i need help with plc's

acidpies

Member
A
Join Date
Jun 2004
Posts
2
hi everyone, i'm new here but i was wondering if i could get some help with a question i got on my plc's course because i don't know the answer an i have looked for it but still can't find it.the question is:produce a ladder diagram, programme the P.L.C. and carry out testing for the following problem:

A Reactor Protection System has four Guardlines each of which provides a contact which is closed in the healthy condition.
A Reactor Trip signal is to be provided in the event of any three of the four Guardlines tripping i.e.contacts opening.

if anyone can help me i would be so gratefull, you could email me at [email protected].

thanks again

chris :)
 
Maybe its a trick question.
1. You wouldnt let a PLC handle safety, unless it is a dedicated "safety PLC".
2. Should someone really grab at least 3 guardwires before the damn thing will stop ?

But OK, if it has to be so, then you could do like this:

Guard_1      Guard_2      Guard_3        Trip

--|/|----------|/|----------|/|-----------( )

         |             |             |

Guard_1  |   Guard_2   |  Guard_4    |

--|/|----------|/|----------|/|------

         |             |             |

Guard_1  |   Guard_3   |  Guard_4    |

--|/|----------|/|----------|/|------

         |             |             |

Guard_2  |   Guard_3   |  Guard_4    |

--|/|----------|/|----------|/|------


There could be other ways to do it, like counting the number of activated guard wires.
 
Ah, I see you made an edit to N.C. contacts... :D

Wouldn't you want to lose the branches as well?

Guard_1      Guard_2      Guard_3        Trip

--|/|----------|/|----------|/|------+----( )

                                     |

Guard_1      Guard_2      Guard_4    |

--|/|----------|/|----------|/|------+

                                     |

Guard_1      Guard_3      Guard_4    |

--|/|----------|/|----------|/|------+

                                     |

Guard_2      Guard_3      Guard_4    |

--|/|----------|/|----------|/|------+


beerchug

-Eric
 
Let's hope his exercise isn't based on ACTUAL reactor programming standards. These sound like Chernobyl standards... :p

beerchug

-Eric
 
thanks

thank you people, if there is any other ways to go about the question i would to know.thanks for the help.

chris :D
 
How about this:

---------------------CLR GuardCounter

Guard 1
---]/[--------------- GuardCounter = GuardCounter + 1

Guard 2
---]/[--------------- GuardCounter = GuardCounter + 1

Guard 3
---]/[--------------- GuardCounter = GuardCounter + 1

Guard 4
---]/[--------------- GuardCounter = GuardCounter + 1


GuardCounter >= 3----( TRIP )
 

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