Output Will Not Trigger

[set-csg]

Hi everybody,

I'm using SIEMENS S7 212, one imput (I0.0) which was use in the program will indicate ON on the input LED display when pressed, but the connected output in the network (Q0.0) will not switch ON.

Viewing it on the Program Status, I0.0 will not highlight even if the physical input I0.0 is activated.

Output Q0.0 will activated only if input I0.0 is FORCED only.

All other input works properly.

Does anybody can give explanation to this?


Thanks,
SET

 

[Singapore_Mats]

check your wiring again. One + missing i guess.

 

[set-csg]

Thanks for the advice Mats. I will check if there was something wrong with the wiring. This set up is already existing, and we use it in the laboratory here in our school.

Thanks

SET

 

[khalil]

when you force the input I0.0 this means you are using the software to write (force) a value to the plc register, hence output Q0.0 is activated, and if you are trigering I0.0 and it is not activating Q0.0 then its whether:

1)- you input is damaged

2)- you have some wires connected wrongfuly

try this..

connect a wire from L+ to 1M

and then connect one side of your Pushbutton to M and the other side to I0.0..and try

hope this help. Khalil

 

[set-csg]

Thank you very much Khalil, I will try to check it to what you have suggested.

By the way, If input I0.0 is damaged, why is it that the output Q0.0 will try trigger if it is program in interrupt routine using I0.0 on the rising edge.

Can you give and explanation to this?

Thanks in advance Khalil.

SET

 

[Nick B]

I'm assuming your writing to I0.0 elsewhere in your program. In Microwin you are allowed to write to INPUT. The input is being scanned at beginning of program but if you write to the input again elsewhere it will update the Process Image area and thus you get this "funny" result.

Go to cross reference area and check for all occurrences of I0.0 IB0 IW0 or ID0.

Q0.0 is OK because a Force on I0.0 makes it work. Change I0.0 to other point and see if problem follows it. Check status chart for what's happening to Input...you can also throw it into a counter to see whether it's oscillating etc.

Nick

 

[khalil]

in addition to what Nick said,

did you try and UNFORCE ALL from yuor program editor??

if the input I0.0 is forced off and you trigger physical input...the output wont work..

well..unforce all inputs..(clear PLC if necessary)

then try connecting the wires as I said

and it should work..there is nothing more to it..

hope this help. K

 

[kurt.brinker]

not sure if this relates but i had a simliar problem. (Using rs500 and a slc 5/05) I added another ladder to my program and the output would only work when forced on. It ended up being that i forgot to jump to that subroutine in the main program. once i added the jsr, all was well