Today's Message Index:
----------------------
1. 02:49 AM - electrical interfaces [was: EFIS 1 and SL-30] (Rowland Carson)
2. 08:31 AM - Re: electrical interfaces [was: EFIS 1 and SL-30] (Martini Luc J.R.)
3. 11:05 AM - Re: electrical interfaces [was: EFIS 1 and SL-30] (Doug McNutt)
4. 01:40 PM - EFIS1 and SL-30 (Mark Taylor)
Message 1
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| Subject: | electrical interfaces [was: EFIS 1 and SL-30] |
--> Avionics-List message posted by: Rowland Carson <rowil@clara.net>
At 2004 04 09 02:06 -0400 Dean Psiropoulos wrote:
>Years ago
>aircraft instruments were
>electro-mechanical devices
>interfaces were mainly resolver and synchro
Dean - thanks for that good explanation. I wonder if you are the man
to point me in the right direction for some more information which
harks back to the steam-radio era.
I have a S/H air-driven directional gyro which came from a
single-engine aeroplane that wasn't going anywhere any more. It has a
heading bug, and a 4-pole electrical connector on the rear which the
guy breaking the aeroplane assured me was for an autopilot. My tame
gyro expert has given the mechanical parts a clean bill of health,
but I haven't been able to get any info from the (French - Badin
Crouzet) manufacturers on the electrical interface. They seem to have
gone out of the light single business some time back. I am hoping
that the electrical interface on DGs might be standard (or maybe the
French do not think the same!) and that I could perhaps put together
some sort of wing leveller that would work in the Europa I am
building (although the panel is a long way away yet). As a retired
electronic engineer I am happy to get into circuit design if I have
some clue about what is supposed to go in or come out of those 4 pins
on the back of the DG. From my initial careful proddings with a
meter, it appears all pins are connected by some sort of fairly
symmetrical resistive mesh - perhaps a resolver could look like that?
I'll have to look back at my old "servos and control systems" notes
of 40 years ago to remind myself how resolvers & synchros work!
Am I on the right track here? Do you know anything about how heading
bugs on DIs interface to simple autopilots? Or do you know where I
might expect a good answer to this question?
regards
Rowland
--
| Rowland Carson PFA #16532 <http://home.clara.net/rowil/aviation/>
| 660 hours building Europa #435 G-ROWI e-mail <rowil@clara.net>
Message 2
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| Subject: | Re: electrical interfaces [was: EFIS 1 and SL-30] |
--> Avionics-List message posted by: "Martini Luc J.R." <martini@foxinternet.net>
Hi
I thought I would put two cents worth in here.
I also am an Electronics Engr. type. I happen to have a Dornier Do-27 built
in 1959, that I am restoring. The airplane lives at Crescent City, CA,
which is known for its unpredictable fog, so, I have upgraded it to a
minimum IFR capable bird. To make matters as hard for me as possible, I
wanted to retain to the greatest extent possible, the original not only
INSTRUMENTATION, but AVIONICS as well. The restoration is that of the
Israeli version of the airplane as it existed in the Yom Kippur War of 1973.
To do that, I am replacing only ONE guage on the pilot's instrument panel, a
Course Deviation Meter (AN Beacon type guage) is being replaced with a
SANDEL SN3308 EFIS. That great instrument requires an input from a Gyro
to tell it where to point the heading card .
The original Gyro, was a SPERRY OF LONDON, 5 1/2 inch beauty, combo 3 phase
110VAC Gyro & Indicator. It also was a compensated Gyro, with a Flux
Gate out in the wing, and an old tube Precession Amp and a Lattitude
Correction Box under the back bench of the airplane. No data was available
(although I eventually did find a few things) so I set about building my own
schematic and wiring diagram for the system. I had hoped that I could tap
into the Fluxgate signal to get the input to the EFIS that I needed (3 phase
signal representing North, and a Reference Phase preferably that driving the
Fluxgate). Alas that did not work, for the signal level was way too low. I
got lucky and found a guy that had a Canberra Bomber, which also used a
similar for different model of this Gyro. The Canberra of course had an
autopilot, and indeed this gentleman had acquired several spare resolvers
when he got his Canberra. He also happened to be an Avionics Tech, and
modified my Gyro Instrument by putting in one of these spare Resolvers, and
wiring that to to a few spare pins on one of the connectors. Yep, 4 Wires,
Phases A,B and C which are the Compass Card Position Signal, and a 4th pin
used as the "Reference Phase" which is usually Phase A, which can come
directly off of the Dynamotor ( usually goes directly to the Gyro Drive
Motor Stator as well as the Fluxgate) which feeds these usually 110 VAC
systems. (you then of course use the same "C" pin as the common "Low or
signal ground".
If indeed you already have a resolver in your Gyro Instrument, then you most
likely have it whipped. To test it out, you can buy one of the single
needle ADF gauges (nothing more than a compass rose and a needle) that you
find on e-bay all the time from 1960's era airplanes. The only other thing
you will then need is a 26VAC 3 phase source, which you can probably throw
together with some old radioshack analog chips... and maybe a couple of Q's
to give it about a 1/4 amp current capability.
Careful here, the 110 VAC 3 Phase drives the Gyro, but the Resolver signal
level is 26VAC or less. If you have a Fluxgate, that signal also changes
the frequency (doubles) to 800 cyles.
Luc
----- Original Message -----
From: "Rowland Carson" <rowil@clara.net>
Subject: Avionics-List: electrical interfaces [was: EFIS 1 and SL-30]
> --> Avionics-List message posted by: Rowland Carson <rowil@clara.net>
>
> At 2004 04 09 02:06 -0400 Dean Psiropoulos wrote:
>
> >Years ago
>
> >aircraft instruments were
> >electro-mechanical devices
>
> >interfaces were mainly resolver and synchro
>
> Dean - thanks for that good explanation. I wonder if you are the man
> to point me in the right direction for some more information which
> harks back to the steam-radio era.
>
> I have a S/H air-driven directional gyro which came from a
> single-engine aeroplane that wasn't going anywhere any more. It has a
> heading bug, and a 4-pole electrical connector on the rear which the
> guy breaking the aeroplane assured me was for an autopilot. My tame
> gyro expert has given the mechanical parts a clean bill of health,
> but I haven't been able to get any info from the (French - Badin
> Crouzet) manufacturers on the electrical interface. They seem to have
> gone out of the light single business some time back. I am hoping
> that the electrical interface on DGs might be standard (or maybe the
> French do not think the same!) and that I could perhaps put together
> some sort of wing leveller that would work in the Europa I am
> building (although the panel is a long way away yet). As a retired
> electronic engineer I am happy to get into circuit design if I have
> some clue about what is supposed to go in or come out of those 4 pins
> on the back of the DG. From my initial careful proddings with a
> meter, it appears all pins are connected by some sort of fairly
> symmetrical resistive mesh - perhaps a resolver could look like that?
> I'll have to look back at my old "servos and control systems" notes
> of 40 years ago to remind myself how resolvers & synchros work!
>
> Am I on the right track here? Do you know anything about how heading
> bugs on DIs interface to simple autopilots? Or do you know where I
> might expect a good answer to this question?
>
> regards
>
> Rowland
> --
>
>
>
Message 3
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| Subject: | Re: electrical interfaces [was: EFIS 1 and SL-30] |
--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
At 08:31 -0700 4/10/04, Martini Luc J.R. wrote:
SNIP
> The only other thing
>you will then need is a 26VAC 3 phase source, which you can probably throw
>together with some old radioshack analog chips... and maybe a couple of Q's
>to give it about a 1/4 amp current capability.
>Careful here, the 110 VAC 3 Phase drives the Gyro, but the Resolver signal
>level is 26VAC or less.
Perhaps it's nitpicking but selsyn angle transmitters are not really "three phase"
in the same sense that 120 VAC 400 Hz 3 phase drives a gyro motor.
The motor depends on a power source in which three sine waves are delivered 120
degrees apart in time. That is used to make a rotating magnetic field that makes
a rotor spin. It's the same as those 60 Hz power wires you dodge at low altitude.
It's also like the nearly 400 Hz generated in an automotive alternator
before it's rectified to 14 VDC.
The selsyn transmitters and receivers use a single phase, almost always low voltage,
source of AC power and it is usually connected to the R1 and R2 terminals.
It acts as a rotatable transformer which couples to the S1, S2, and S3 terminals
in a way that the amplitudes of the three voltages represent the angle of
the shaft. All three voltages have the same 400 Hz phase as the reference voltage
applied. If you look at the amplitudes for a rotating shaft the mathematics
are very much like three phase power but at a much lower frequency.
There are three phase 400 Hz 24 volt sources on the market though I have never
seen one in an airplane. That's not what you want. Single phase with a pretty
good sine waveform is the goal. A Radio Shack speaker amplifier with a 400 Hz
oscillator is, as the man says, appropriate
If you have 400 Hz power at 120 VAC for the gyro it's possible to derive the 24
volt 400 Hz reference from that using a step down transformer on one of the phases.
Better equipment generates its own sine wave reference with a tightly controlled
frequency.
I have a Lear L3 autopilot, well - - - most of the parts of it, that I removed
from my Piper Apache. All vacuum tubes and a lot of selsyn pickup devices with
electronics that handle the outputs. All vacuum tubes with a motor generator
used to create plate voltage. I had most of a manual but I gave up on maintaining
it. The weight is 75 pounds or so and it's at 00V in Colorado Springs. Ask
off line if you're interested.
--
--> In Christianity, man can have only one wife. This is known as monotony. <--
Message 4
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--> Avionics-List message posted by: "Mark Taylor" <mtaylo17@msn.com>
Thanks guys for input! It's welcomed!
I've posted the same questions on the BMA discussion board too. Maybe
someone can help me shed some more light on this.
As I understood it, I could use the EHSI in EFIS as the OBS head. The
question now is can EFIS1 utilise the serial info output from the IFR Cert
External GPS and display info on the EHSI?
It's a minefield! I want to get this right, and in order to do this I've
been scouring every source possible.
I'll post any findings here too... It's all good information.
Mark Taylor
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