Flashing Bit

[mr_electrician]

For the life of me I cannot figure out why a particular bit keeps flashing even though the logic ahead of it stays true????  I have tried different registers to rule out crossed memory registers and still get the same effect.  I have also tried going around all my compare logic with no effect.

Any ideas?

 

Flashing Bit.mp4

[Michael Walsh]

I am guessing that one of your values (highlighted in yellow) is changing and you cannot see it as it only changes within the scan.

Setup a data trace to monitor these three addresses on every scan with a trigger variable of 4620.00 (off transition).  You should be able to see which of the three is causing your issue.

If the data trace doesn't work, then one of these variables may change in the scan and be put back at the end of the scan.  If this is the case, you may have to add some ladder code after this rung to catch the problem.  Add the code shown below immediately following the rung shown above:

 

 

I arbitrarily chose D5000, D5001 and D5002.  You need to use addresses that you are not using in your code.  The, if D5000 has a value other than 1 or D5001 and D5002 are not equal then one of the three variables have changed.  Remove this code when you are finished.

 

[mr_electrician]

8 minutes ago, Michael Walsh said:

I am guessing that one of your values (highlighted in yellow) is changing and you cannot see it as it only changes within the scan.

Setup a data trace to monitor these three addresses on every scan with a trigger variable of 4620.00 (off transition).  You should be able to see which of the three is causing your issue.

If the data trace doesn't work, then one of these variables may change in the scan and be put back at the end of the scan.  If this is the case, you may have to add some ladder code after this rung to catch the problem.  Add the code shown below immediately following the rung shown above:

 

 

I arbitrarily chose D5000, D5001 and D5002.  You need to use addresses that you are not using in your code.  The, if D5000 has a value other than 1 or D5001 and D5002 are not equal then one of the three variables have changed.  Remove this code when you are finished.

 

Thanks for the reply and suggestion.   I will give it a try however I went around the logic driving the bit and it would still flash.

Stay tuned for updates.

[Michael Walsh]

Perhaps something else is writing to this memory area....EtherNet/IP, Controller link, DeviceNet, etc. could all be writing data to that location and your ladder could be trying to write it back to a 1.  

[mr_electrician]

On 30/01/2019 at 3:36 PM, Michael Walsh said:

Perhaps something else is writing to this memory area....EtherNet/IP, Controller link, DeviceNet, etc. could all be writing data to that location and your ladder could be trying to write it back to a 1.  

On 30/01/2019 at 2:14 PM, Michael Walsh said:

I am guessing that one of your values (highlighted in yellow) is changing and you cannot see it as it only changes within the scan.

Setup a data trace to monitor these three addresses on every scan with a trigger variable of 4620.00 (off transition).  You should be able to see which of the three is causing your issue.

If the data trace doesn't work, then one of these variables may change in the scan and be put back at the end of the scan.  If this is the case, you may have to add some ladder code after this rung to catch the problem.  Add the code shown below immediately following the rung shown above:

 

 

I arbitrarily chose D5000, D5001 and D5002.  You need to use addresses that you are not using in your code.  The, if D5000 has a value other than 1 or D5001 and D5002 are not equal then one of the three variables have changed.  Remove this code when you are finished.

 

Thanks for the reply and suggestion.   I will give it a try however I went around the logic driving the bit and it would still flash.

Stay tuned for updates.

 

Edited February 28, 2019 by mr_electrician

[mr_electrician]

Bit of an update....I could not find the issue but am thinking I accidentally crossed into the devicenet addresses. I ended up re addressing my bits to W bits.

Cheers

[IO_Rack]

14 hours ago, mr_electrician said:

I ended up re addressing my bits to W bits.

That's the very reason Omron gave us the W memory. They promise never to use it for anything. I've tripped on the CIO (old IR) and DM wires several times in the past.