logic pro simulator

Hello everyone;

Have been trying to learn PLCs and have bought a copy of logic pro from the learning pit. I am only just started and am at the door simulator which has a door which goes up and down on motors. I had no problem doing this but cleaning up is putting things to a halt. In the last part they want the door to stop if in the down button is pressed while in the up motion and visa versa. I think this is done with a little more finess than I am used to and the student exercise hints that I should be using binary and interger tables along with my otu and otl statements??? " If the door is currently opening, pressing the Close Switch will immediately halt movement. Door movement will remain halted when the switch is released.
If the door is currently closing, pressing the Open Switch will immediately halt movement. Door movement will remain halted when the switch is released.
Once movement is halted by the either of the foregoing actions, the operating criteria associated with the previous exercise will again take effect.
The utilization of Binary or Integer Table bits to Flag specific conditions within your program would be appropriate. Also, the retentive OTL and OTU instructions may be utilized freely at your discretion.Can anyone give a small sample of utilizing these commands? I appreciate any reply and hope this question makes some sense to some one out there Thanks very much - Gordie

I'll have to give this some thought.


It seems like very basic laddder logic should suffice and they are trying to make it overly complicated.

Maybe I am missing something here.

regards.....casey

Sound like they want to you try the LATCH/UNLATCH command.

Let using my broken english as logical commands and suppose we have a garage door that move up and down.

-IF <UP BUTTON> AND <MOVING DOWN> THEN UNLATCH <MOVING DOWN>
-IF <UP BUTTON> AND NOT <MOVING DOWN> THEN LATCH <MOVING UP>
-IF <DOWN BUTTON> AND <MOVING UP> THEN UNLATCH <MOVING UP>
-IF <DOWN BUTTON> AND NOT <MOVING DOWN> THEN LATCH <MOVING UP>

the logic above is missing a few things but if you can translate them into ladder then you are half way there. Remember, ladder is the easy part. Try write down your logic in plain english first.

To me, it sounds more like they want you to explore the One-Shot instruction.

The thing that trips up most students on this part of the exercise is that the DO manage to cause the door to stop when the button is pressed.

BUT... On the next PLC scan, the button is still active, and the motors are now stopped. "Oh", says the their logic, "a button push on a stopped motor means that I'm supposed to start moving in the direction requested by the button".

And so, pressing the "Down" button when the door is moving Up causes it to move down. <<<BUZZZZ>> - Wrong answer.

The oneshot instruction CAN have a "Button Command" last only one scan, which is enough to STOP a motor on one scan, but not start the opposite one on the next scan.

Good luck.