[amsat-bb] Rotator Positioning questions

Ing. Pavel Milanes Costa co7wt at frcuba.co.cu
Fri Aug 9 06:25:06 PDT 2013

Ok, I have now a paper design with the goal for my rotor project.

This rotor is really a 0-360o, but I have managed (designed) to make it 
full stop on 0-450o (even 540o if I like... with two contact switches 
that cuts power to motor when in position) and will use a mixed 
reference setup, the same for elevation as 0o (horizon) to 90o (cenit)

I can attach a plastic overlay to a wheel on the gear reduction for 
making a 90 shift signal (2 wires for AZ and 2 for EL) an then down in 
the controller a 74hc74 decoding the 90o to say/count not only the 
position, but also the real rotation direction, the reduction cuadrature 
signal outputs ~ 750 pulses for full 450o as per my calculations, this 
after decoding by 74hc74 will be ~375 pulses for 450o and about 1.2o of 
accuracy, and the controller knows if the system if de-phased by high 
winds as it gets extra pulses when no moving was requested... so it can 
correct this deviation... (this is not possible with "simple" pulse 
counting or "time" counting as Bob, WB4APR proposed)

High winds here normal here, and as I say in a previous email the brake 
mechanism is working poorly, remember this is for a "small" camera 
mounted on top the device, not a "sail" of 2 crossed yaguis for 70 and 2 
more for 2m

The "motor running/motor stop" signal will be a current probe on the AC 
24V motor feeding wires down the control, as when the motor reach 0o or 
450o it automatically switch's off

Now the real question is how to orient the rotor physically, I have ZERO 
rotor experience here... knowing it can do 0o-450o...

0o is north, and 450o is east, this is the way I see, so I can do E-W 
north (up) and south (down) ways as well as N-S in east (right) and west 
(left) ways

This is correct?

And from the point of view of the controller and PC, lets imagine a ~NNE 
to NW pass (80o to 300o pass, north way)

The PC(software) knows that ZERO will be crossed and send the controller 
a 450-(real zimuth) to the controller?

Or this job must be done IN the controller it self?

With Azimuth and Elevation you can flip the direction of the pass an 
then flip elevation 180o and cover it 100%, but how to do this in 
azimuth only rotors?

Another... in 450o rotors (no elevation) How you cover a 110 to 300 
(~SEE to ~NNW) pass if 450o is East and 0o is Noth?

Assuming the software can figure the ZERO crossing and can do the math, 
110o is beyond the 450o (450 = 360+90)... How to manage this?

If I make a 540o rotor: softwares can manage it? (1+1/2 turns against 
1+1/4 turns of 450o?)

I have the serial comms working on the pic (MCU) but this questions are 
hammering my head...

Can anyone help me with this?

73 the CO7WT

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