3 Axis DC/DC Gyro

[padu]

Hi Folks!

Just bought this beauty:

**broken link removed**

Looks very sturdy. It is a 3-axis DC/DC gyro. I believe it is
eletromechanical. I couldn't find any online reference on the pins and how
to operate it. Anybody has any suggestion before I start messing around with
it?

The label reads:
NORTHROP CORPORATION
Precision Product Division
FSC 51834
Mfr. P/N: 50162-317
3 AXIS DC/DC GYRO PKG.
P/N 50162-317
SER.NO 104
WT. 1,8 LB


It has a 10 pin circular connector (milspec type). Since it is analog, I believe that a pair of pins is for power (voltage?), and there should be one pair for each axis that should be proportional to
the rate of rotation.

Any pointer appreciated.


Cheers

Padu

 

[bryan1]

Well I took a look at the ebay site where you got it from and MAN $51.00 for that . Now Northrop is a defence company from memory so that item might be surpus military gear. If this is the case then finding any data will be harder than picking the winning numbers in lotto. Anyway at over a pound it will make a good anchor for your model boat if you own one

 

[Papabravo]

The good news is that Northrop as a company is still around. The bad news is I don't think they have much experience dealing with the public. You might try calling or writing to them.

Your last hope might be a group of guys restoring old warbirds like the Yankee Air Force. They specialize in making old planes fly again and that might include items such as the one you have.

Some years ago I remember a story about a guy who built a fully flyable F-104 from surplus parts. I think his name was Dan Greenemeyer. He must have had one awesome Rolodex full of contacts.

 

[dknguyen]

Oh wow that's an awesome find...if you can figure out how to use it. Talk to Northrop and be patient...

 

[Papabravo]

You might try the curator at the Air Force Museum in Dayton, OH
You might try the Henry ford Museum in Dearborn, MI

 

[padu]

The good news is that Northrop as a company is still around. The bad news is I don't think they have much experience dealing with the public. You might try calling or writing to them.

Your last hope might be a group of guys restoring old warbirds like the Yankee Air Force. They specialize in making old planes fly again and that might include items such as the one you have.

Some years ago I remember a story about a guy who built a fully flyable F-104 from surplus parts. I think his name was Dan Greenemeyer. He must have had one awesome Rolodex full of contacts.

Amazingly enough, I found a couple of people in different divisions of Northrop with a very good will to help me. The problem is that neither the part number or the FSC number were found in any database. To be more precise, one guy from Burbank found from the FSC number which division used to manufacture that part and forwarded my request to that division in El Segundo. The guys from El Segundo were able to find out that the part number provided was manufactured by a division that was sold to Allied Signals, that was sold to Honeywell.

They gave me the contact of Honeywell, I called them but they were unable to find the part number. The lady told me that the number is not on the computer, but she would do a search on the physical archives but I don't have my hopes high....

Another hope I have is one guy named Stephen Bruder who wrote a paper on autonomous navigation on 1998 using this gyroscope. I was able to talk to the guy and I'm still waiting if he's going to be able to find a datasheet or something.

Next step will be starting to probe it with an oscope and a bench power supply until I see white smoke coming out of it...

In that respect, anyone here has any experience with DC avionics (I'm guessing that the part was used on aircrafts)? Any suggestions on how to discover how this thing works?

Cheers

 

[Papabravo]

There are two things I know about aircraft electrical systems.
1. There are two DC power busses, one is 28 VDC, [24..29] and the other is 270 VDC, [260..280]. I also include the tolerances.
2. There is an AC supply of 113 to 118 VAC, BUT at a frequency of 400 Hz.

The 270VDC bus is used to move the DC electric servos which articulate the aircraft control surfaces. The 28VDC operates the radios.

The gyro could be run from a vacuum pump as easily as a motor. Do you see any plumbing connections on it?

Awesome start on the detective work by the way.

 

[padu]

There are two things I know about aircraft electrical systems.
1. There are two DC power busses, one is 28 VDC, [24..29] and the other is 270 VDC, [260..280]. I also include the tolerances.
2. There is an AC supply of 113 to 118 VAC, BUT at a frequency of 400 Hz.

The 270VDC bus is used to move the DC electric servos which articulate the aircraft control surfaces. The 28VDC operates the radios.

The gyro could be run from a vacuum pump as easily as a motor. Do you see any plumbing connections on it?

Awesome start on the detective work by the way.

The device label says "DC/DC Gyro", so I guess it is moved by DC.

It has only one interface, a milspec 10 pin circular connector. I opened the device and started to follow wires around. Unfortunately all the circuits are inside a black box that is impossible to open without breaking it.

From the 10 pins, only 9 (or 8, I don't remember now) are connected, and two of them are connected to a little bit thicker wires (red and black) which I assumed are the Vin and GND pins. Besides the black box, there are two big horizontal cylinders on one axis, another smaller horizontal cylinder orthogonal to the two cylinders and another small vertical cylinder. I believe these cylinders are the DC motors that spin to detect the gyro effects.

I've done some tests first using 6VDC on these two pins. There is an almost unheardable high frequency sound, and a very irregular but constant wave form on all other pins.

At 12VDC, the volume and pitch gets a bit higher, and the waveform gets stronger, but it doesn't change (at least not in a visible way) as I turn the unit around.

I stopped there afraid that I would burn the device if I increased the voltage... I'm working on other things of the project, so I don't need to rush. If I don't find any information at all, then I'll start playing with it more aggressively.

Cheers

Padu

 

[padu]

For the ones that are keeping up with my saga:

> Hi,
>
> A couple months ago I bought a 3-axial gyro from ebay. I've looked
> everywhere for its datasheet and couldn't find any information. It is
> (was) manufactured by Northrop Corporation (see info below).
>
>
> NORTHROP CORPORATION
> FSC 51834
> Mfr. P/N: 50162-317
> 3 AXIS DC/DC GYRO PKG.
<snip>

I gave up on trying to find the datasheet for this part (long story),
therefore I started doing some tests this weekend using an oscope and a
bench power supply.

I was able to find the VCC and GND pins. As I mentioned before, all the
other pins output a kind of irregular periodical waveform that varies in the
following way when I increase voltage from 12VDC to 24VDC: amplitude
increases from +4/-4V to +8/-8V; wave period decreases from 2.15ms to 1.2ms.
When I measure each individual pin, there's no significant wave change when
I rotate the device its 3 axis, but if I measure two channels together in
X-Y mode (thanks Russel, I wouldn't try it by myself if not by your
suggestion), I was able to find the pins that are sensitive to each axis. It
is entertaining to turn the device on and off, it makes a noise similar to
jet engines starting or stopping. At 24V it stays warm to the touch, but no
smoke out of it.

It's like this: There are 10 pins, being that only 9 are connected. 2 of
them are for power, pins B-C are related to axis A (this is how axes are
labeled in the device), D-E are related to axis B and F-G are related to
axis C. I couldn't find out what pin K is for, its waveform is slightly
different from the other pins.

When I put a pair of pins on the oscope (X-Y mode) I see a diagonal of
increasing slope (0 deg phase shift?). If I spin the gyro about the axis
being measured, this diagonal line moves up or down on the other diagonal
(perpendicular to itself) depending on the direction I'm turning the device.
The displacement is proportional to the acceleration of the spin. I guess
that's why they call it a rate gyro? If I turn very slowly, the line
movement is almost imperceptible.
On the other hand, if I display both signals on time domain on ALT(ernate)
mode and turn the gyro, one waveform goes up and the other one goes down.
I'm not so experienced measuring things with oscopes, so I may be doing
something wrong (I have a 100MHz tek 465M).


So my question follows: how do I translate that type of signal to useful
digital values? (i.e. How many degrees turned on each axis)?


Cheers

Padu