Once again, many thanks (and BrianD, too).SET turns the contact "ON" and RST (Reset) turns it off.
The contact will stay on even when the logic in front of it goes false
so when the logic driving the "Output" is true it sets it to "ON" , it then stays on even when the logic goes false until it is reset by a "TRUE" condition in the following rung that resets it.
The only caveats are that in PLC's there are retentive memory and none retentive memory, so if the PLC is switched off a coil or contact that has been set to ON will stay on when the PLC is switched back on if the bit memory is retentive, however, if it is a non retentive memory it will be reset on the PLC being switched back on and will require a SET rung to go true to switch it back on.
However, I'm concerned about the logic you show, because the selection bit M367 is on to select the pump, this means if the selection bit is turned off the pump continues to run and cannot be stopped unless there is another reset of the pump elsewhere.
...
To test this out, we started the motor (by clicking PLC button M367, then pressing the START p/b).
I then pressed the PHYSICAL STOP button X213...outcome...motor kept running.
Then we clicked M367 again and then pressed the physical STOP button X213...the motor stopped.
No - I clicked on M367 first (when 'active' it goes from a dull colour to bright green), then pressed the physical STOP p/b.By "clicked ... M367," do you mean "held M367" while you pressed the STOP (X213)?
Hi, In my case, it's not touch-screen (although I did use the word 'screen' in post #1, apologies). It's just a PC with a mouse pointer. Not sure what causes M367 to reset, but (as mentioned in the reply above) it appears to be linked to pressing either of the physical push-buttons.Because M367 is controlled via the HMI I suspect it is set in the HMI as a "ALTERNATE" (ON/OFF or toggle) so pressing it once sets it pressing it again resets it to off. It would not make sense to hold a button on an HMI as I think most will only allow one button to be pressed at a time (note: I believe the screen is a touch screen and most will only allow one touch area at a time in run mode). In saying that it is only a guess as there is also another function where rather than using standard built in functions for a button there is also a script function so anything is possible for example, on the start button it could run a script that not only set the start bit but reset the select bit M367.
There's 3 vac pumps. Each has its own Mxxx on the PLC, but they all use the same physical START/STOP pushbuttons to turn them ON/OFF.Soft Got is almost the same as GT Designer so I expect it has the same functions so they could be using a script to set the start bit and at the same time reset the select bit. I really do not see the point in the vac pump select unless there is more than one...
My apologies once again. I wish I were more knowledgeable to realise the significance of mentioning the other pumps.Ah.. now I understand, that's where the more complete the information given by OP's helps posters to give more accurate replies.
I'm wondering if they select more than one pump enable more will start or have they interlocked the pump enables so pressing the enable for pump 1 resets the enables of pump 2 & 3 and so on.
Yes, I think that's the idea, it's some kind of space saving probably. There's 3 vac boost pumps, making a total of 6 vac pumps. One thing's for sure...the physical START/STOP pushbuttons have had a lot of use, and have definitely seen better days.Yep I totally understand, the idea of the enables is to use only the Two stop & start buttons but allow starting & stopping of individual ones even though it is unlikely you will run with less than 3 pumps. Not sure why they went for this approach as 3 enables & 2 buttons = 5 whereas 3 stop/starts = 6, not much of a saving, however, I suppose there could be some other reason.