special build in bits

[machinemaker 0]

Does AB have one sec, 500ms bits like Automation Direct. If so, where are they? If not, wow. What about the always on and always off bits?

[Michael Lloyd 85]

AB what? Micrologix? SLC? Compact Logix? Control Logix? You can use a bit in the free running clock S register (S4) in the SLC / Micrologix line. Always off is the opposite of always on... Just build a rung with a Binary (B3:0/0 for instance) with a normally open contact to an output (both the same address). That makes B3:0/0 Always Off. A NOTed B3:0/0 is an Always On. Compact Logix / Control Logix gives you a little more flexibility. I have a standard routine that I load for the OFF, ON, Flash Slow, and Flash Fast bits. It's written in structured text and uses a couple of UDT's for the tags. It looks like this: GSV(WALLCLOCKTIME,,DateTime,CLOCK.Year ); GSV(FAULTLOG,,MinorFaultBits,Minor_Faults ); GSV(TASK,MainTask,LastScanTime,IO_Test_Info.Last_Scan ); GSV(TASK,MainTask,MaxScanTime,IO_Test_Info.Max_Scan ); GSV(TASK,MainTask,Watchdog,IO_Test_Info.Watchdog ); ITI.Last_Scan := IO_Test_Info.Last_Scan / 1000.0; ITI.Max_Scan := IO_Test_Info.Max_Scan / 1000.0; ITI.Watchdog := IO_Test_Info.Watchdog / 1000.0; Flash.S := CLOCK.Second.0; Flash.F := CLOCK.Microsecond.19; OFF := 0; (* Always Off *) ON := 1; (* Always On *) ID := 0; (* PID Increase / Decrease Control Action *) II := 1; (* PID Increase / Increase Control Action *) Edited 29 Sep 2012 by Michael Lloyd

[b_carlton 61]

What Michael is trying to emphasize is that you will learn to appreciate specifics of one family of PLCs but come to realize that there are concepts which apply to all. You just have to look for them. Let's think about a 500 ms contact. Does the particular PLC you are checking out have EXACTLY that? Great. Otherwise, does it have components that I need to put together to give me that? Also, do I need precisely 500 ms? can I get by with something close? Make sure to distinguish between concepts and the particular way that a given PLC operates. learn about the new target PLC. You may even find that BETTER WAYS are offered to accomplish what you want. 'Always On' - hmm, if I don't see one can I make one? What is an 'Always ON' except a location whose value is 'always one'? Is there any way to create that? Start thinking outside the box created by the first PLC you used. You will be much better off for it.

[BobLfoot 302]

Spoken like somone who had to program a GE9030, a Siemens - S7, an Omron - C200H, a Toshiba-T3, a PLC5 and a ControlLogix all in the same month. Talk about the same concepts implemented differently.

[machinemaker 0]

So true, it is just that I got use to somethings that were taken for granted, like the 1 sec bit in AD verses in AB I have to build it! Our company is going through big changes and the new bosses refuse to look at anything else besides AB products. AD is pretty much dead at our plant. Michael thanks for the examples. Just to do a slow, fast timing operation, you had to come up with that routine. That is amazing to me. I am going to miss the Iboxes and stage programming not offered in AB. I am presently using the Micrologix 1400. The SLC, & Compact line is so expensive they decided to go with Micrologix. Sure seems like a big step backwards, but I am sure I will learn how to build ladder rungs to do what I use to do.