one shot generation in controllogix 1756-L61

Hi

I am new in ControlLogix, so I don't know the details of the scan cycle, I have been checking a couple of programs and I have found the following one shot generation logic (see the attached file)

I:060 is a sensor that goes low when a carton is detected.
From the comments of the logic I know that a one shot is generated, but not sure how is working under the scan rules for contrologix

Can someone explain the details ?

Thanks

Welcome to the Forum !

Can you take a screen shot ? Text-based ladder is notorious for being hard to format on the Forum.

ControlLogix is very similar to SLC or PLC-5; it solves left-to-right and top-to-bottom.

On the routine scan when the Carton Detected sensor bit is first False, the top level of the rung is evaluated. Because B3[16].2 Shot Complete is not yet true, the B3[16].1 Start-Shot bit is set true.

On the same scan, the second level of the rung is evaluated. It sets the B3[16].2 Shot Complete bit true.

On the next scan, the Carton Detected sensor bit is still False, but now the B3[16].2 Shot Complete bit is true. That makes the Start-Shot bit false for this scan, and all subsequent scans until the Carton Detected sensor goes true then false again.

This is one way to do a One-Shot, but I prefer to use the built-in ONS instruction in the ControlLogix. It uses a single BOOL to store the state of the function, but it's obvious what it's doing when you see it onscreen.

A plug for FastStone Capture, my favorite screen-capture utility. I realize there are others, and SnagIt is a favorite, but this is the one I like best.

http://www.faststone.org/FSCaptureDetail.htm

Hi

Thanks a lot for the help Ken,It was very useful!!

Ken Roach said:

A plug for FastStone Capture, my favorite screen-capture utility. I realize there are others, and SnagIt is a favorite, but this is the one I like best.

http://www.faststone.org/FSCaptureDetail.htm

Click to expand...

I wholeheartedly second that plug - I've been using it for many years...

Earlier versions were "shareware", and the later versions need a purchase, but if you can get to try it out, it is well-worth the small cost.

One of the great features is that is a portable application, that doesn't have to be installed on the machine you run it on. This is handy for grabbing screenshots of SCADA nodes etc. Just plug your USB stick in with FSCapture on it, run the program .exe and capture away! No "install" needed, so you can leave the target machine "untouched".

attached pic took about a minute to make....