CY545 Stepper System Controller
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CHAPTER 13 - THUMBWHEEL SWITCH SUPPORT
Thumbwheel Switch Support
A very important feature for stand-alone control is the ability to define variable parameters for
the control functions. In many applications, the basic function is similar for a whole set of
operations, but the exact numbers will vary with the particular operation being selected. For
example, a machine could be designed that takes raw stock, such as lumber, and cuts it to
specified lengths.
As a CY545 program, such an application is fairly simple. If the stepper motor controls the
feeding of the stock, you must simply move the motor a specific number of steps that
correspond to the desired length, then activate a cutting mechanism. This function then repeats
as long as stock is available, or for the number of final pieces desired.
If you now wish to cut stock of another length, the same command structure as before could be
used, with only a change to the number of steps to move.
A number of options exist for implementing such a system. First, a host computer could be used
to enter the desired function, and the computer program could generate the proper command
sequence for the CY545. While this approach is quite practical, the host computer may be too
expensive to justify for such a simple task.
Next, the external memory support of the CY545 could be used to hold several programs, one
for each of the desired lengths needed by the application. Some mechanical selection process
could then choose which program the CY545 would run, based on the desired length. This
approach is also practical, so long as you can define all the required lengths within the memory
contents. If a new length is desired, a program for that length must first be defined in the
memory before it can be run. This requires the machine to be stopped, while a programmer
enters the proper commands to the CY545.
Finally, it would be nice if only one program were required, since the basic function is always the
same. This requires the CY545 to accept variable parameters, fixed at the time the program is
run. This would allow any length stock to be selected, with a resolution of one step from one
length to the next, without using a host computer or additional programs in external memory.
The CY545 provides such a function, using external thumbwheel switches to specify the
parameter values. All examples shown so far have used fixed parameters as numeric
arguments to the CY545 commands, such as Rate and Number. For example:
R 123<cr>
N 4321H<cr>
When such commands are read by the CY545, either from the command interfaces or from the
external memory, the parameter value is fixed by the numeric argument, and is a constant for
that command.
© 2002 Cybernetic Micro Systems
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Chapter 13 - Thumbwheel Switch Support
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