Not seeing an input

[DLTimmons]

I got one that's got the better of me. I have a Do-more with a 32 point dc input card that is connect to a zip sensor module that being feed from a reflective photo eye that is reverse logic, that is the inputs off when the sensor see the reflector. I look for the reflector thru a hole in a cart as a home position sensor. Been running over a year, now it will not see the reflector unless I slow the cart down. You can see the sensor indictor make and the led on the input module go off but the program will not see it. gone as far as a latch circuit that if it see the sensor one scan it latches on. still will not see it. I am running the motor at 50 Hz was running 60Hz.

The sensor is a DMP-0P-1H
Avg scan time 2.5 ms peak 5.6 ms

[franji1]

You might look at any I/O warnings.  Look at the I/O System view under PLC->I/O System menu.

One way to ensure that it's not logic issue, put the PLC in Program mode, but then monitor the specific X input in a Data View.

Does the X input turn on and off in the Data View as the LED on the I/O module goes on and off?

If the two are not synchronized, make sure your I/O mapping hasn't been tweaked (e.g. X0 is really mapped to X40).  This is in the System Configuration dialog, under the I/O Mappings configuration entry.

[DLTimmons]

Will check Tuesday 3 day week starting in a few minutes

[Mike Nash]

The logic isn't in a program or task that isn't being run is it?

Or how about, the RUN instruction is enabled, but it ain't working because you completed it via EXIT and haven't started it back running because the RUN instruction is EDGE TRIGGERED, ARGH!!!

OK yeah, that last one was self-inflicted.  

Worse, after I figured that out, I modified the logic - dropping one of the conditionals to cycle it - but was turning the conditional back on before it got to the RUN instruction. I think I already mentioned ARGH!!!

[DLTimmons]

Mike

I think I found the issue seams that I was faulting out of a Modbus read that skipped the stage that reads the sensor.

Now to find what causing the fault in the read

Thanks All