On Wednesday 26 November 2008, Bob Freeman wrote: >Hello, > >Am interested in using EMC2 to control some traditional antenna >rotators, like the Alliance U-100. These are AC motors that are turned >on/off and reversed using relays (have known these to be called >"bang-bang" controllers). > >I would like to use a triac and encoder feedback to control these in >EMC, maybe, using PWM. Anyone done this type of control in EMC, or have >some pointers, or both? > >Thanks to the developers of EMC! And, thanks for any information offered. > >Regards, > >Bob > These are AC _synchronous_ motors, designed to run on 60 hz power. The relay applies power between the two top legs of its winding, with a capacitor sized for the 60 hz power frequency connected between the 2 top legs of a Y, so the capacitor causes a phase lead on the unconnected leg, and this determines which direction they move. The control box also has an identical motor in it that runs the direction arrow you see, and since they are synchro motors, the antenna and the arrow generally stay pretty close to each other. If in doubt, just run it to both stops and that re-syncs the motors to each other. They get off on a busy system because the motors coast a few turns when shut off, and both motors rarely have the same coasting to a stop profiles.
I suppose, if the gear ratio could be determined, a circuit could be made to enable it to turn a certain number of degrees by counting the cycles of the AC power being sent, but TBT, the directionality of even the 14 foot long log periodic all band tv antenna is so broad that any circuit that did that would be a thousand times more accurate than is required for the job. 10 degree errors in pointing are for all practical purposes, un-detectable. I have a U-105 swinging such an antenna about 20 feet above my head. 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. :-) -- 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) The meek shall inherit the earth -- they are too weak to refuse. ------------------------------------------------------------------------- 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
