Stumped on PLC hwk question

[chui84]

i have a hwk question that i cant get fixed right.

attached is the jpeg of what i have done soo far and question is attached as well any help is greatly appreciated.

 

[widelto]

what is your question ??

 

[chui84]

Thanks for the quick reply.
well i am confused on how to implement

LEQ 12 WALK_EW 12 seconds Goes OFF 2 sec before R1 expires.

and

LEQ 24 & GRT 12 WALK_SN 12 seconds Goes OFF 2 sec before R2 expires.

plus my green lights both turn on on both sides causing a crash.

 

[harryting]

hwk?

 

[chui84]

yup its hwk for a college class i am taking using TLP Logix pro simulator .

 

[dburnum]

Rung 8 has a GRT, and should be a LEQ.

 

[chui84]

Aahhh! Thanks fixed that part!!

 

[dburnum]

Your WALK_SN & WALK_EW look to be implemented the same way as your 6 traffic lights.

Use the ACC as LEQ 12, and the other at (GEQ12 & LEQ24). The latter being a series argument same as rungs 3 or 5.

Both would need assigned a separate Output channel

 

[chui84]

so implement both as separate rungs?

Thanks.

 

[Firejo]

So one of the problems you’re going to run into is that you will have overlapping outputs (lights). For example, on rung 1 you have output O:2/0 come on when the timer is less than 140 however you also have output O:2/0 come on when the timer is less than 220. So when the timer is at say 100, 100 is less than 140 and 220 so both outputs will be on. You could add more “GRT” blocks or you could use EQU blocks instead of GRT blocks and MOV blocks instead of outputs. Given that this is homework, instead of my just creating logic, I’m going to ask, do you see what I mean? Keep in mind that the outputs are bits in a word.

 

[dburnum]

yes....with separate outputs. Your assignment didn't really give you outputs to assign, but a "walk" sign would be a separate output for each. Presumably 0.2/3 and 0.2/7

 

[dburnum]

Typically, try to place one output per rung, with all arguments for that output before the output. Some have put the same output on multiple rungs, but that is typically bad program design. Simple rule to follow makes following a program for troubleshooting much easier.

 

[dburnum]

Double make sure that your arguments before the "event" output, match your assignment. There are some mistakes in there.

 

[Firejo]

I'll give you a little teaser.

 

[chui84]

i noticed that @Firejo