avionics instrument, motor

Go To Last Post
26 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I have the instrument shown in the photo and I want
to play with it. There are resolvers in it.
They are not the problem. But there are motors inside
of a type I dont know.

The motors have a motor part and a tacho part.
The motor part has two windings and an
additional winding labeled "ref 26V 400c/s" .

It might be a "two phase AC torque motor" but I am
not sure. I there an avionics expert there to help me ?

Attachment(s): 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Try asking the guy on http://www.mikesflightdeck.com/

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It's a VOR with ILS support by the looks of it. IOW an HSI. Something like:

http://ericgideon.com/lessonplan...

BTW looks like someone's nicked the DME from the top left.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ossi,

I used to work on this type of instrument.

Is there a manufacturer's name on the instrument?

Are there any identifying names, numbers, etc on the "motors"? How many total wires on the motor part? (not the "tach") What are the colors of the wires?

Are you knowledgeable about synchros and resolvers?

The "two-phase AC torque motor" might actually be a resolver (or synchro). Resolvers are used as position sensors as well as rotary positioning "drivers". Most avionics resolvers (& syncros) run on 400 Hz, 26 Vrms as your quoted nomenclature attests.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
It's a VOR with ILS support by the looks of it.
Only has localiser indicator, no glide scope, but yes, definately a VOR. I guess the 'Glide' flag could be enabled when actually on the glide slope, but it's not of a type I'm familiar with.

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thanks for all the hints !
There are two typs of motor/synchro things.
One type is labeled
"MUIRHEAD Synchr control transformer"
It has a three wire primary 11.8V, I suppled 400Hz
quadrature voltages to them. The secondary is one
winding, and I get a nice resolver signal witth
phase=angle from it. So I concluded that are the
resollvers/synchros, so the others must be the
motors.

They have a label SMITHS size 08 on them
(probably manufactirer)

then it has written:
Control 20V 400Cs
RESID 15mV
no load speed 5600rpm
stall torque15 gm cms
0.31V/1000 R.P.M. (probably tacho conversion factor)

motor part has 6 wires in total.
probably two windings with same data and wire
colors:
winding 1: red and red-blak
winding 2: green and black
then an additional (control ?) winding
Ref. 26V 400C/S the wire colors:
white and yellow

And now the AVR part:
I am currently generating sine and cos 400 Hz signals
with an ATmega88 via PWM to feed the servo. Then
I will use the ADC to get the reading and convert it
to degrees and output via RS232.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

OK, good info so far.

What are you trying to do with this?

Do you know the difference between electrical phase and mechanical phase in synchros and resolvers? Please elaborate on what you mean by "sine and cos 400 Hz signals" so I know we are talking the same terminology?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi Chuck-Rowst,
first of all I know nearly nothing of avionics.
With sin and cos signal I mean the two Voltages
have a phase difference of 90 degrees.
Like shown here:
http://de.wikipedia.org/wiki/Res...
(sorry its german, but the english wikipedia
didn't have it).

I have no specific plan what to do with it.
First of all its just to learn and play.
Then perhaps I will built a "clock"
with it.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You could build an HSI interface for M$ FlightSim :)

See '4.2.1 The Dowson route: FSUIPC' at
http://www.fscockpit.com/interfacesoftware.html
For Peter Dowson's incredible interface software.

--greg
Still learning, don't shout at me, educate me.
Starting the fire is easy; the hardest part is learning how to keep the flame!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ossi,

Yeah, my technical German is a bit rusty!

But let me explain something about synchros and resolvers that is widely misunderstood.

The term "phase" when applied to synchros and resolvers does not usually refer to the electrical phase of the 400 Hz signals. It refers to the "mechnical phase". I'll explain. In a typical synchro or resolver mechanism all of the 400 Hz sine waves on all of the windings (primaries and secondaries) are either electrically in-phase or 180-deg out-of-phase - meaning the sine wave is electrically inverted. There are some electricla phase shifts between all of these signals, but they are typically very slight - one degree or so.

The "phase" refers to the angle of the rotary shaft with respect to a reference mark on the case of the S or R. Thus the term "mechanical phase".

Synchros and resolvers are essentially "rotary transformers". Typically, the primary is wound on the rotor, and the secondaries (2 for a resolver, 3 for a synchro) are wound in the stator and fixed to the case.

If you excite the primary with the rated signal - in your case a 26 VRMS, 400 Hz sine wave of adequate drive capability (the current draw is typically a few hundred mA), and observe the resulting, induced signals on the secondaries you will notice that their amplitudes vary as the shaft is rotated thru its 360 degrees of travel. (Often, S & R's have a mechanically limited range of travel - often one full turn.)

If you plot the AMPLITUDES of the secondary voltages on a resolver you will find that they vary as the sine and cosine of the shaft angle. If you remember your high-school trigonometry, the sine and cosine have the same sign (polarity) from 0 to 90 degrees. From 90 degrees to 180 degrees the cosine goes negative. In resolver-land that means the induced sine wave will be inverted (180 deg out-of-phase) with respect to the excitation sine wave applied to the primary. What really "counts" is that the ratio of the secondary amplitudes are equal to the ratio of the sine and cosine of the shaft angle. You can do the math for all of this on any scientific calculator. (It's also important to load the secondaries with the rated load - usually 600 ohm resistors of suitable wattage.)

A synchro works similarly except the three secondary voltages are all out-of-phase mechanically by 120 degress of shaft angle (1/3 of a revolution). The trigonometry math is a bit more tricky here. But the thing to remember is that for each shaft position in a revolution there is a unique set of three amplitudes on the secondaries.

The one component you identified as:
"MUIRHEAD Synchr control transformer" is more than likely a synchro. Often, the three secondaries are hooked up in a delta connection (three wires to the outside world) but someitmes a wye connection is used (4 wires). If you don't realize what you are dealing with you might ohm these out and think you are dealing with two windings instead of the actual three.

This is a pretty esoteric technology, and today on the verge of complete extinction. But, definitely a topic of interest for the excessively curious amongst us!

Having said all of that, it is possible to drive resolvers and synchros with electrically phase-shifted signals and make them rotate continuously like a motor. That may be what your component with the RPM rating is. Unfortuneately, I don't have any experience with this use of S & R's.

Synchros and resolvers were invented in WWII. Their original use was to transmit a rotary position from various "sensors" to the cockpit needle instruments. The synchro that was connected to the "sensor" (perhaps a gizmo that mechanically converted wing flap angle to synchro shaft angle) was called the "transmitter" it was wired to a dash mounted synchro called the "receiver", which has a pointer needle attached to its shaft. The "transmitter" and the "receiver" were wired directly together (no amplifiers, or other electronics). The "magic" was that as the shaft of the "transmitter" was turned by the "sensor" the needle pointer on the "receiver" would automatically turn with great precision to the exact shaft position of the "transmitter". Add some ingenuity and in a few years just about every instrument on military and commercial aircraft had a synchro or a resolver involved somehow.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi Chuck-Rowst,
thanks for your explanation. Do you have any
information about the motors used in this unit ?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I got the motor running. :lol:
I supplied the phase labeled "ref" with 20V 400Hz and
one of the other windings with 400Hz but phase shifted
about 30 degrees. I am not sure whether that's the right
way but it works for me. So I can now think what I will
do with this gadget.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

A sin-cos DC torquer will position itself to any angle 0-360 if you apply DC sin(angle) to one coil and cos(angle) to the other coils. Same as an automotive aircore motor. Easy to generate with dacs and a buffer amp. The CT is a control transformer. You apply the sin and cosine and the ref as inputs, and the output is the secant.... sin/cos, the ampl of which represents the error between the sin cos input and the ref. You can decode with a 'synchronous rectifier' which uses an analog switch to switch between something and something else, which I am obviously not to sure about.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

sin/cos = tan?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I typed that from memory. Sorry if my trascendental identities are upside down. The part that is correct is the CT outputs the secant as the error signal

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ossi,

Good Job!

Like I said, I don't have much experience with this type of motor, but I think you've probably got the right idea based on my static resolver experience.

The only thing I would suggest is experimenting with different phase angles for driving the coils. It's more likely the phase angle should be 90 degrees or close to it. You may find that the resulting shaft torque is greatest for a certain electrical phase angle difference between the windings. For this size motor simply pinching the shaft between your fingers and manipulating the phase shift may be a good enough indicator of when you get it right.

Just for clarity: If you take a sine wave and shift it by 90 degrees, it is then a "cosine" wave. Of course, like all phase shifts, these sine & cosine wave phase shifts are relative to each other. The sine vs cosine designation for waves is only relevant when you have both together in one system. Viewed individually on a scope they look identical in shape. Only when you trigger the scope off one and view the other do you see the phase shift.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The good thing is, that I can use squarewaves to
drive the motors. Making 24Vpp squarewave is much
easier than 24V sine. I now us a simple halfbridge
made from darlingtons. Works fine.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

OT: It looks very nice, would you mind sharing some more photos of the interior?

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ossi,
The harmonic remainder of the square waves will likely end up as heat being dissipated from the motor windings. Keep an eye on the motor case temperature to make sure you are not baking the motor to death. But, I'd guess you would be OK in this type of low-load low-torque application.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

My first project is probably a kind of clock. In that
design I would move the dials to the right position every minute or so. So most of the time the motors will
be off. So danger of baking them will be low. But
thanks for the recommendations !

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Here are some more photos for daqq.
And I have a video on youtube:

http://www.youtube.com/user/ossi...

Attachment(s): 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

another photo

Attachment(s): 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Yam yam.
Beauties of engineering. Those will keep you busy for a while.

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia and Tessa, You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thanks for the photos ossi! A beautiful piece indeed!

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

For those who are interested in synchro/resolvers:

Synchro/Resolver Conversion Handbook

www.ddc-web.com/documents/synhdb...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

This site has the HSI rear connector pinout
http://aviation.watergeek.eu/f4b...

Imagecraft compiler user