An ounce of experience is worth a tonne of theorising!
Duncan McFadyean
On Friday, March 22, 2002 10:01 AM, Klaus Dietrich
[SMTP:Klaus.Dietrich@oracle.com]
wrote:
> I have a red 12V LED installed for the Alt warning light and it works fine.
> Klaus
>
> Tom & Cathy Friedland wrote:
>
> > Hi Europaphiles
> >
> > I plan to use red, green and white LEDs under molded plastic lenses for
> > position
> > lights. There of course are lots of advantages, low power consumption, long
> > lasting, bright, etc. I just need to make the lenses!
> >
> > Tom Friedland XS Mono N96V
> >
> > Fred Fillinger wrote:
> >
> > > Hi, Troy -
> > >
> > > LEDology simple for autos and planes, as you can assume the extra
> > > volts when the alternator is working equals the forward voltage of the
> > > LED. Divide 12 volts, not 13.75V, by .020 (typical current figger),
> > > and that's a 620 ohm, 1/2 watt resistor.
> > >
> > > Some LEDs have internal dropping "resistor," and your "12 volt rating"
> > > sounds like just that, and they should take 13.75. No drop resistor,
> > > but I have some suggestions that can deny their use.
> > >
> > > Another factor is viewing angle. Too wide are dimmish. Too narrow can
> > > be annoying, esp with clear lens, or miss the warning cue. Color,
> > > too, in sunlight, and there's whites and blues nowadays. LEDs are so
> > > cheap, for sunlight use, I buy an assortment and make them show me
> > > something outside. And there's .4" square, white diffused lens jobs
> > > that can be black-letter, clear-labeled on the face. Real cool are
> > > LEDs with built-in flasher chip.
> > >
> > > Alt warning lite may be a problem, as its operation may depend upon
> > > the low resistance
> > > of the incandescent lamp (Tony, Rotax Dealer?). Wouldn't bet what an
> > > LED will do when the "L" line goes low on all faults, thus requiring a
> > > 10# sledge hammer to fully test. Safer bet is an NPN transistor
> > > circuit, reverse biased to off at the emitter when that line is high,
> > > like when alternator is OK, equivalent lamp resistance emitter to
> > > ground, unfortunately wasting c. 1/4 amp. LED/dropper in collector.
> > > Further details on request.
> > >
> > > For door ajar, you can pop-rivet springy tangs or coils, out of a
> > > battery compartment from junk electronic stuff, to contact each shoot
> > > bolt, wired in series from through the internal metal of bolt
> > > mechanisms, port to starboard, to a ground. You'll need an NPN
> > > transistor circuit to sense an open:
> > >
> > > Tie base and collector together to really annoy the transistor. 14V
> > > through LED dropping resistor to base-collector. LED from emitter to
> > > ground. Base-collector to the shoot bolt circuit open end. It's an
> > > unswitch - when shoot bolt switch turned on, grounding base, it
> > > doesn't do anything. The triple-duty resistor also limits current
> > > flowing through exposed door hardware and minimizes effect of
> > > dirt/grease on the shoot bolts.
> > >
> > > Further, seems you can take the ground from the shoot bolt circuit
> > > through a lever-type microswitch in the throttle housing, affixed to
> > > close at above runup throttle position. No door alert until plane
> > > thinks you're taking off; could even quick-nudge the throttle in runup
> > > to check the doors. But that could make you insufferable at a fly-in,
> > > showing off features like that.
> > >
> > > For oil press, there are oil pressure switches like to fire up a Hobbs
> > > meter. But you don't want to plumb a tee in the Rotax oil pressure
> > > sender, a potential engine failure looking for a time to happen. To
> > > electrically tap the Rotax sender, your oil pressure gauge circuit
> > > would have to see at least .7V there, at alert PSI, and an add-on
> > > transistor circuit must not load or bias it so as to cause inaccurate
> > > gauge reading. A more complex IC comparator circuit may be the only
> > > way.
> > >
> > > For "master on," an LED always on, off when shutting down, is not a
> > > good alert. I'd try to invert the logic, with flashing LED (or see
> > > below), by grounding LED circuit through again the "L" thing on the
> > > alt reg. It looks good on paper, and would alert only between engine
> > > and master off.
> > >
> > > For vital warnings, there's also "Sonalert" type devices. Whistles,
> > > warbles, buzzers, chimes, sirens, and up to enough decibels to cause
> > > soiling of the shorts. We go to power transistors where needed then,
> > > due to current.
> > >
> > > Best,
> > > Fred F.
> > >
> > > TroyMaynor@aol.com wrote:
> > > >
> > > > Hi Gang,
> > > > I have searched but can't find it in the archive. Someone mentioned the
12v
> > > > 3w lamp that is the alternator warning lamp being changed to an LED and
that
> > > > you had to add a resistor, I think, to make the regulator function
> > > > correctly.
> > > > Does anyone know what will work for sure on this? I have some nice LEDs
that
> > > > are 12 volt rated that I want to use. In fact I want to make a series of
5 or
> > > > 6 warning LEDs on a little panel to operate at the correct intensity
> > > > with
a
> > > > 12 volt input to each. I am planning to use one for oil press./master
> > > > on;
one
> > > > for alternator; one for door ajar; one for engine monitor; and starter
> > > > engaged. The alternator one is the one I was concerned about. Is this no
big
> > > > deal to do? I am electronically challenged. Please help if you can.
> > > > Best Regards,
> >
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