From: monty@sagpd1
Newsgroups: comp.robotics
Subject: Re: balancing_act
Date: 20 Aug 92 23:17:59 GMT
Reply-To: monty@sagpd1.UUCP (Monty Saine)
Organization: Scientific Atlanta, Government Products Div, San Diego, CA

In article <1992Aug20.144448.5564@sagpd1> monty@sagpd1.UUCP (Monty Saine) writes:
>In article <1992Aug19.210807.27401@constellation.ecn.uoknor.edu> rwmurphr@uokmax.ecn.uoknor.edu (Robert W Murphree) writes:
>>See my post on wedge innovations electronic spirit level. 
>>I suppose  my inclination would be to go with accelerometers at
>>3 perpindiculars and some kind of cheap gyroscope.  
>>Some cheaper gyroscopes, where cheap means on the order of 
>>1000 dollars are now being made available.
>>
>
>	I ran across an ad/article about a very small (golf ball size) gyro
>    a few months ago and posted information to this group. Since that time I
>    have mislaid the orginal article. If any one out there is archiving this
>    group, could you please look back and see if you can resurrect my orgianl
>    post. This gyro (if memory serves) was real cheap, i.e. about 1-200 dollars
>    and was extremely small.
>
>
>	In the mean time I'll dig through my paper archives and see if I can
>    find the orginal.
>
>    Monty Saine

	Excuse me for posting a followup to my own article but I found the
    article about the small gyro. It was in the Nov 91 issue of Computer
    Design pg. 56. The article did not specify a price but made a comparision
    between "expensive" gyros costing $1000-$200,000 and their much less
    expensive GyroEngine. The device measures 1.25x1.75 in., consumes 0.1W
    at +3v. The device is made of injection molded polycarbonate plastic.
    The following is extracted from the article:

	"One of the major breakthroughs in the GyroEngine was the development
    of an optical motion sensor. The optical sensor requires only one sensor
    for two degrees of motion and it gives a direct digital readout with out
    analog to digital conversion. An LED shines light through a ring 
    perpendicular to the spin axis of the wheel. On the ring are lines for
    optical sensing. In a hole at the gimbal bearing perpendicular to that 
    axis is another grid with radial lines which light also passes. The 
    interference or moire pattern created by the two grids changes 
    characteristically when the housing is rotated along either axis. A 
    quadrature photosensor picks up the changing pattern which is interperted
    by a microcontroller on a small external board.
	The grid resolution is 2,300 lines/in. and the angular resolution
    is currently 10 bits/degree. Gyration can produce GyroEngines with greater 
    or less accuracy, with corresponding differences in price, depending on 
    customer needs, says president and CEO Tom Quinn. The raw output of the 
    GyroEngine is parallel, but is also convertible to RS-232 or RS-422 for
    use in a cursor pointing device for example."

	The article goes on to tell about a pointing device that they are
    developing using this gyro and vehicle navigation posibilities, robot
    arm motion and ... .

	The company is Gyration, Saratoga Calif. and the number given in the
    article for more information was (408) 255-3016.


    Hope this helps someone...

    Monty Saine