Hello, EMCers, Am back from Mom's and Thanksgiving--sorry to see I missed out on the conversation regarding antenna rotor control! Thanks, Kirk, Gene, Jim, and others for great comments on these rotor/controllers.
There was some question about how the controller would be used. My hope is to use a pair of rotators for AZ/EL antenna positioning in the EMCAR project for antenna measurements. And, I would like to pipe position commands from a Predict daemon to EMC and use this for LEO satellite tracking for Amateur Radio communications (of course, real-time control would help here a lot). Commercial controllers for these applications are relatively expensive; so, I think other hams and antenna folks would be interested in this approach, as well. As for control, there is one article in QST, 1998, p42, that describes a homebrew controller for the U-100 rotor (that I have). The circuit is microcontroller based and controls a Crydom CTX240D30 solid-state relay module that serves to power the rotor motor. Direction is controlled by which of two motor windings are used. My hope would be to keep the smarts inside EMC and build a motor interface based on either a triac or an off-the-shelf solid-state-relay, similar as the one above. I need to make a few measurements to see how/if the motor responds to pulsed control signals. I think that is my next step before proceeding with any circuit design. Thanks again for all the comments. Regards, Bob > Message: 1 > Date: Fri, 28 Nov 2008 19:26:43 -0800 > From: Kirk Wallace <[EMAIL PROTECTED]> > Subject: Re: [Emc-users] Control of AC motor in antenna rotor > To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain > > On Fri, 2008-11-28 at 19:45 -0500, Jim Coleman wrote: >> could you use 3 outputs from a parport to control the sync. motors? an >> enable pin, and then 2 of them on H bridges pulsing 90 degrees out of phase >> to run the motors? > > That is close to what I did here: > http://www.wallacecompany.com/E45/rotor_cam.html > but I use four lines driving the two h-bridges. Theoretically you can > use two lines, one for each h-bridge, but the problem comes about when > the signal is in transition. The time when the bridge input is in the > middle of the transition, both high and low transistors conduct causing > a dead short. The four lines allow me to turn one transistor off before > I turn the other on and parport pins are cheap. > >> also, am i missing something big here, or would these >> motors run kinda like bipolar steppers, but designed to turn constant speed >> instead of being more position oriented? > > Yes. The major difference is that a stepper has a permanent magnet rotor > and the rotator motor has and inductive rotor which needs a changing > magnetic field in order to create motion. > >> wondering if a stepper drive would >> be easily adaptable to run a rotor. > > It could be done, but for my project I wanted to use as much off the > self with the least amount of modification. > >> another thought regarding the 'home', how hard would it be to put a little >> microswitch on the hard stop so just as it's about to hit the hard stop it >> can close the switch and gently coast into the stop instead of whackin it >> full speed? also, MPJA.com has proximity switches for $20, not sure if >> that's expensive or not in todays market, I just know ive seen receipts at >> work for replacements on machines that make the $20 look cheap. > > TV antenna rotators are cheap, so if you blow one up, it's no big deal. > Also they are designed to find home this way, and could do so all day > probably. Installing a home switch would be better. When activated, if > the motor coasts a little before it stops should not be a problem > because the output shaft will move very little due to the gear > reduction. If it becomes a problem, you could use the four wire control > to turn both low side transistors on to brake the motor. This should > stop the motor very quickly. > >> I'm interested in a project like this for aiming wifi antennas with tight >> radiation patterns, like 7 degrees or less. also, a coworker has a rotor >> with a broken control box, if something was simple enough to impliment he >> might swing towards something like that rather than just not watchin certain >> channels. > > I have spare controllers, so does eBay, but shipping can be a pill. > >> last thought regarding the UPS / generator. couldnt you use an old laptop >> with a rebuilt battery pack in it, and keep it in standby and have it wake >> when power goes out? not sure off hand how you could impliment the wake, i >> have no idea how the wake on LAN connector on the motherboard works, and >> dont know if you'd be able to poll the parport while in sleep. maybe a >> modem with wake on ring, and somehow send an AC signal to that when the >> power drops off? I've never implimented wake on LAN or wake on ring, so all >> of this is just wild guesses on my part. but I'd definitely like to see >> what you come up with, if nothing else im sure it's be a good read or some >> pretty pictures to gander at. > > Laptops seem to be more trouble than they are worth for machine control. > I am tending towards having a full time lower power miniATX motherboard, > maybe with a C7 processor, that would do web-based whole house power > management. Normally it would monitor voltage on the mains and current > on each power panel breaker, and also test and maintain backup batteries > and generator. For an outage, it would manage the transfer from > batteries to generator and control voltage and frequency. When the mains > power returns, it will manage the transfer back to normal mode. It's a > good thing this stage of the planning is cheap (free, except for the > beer). > --------------- > Kirk > http://www.wallacecompany.com/E45/rotor_cam.html > > ------------------------------------------------------------------------- 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
