start/stop using one push button

[gryskop]

Infortunately this logic will revert back to the "un-toggled" state in the event of power-loss, or a change from RUN to PROG and back to RUN, which I doubt is what you want to happen to the "duty" pump selection.

As I have stated already, a "toggle" should not be affected by any other event than the logic that drives it.

If you want a toggle to reset on restart, then program it in the start-up section of the code for all to see.....

Daba, perhaps then you can help me with my current AB project.

HISTORY: I’ve been an ABB man for 14 years, and the last 4 years I spent on SIEMENS PCS7 and S400 series PLC’s. To be quite honest, LADDER programming is not my forte, and AB plc’s are quite new to me in the sense of how the hardware structure works with regards to retentive memory.

Our application is for gold mining process plant automation. Not really critical application like a power station. “If the power fails, so what, we’re basically just pumping mud, that will spill into contained spillage bunds that can be recovered.” These are the words of our process engineers, not mine.

As for the PLC (which will be Control Logix L74 PLC’s) how do I make area in the defined variable tags “Controller Tags” to retain their memory during either a power failure or re-load of software? The same can be asked then for counters and timers? How do I make them retain their values?

Thank you.

 

[DwSoFt]

glad someone else thinks like i do... :nodi:

sadly some people do not think like that

they think of job security
ive seen password protected plcs, where the owner didnt get the password. ******** indeed. or where the code will (after warranty period) randomly go down so the programmer gets paid tyo come back and "fix" the plc problem. that is retarded

or even better, using internal relays for every input, so that the input numbers dont line up with the internal relay numbers, thus making it woy over complicated.

should start a thread about horrible codes actually. yeah im gonna post that thread now, after i do a search an see if its been done before haha

 

[daba]

....As for the PLC (which will be Control Logix L74 PLC’s) how do I make area in the defined variable tags “Controller Tags” to retain their memory during either a power failure or re-load of software? The same can be asked then for counters and timers? How do I make them retain their values?

Thank you.

The simple truth is that ALL memory values are retained. There are no special areas of memory that need to be assigned as "retentive".

However, A-B PLCs perform what is known as a "Pre-Scan" on startup....

During the Pre-Scan, the logic is scanned once, and all non-retentive data is reset, or initialised.

Specifically, BOOL tags that are operands to OTE and ONS are reset to 0. TON tags are reset (control bits reset, and accumulator set to 0), etc.

The instruction help describes the pre-scan actions for all instructions.