On Thursday 27 November 2008, Kirk Wallace wrote: >On Wed, 2008-11-26 at 23:00 -0500, Gene Heskett wrote: >... snip > >> Emc could probably be massaged into doing it, and there would be a >> certain cachet to the geekiness of it all when bragging rights are >> being displayed to the visiting Joe Sixpacks, but why? It actually >> works pretty well as is. :-) > >I don't know what Bob wants to use his rotator for, but I wanted to use >one to point a weather webcam, so getting the direction fairly close >would be good, though not essential. It also has to be computer >controlled. The control boxes that I had, did not cater to hacking an >interface to a PC, so I decided to have the PC create the 24 Volt "AC" >that the original control box put out. > >I recently got a new rotator and found inside the controller, a >microprocessor, relays and transformer, instead of the old synchronous >motor. After thinking about it more, since the normal signals are 60 Hz, >pointing could be controlled with just a decent control of the amount of >time a forward or reverse signal is on. I could reuse the 120VAC to >24VAC transformer and phase shifting capacitor from the original >synchronous controller, to create phase A and B. Then use HAL and >realtime to output forward or reverse signals with closely controlled on >time. I seem to recall that it takes about 20 seconds for a complete >rotation, so controlling within .01 seconds, would be close to .2 >degrees. The other method above has the advantage of not needing >realtime, but for my weather-cam application I need to run some other >software (gPhoto, ImageMagik, FTP) so Ubuntu would be running anyway. I >just need to find the time to try it.
Somewhere in that controller there should be the equ of a turn left or turn right switch. That is where I'd hit it with a pair of reed relays driven by the pc. The older version had them obvious, right in the dial you turned. If it can make a full turn in 20 seconds, that's about 10x faster than mine, which is the old drive two motors design. The image would go flying by so fast there would be lag blur in most of the ccd sensors. Emc could I'm sure count the power pulses going out to the top motor, using a neon lamp and a photo transistor, you would have either 120 or 100 pulses per second to count depending on where you lived and its power standard. To use, put the neon lamp across the primary & keep track of which direction in emc. Don't forget the series r for the lamp though. Or another idea, use optocouplers, one across each motor winding and emc can decode those just as if it were following any quadrature encoded signal because there will be a timing difference in the two optocouplers outputs depending on which direction the motor is being driven. I rather like that and it only takes 5 wires including ground to do. That hal component may already be part of the recent emc package. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If Machiavelli were a programmer, he'd have worked for AT&T. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
