Startup/Commissioning

dan · Nov 29, 2003

what r the best instructions to use to check if i/p swtches are in the positions they should b @ startup, if the proc. doesnt support FBC/DDT?
thx

ndzied1 · Nov 29, 2003

To me, the position of i/p (I assume you mean inductive proximity) switches is more of a mechanical than electrical issue. And that really depends on what they mean to accomplish in the scheme of the system you are working on. For instance, a prox that senses when a cylinder is extended should usually not be positioned so that the target passes the switch in the extended direction. If it does, then the signal will show up and then go away and may confuse the program. On the other hand, maybe a function has to occur at a specific place within the stroke of the cylinder and then this positioning of the switch would be desired.

I have no idea what FBC/DDT are but to verify wiring on commissioning, I usually just wave a screwdriver or quarter in front of the prox and see if the right LED on the PLC input comes on.

Maybe with a more specific question you will get a more direct answer.

Hope this helps somewhat.

ndzied1 · Nov 29, 2003

OK, i re-read your question and I think you are asking about after commissioning and when you turn power on a machine. Again, not sure what the FBC/DDT refer to but if your processor has ladder logic programming, just string together the conditions for the positions you require before starting a cycle and use the output of that rung to permit or inhibit the cycle. for instance:





  tool 1     tool 2   index in    drive      cycle

  returned  returned   position   faulted    enable

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

Vetteboy · Nov 30, 2003

I'm from Alberta too, and by I/P he means Current(I) to Pressure(P) Transducer. FBC and DDT are both shortcuts to supervise the status of bits in a word or words. Use the long way if the processor doesn't support them. What processor are you using and I might be able to help with instructions that you could use instead. Otherwise you can use EQU, MVM, etc. Also, an I/P is not a discrete switch, but an analog device, so you should be more specific in your question. Remember Dan, these are PLC experts, not Oil & Gas Process experts.

Eric Nelson · Nov 30, 2003

Expanding on what Norm said, you can accomplish a simple 'startup check' like this:



|                                                    STARTUP

|                                                  FAULT TIMER

|  STARTUP                                          +--------+

|----] [--------------------------------------------| TIM 1  |

|                                                   | 3 Sec. |

|                                                   +--------+

|

|              TOOL 1    TOOL 2   INDEX IN   DRIVE     STARTUP

|  STARTUP    RETURNED  RETURNED  POSITION  FAULTED   SUCCESSFUL

|----] [---+----] [-------] [-------] [-------]/[---+---(   )

|          |                                        |

|          |  STARTUP                               |

|          | SUCCESSFUL                             |

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

|

|             STARTUP                                  STARTUP

|   TIM 1    SUCCESSFUL                                FAILURE

|----] [--------]/[-------------------------------------( PD ) <--One-Shot

|

|  STARTUP     TOOL 1                                   TOOL 1

|  FAILURE    RETURNED                                NOT RETURNED

|----] [--------]/[-------------------------------------( SET )

|

|  STARTUP     TOOL 2                                   TOOL 2

|  FAILURE    RETURNED                                NOT RETURNED

|----] [--------]/[-------------------------------------( SET )

|

|  STARTUP    INDEX IN                                 INDEX NOT

|  FAILURE    POSITION                                IN POSITION

|----] [--------]/[-------------------------------------( SET )

|

|  STARTUP     TOOL 1                                    DRIVE

|  FAILURE    RETURNED                                   FAULT

|----] [--------] [-------------------------------------( SET )

I use something similar to allow cylinders to reach their 'home' position after turning on a soft-start valve. If a cylinder doesn't reach its 'home' position within a few seconds, I latch the fault and dump the air. The one-shot is necessary to avoid erroneous faults if other cylinders move off position when the air turns off.

beerchug

-Eric

Eric Nelson · Nov 30, 2003

OK, now that vetteboy has cleared up the 'i/p switches' confusion, you can ignore my response...

I ain't deleting it 'cause it's still helpful info, even if it doesn't pertain to the thread... moon2

beerchug

-Eric

Gerry · Nov 30, 2003

OK, now that vetteboy has cleared up the 'i/p switches' confusion

I suspect the confusion has been augmented rather than cleared up.

It's not uncommon in my experience to see and use the abbreviations i/p and o/p to refer to 'input' and 'output' respectively.

I know i/p can refer to an I-to-P converter, but Dan said i/p switches, and referred to FBC and DDT instructions, which many here will recognise as A-B PLC ladder instructions for analysing the status of bits. I suspect Dan is aware that they are not relevant to analogue inputs.

I ain't deleting it 'cause it's still helpful info, even if it doesn't pertain to the thread.

It is pertinent.
beerchug

Startup/Commissioning

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ndzied1

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Gerry

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