Help with simple circuit

[René]

Not too worried about having just the strobes on without the Nav
lights...
I don't think I would ever use the strobes without the Nav lights.

I just want to be able to have a way to turn off the strobes so I don't
piss off other pilots while taxiing...

To add to the complexity - one must take care to keep both wings in
sync if the switch is cycled trough the desired states.

(the positive thing is that I did not see any "use a PIC / 555"
answers (I would use a 4017 or a Tiny15)

 

[RST Engineering \(jw\)]

Jim,

Even if the FAA OKs this mod, the OP should be made aware that this mod
can affect other systems in the aircraft, particularly heading compass
that uses magnetic sensing (flux valve).

I don't know of any compass that doesn't use magnetic sensing. As for flux
valve (remote sensing) compasses, the OP stated that it was a light
aircraft. So far, after 40 years as a mechanic, I haven't found a flux gate
installation for the primary compass in any airplane I've worked on or
inspected. Rarely an autopilot installation, but a whiskey compass is
standard on light aircraft AND heavies for that matter.

Any mechanic willing to sign a logbook entry without checking for compass
errors after an electrical installation won't keep his ticket for very long.

It's good practice to use two wires (signal and return). They should be
twisted wires to reduce magnetic effects on the compass system.

Your "good practice" conflicts with Cessna, Beech, Mooney, Piper, Van, and
half a dozen other players' "good practice". You have done certification
work on light aircraft before giving your opinion, yes? You have your FAA
and FCC certificates and such for both original certification,
modifications, and maintenance, yes? You've at least bent one wrench on a
light aircraft, yes?

Of course, none of this matters if you don't care if you arrive at your
intended destination...

That is just a plain stupid statement.


Jim

 

[RST Engineering \(jw\)]

To add to the complexity - one must take care to keep both wings in
sync if the switch is cycled trough the desired states.

Yeah, I was thinking about how to avoid that little problem for a good long
while last night. There is 30' of span between the wingtips on the average
and how does the right tip know what the left tip is doing.

You can force a given state in both units with the first "on" command, but
how do you keep them from glitching once that happens? And, once they get
OUT of sync, it would be damned near impossible to get them back without
returning to the "off" state to resynchronize. You could put a third copy
of the circuit in the cabin with either a bicolor LED or two LEDs to show
what state the third copy THOUGHT both wingtips were in, but how do you know
for sure? A sense wire from both wings would let you do a comparator trick,
but now you've run a second wire to both wingtips, and if you are going to
do that, you've defeated the purpose of the OP.

At night it is fairly simple ... you can see that strobe flash quite easily,
and the little lucite indicator below the lamp tells you whether or not the
nav light is on ... but for daytime????

(the positive thing is that I did not see any "use a PIC / 555"
answers (I would use a 4017 or a Tiny15)

Amen, brother.

Jim

 

[RST Engineering \(jw\)]

Most of us fly with strobes on all day long without the nav lights just to
minimize the possibility of both aircraft trying to occupy the same airspace
at the same time. At least that's what I teach MY students -- and that's
what the FAA suggests that we teach.

What marque of homebuilt?

Jim

 

[Phil Hobbs]

I don't know of any compass that doesn't use magnetic sensing. As for flux
valve (remote sensing) compasses, the OP stated that it was a light
aircraft. So far, after 40 years as a mechanic, I haven't found a flux gate
installation for the primary compass in any airplane I've worked on or
inspected. Rarely an autopilot installation, but a whiskey compass is
standard on light aircraft AND heavies for that matter.

Gyrocompasses, both rotating and laser, don't rely on magnetism. They
work fine at the poles.

Cheers,

Phil Hobbs

 

[RST Engineering \(jw\)]

(a). I said COMPASS, not gyrocompass.

(b). We postulated a light aircraft. So far as I know, there are no
gyrocompasses installed on anything smaller than a bizjet.

Jim

 

[MacGyver]

One word...

GPS

 

[RST Engineering \(jw\)]

To turn the nav lights and strobe on???

BTW, I think this would make a good subject for my column in Kitplanes.
This month's (due on Monday) is going to be the design and construction of a
marker beacon generator but certainly this is a good idea for NEXT month's
column (due out in the March '06 issue).

Jim

{;-)


Jim

 

[MacGyver]

Wag-aero Supercub (metal spar wings) is the first intended testbed.
But if this works out, I am going to put it on a 1966 Cherokee 140 as
well & then get the field approval. I have a very cool mechanic that
is more than happy to help make this happen on the cherokee legally.

 

[John Fields]

You actually have four functions that are necessary:

Off
Nav Light On
Strobe On
Nav Light and Strobe On.


Think about it.

Off is obvious

Nav Light On when flying in darkness in cloud. Strobes induce vertigo when
you are in IMC, but the nav lights by law have to be on at night.

Strobe On would be daytime use when you want to be seen but not keep a $5
lamp burning for no good reason.

Nav Light and Strobe On for VMC at night when you need not only nav lights,
but to be seen at a distance as well.

NOW the problem complexes itself up, but shouldn't be a problem with a few
well chosen capacitors and a simple counter.

 

[John Fields]

Wag-aero Supercub (metal spar wings) is the first intended testbed.
But if this works out, I am going to put it on a 1966 Cherokee 140 as
well & then get the field approval. I have a very cool mechanic that
is more than happy to help make this happen on the cherokee legally.

 

[Phil Hobbs]

(a). I said COMPASS, not gyrocompass.

(b). We postulated a light aircraft. So far as I know, there are no
gyrocompasses installed on anything smaller than a bizjet.

Jim

Well, if you're defining "compass" specifically as relying on magnetic
sensing, then it isn't much use saying that you don't know of one that
doesn't. However, that's a private usage of yours.

Saying that a gyrocompass isn't a compass does sort of suggest that
emotion has eclipsed thought in this discussion. Not that that's
unusual on s.e.d, of course.

Cheers,

Phil Hobbs

 

[Rich Grise]

[...]

If the wing is made of metal, it is the return path. Its a lot like what
is done in cars.

I don't think that is legitimate in aircraft. I think the OP is
heading for problems with the FAA, unless his craft is "experimental".

Lots of aircraft have lots of currents flowing in the skin. If the
factory made it that way, getting rid of the current in the skin will get
the FAA spun up.

ISTR he said it's an experimental plane, so I'd think he can do pretty
much whatever he wants to. ;-)

Cheers!
Rich

 

[MacGyver]

Hey John thanks for reading... The spars are really the ground, but for
all intensive purposes it's the whole wing minus the fibreglass tip.
Not looking to profit from this, just want to get it done. I just
don't see much of a market for it. Not too many planes are out there
these days without strobes already installed.
At least not at my airport. I am really looking for a jpeg diagram &
parts list, as I am having trouble following the ascii diagrams in this
page.
Thanks so much for any help you can offer. I honestly thought this
was going to be a simple circuit!
[email protected]

 

[John Woodgate]

I read in sci.electronics.design that Phil Hobbs

Gyrocompasses, both rotating and laser, don't rely on magnetism. They
work fine at the poles.

So what do they indicate at the North Pole?

 

[Jeroen Belleman]

In sci.electronics.design, Phil Hobbs wrote


So what do they indicate at the North Pole?

Straight up ;-)

Jeroen Belleman

 

[petrus bitbyter]

Hey John thanks for reading... The spars are really the ground, but for
all intensive purposes it's the whole wing minus the fibreglass tip.
Not looking to profit from this, just want to get it done. I just
don't see much of a market for it. Not too many planes are out there
these days without strobes already installed.
At least not at my airport. I am really looking for a jpeg diagram &
parts list, as I am having trouble following the ascii diagrams in this
page.
Thanks so much for any help you can offer. I honestly thought this
was going to be a simple circuit!
[email protected]

What about the old, analog way? Insert a sinewave of - let's say - 1kHz/1V
on the nav lights line when you want the strobes on. At the tip you filter
the sinewave, amplify it and power a relay with it which switches the
strobes on. As you send the signal from a central point, sync will be no
problem. Of course, you will have to do some extra work as you want to keep
that sinewave out of the rest of your boardnet.

Another method may be to interrupt the nav lights periodically. Let's say
every second for one ms or less. Lightbulbs will not be effected but these
interrupts can be detected by electronics relative easily. (Supposing DC
power of course.)

In AC nets, signaling is often done by shorting the sine shortly before
zerocrossing. I know it is done in 240/380Vac mains nets but I don't know
what it needs to detect it.

I have no idea whether safety regulations will be effected.

petrus bitbyter

 

[Ken Smith]

What about the old, analog way? Insert a sinewave of - let's say - 1kHz/1V
on the nav lights line when you want the strobes on. At the tip you filter
the sinewave, amplify it and power a relay with it which switches the
strobes on.

I like this idea. You don't need a very good sinewave so you could use a
555 to create the sine wave and a PIC to detect it in the wing tip.

Actually, I think you want 2 sine waves. One tone means "strobe only" and
the other means "lights only". Both tones should cause both on, not both
off, as should no tone.

 

[Jim Thompson]

Straight up ;-)

Jeroen Belleman

Or straight down ?

...Jim Thompson

 

[Fred Bloggs]

At least I think it is simple...

I have 2 12v wingtip lights that I need to be able to control with
one switch and one wire running through a wing in an airplane.
This is for just one wing. That's the gist of it.

I just bought piggyback strobes for the wingtips, but I don't want to
have them on all the time that I have the navigation lights on.

I was thinking of a relay that has a remote control, or has a signal
run through the positive wire or could possibly have a low & high
setting and if we send 12 volts to the relay it trips, but it won't
trip at say 10 volts.

Also was thinking about if I turn the switch on once just the light
comes on. Flip the switch off & on again in under 2 seconds and the
lights & strobes come on. Leave the switch off & everything turns off.

I was thinking about relays with a capacitor to keep the line live for
2 seconds to be able to flip another relay... but now I am confusing
myself again.

The ruggedized approach uses an SCR latch. The timing components are the
2.2U and 2.2M. If the circuit is switched on when the 2.2U is
discharged, T1 is triggered immediately and grounds out the gate of T2
preventing it from triggering. The strobe lamp remains OFF, and the 2.2U
charges to the battery voltage. When SW is turned off, T1 turns off and
2.2U discharges very slowly through the 2.2M with a 6 second time
constant. If SW is turned on before the 2.2U has discharged to
approximately 6V, T1 is prevented from triggering by the zener diode,
ZD, and T2 is now allowed to trigger and activate the STROBE lamp.
View in a fixed-width font such as Courier.

..
.. SW >---+------------------------------------------+
.. | |
.. V strobe
.. - lamp
.. | |
.. +----------------[1K]----+----------+ +-----+
.. | | | | |
.. [1K] | | | |
.. | | | | |
.. V | | | |
.. - | | | |
.. | [100] | | |
.. +----+ | | | |
.. + | | | | T2 | |
.. === [2.2M] | | --- |
.. 2.2U| | +-[1K]-+---------\ / |
.. +----+----[100K]-----+ | | | --- |
.. | | | | | | |
.. | ZD |T1 | | | | |
.. | 6.2V | --- [1K]=== | [100]
.. +------|<|--+---+--\ / | |0.1U | |
.. \ | | --- | | | |
.. [10K]=== | | | | ===
.. | |1n | | | | |0.1U
.. | | | | | | |
.. +---+---+------+---+------+-----+
.. |
.. ---
.. ///
..