LogixPro PLC Simulator - Can Anyone help, please?

[JerryRecords]

hello, all! I'm tryin to design this ladder diagram for a project me and my friend are doing that have to do with a rail road crossing at a road.

I'm using "LogixPro PLC Simulator V.1.60"

now, my circuit is pretty basic. I've tried doing the following just to see if it worked, but it didn't.

My circuit consists of 'SENSOR A' AND 'SENSOR B'. Each of those sensors being triggered, turn on their own PILOT LIGHT: 'PL

A' AND 'PL B', RESPECTIVELY.

Now, having a train come "for example" and trigger 'sensor' 'A' or 'B' depending on which direction is coming, would ENERGIZE

'GATE A' to close gate for both directions on that road, and prevent cars, "for example" to cross.



The circuit i thought about goes as following.

'GATE A' IS PARALLEL TO 'PL A', BOTH ON THE FIRST RUNG, AND 'GATE A' IS PARALLEL TO 'PL B' ON THE SECOND RUNG.

when i tried turning 'on' sensor 'A' it would only ENERGIZE 'PL A' and NOT 'Gate A' on the first rung.

In the other hand, when i tried turning 'on' sensor 'B', it would then ENERGIZE 'PL B' AND 'GATE A', all together on the second rung.

Why would it only do it for the second rung and not both? I've implementing this on two pc's, maybe thought it had to do with the way it was scanning it. Any thoughts? I would appreciate the help!

 

[Kyle Grathwol]

Rule No. 1. You cannot use an output twice. I:1/0 won't energize your output O:2/0 because it is false on the next rung in scan order. It works on the next rung because of the scan order. You cannot use O:2/0 twice. You should also get rid of rungs 2 & 3.

 

[JerryRecords]

oh ight, makes sense. would there b another way of tryin to come up with this logic? mine seems right but it just doesnt work. and yea, the 2nd and 3rd were there because i was tryin to make the program bigger.

 

[bradal]

Here is an example:

 

[Mickey]

Jerry,
Kyle is right but he should have said you shouldn't use the output O:2/0
twice. Its called "double coiling". Even the real SLC500 processros will let you but it is bad practice. The last rung always wins.
So now that you have seen that you shouldn't what option do you have.Hint: "internal logic bits". Give it some thought and see what you come up with.

Edit:
bradal types faster then I and did your homework for you.

 

[bradal]

Remember elementary digital logic, parrallel contacts are "OR's" while series contacts are "AND's". Last rung means sensor A OR sensor B will turn on the coil.

As already stated, you should NEVER use more than one coil of one address, output or internal bits!

 

[JerryRecords]

i dont even kno what you're thnkin.


got it! but i meant with the internal bits.

 

[JerryRecords]

thanx for those that assisted me with this. I re-wrote the whole program, and came up with the following:

later on, i went ahead and worked on the following lab, it's a 4 way intersection, but i'm trying to add a 10 sec. left turn signal, while theres a red light delay for all directions. I would want to keep the O:2/3 & O:2/7 outputs as the do not walk signals. i tried adding more counters but i somehow can't seem to add anymore with all the logic, i keep messing up. by the way, i started this ladder diagram with some examples from the book, then i added the do not walk signs, and finally the 2 sec. delay on the red lights.

i got:

Red light (N/S) 0:2/0
Amber light (N/S) O:2/1
Green light (N/S) O:2/2
red light (E/W) O:2/4
Amber light (E/W) O:2/5
Green light (E/W) O:2/6
TON T4:0
TON T4:1
TON T4:2
TON T4:3

these two add the 2 sec. period when both directions are red.

TON T4:4
TON T4:5

would anyone please help me? i'd appreciate it, again, thanx!

 

[bradal]

Jerry,

Don't have time to fully reply but your first example makes no sense. The GATE 2 rung, has the two contacts before it that are in parallel. This is pointless, when one closes, the other opens, essentially always passing power.

What are you trying to accomplish with the first picture, describe the inputs. Maybe we can point you in the right direction.

 

[bradal]

Also just a note, a Normally Open .EN bit and a Normally Closed .DN bit in series, is the same as a .TT bit.

 

[JerryRecords]

sorry, i should've elaborated more on the question, please give me sometime to respond. till what time are you going to be available?