The conditions being that the motor is stopped, and all switches are released. Hint: If you review the foregoing criteria carefully, you should note the the motor should only be permitted to start after a specific set of conditions have been met. Also, the retentive OTL and OTU instructions may be utilized freely at your discretion. The utilization of Binary or Integer Table bits to Flag specific conditions within your program would be appropriate. Once movement is halted, and all push buttons have been released, then door motion in either direction can once again be initiated by pressing the appropriate Open or Close button.
Door movement will remain halted when the switch is released. If the door is currently closing, pressing the Open Switch will immediately halt movement. If the door is currently opening, pressing the Close Switch will immediately halt movement. As we don't need much of a delay, the following additional criteria should suffice: We want you to modify your program to prevent the possibility of immediate reversal. Starting and stopping the door motion obviously puts a strain on the door hardware, but reversing the direction of the door without giving it a chance to fully stop causes an even greater strain. In this exercise we want you to add one final touch which will possibly extend the life of the door hardware. In case you can't get a copy, here is an excerpt (for educational purposes as allowed by copyright law) from the ProSim Student Instructions: What if you don't get a motor unlatched? It could suddenly take off running the next time that power is restored. That only leads to trouble and extra logic to unlatch the bits. Avoid using Latch and Unlatch for the motor outputs. You need to use the Motor Up and Motor Down Limit Switches to prevent door overtravel. Also your motor output rungs are much too simple.
Bill Simpson even told you WHICH bit to use for the flag! (However, if you use TWO flag bits, you can do the Motor Up with one rung, and the Motor Down with one rung.) Set up your very FIRST rung to look like the attached picture. The Exercise 4 instructions advised the use of "flag bits". I have not met a student here yet who actually read and studied the instructions for their project). Did you read the instructions for LogixPro Door Opener Exercise 4? (Probably not.
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