Omron SYSMAC C Series User Manual page 49

Chapter 6 Application examples
Overview
Automatic control of
warehouse door
As amember of the SYSMAC C-Series programmable controllers, the
C20 is intended for economical control of operations that have a relatively
restricted number of automated tasks. Nevertheless, the number and
types of applications possible for equipment and process control using
the C20 are practically limitless—ranging from automatic door operation
to many types of assembly !ine applications.
This chapter presents examples of some of those applications. In each
case an explanation of the application program, its ladder diagram, and
the coding chart are given. These programs are intentionally simplified
and are meant for instructional purposes only.
In this example, the programmable controller is used to open and close
an automatic door to a warehouse to allow an approaching object
(automobile or other vehicle) to enter or leave. The C20 makes it possible
for two different sensing systems to be used to control the door operation.
Door position motor
Explanation
As input devices that send control input signals to the C20, an ultrasonic
switch and a photoelectric switch are employed.
The ultrasonic switch emits an ultrasonic wave. When there is an object
(vehicle) in the way of this ultrasonic wave, the wave reflects back to the
ultrasonic switch which detects the object.
The photoelectric switch used in this example consists of two elements: a
light source and a receiver. The light source emits a light beam that is
constantly received by the receiver. If a vehicle or other object interrupts
the light beam, the photoelectric switch detects it.