Unit installation

E-1

Appendix E: Controlling a Rotor

The RLC-3 will evenually 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. If you want to make this macro have a nicer message, use

Command 036 to build the message and speak variable word 512 (or one of the words

nearby if you are using a different analog input) to insert the actual analog reading.

• 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