Northrop DC/DC Gyro

Hi Folks!
Just bought this beauty:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item `46670961&ssPageName=STRK:MEWN:IT
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?
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
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Padu wrote:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item `46670961&ssPageName=STRK:MEWN:IT
That's nice.
A part number would be useful. In fact, the original seller should have posted a picture of the data plate when selling the thing.
                John Nagle
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"John Nagle"

Hi John,
Here's what's in the label:
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 seems it is a really old part (well, it's still northrop corp. instead of northrop-grumman). I've contacted Northrop-Grumman (the division that makes high end gyros nowadays) and I was lucky enough to speak to a guy who really tried to help me. He couldn't find anything about this part#, but through the FSC code, he thinks this part was manufactured in their El Segundo division. I was also able to find a paper online of a guy who created a robot using this gyro, I have his phone number, but it's really hard to find this guy.
I already have a solid state gyro for my robot (from freescale), but since this one was cheap on ebay, I got it, and now I want to compare both. It looks really rugged though.
I wanted to get some info on how to interface with this unit before I start playing around and possibly breaking the thing.
Cheers
Padu
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"Padu"

Some advances: I opened the case and followed the wires around. I was able to locate the red and the black wires, and they are a little bit thicker than the rest of the wires, therefore I think these are the power wires. I've testes putting 5V, 6V and 12V to these wires. At 5V and 6V, there's a very faint noise, at 12V the noise increases a bit in volume and pitch. When I opened the case, I saw two long metal cylinders along the Y axis, one short cylinder along the X axis and a very small cylinder along the Z axis. I believe that something physically spins inside these cylinders, therefore I think the high-pitch noise is normal. On the oscope though, all the other pins present the same weird waveform, and no matter how I rotate the unit, the waveform doesn't change.
Do you know by any chance how analog (DC) gyros work?
Cheers
Padu
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Are there any power supply bypass capacitors with voltage ratings? A lot of aircraft electronics run on 28 vdc. You could try that as a last resort -- but if it really is a 12v part that will almost certainly let out the magic smoke.
chris
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Unfortunately, all the electronics are inside a black box and there's no way to open it without breaking it.
While doing some research, I got that info too (28V, sometimes 24V), but once you supply the correct voltage, how do you take the measurements? If I go by the number of pins (that are actually connected to something), then there would be 2 wires per axis. Do they output a voltage proportional to the rate? Or do they vary resistance?
Cheers
Padu
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Padu wrote:

I caught this late. As a note, older avionics equipment may also run at 400 Hz, with voltages from 28 to 115 vac. I assume the "DC/DC" gyro spec is based on DC gravity, not DC voltage. The vintage of the unit is a little hard to tell from the one picture, but it may not be older than Vietnam era.
-- Gordon
-- Gordon
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"Gordon McComb"

What is DC gravity?
Cheers
Padu
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Padu wrote:

A redundancy, actually. Gravity is a constant (DC) acceleration. For example, a semiconductor (but not piezoelectric) accelerometers always register a value due to gravity. It's 1g at standstill. Gravity affects a gyro causing precession, which in a 6-hour flight could cause a plane to land quite a few miles off course. So naturally they try to fix this.
Then again, "DC/DC" in the spec may well mean the power supply input, and/or the signal output. Nothing like considering the easy answer first! <g>
-- Gordon
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Gordon McComb wrote:

A lot of avionics stuff used resolvers for control surface position feedback and stuff like that. Resolvers are AC devices, basically the armature is a rotatable primary for a transformer. Two secondary windings oriented 90 degrees apart give you the output. As you rotate the primary inside the orthogonal secondaries, the ratio of the voltages out of the secondaries changes with the coupling angle. I think it is the arctan of the ratio of the output voltages is the shaft angle. Analog Devices used to make resolver to digital converters and still might. I have never used a resolver hands on, so my description may be an approximation at best. There is a whole family of stuff like this, selsyns, syncros...
I think and might even bet a beer that this DC/DC gyro takes a DC drive voltage and outputs a DC signal (or at least if it is not moving in the sensitive axes).
Good Luck, Bob
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