I have come by some heavy duty pan and tilt motor units as used for large security cameras. I am planning on replacing the original control circuit with a PICAXE based controloler so I can use this as an altitude-azimuth drive for satellite antenna use with amateur radio satellites.
These Pan and tilt heads are powered by large motors marked as 'synchronous reversible motors 24V AC 50Hz' and have two identical windings. They are not used quite that way! In fact they are driven by 'H' type drivers with square waves at 24V DC, a bit like stepper motors. The two winding are fed 90 degrees out of phase at about 83Hz at the highest speed. The phase reverses to reverse the motor. When idle there are some very short 2 or 3 uS pulses at high frequency which do nothing obvious. So I have some idea of what goes on when it gets left-right-up-down, goto preset etc. that the camera PTZ (Pan-Tilt-Zoom) command protocol provides.
When powered up the controller tracks to one end stop, reverses and then tracks to the other end stop (up to 360 degrees azimuth). I guess this calibrates the system. Thereafter it seems to locate it's position by driviing the correct number of 'steps'.
My requirement is to drive the motors through the calibration sequence then get them to step to altitude and azimuth information fed to the PICAXE chip as degrees (0 to 360 degrees Azimuth and 0 to 90 degrees Altitude) so will have to keep count of 'steps' clockwise/anticlocwise and calculate correct number of steps to reach the required position - for two motors! To make things more difficult I am thinking of slowing the pulse rate when, say, ten steps from target count so as to reduce overshoot.
Having never used PICAXE for PWM or stepper motors can anyone get me started on the best way program outputs for the two sets of pulse outputs at 90 degrees phase and maintain a count of pulses sent.
Hope this all makes sense!
Richard
These Pan and tilt heads are powered by large motors marked as 'synchronous reversible motors 24V AC 50Hz' and have two identical windings. They are not used quite that way! In fact they are driven by 'H' type drivers with square waves at 24V DC, a bit like stepper motors. The two winding are fed 90 degrees out of phase at about 83Hz at the highest speed. The phase reverses to reverse the motor. When idle there are some very short 2 or 3 uS pulses at high frequency which do nothing obvious. So I have some idea of what goes on when it gets left-right-up-down, goto preset etc. that the camera PTZ (Pan-Tilt-Zoom) command protocol provides.
When powered up the controller tracks to one end stop, reverses and then tracks to the other end stop (up to 360 degrees azimuth). I guess this calibrates the system. Thereafter it seems to locate it's position by driviing the correct number of 'steps'.
My requirement is to drive the motors through the calibration sequence then get them to step to altitude and azimuth information fed to the PICAXE chip as degrees (0 to 360 degrees Azimuth and 0 to 90 degrees Altitude) so will have to keep count of 'steps' clockwise/anticlocwise and calculate correct number of steps to reach the required position - for two motors! To make things more difficult I am thinking of slowing the pulse rate when, say, ten steps from target count so as to reduce overshoot.
Having never used PICAXE for PWM or stepper motors can anyone get me started on the best way program outputs for the two sets of pulse outputs at 90 degrees phase and maintain a count of pulses sent.
Hope this all makes sense!
Richard
