nulrich(at)technq.com
Guest
|
 Posted: Sun Dec 17, 2006 7:07 am Post subject: Annunciator details |
 |
|
Alan et al:
I don't have a schematic of the annunciator panel. I was bad and just did
the layout directly. It's a bunch of identical very simple circuits: low
inputs ground the LEDs directly, high inputs ground them using a transistor.
Then there are a bunch of diodes in the obvious places. I use 1/2 watt 240
ohm resistors with the bar LEDs to give ~30 mA on a 14 V supply voltage,
higher value resistors on the discrete LEDs to balance the light output (to
my eye). It is fed by 14 V directly when the nav lights are turned off, by
the panel dimming rheostat when the nav lights are on. Not perfect, although
these bar LEDs seem to track voltage fairly well, a microprocessor could do
a better job.
I added another photo of some of the annunciator components to
picasaweb.google.com/nathantu although I didn't take any detailed photos of
the assembly. Have to work on that.
I was limited somewhat by two things: (1) My Bonanza is a certified
aircraft, so putting a bunch of discrete components and lights in a box was
deemed acceptable by my IA, whereas programming a microprocessor, even a
little PIC, would require a 337 at the very least. (2) I'm a mechanical
engineer, not a EE  .
My packaging constraints were very tight, and I had some unique needs, so my
mechanical design isn't appropriate for broader uses. Given that my business
is product development (though not in the aircraft world I've thought
quite a bit about a more general purpose annunciator product. I would
probably do the following:
Build it in a more modular fashion, with replaceable "tiles" of reverse
engraved material that is also colored (green, red, or yellow) depending on
the warning. That would allow the use of clusters of surface mount white
LEDs instead of colored bar LEDs. Probably makes sense to have modules of 4
or 8 tiles which can be clipped together. Whether there is one processor per
module or master and slave modules is a question for you EE types.
Of course, if you make it too modular, then you are approaching the Korry
type discrete annunciator light/buttons for certified aircraft (~$400 each
last I checked, though).
I'd be glad to give some feedback on the mechanical design issues when you
guys settle on a spec. If there's enough demand, we have good CNC
capabilities and could make up the housings in reasonably sized batches if
it goes that far.
Nathan
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
