DRSapach
Member
I was having a problem with a MicroLogix 1000 processor (DC model 1763-L16BBB) missing pulse counts from a hall effect (NPN open collector) flow sensor. Flow generating up to about 30 pulses per second would register but above that no pulses would be counted. I have the sensor connected to input 0/0 of the processor which supports high speed counting. After much troubleshooting which included connecting an digital storage scope to the input and verifying that the sensor was operating correctly (i.e., outputting a proper square(ish) wave form), I was able to find the problem with the help of Rockwell Automation Tech Support and want to pass it on here...
The issue was an obscure project setting for the PLC program. This setting was set to a generic processor type which configured the inputs to be 'regular speed'. Once I changed the processor type to match what I had, things magically worked. Here are the details on what to change in RSLogix:
In OFFLINE mode:
- From the project tree, open the Controller folder and double-click on IO Configuration.
- Double-click on the first item in the part list which should be the processor (MicroLogix 1100).
- On the first tab change the Base/Type from Any Base to the processor type you have (BBB Base in my case).
- Click OK to save the change.
- Save and download the project to the PLC.
Also, if you need to count very fast pulses, you will likely need to use the High Speed Counters. These are also enabled on the IO Configuration for the processor.
Hope this helps...
The issue was an obscure project setting for the PLC program. This setting was set to a generic processor type which configured the inputs to be 'regular speed'. Once I changed the processor type to match what I had, things magically worked. Here are the details on what to change in RSLogix:
In OFFLINE mode:
- From the project tree, open the Controller folder and double-click on IO Configuration.
- Double-click on the first item in the part list which should be the processor (MicroLogix 1100).
- On the first tab change the Base/Type from Any Base to the processor type you have (BBB Base in my case).
- Click OK to save the change.
- Save and download the project to the PLC.
Also, if you need to count very fast pulses, you will likely need to use the High Speed Counters. These are also enabled on the IO Configuration for the processor.
Hope this helps...