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eHam Forums => Elmers => Topic started by: KN4GE on March 18, 2010, 11:24:45 AM



Title: Plc's and az el rotators
Post by: KN4GE on March 18, 2010, 11:24:45 AM
Does anyone have any experience using a PLC to control an azimuth elevation rotator? Specifically I am trying a yaesu g5500 with an allen bradley scl500. I have no trouble reading the positions through the analog ports or controlling the rotor with switches or presets but my issue is how to take data from one of the tracking programs to determine what the rotor should be doing to track a satellite. This level of ladder logic is over my head.


Title: RE: Plc's and az el rotators
Post by: N3OX on March 18, 2010, 12:35:15 PM
What kind of I/O do you have on the Allen Bradley unit ?  USB?  Ethernet? RS-232?  RS-485?  Just plain vanilla analog or digital?

If you've got a RS-232 port and also have software that's sending Yaesu-version GS-232 commands, the commands you can expect to need to intercept are in here:

http://www.g6lvb.com/gs232a.pdf

If you can configure your unit to catch those commands, you're good to go... but I don't really know what your controller is capable of (seems like it could be anything depending on add on units).

Making the unit pretend it's the Yaesu control box is probably the way to go.

73
Dan





Title: RE: Plc's and az el rotators
Post by: K9WJL on March 18, 2010, 02:48:27 PM
I had to think about this for a bit... I work with controllers, but the Analog stuff is new to me. I wonder if you can read the voltage from the potentiometer in the Rotor, using a analog input card. The voltage would probably have to be rectified and presented to the controller as DC input, and maybe -5vdc to +5vdc, but AB may have a card that reads AC.. I don't know.
 Then you have a voltage that corresponds to a position in degrees on the rotator, Right?
 Then an analog output card could be configured to move the rotator up or down depending on the logic you use in the controller. The Analog output card we use where I work is (I believe) +12 to -12vdc and its used to shift a proportional control valve in a hydraulic press I work with. The valve moves the press up with the negative voltage, and down with a positive voltage, and it stops with 0vdc. More (+ or -) voltage is a faster movement.
 This proportional valve is +10 vdc to -10vdc max, so the logic in the controller is used to scale down the voltage from the output. If you read the instruction sheet for the analog card you use its fairly easy to understand.
 So i guess then you'd have to convert it to AC to drive the rotator.
 Anyway, hope this helps. I'm sure theres someone else out there that knows a hell of alot more about it than I do.
 73,
 Bill K9WJL


Title: RE: Plc's and az el rotators
Post by: NI3S on March 18, 2010, 05:52:26 PM
If you have an idea of how the data from the PC is going to be packaged, I can probably help you.  The trick is going to be picking the important pieces of data out of everything else.  Once that is done, the rest is easy.


Title: RE: Plc's and az el rotators
Post by: KN4GE on March 19, 2010, 03:36:46 PM
Thanks for the replies. I read position from the rotator no problem. Output to the rotator is just 4 switch closures so that is no problem. I don't have any tracking software yet. I have looked at a few but that is an area that I could definitely use some recommendations. Hopefully something that stores position data in a manner That I could get access to (and make sense out of) and eventually use as az el positions in the ladder logic program.

The PLC connects to the computer through a dh485 interface and serial port but I am not sure of how to use it to do anything more than use the RSLogix software to talk to the plc.

My biggest obstacle seems to be getting data (and understanding how to use it) into the PLC.

Hope I hit all the points. Thanks again for all the input.


Title: RE: Plc's and az el rotators
Post by: NI3S on March 19, 2010, 08:01:11 PM
I was thinking about this today.  I am wondering if you can get the PLC to do the calculations itself.  It would take some work but it could be done.  Pick a satellite, the PLC knows the date and time, and it could track from either a preprogrammed set of tables of actually od the math on the fly.  The best thing you could do for yourself is figure out how to provide some form of feedback.  Either a zero pulse and a series of pulses or a pot and analog card (at $800 for the card, probably not a great idea).  

This is doable, just going to take some time.