Alcorn Mcbride V+ series, User Manual

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Application Notes 7-29
Controlling Automatic Doors
There are many applications where an Alcorn McBride Show Controller
can perform non-safety-related duties normally delegated to a PLC. One
application that immediately comes to mind is automatic theatre doors.
These doors open when the main show is loading/unloading (as in the Large
Theatre Control example). The Show Controller should automatically
open/close the doors as dictated in the script except when overridden by an
operator control switch.
This simple example utilizes a three-position maintained switch to provide a
Show Controller with two inputs:
Open and Close . The center position is
Auto, and can be deduced by the absence of both Open and Close inputs.
When the switch is in the
Open
position, the Show Controller should keep
the doors open, regardless of what the show is doing at the moment. The
same is true with the
Close position; the doors should remain closed
regardless of the status of the show. In the
Auto
position, the Show
Controller can dynamically open and close the doors at the appropriate
time. A flag will provide automated control of the doors from within any of
the other sequences: the sequence will turn the flag on to open the doors
and off to close the doors. If a set of doors is in
Auto
mode, our looping
sequence should open/close them based on the state of the flag. If the doors
are in
Open or Close mode, the other sequences may still turn on and off
the flag, but the doors will not be affected.
We will perform this function by using one
Loop Enabled
sequence that
continuously checks the inputs and opens/closes the doors if necessary.
The figure below shows the events of our sequence, OpenCloseDoors .
This sequence loops every 10 frames and update the state of the doors based
upon the switch inputs (
DoorOpenInput and DoorCloseInput ) and the script
open/close flag ( DoorFlag ). The sequence first checks if either input is on.
If the operator has moved the switch to the
Open
position, the doors should
be opened. Similarly, if the operator has moved the switch to the
Close
position, the doors are automatically closed without regard to DoorFlag .
Finally, if the doors are in the Auto position, the status of DoorFlag is
checked. If DoorFlag is "on" the doors are opened, and vice versa.