Link Communications RLC-4, Manual

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E-1
RLC-4 V1.79 Copyright © 1998 Link Communications Inc. 9/18/98
Appendix E: Controlling a Rotor
The RLC-4 may eventually have specialized commands for controlling a rotor using the I/O lines on
the I/O board, but you can do it now with a little work.
• Connect the rotor controls to two of the output lines. We will assume that you have one
output for on/off and another to select the direction.
• Write a macro to turn the motor off. We will call this the "motor off macro"
• Write another macro that makes the rotor turn clockwise, the "clockwise macro". It should
set the direction and turn the motor on.
• Write a macro that make the rotor turn counter-clockwise, the "counter-clockwise macro".
It should set the direction and turn the motor on.
• Next, connect the output from the rotor that indicates the direction it is pointing to one of
the analog input lines. If the voltage from that output ever goes above 5 volts (most go to
the power supply voltage, about 13 volts), you should turn on the voltage divider dip switch
on for that analog line. You should also make sure that the dip switch used to power a
temperature sensor on that analog line is turned off.
• Use Command 053 (or your favorite macro programming command) to program one of the
user macros to execute Command 100 and make it read the analog line you hooked up in
the previous step. Turn the rotor and make sure that the number it tells you changes. If it
doesn't, check and make sure that the voltage going into the input line changes and that you
have the dip switches set correctly. Don't worry about what number it tells you, just that it
changes with the direction.
• This whole step is optional. If you do not want to know what direction the rotor is
pointing, just have presets, skip this whole step. Most rotors indicate 180 degrees at south,
increase as you go clockwise to 360 degrees at north, then jump to 30 degrees or some
small reading and work their way back up to 180 degrees at south again. The direction
voltage that is output from the rotor usually starts at 0 volts when the rotor is pointed south
and increases to half scale at north and full scale when it gets all the way around to south on
the other side. This makes it very difficult for the controller to calculate the degree reading,
since it has a big break in the middle. Instead, we will make the controller read back the
number of degrees clockwise from south. This is accomplished by setting the conversion
ratio for the analog input with Command 102. The following calculation assumes that you
get 0 volts with the rotor all of the way counter-clockwise and 13 volts with the rotor all of
the way clockwise.
13 = 360, X = 25 * 360 / 13, X = 692
25 X
This calculation shows that to get 360 degrees at 13 volts, we need to set the analog input