Good and old flickering

Hi, everyone,

OUTPUT_MAIN is flickering after OUTPUT_RELEASE is ON. How may I stop this flickering?

I need OUTPUT_MAIN to go ON when START_MAIN goes ON, go OFF when OUTPUT_RELEASE goes ON and remain OFF until START_MAIN goes ON again.

AB Micrologix 1400. I attached the program and a picture. Any suggestion/explanation is appreciated.

Thank you!

Put your holding contact (should be XIC) around START_MAIN.
BST XIC START_MAIN NXB XIC OUTPUT_MAIN BND XIO OUTPUT_RELEASE OTE OUTPUT_MAIN

Thank you very much, rdrast. I do like the simple and yet elegant solution and this does take care of the flickering. However I don't see how this setup would allow OUTPUT_MAIN to be ON by turning START_MAIN on again.

Hmm.. I tried using latching and unlatching. It does seem to work although as a beginner who can't even predict some basic flickering I would rather use an OTE instead. I attached a picture of using latching/unlatching. Any considerations I should keep in mind?

Actually my solution does not work because once I toggle START_MAIN again, OUTPUT_RELEASE is true, which will go straight to the OUTPUT_MAIN OTU and the output main output will not be true again. Ooops.

At first I didn't understand at all why you wouldn't just use a 3 wire start/stop circuit (sometimes called a holding or latch circuit), but I understand now after seeing your picture. I believe you used the wrong type of contact for your latch, normally closed (XIO) instead of normally open (XIC). You also had an extra instruction that didn't need to be there.


Your ladder should look basically like this.

  OUTPUT_RELEASE    START_MAIN                        OUTPUT_MAIN

-------[/]--------------[ ]-------------------------------(OTE)----

                  |             |     

                  | OUTPUT_MAIN |

                  |-----[ ]-----|

I apologize that I can't post an actual RSLogix screenshot, It is very difficult for me to move things between our office network and our control network.

As for your JSR, Typically what we do is that we save LAD2 just for JSRS, then essentially use different ladder files for organization. I've never found it necessary to use it in the middle of the program like in more computer-y languages.

Hi, Sandwich!

The solution you provided seems identical to that of rdrast, which would work wonders if I didn't have to toggle the process on again by toggling start on. Although I do wish that OUTPUT_RELEASE will clear OUTPUT_MAIN, in this setup it is not possible to trigger OUTPUT_MAIN ON again by triggering START_MAIN ON a second time, or am I missing something?

Also I do have LAD2 calling all my subroutines like you suggested, but in order to save time when getting some help here I cleaned and organized it to show the source of my problem so that it would be easier to see

Oops, I didn't see rdrast's ladder. So to get this straight. For sipmlicity's sake, let us just pretend that your START_MAIN and OUTPUT_RELEASE are tied to regular momentary push buttons. You want to be able to push the START_MAIN pushbutton, which then will hold OUTPUT_MAIN on until OUTPUT_RELEASE pushbutton is pushed, correct? When you push OUTPUT_RELEASE, it drops out OUTPUT_MAIN until START_MAIN is pushed again, correct? The ladder given to you by myself and rdrast will do that. When you press START_MAIN, it will latch just like before, until OUTPUT_RELEASE is triggered, just like before.

I hope that we are on the same page here! Sometimes I have trouble understanding technical things through a text medium.