S7 untidy stl

[barryoc]

Hi,

I'm doing a compare in s7 stl. The code i have written works fine but looks messy. What I'm trying to achieve is to set m9.0 when the PLC clock hour is 0, 4, 8, 12, 16, or 20 and then reset at half past the hour. Attached is the working code but if anyone has comments or suggestions to improve the code they are welcome.

Thanks,
Barry.

 

[PeterW]

Possibly do something along the lines of dividing the time of day by 4 and if the result is a whole number then use a JL instruction.

or tidy that code up

A(
L 0
L time of day
==I
)
O(
L 4
==I
)
O(
TAK
L 8
==I
)
O(
TAK
L 12
==I
)
O(
TAK
L 16
==I
)
O(
TAK
L 20
==I
)
S M 9.0

 

[MOeZ]

Hello,

I think, you STL is neat and simple. For Keeping your code simple will let you find easily when there is a problem or need to modify existing code or after time passed by. May be this is my personal (beginner) thought. or otherwise, you can loop check by adding constant (since offset is +4), but scan time will increase. Waiting for expert idea to come in.

By the way, what step 7version you are using? It's TIA? thanks!

 

[Jeebs]

L "Time Of Day".Hour
L 4
MOD
L 0
==I
S M 9.0

L "Time Of Day".Minute
L 30
==I
R M 9.0

Just a thought......

 

[L D[AR2P#0.0]]

Are you executing this code all the time?

If the code is executing all the time M9.0 will be true until 0:30, then it will be false for 1 minute then back true again at 00:31

 

[barryoc]

Jeebs,

Excellent. I never thought of the MOD instruction.

LD,

Yes, this code will be excuting all the time. Good observation, I have only tried it on plcsim and only tried the hour to switch on and the 30 minutes to switch off. I will change the M9.0 reset this evening when i get a chance.

Many Thanks everyone,

Barry.

 

[balash]

Are you executing this code all the time?
If the code is executing all the time M9.0 will be true until 0:30, then it will be false for 1 minute then back true again at 00:31

maybe a little change in Jeebs code could help if minute > 30 to reset

L "Time Of Day".Hour
L 4
MOD
L 0
==I
S M 9.0

L "Time Of Day".Minute
L 30
[COLOR="Red"][B]>[/B][/COLOR]I
R M 9.0

 

[Matchu04]

Hi LD

Go easy on me as this is one of my first posts and also just getting to grips with STL. Could you please explain why m9.0 would be false for one minute. I Keep trying to get my head round it but I feel its going to explode.

 

[L D[AR2P#0.0]]

What do you think the orignally posted code will do? - consider the following times and evaluate the logic.

Firstly, if the hour is zero then M9.0 will be set to TRUE
Secondly, if and only if the minute is 30 will M9.0 be reset to FALSE

Remember that this logic is evaluating every scan.

HH:MM
-----
00:00 M9.0 will be set true, M9.0 will not be reset false
00:29 M9.0 will be set true, M9.0 will not be reset false
00:30 M9.0 will be set true, M9.0 will be reset false
00:31 M9.0 will be set true, M9.0 will not be reset false

 

[L D[AR2P#0.0]]

As this thread has been revived, here's my coding. No SET/RESET, but a list of comparisons that determine when you want M9.0 to be ON

 

[Matchu04]

I take it this would happen ever half hour if the original code was used?

 

[L D[AR2P#0.0]]

Only when the hour is 0, 4, 8, 12, 16, or 20

for the other hours, the following will happen

00:31 M9.0 will be set true, M9.0 will not be reset false
M9.0=True
01:00 M9.0 will not be set true, M9.0 will not be reset false
01:29 M9.0 will not be set true, M9.0 will not be reset false
01:30 M9.0 will not be set true, M9.0 will be reset false
M9.0=False
01:31 M9.0 will not be set true, M9.0 will not be reset false
M9.0=False

You cannot assume or guess with plc logic, get the data, execute the logic.

 

[Matchu04]

I thought that this was the case. Just out of interest on the code that you have submitted you load the accu with "tod#0.0.0.000" for example and compare it with the actual time.

Do you have to express how the clock function works, or are you just inputing a spectic time of day figure to compare to hence the tod#? like if you was dealing with a real number you would put ==r, but for time its tod#.

Or am I barking up the wrong tree?

 

[L D[AR2P#0.0]]

I must be in a different forest as I don't understand your question.

 

[Matchu04]

I think I've found the answer to my question. What I was unsure about was the load tod# part but I have found its the format you would write the time of day to the accum. I think?