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From: dan@quark.nsc.com (Dan Hariton x5596)
Subject: Re: More Gyro details. (Was Inertial Gyro Specs)
Message-ID: <D01zGz.9zx@voder.nsc.com>
Keywords: Gyros
Sender: news@voder.nsc.com
Nntp-Posting-Host: quark.nsc.com
Reply-To: dan@galaxy.nsc.com
Organization: National Semiconductor Corporation
References: <calvinCznKqw.A9C@netcom.com> <nagleCzoJ12.IDA@netcom.com>
Date: Tue, 29 Nov 1994 23:48:34 GMT
Lines: 97

correction to (john nagle's) pin description:

"...
THE ETAK/BOSCH RATE GYRO

	The ETAK gyro is a six-terminal device.  Pinout is as follows:

was >>>>>>>>>>>>	1 (clear)	unused
			list...."

     
should read >>>>	#1 un-isolated, SHIELD, connect to GND

there is an Al-foil shield inside the black cable, wrapping all 8 conductors.
this shield is in contact with the unisolated wire (#1).
and the unisolated wire (#1) is making contact with the case.
this may resolve some of the capacitive parasitic effects.

dan 

In article <nagleCzoJ12.IDA@netcom.com>, nagle@netcom.com (John Nagle) writes:
|> calvin@netcom.com (John Calvin) writes:
|> >Greetings again.
|> >I've had a suprising number of inquires regarding the $2.00 Gyro's I 
|> >located in Haltek in Mountain View Ca. (Phone (415)-969-0510).  
|> 
|>       Here's the spec on these things.
|> 
|> THE ETAK/BOSCH RATE GYRO
|> 
|> 	The ETAK gyro is a six-terminal device.  Pinout is as follows:
|> 
|>           1 (clear)	unused
|>           2 (Brown)	+5V, 50mA   
|>           3 (Yellow)	GYRO YAW (5v digital pulse output)
|>           4 (Green)	GND
|>           5 (Red)	PITCH INCLINOMETER  (0..5v analog output)
|>           6 (Black)	ROLL INCLINOMETER  (0..5v analog output)
|>           7 (Orange)	GYRO PITCH (0..5v analog output)
|>           8 (Blue)	unused
|> 
|> The colors apply to the cable from the compass.  These colors can be seen
|> inside the transparent modular connector.  The pin numbers above read
|> from right to left viewing the plug from the contact side.
|> 
|> 	There are thus three analog outputs and one pulse train.  The
|> frequency of the pulse train varies from 0 to 70KhZ.  The pulse train
|> is a strange beast.  It is not a variable frequency; it is a fixed
|> frequency pulse train with some pulses missing.  Counting the pulses
|> produces an angular rate.
|> 
|> If the rate limits of the gyro are exceeded, the pulse train output
|> will appear as a solid 1 (for one direction) or a solid 0 (for the
|> other).  
|> 
|> The pulse train output is an open-collector TTL output, and requires
|> a pull-up resistor or other suitable input.  1M appears to work.
|> 
|>       The terminology above assumes that the long axis of the gyro is
|> aligned with the vehicle's long axis.  (ETAK's drawings are labelled
|> differently, assuming a different mounting).
|> 
|>       Physically, the gyro/inclinometer unit is a box with a circular
|> projection housing the motor on one end.  A screw hole for mounting
|> appears on the bottom.  The motor housing should face fore or aft, (we
|> can compensate in the software) and the bottom should face down.  
|> The inclinometers actually appear to work with the unit inverted,
|> but the design is intended for use in the standard orientation.
|> 
|>       Internally, the gyro is simply a motor spinning a thin plate
|> which flexes as the gyro is turned.  The deflection of the plate is
|> measured capacitively at two points, producing two angular rates.
|> The inclinometers are a cylinder of liquid whose position is, again,
|> sensed capacitively.
|> 
|>       The inclinometers are good to about 1 percent accuracy and
|> produce meaningful values only for rotations under 45 degrees or so.
|> Response of the inclinometers is about 1Hz.  The poise of the liquid
|> used in the inclinometer has been carefully chosen to obtain good
|> response under vibration.  If a 1Hz low-pass filter is used on the
|> inclinometer outputs, the output values should be good, although they
|> will, of course, lag the current situation slightly.
|> 
|>       The gyro has some serious limitations.  At best, it is only
|> about 1% accurate.  This degrades sharply under some conditions.  The
|> unit is temperature sensitive, enough so that holding the unit in hand
|> will induce errors.  (This may improve in later units).  The unit is
|> limited to angular rates of about 45 to 60 degrees per second.
|> (This, too, may improve in later units.)
|> 
|>      This specification applies to board 03-1204-02 rev X2, which is a 
|> prototype version dated 8 FEB 1988. Production boards may be slightly 
|> different.
|> 
|> 					John Nagle
|> 
        
