Ken Roach

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About Ken Roach

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  1. 1756-hsc/b problem

    Does the control room meter display get its signal from the same flowmeter output ? When you change over a PLC to a new model, most of the I/O and signals work in a similar way.   But they aren't always exactly the same, so you need to research signals like this one. I don't think it's fair to say "it's very strange" until you have examined the whole system and program.
  2. 1756-hsc/b problem

    Thanks for the screenshots ! Those appear to show that your PLC-5 code used a data block starting at N9:84 that was 44 Words long to configure the 1771-VHSC.    The screenshots of N84 show that all the values in that data block are zero, which suggests that the VHSC was configured for all defaults, which you've assessed to mean Counter Mode, No Store, Rollover = 0, Preset = 0, and Scaler  = 0. What kind of pulse signal does your flowmeter generate ?   What's the voltage, what's the pulse rate, and how long (in ms) are the pulses ?   I'd have to look up the default filters on the 1771 and 1756 modules to see if they're similar. How do you evaluate your flow;   do you count up a number of seconds then capture the Accumulated Count, then calculate the flow ? Could the logic that triggers that calculation be different between the two systems ? Is the ControlLogix sending this flowmeter data back to the PLC-5 for you to do that calculation (I see that there's some copying of the 32-bit value into ControlLogix tags that are equivalent to N8:70-71 and N8:72-73)  ? Is the deviation of the volume flow consistently above the old measurements, or consistently below, or is it always different ?  
  3. 1734-232ASC

    You will have to do it in blocks. Most ASCII devices like label printers use a delimiter (usually Carriage Return and/or Line Feed) instead of a timeout.   You will have to split up your string into multiple sections and use a sequencer to send them one at a time, with the delimiter on the last one.
  4. I did a lot of searching for a hardware interface or method to talk via Ethernet to a Fanuc 30i family controller and did not find one. I used the FOCAS OPC Server product directly from Fanuc Support North America.   Relatively inexpensive, but the jury is still out on the reliability;   I had some trouble understanding the update mechanism and some "stale data" issues.
  5. AB Micrologix atomic memory read

    Thanks for the clarifications and follow-up ! A MicroLogix or SLC-500 does not service communications during the program execution (with the exception of explicit SVC instruction interrupts), so there is no risk of having your loop or COP instruction be in between the instructions that assemble your data into the Integer data table when the data is read by the external program. There is definitely that risk in ControlLogix. CPW was added to the instruction set for the MicroLogix 1500, and then moved forward into the 1100 and 1400 controllers.    It was built to accept operands of differing data types, in part because of the addition of Modbus RTU to those controllers and the need to pack 32-bit Floating Point data into Modbus Holding Registers.   As you have found, it's also useful for manipulation of Long Integer data tables.    
  6. AB Micrologix atomic memory read

    The MicroLogix and SLC-500 operating systems are functionally single-threaded, so they service communication requests based on the data table values in between execution cycles of the control program.    There's no way that I am aware of for an element of a data table to change during the reading of an array of elements, even if it is changed by a Routine that is executed by a Periodic or Event interrupt. Strictly speaking the data tables are "atomic" down to the Element level;   if you read N20:0 through N20:3, that's four elements, not one. This is different in the ControlLogix family, which has a task scheduler and communications services in the background.   You can encounter (and I have) circumstances where data in an array changed during a communication operation.  I use the Copy Synchronous (CPS) instruction in ControlLogix to lock the source and destination tags when I need to assure integrity of an array of data.
  7. You can "fake out" the older controller by entering the L33ER as though it was an old 1769-L35E.    There is no version dependency that I am aware of that prevents any ControlLogix or CompactLogix from exchanging Produced/Consumed Tags with any other ControlLogix or CompactLogix that supports the same networks.  
  8. The "remote" 1756-ENxT, the chassis that contains it, and the "Producing" 1756-L73 controller must all be in the I/O tree. The 1756-L73 is definitely supported by Studio 5000 v30.
  9. Studio 5000 and different PLC versions

    Take a look at what's in the contents of those "DVD images";   for better or for worse it's every support file in every language. When I download a Rockwell software product, I put the .RAR or .ISO or .ZIP files onto our big file server once I'm done with my installation;  no reason to keep them on my relatively small SSD.
  10. SLC500 Chassis

    Yes.    The very oldest Series A chassis had some MOV's under the processor slot that were notorious for getting bent and damaged, and Series B improved that design. 1746 chassis of any Series are 100% compatible with all controllers, modules, and power supplies.
  11. ML1000 MSG Instruction

    OK, that's a different set of conditions and devices. Is your communications over serial, or over TCP/IP ? What revision of firmware is the CompactLogix 1769-L32E running ?  What protocol are you using;  DF1 full duplex, or half-duplex, or half-duplex Radio-Modem ? Telemetry can be hard to troubleshoot, and the tools and techniques aren't as commonplace as ordinary automation electronics.  I used to make my living hooking up protocol analyzers and hunting for the correlation between communication failures and weather/temperature/vibration/traffic/time.
  12. ML1000 MSG Instruction

    What is your master controller ?   When you say "some of the messages do get through", do you mean that of the three to that site two of them always get through, or some of each of the three sometimes get through ?    Does your system do any statistical collection on error rates or counts ? Have any changes been made to the system lately ?   Do your radios have any independent diagnostics ? In general, Error code 0x37 really does mean "timeout";   the local controller sent a query to the remote controller, and never got a reply. This is different from the sort of error that you would get if the data table was unavailable, or there was a corrupted value like a CRC error.   With a MicroLogix 1000, the data tables are fixed in size and type, so the risk of mis-addressing is mostly limited to typos at the master side.  
  13. Yes, that is definitely possible.    FactoryTalk View's diagnostic log will generally indicate the data table addresses it cannot read or write.
  14. There is no difference between the 16K and 32K controllers in their ability to communicate via the serial port. So your problem could be in the configuration of the serial port, or with physical damage to the serial port, or with differences in the data table addresses that you are attempting to read and write.   But it's not a firmware problem.
  15. FT View Basic Error

    I don't like to directly address Inputs or Outputs;   FactoryTalk View has had some SNAFUs with the drivers, and in general I just don't like to risk the possibility that the HMI will write to something that the PLC is also trying to write to. Is your multi-state indicator configured for 2-state (which could address a Bit) or Integer state (which would have to address a whole word) ?