    LOWCOST AUTOTRACKING for SAT and EME with ROTORSYS
----------------------------------------------------------

Raimund Eisenstecken, IN3HER, Oberdorf 99, 39040 VAHRN, Italy  


ABSTRACT
This program is able to calculate the position of moving targets (i.e. moon,
satellites, cosmic noise sources) and to follow them. To read the azimuth and
elevation angle, the mechanical parts of a computer mouse and its interface 
are used. The steering of the rotors will be done via the parallel interface, 
you only need a few components. That means with a mouse, 2 ICs und 4 relays  
you can realize a lowcost autotracking system.

SYSTEM REQUIRMENTS
The program is written in Turbo Pascal and is running on an IBM-compatible PC 
with EGA or VGA graphics. The mousedriver must be loaded before invoking the
ROTORSYS program.

OVERVIEW
With the parameter /E you can start the english version. /H shows a short help
info. /BW choses the monochrome monitor. The screen is devided in two sections.
The outer one shows the actual position of the rotaries, the inner area the 
basic calculations.

THE MENU
F1  starts or stops the automatic tracking 
F2  select the desired object with pageup / pagedown
F3  tracking time interval between 1 and 15 minutes with pageup / pagedown 
F4  azimuth offset -9.9 to +9.9 degree with pageup / pagedown
F5  elevation offset -9.9 to +9.9 degree with pageup / pagedown
If you didn't activate the autotracking mode, you can move the rotaries 
with the cursor keys.

FUNCTION
After loading ROTORSYS, the program needs to be calibrated at the reference 
positions, which should be set close to the parking headings, in order to 
shorten the calibration procedure. The reference position is marked with a
double arrow behind the display of the angle. The azimuth reference is
reportet by the left mouse key, the elevation reference by the right one.
After selecting the object to follow and the time interval, the tracking may 
be started by F1. An existing offset in azimuth or elevation may be corrected
using F4 or F5, respectively. If the calculated elevation is negativ, the 
rotaries won't be activated. The ESC key will terminate the program.

CONFIGURATION
A number of parameter may be defined in the file ROTORSYS.CFI using Keywords.
It should be noted, that the keywords may not be changed, otherwise the 
numerical value cannot be evaluated correctly. An overview about the valid
keywords is shown below.

MYCALL = Own callsign
MY-LOC = Own LOCATOR (the geogr. position can also be defined in MY-LAT and
         MY-LON ( i.e. MY-LAT  +46.729,  MY-LON  -11.625, )
LPT-NR = Used printer interface LPT1 or LPT2.                    (default 1)
AZ-REF = AZ-angle, on which the sensor is activ.                 (default 180)
AZ-P/G = Number of azimuth-pulses per 360 degrees.               (default 360)
EZ-REF = EL-angle, on which the sensor is activ.                 (default 0)
EL-P/G = Number of elevation-pulses per 360 degrees.             (defauld 360)
MY-QTR = Timedifference UTC - localtime. (i.e. GMT = MY-QTR -1,) (default 0)
AZ-ERR = Tolerance of the azimuth-tracking. ( depens on the play in drive and 
         the speed of rotation )                                 (defauld 0.5) 
EL-ERR = Tolerance of the elevation-tracking. ( depens on the play in drive 
         and the speed of rotation )                             (defauld 0.5) 

INTERFACE
The rotaries are controlled via the data lines of a parallel port (active high).

PIN 2 = AZ rotary moves clockwise
PIN 3 = AZ rotary moves counter clockwise
PIN 4 = EL rotary moves clockwise
PIN 5 = EL rotary moves counter clockwise
PIN 6 = AZ rotary moves fast (delta > 10 degree)
PIN 7 = EL rotary moves fast (delta > 10 degree)
PIN 25 = ground

Figure 3 proposes a circuit.

OBJECTFILES (.DAT)
ROTORSYS suports up to 50 objectfiles (.DAT). They are created with an ASCII
editor. The element sets are introduced with the line "OBJECT:   SAT,". The   
keywords have to be used unganged (e.g. EP-DAY), and the numerical value must 
be followed by a comma. With radio stars, the first line must be 
"OBJECT:   STAR," followed by right ascension and declination. Fixpoints like 
TVSAT ASTRA or METEORSAT can also be defined, in this case the first line 
is "OBJECT:   F_P,". 

ADAPTATION OF THE ENCODERS
This part of the work needs a bit of subtile intuition, since there are 
different ways of encoders mechanics used in a mouse. Of special interests 
are those with tow physically separated encoders. In principle , they mast be
demounted from the circuit board of the mouse and attached to the axis of the
rotary. The same applies to the reference sensor. This task has to be solved 
individually, of course. Aditionally, so far the necessary experience is 
missing to provide a patented recipe. The tests were carried out using a
Genius mouse, in which encoder weels with 45 slots are mounted. With this
wheels, a resolution of 360/(45*4) = 2 deg is achieved. The mouse electronics
evaluates the signal coming from the opto coupler. It can recognize even a
quarter of a period, since the opto coupler are mounted at 90 to each other.
Also a professional incremental encoder (1250 pulses per 360) was tested 
after connecting it to the mouse electronics (resolution = 0.072). This, of 
course, is the best solution, but also a bit more expensiv. It should be 
noted, that rotary speed must be decreased with rising pulse rate.

FINAL NOTE
With this program the author tried to find an inexpensiv solution for the 
problem "autotracking". Of course, this system can be improved. This should
be a stimulus for further experiments to replace the perhaps existing analog
system with a digital one. Any hint about mistakes or news ideas are welcome.


LITERATURE / REFERENCES
NOISE MEASUREMENTS OF COSMIC OBJECTS  (DUBUS TECHNIK 2  Jan Bruinier DL9KR)
RADIOASTRONOMISCHE METHODEN (Antennen Band 3: Messtechnik  Edmund Stirner) 
LOCATING THE MOON (THE RADIO AMATEUR'S  HANDBOOK 1982)
EPEMERIDEN - PROGRAMM MOND (CQDL 1/86  Manfred Belter)
MINI CALC (AMSAT JORNAL 5/6/85  Dr. Karl Meinzer DJ4CZ)






