Two button anti tie down

[robh 12]

I am getting irritated that I can't figure this out, but its Saturday and I have been at work since 0300 and I am tired. Maybe I will retreat and attack Monday. I have two n.o. push buttons that are each connected to their own plc input. I want the operator to have to push both buttons and release both buttons each time to start a cycle, but not be able to put a brick on one button to eliminate the need to push both buttons. The buttons do not necessarily have to be pushed at the same time. THIS IS NOT FOR SAFETY TYPE ANTI TIE DOWN TWO HAND CONTROL. Operators are protected by light curtains, guards, and a safety controller. This is more to make sure they are paying attention to the process more than anything. Thanks, Rob

[Bering C Sparky 7]

Hello Rob, Try this one, it takes 3 rungs to make it happen but it works. Input #1Sart Button - ONS - (L)#1 Input #2 Start Button - ONS - (L)#2 (L)#1 - (L)#2 - (Output) Input #3 Stop Button - (U)#1 (U)#2 Inputs will need to go from false to true in order to initiate the one shots and latch junk outputs. Stop button will unlatch both junk outputs on rung branch. Granted the first initiation of the sequence they would still be able to use the brick on one button but after the first unlatch both inputs would need to go falce then true to achieve a true output. Will give it a little more thought on how to be able to get around the brick 100% I attached a RSS file using junk bits to test online. Have a good one. Charles TWO BUTTON START.RSS

[Bering C Sparky 7]

Hello Again Rob, I got a few miniutes and sat down and came up with this one. Its kind of long ( 7 rungs ) but no way they can use a brick against this one. ( unless they use it to smash the PLC ) Same senario as the last one I posted exept added a timer off the latches from the one shots. Both push start buttons will have to go falce to true within a designated amount of time in order to make a third latch that puts your output true. If both buttons are not pushed within a specified amount of time the oridginal two latches will unlatch stopping the timer. Its a little long for such a simple process but it will work if you dont think of something better. I have attached the RSS file to this post. (Brick Stopper ) Good luck, Charles BRICK STOPPER.RSS

[panic mode 246]

seems that operation is same as if it was safety anti tie down, try this:

[Chris Elston 79]

Here is an article I wrote for the same reasons. http://www.mrplc.com/kb/index.php?article=13 but most have already posted examples that should work as well.

[robh 12]

Thats what I was looking for Panic, thanks. Not sure why I couldn't move it from my brain to the PLC. Thanks for the other suggestions too Bering C. Thats a good article Chris, I read it about 3 times. Yes it is about the same. I just didn't want this to turn into one of the many other topics (err arguments) I read Saturday about anti tie down, safety controllers and push buttons to plcs. Thanks again, Rob Happy Monday