Stupid basic question

DrOrpheus

Member
Join Date
Aug 2016
Location
Washington
Posts
32
I'm kicking around revisiting an idea I had a few years back. I have very little programming experience, just from school a few years ago. I had difficulty with getting a momentary bit input to stay on long enough to complete the line of code. I had to resort to using a TOF set to like a second or so to get through, or latch and unlatch. Is there a better way to go about it?
 
When you write momentary input bit you think about digital input or memory bit or something else? What PLC? What is the line of code you are having problem with?
 
A PLC usually loads the values of I/O, then runs all the code, then writes to the outputs, I would be amazed if the PLC wasn't fast enough to see the input unless the input is incredibly fast or your program runs very slowly. If the input really is that fast and I was using a Siemens S7-1200 range I would set the input to 'Pulse Catch'.
 
Don't get caught up in the saying "Don't use a Latch or Unlatch bit". That's what they are there for. Sometimes the PERFECT solution is to use a latch/unlatch, you just need to really understand how they work in your program.
 
I think that you didn't define question clearly... If I understood good you need following:
1. Use rising pulse of momentary bit to set on memory bit ("M1" for example)
2. Add in your line of code at the end "RST M1"
 

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