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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