You‘re a technician who has been assigned
to design an electronic control system for two spot-welding guns that
are operated by two robots. The first robot makes a series of welds on
an automobile body on a production line, and the second robot makes a
different set of welds. The electrical bus that supplies power to the
welders is not large enough to allow both welders to be operated at the
same time. The control system that you’re designing should use solid-state
components described in this section and it should provide the following
functions: (1) ensure that both welders don’t operate at the same time,
(2) keep track of good and bad parts, and (3) provide 20 seconds of
warm-up time for each welder when it’s first energized. For an extra assignment,
design a means for the system to keep track of present or missing automotive
bodies as the production line passes the robots. You may also design
a circuit to keep track of faults as they occur. Carefully read the
information provided in this section to help in designing this control system.
Solutions to this problem are at the end of this section.