Today's Message Index:
----------------------
1. 12:10 PM - LED position lights (Shaun Simpkins)
2. 07:59 PM - Re: AOA//LED's for cockpit (Paul Messinger)
3. 09:53 PM - [Please Read] SPAM Filter Could Be Causing Posting Problems (Matt Dralle)
Message 1
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| Subject: | LED position lights |
--> AeroElectric-List message posted by: "Shaun Simpkins" <shauns@hevanet.com>
Eric, all:
You're close. The emitters appear to be the 1W Luxeon Star-O in a custom heat
sink/circuit board.
These units run at 350mA and 4.0V worst case ( about 3.3V for red ), so 7 of them
in series just
fit in a 28V system. No 28-to-56V step-up unit required. The Star-O, because
of its optics,
can put out a really bright beam - over 180 candela.
If you check out the FAA Advisory Circular 20-74, you will see that position lights
radiate most of
their energy in a tight beam about 20 degrees wide and 30 degrees high aimed about
10 degrees
outboard of dead ahead.
The spec sez minimum 40 candela from 0 to 10 degrees, 30 candela from 11 to 20
degrees, and 5 candela from
21 to 110 degrees. The vertical beam half-power width is about 30 degrees. Therefore,
the skirts of
a well-focused emitter will probably provide the required sideways brightness.
The 70875 emitters are angled about 10-15 degrees outboard, the approximate center
of a tight beam
meeting regs. Two or three of the emitters may be angled further outboard or up
and down to fill out the
rest of the radiation pattern, but this isn't obvious from the pictures, and in
any case only a few degrees of
skew would be required. It's likely, as you say, that they're using custom PMMA
lensing.
This is Whelen's second version of an LED position light. The prototype was covered
in a trade magazine two years
ago, and used "piranha package" LEDs in a hemispherical armature with reflector
wings - really complicated.
About this time the Luxeon Stars came out, and Whelen apparently abandoned their
Rube Goldberg arrangment.
I like this design much better.
Price: Star-Os are less than $20 each in unit quantities. I would doubt that there's
more than $120 in parts.
Shaun
>Diagnosis--The LEDs are likely to be seven pieces of LXHL-PM02 Luxeon
>Emitter V Green Lambertian 120 lumens 150 degrees 6.84V and 700 mA or their
>red equivalent.
>Now for the photometry. How do they get the 2 candelas pointing up and down.
>Is this scattered from the polycarb? Whelen may have tweaked custom molded
>methacrylate aspheres to cover this area.
>Price: Someone will post it later (I write this Saturday evening). Rob
>Housman reported that Whelan charges $428.95 for their LED tail light. The
>Luxeons Emitter V's cost retail $40 each or $280 for the set and maybe $150
>for the other parts. That's $430 just for parts (!) Add your own profit
>margin but my guess is Whelen struggled to price it just under a Federal
>Reserve Note with a picture of Grover Cleveland on it. EACH.
>Eric M. Jones
Message 2
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| Subject: | Re: AOA//LED's for cockpit |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
The AOA design you referred to was not produced for reasons not public.
I have fully flight (June 2000) tested that version as well as a very simple
one (Sept 2000) using the National IC.
The high cost item is the pot for a vane sensor or the ultra low pressure
sensor if a pressure probe is used.
One needs at least 2 deg accuracy over all conditions and one deg
repeatability.
Consider the restoring force on a few sq inches of flat plate vane with
deflected angle of 2 deg at 40 mph.
Typically the vane needs to be a double wedge (based on windtunnel and
flight testing). The front 2/3 is perhaps 7 deg wedge with the back 1/3 15
deg wedge included angle (angles vary with the specific design) . Then
consider the restoring force on a 16 deg plate vs the force on a 12 deg
plate at 40 mph and consider the total area is 3 sq in and the lever arm is
4" (the case with a 2 deg vane error to the true AOA). If you run the
numbers you will see why friction is so important and or a very low
differential pressure gauge is needed. Then there is the environment of
temp/voltage drift etc etc and its not simple to do. Once the angle is
converted to volts its easy.
The above does not consider the need for proper location as the air near the
wing (think feet not inches depending on where relative to the wing) is in
the influence of the wing and does not reflect the true angle.
Pots cost $50-$100 each in small quanity for the needed low friction design.
The pressure sensors needed are 1-2" of water full scale differential and
are not inexpensive. The rest of the parts can cost as little as $25 incl
case in ones quanity. That is; If you are willing to do manual calibration
and no audio, IE dirt simple. As for calibration, its a one time job so a
little work is no big deal in my opinion. Adding offset for flaps in no big
deal either but even with the huge flaps of the C150-172 there was really
little need for flap correction just look at the higher red vs the lower one
for stall.
As for the LEDs I found some that are great and reasonable cost in the
$0.50-$2.00 range that are too bright to look at and wide angle in one
direction.
I am using two only for full panel lighting at night with leds in overhead
behind me or approx 40" away. They are oval with 35 x 70 angle illumination
and quite good in covering the area of interest.
Why have lots of leds when a couple will do.
They are currently in stock at Newark. Try HLMP-BD16 as an example. Red,
amber (yellow), and green, are available. Green is much higher cost with the
others around $0.50 each.
These were the LEDs on display at SnF 2000 in the full sun and driven at
that time at 15 ma. 20 ma hurts the eyes indoors.
Interestingly using a common voltage dimmer for the AOA where the three
colors need to be similar brightness over the range, using one common
variable voltage resulted in close tracking with red being somewhat brighter
but from full sun to full dark. Using one Light sensitive resistor tracked
well in the pre production displays. Note the voltage drop thru the
different colored LED's is different and also the specified ones are nicely
balanced with respect to our eyes so the intensity tracked well between the
colors and light level.
The current AOA design from your referenced MFGR is totally different except
for the LED's I located.
These LED's are a real sleeper and have been around for many years. I do not
understand why they are not better known.
As with all LED's there are a wide range of brightness in the same stock
number but I got several hundred from Newark in 1999 and they are the ones
that today light my acft panel so well. All I have tested are essentially
the same brightness.
When I have time I will document the electronics design etc. The current
unit is approx 1"wide and 2" high and 3" deep in a snap in mount. It
includes auto dimming as part of the display.
I will notify this list with the location of the info when it is available
sometime early next year.
This post is longer than planned but I felt the need to provide some info
for any interested in AOA design and or suitable LED's for panel
illumination.
Paul
Aero engineer as well as Electronics engineer for those interested.
----- Original Message -----
From: "william mills" <courierboy@earthlink.net>
Subject: Re: AeroElectric-List: AOA
> --> AeroElectric-List message posted by: william mills
<courierboy@earthlink.net>
>
> Hi Paul -
>
> I followed your original design and development efforts for an AOA
> system on the Kitfoxlist a few years back, and I know it is now being
> marketed commercially and is flying in a number of planes.
>
> I appreciate the work you've done in bringing this instrumentation to
> the little guys. I knew I was right to hold off on buying one a
> little longer - I'll be watching ;-)
>
> I wish you all the best - and thank you again.
>
> Bill Mills
> RANS Courier/912uls
> covering
> SF bay area CA.
> do not archive
>
Message 3
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| Subject: | [Please Read] SPAM Filter Could Be Causing Posting |
Problems
For Some Members...?
--> AeroElectric-List message posted by: Matt Dralle <dralle@matronics.com>
Dear Listers,
Matronics is now utilizing a SPAM filter appliance to filter out the
excessive amounts of inappropriate email that bombards the Email List
Forums each day. The filter is reporting that over 66% of the email
messages sent to Matronics email destinations are of SPAM content and
reviewing the logfiles, it would appear to be true. That is indeed great!
While the Lists are enjoying the breath of fresh air afforded by the new
appliance, I am suspecting that a few legitimate email List posts are being
blocked as too, although I can't confirm this. It is difficult to churn
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