Need Help with Omron CP1H

[Manthan]

I have a question about SET instruction in Cx-programmer. When condition goes true it is supposed to give value 1. But, my controller is giving 0. As you can see in the attached picture. All I want to know is how? And why? Is there something I am missing?

Rung 7
SET > H77.00 > should give 1 but giving 0.

Rung 8
H77.00 NO contact should give 1 as soon as SET gives 1.

 

[parky]

Not familure with CX or Omron but one of two things:
Either it is being reset elsewhere i.e. RST H77.00 (Do a search for that contact) or if this bit is part of either some communication card or special card it could be being reset within the special card by it's own software, I know this happens in some other PLC's.

 

[Manthan]

So, that H77.00 bit is used to turn on T39. T39/DN resets H77.00.
Reset bit turns on T16. T16/DN bit SET H77.00

It is being used to turn on and off solenoid signal until MAG_XFWR_SER2 detects MAG.

 

[kckku]

So, that H77.00 bit is used to turn on T39. T39/DN resets H77.00.
Reset bit turns on T16. T16/DN bit SET H77.00

It is being used to turn on and off solenoid signal until MAG_XFWR_SER2 detects MAG.

T39 OFF resets H77.0? Is this what's happening?
Both of these set and reset H77.0 from what I am reading.

 

[Manthan]

Sorry, not T39. T25 it is. See attached picture.

So, this how program works.
T16 would turn on at the start of cycle. And if there is no MAG on conveyor, it would SET H77.00. As soon as SET H77.00 gives 1, it turns on T25. T25/DN goes to RSET H77.00

RSET H77.00 turns on again T16 and if still no MAG at sensor, repeat the cycle until sensor detects it.

 

[kckku]

Sorry, not T39. T25 it is. See attached picture.

So, this how program works.
T16 would turn on at the start of cycle. And if there is no MAG on conveyor, it would SET H77.00. As soon as SET H77.00 gives 1, it turns on T25. T25/DN goes to RSET H77.00

RSET H77.00 turns on again T16 and if still no MAG at sensor, repeat the cycle until sensor detects it.

Sounds to me it's doing what it's supposed to if there's no MAG at sensor. The PLC sets H77.0 and immediately resets H77.0 because there's still no MAG at sensor. The scan time of the PLC is so fast that you never see H77.0 turning on with the SET instruction.

Is this what's happening?

You can right click on H77.0 and select Differential Monitor (and rising) to see if H77.0 actually changes state.

 

[Manthan]

By looking at it, count stays 0 on rising edge all the time.

 

[kckku]

By looking at it, count stays 0 on rising edge all the time.

Something else must be keep the value at zero then.

Can you do a 'Find' in PLC for this address (H77.0) and see where it's used?

I have gotten caught before because there's a BSET (or MOV) instruction somewhere else in the code to always made a word to zero.

 

[Manthan]

There is an ANDW (034) instruction between H77 and H76 and result word is H77.

 

[kckku]

If you can, send a screenshot of the cross reference report for H77.0

Maybe there's something that we are missing if we look there. This is quite a mystery.

 

[Manthan]

Please find it attached.

 

[parky]

Did it work before ?, is the program working if so then it will not be a program error, it must be something else, if the logic for that bit is working then it could be that it is too fast for monitoring.

 

[parky]

There is a reset on rung 54 show a screenshot of that when the set rung is true but not setting H77.00

 

[kckku]

Yeah, it's really weird. I don't see what else it can be in the PLC code.

Not sure if you have a HMI also that can be setting this bit to 0 indefinitely. This has happened to me before. There's some mode on the HMI that someone programmed to reset a bit indefinitely.

 

[Manthan]

@parky

Yes, Program was working fine. Line was down from a long time. We have been asked to get it running for production. So, fine tuning was needed here and there.


If it was related to something else, solenoid or connection, I would have found that out. When I do force On/OFF, cylinder extracts and retracts. I don’t see o/p LED coming up, even for a sec. But, with force on/off, it does.