Questions?!?

[randylud]

Okay, so more or less I can set it up for what I want it to do? I am writing a program that controls a conveyor system that brings meat up two seperate belts onto one big belt. If the E-Stop is triggered, I have it setup to kill power to everything (including the PLC).

Lionel, you need to be very careful how you E-Stop. Consult the NEC and your local authority if necessary. There are serious legal considerations on what happens if someone is injured due to an E-Stop or recovery from an E-Stop. My .02$

 

[snewman24]

"I always reset all of my outputs and all of my timers with S:1/15 ... even though I realize that I don't really need to do it ... because ... it helps the maintenance technicians understand that each and every time the machine starts up, these items will definitely start out at a known and predictable state ... "

How does one reset outputs using the S:1/15 first pass bit?
Maybe use S:1/15 to go to a subroutine on only the first pass and use a XIC "always false" bit to make a rung false and therefore set the outputs to off?
Steve in Omaha
PLC student

 

[Lancie1]

Steve,



A subroutine is not necessary to use the S:1/15 "First Pass" bit to reset a bit. For example, this rung, to reset Counter C5:0, could appear anywhere in the program:

 

|                   |

|  S:1/15     C5:0  | 

+----||------(RES)--+

|                   |

|                   |

 

[just_lionel]

Alrighty Guys,

I have worked on the program I was telling you about. I would like (if you have time) for you to review it and give me suggestions on what I could improve on.

As I said before, this is nothing major. Acutally will not be ran. I may wire it up here at my house to make sure it does what I want it to do. I have ran it on Emulate500 and it seems to work like I figure it would.

What I plan to do next is to add logic to flip flop inbetween the two infeed belts. IE: Run Right Infeed for 15 secs, then Run Left Infeed for 15 secs.

Be honest with me. Let me know what I can do to improve myself.

Edit: Guess it helps to add the file?

 

[just_lionel]

I have made a few changes since my last post.


1. Added in Manual Bypass switch to run all the conv.
2. Added in a Saftey Relay (internal) (first time I used an OSR)

Once again, any advice, suggestions, beer, will be taken

 

[Lancie1]

Lionel,

I reviewed your program. On Rung 000, the "RUN/OFF SWITCH" I:1/2 is not a true safety condition as are the other inputs on the rung, with an output called "SAFETY CONDITIONS MET". I suggest moving I:1/2 to Rung 005. oN rUNGS 005, 009, 012, what happens if there is a power loss, evebydoy takes the rest of the day off and goes home, then the power is restored. All your belts will restart! Rung 005 should be probably be set up something like this, with a seal-in contact to drop out the motor upon power loss:

 

|    B3/0              T4:2/DN        I:1/2           O:2/0     |

|SAFETY CONDITIONS  STOP BLUE BELT   START PB      BLUE STARTER |

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

|                                 |            |                |

|                                 |   O:2/0    |                |

|                                 +----| |-----+        

|

 

[leitmotif]

Whichever two you want, but only two on any given project.

Good and fast won't be cheap. That's because I've got to drop everything else I might be doing to get your job done fast and still do it well.

Good and cheap won't be fast. You want good work at a discount price? OK, but when somebody else comes along willing to pay full price, whose job am I going to let slide?

Fast and cheap won't be good. Needs no elaboration.

STEVE

Been laughing to self most of today. Boss wanted a dirty room built (welding painting sanding) wanted it able to put stuff on top. Did not want 50 lb per sq foot cap.
Boss wanted it quick and cheap.
Contractor wanted out the door "I will have to do this cash - I do not want my name on any paper associated with this"

Been grinning all day.
My come uppance tomorrow - gotta hook up an air compressor - 2 HP unit and just plug into 60 A receptacle. Gonna try to do it right of course (I got a licene to protect and there is always liability and personal responsibility),,,,,
BUT he is the boss.

Already told him to not call me if it melts down.

Dan Bentler

 

[just_lionel]

Lionel,

I reviewed your program. On Rung 000, the "RUN/OFF SWITCH" I:1/2 is not a true safety condition as are the other inputs on the rung, with an output called "SAFETY CONDITIONS MET". I suggest moving I:1/2 to Rung 005. oN rUNGS 005, 009, 012, what happens if there is a power loss, evebydoy takes the rest of the day off and goes home, then the power is restored. All your belts will restart! Rung 005 should be probably be set up something like this, with a seal-in contact to drop out the motor upon power loss:
|

Thanks for that tip Lancie1. I didn't even think about it!

How about this? (I have to figure out how to do it, but this may work) If power is loss, it actiavtes the saftey relay, that way you have to press reset. That would allow it not to come on if power loss occurs. Now..just figure out the logic!

 

[Ron Beaufort]

a specific answer to a specific question ...

from snewman24,

How does one reset outputs using the S:1/15 first pass bit?

the way that you mentioned would work ... but ...

the method that I’ve shown should be more easily understood even by a technician with minimal PLC training ... and there are other ways ... but probably nothing else that will nail down the “this-thing-needs-to-be-off-at-startup” idea as well as the method I’ve shown will ...

as I said earlier, IF (big IF) all of the outputs are held on by using "seal-in" rung constructions, this technique will not be necessary ... but it might make things easier for the technicians to understand just what happens at startup time ...


secret handshake: when an OTU (Output Unlatch) is executed with TRUE logic, it just writes a 0 into the bit/box ... you’re not required to have an OTL (Output Latch) instruction in order to use an OTU ...

 

[just_lionel]

Would this new addition (using First Pass Bit) work?

 

[just_lionel]

Another question!

Working on programming a selector switch in. If in Mode 1 Then it will run both belts (like the program is now). If in Mode 2 it will alternate belts (run right, then run left, repeat)

Question is..can I do this with a simple flip flop that is determined off a timer? Or do I need to use a sequencer setup? Or I am just missing the boat completley. Like I said before, if I am wrong, give me a hint towards the right answer, just don't give me the answer.

Thanks for all the help guys!

 

[sportster]

Yes, the program with the first pass bit will work. I would move that bit to rung 0002 and add it to the branch to make things easier to troubleshoot later on. Also, look back a few posts and read Lancie1's suggestion. As for the toggle switch...don't use a sequencer; go with the other idea. Hope this helps. (Hope I didn't help too much!)

Patrick

 

[just_lionel]

Yes, the program with the first pass bit will work. I would move that bit to rung 0002 and add it to the branch to make things easier to troubleshoot later on. Also, look back a few posts and read Lancie1's suggestion. As for the toggle switch...don't use a sequencer; go with the other idea. Hope this helps. (Hope I didn't help too much!)

Patrick

Okay. I didn't know if standard was having the first pass on a rung by itself or not (THat is how I have seen it).

I have done what Lancie1 suggested (I think), just havent posted the updated program yet.

As for the toggle switch, thanks for the input!

 

[just_lionel]

Argg.

Im having problems with the alternating belts

I'm just at a complete loss.

I can get it to run one belt, then the other, but I cant get them to reset.

I have them running off the timers where if Timer Right = Done Turn on Timer Left. I dont know how to get them to reset.

 

[Ken Moore]

Are the times for each belt equal? If so you could use a time driven flip-flop circuit. See below: