aircraft's dimmer pot (the side of the pot connected to
+12 volts). Is this diagram correct and do I have to connect this wire
to
the input side of the dimmer control?

--


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jschroeder(at)perigee.net
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PostPosted: Mon Feb 13, 2006 8:57 am    Post subject: Panel lighting questions Reply with quote

Dean -

We have the same instrument and did not bother with the current flow. It
is very low and I'm guessing that it is no more than 0.2 amps.

Am sending you two .pdf pages to your email address from my wirebook
showing the trim setup and the MD200 feed.

John
On Mon, 13 Feb 2006 01:24:43 -0500, DEAN PSIROPOULOS
<dean.psiropoulos(at)verizon.net> wrote:

Quote:
2)Mid Content Instruments MD200-306 VOR/ILS indicator internal light
dimming. Thanks for giving me the scoop on the connections here.
NOW.....I
need to know how much current the internal lighting needs at maximum
brightness. Anybody know the answer to this one? Can't seem to locate an
answer in the manual I have. I need to know this so I can determine the
current capacity of the dimming control circuit.

--


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