Morning,
TIA V17, CPU 1511-1 PN, KTP900, a mixer skid we shipped in the spring. The batch sequence is a CASE on an integer Step in SCL, 18 steps. E-stop drops the safety relay, the PLC sees safety OK go low and sets Step := 0, so after the reset it starts again at step 1, drain and rinse, and the half made batch goes down the drain. The customer's dumped four batches now.
I tried leaving Step alone on the E-stop, and then the mixer carries on from step 12 and the dosing valve opens the moment the relay resets with nobody having pressed anything. A retentive Step does the same.
I never wrote a resume into this program at all. What's the right structure for one? Something that holds at step 12 and waits for somebody to press a button before a valve moves, is that the shape of it?
V17, noted. What tells the sequence it's allowed to move again, the relay reset or the operator? From your post it sounds like the relay. And was a timer mid count when they hit the stop, agitation or dosing?
The relay, at the moment, nothing else. There's no Resume button on the panel because there was never a resume, it was Start or nothing. Agitation, 40 s IEC TON, and it had about 5 s left when they hit the stop.