Micrologix Communicating with PLC-5

[mjggjm12]

I need to moniter some pressures for spikes and what state the machine is in when it happens. I am putting additional pressure transducers on the machine that are higher rated than the ones used in the process to catch the spike. I have programmed a micrologix 1200 for the tranducers and to capture the event. The machine itself has two stations each with a PLC-5. All that I need from the two PLC-5's is the state each one is in in the program when a pressure spike happens. The state is stored in R6:0 on both PLC-5's. I am using the micrologix because I have to be as minimally invasive as I can to the machine because any code change, even for testing, requires a mountain of paperwork wich can take months to get all the signatures required. So after all this rambling my question is can I get the micrologix to communicate with the PLC-5's and do it without doing any program changes to the 5's. The PLc-5's have the 5/11 CPU and do not have ethernet cards in the rack. I was hoping to use the Rs232 communications. If this will not work what could I do instead. I also have the parts to put together another PLC-5 instaed of using the microlgix but I have never programmed PLC-5. Thank you for any advice and solutions.

 

[dmargineau]

You could use DF1 Half-Duplex over a RS232 Serial link where one of the PLC5 CPUs will be the Master while the other one and the ML1200 will be the Slaves, however, the distance between the drops is restricted to less than 50 feet unless special, low capacitance cables are being used or modems/line drivers are being inserted within the circuit.
Refer to: http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1785-rm007_-en-p.pdf
Chapter 10 of http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf
and Chapter 4 of http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1762-um001_-en-p.pdf

Another option will be to use two 1761-NET-ENI modules (one for each PLC5 CPU) and connect the established EtherNet/IP subnet to the ML1200 Ethernet port; this will allow using peer-to-peer explicit DF1 (Full-Duplex) messaging between the enhanced PLC5 controllers and the ML1200 one.
Refer to http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1761-um006_-en-p.pdf

 

[mjggjm12]

Thank you very much for the reply. I have a couple of questions I am a rookie when it comes to network stuff.
1: I see the PLC-5 communicates with DH+ and the ML1200 uses DH485 is that going to be a problem?
2: Can the ML1200 be the master? If so can it go in and pull data out of the PLC-5 data table without a MSG write instruction from the PLC-5?
3: If I have to use a MSG write instruction in the PLC-5 can I make that rung true all the time so when a pressure spike event is detected by the ML1200 the Data in R6:0 is available or do I have to send a discreet signal to the PLC-5 from the ML1200 to trigger the MSG write command?
The least amount of program change on the PLC-5 I have to do the easier it will be to get the paperwork through.

 

[dmargineau]

1. The PLC5 supports DH+ communications on Channel 1A; you will not be using Channel 1A; for Serial RS232 DF1 Half-Duplex communications you will be using the PLC5 Channel 0 set (via SW2) to RS-232C and in User Mode(Again, see Page 10-2 of http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf)
The ML1200 CPU can communicate via DH485 over the Serial Port; you will not be using DH485; you will ne using Serial RS232 Half-Duplex over the same port, configured accordingly and eventually connected to a 1761-NET-AIC module.(Again, see Chapter 4 and page 4-8 of http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1762-um001_-en-p.pdf)
The communications between the three devices will be established via DF1 Half-Duplex over an RS232 (or RS-485 if the NET-AIC modules are being used) "electrical layer".

2. I have never set a ML CPU as a Master within a Half-Duplex DF1 network, however, it might be very well a viable option, with the PLC5 CPUs being the slave nodes.

3. For a handful of MSG instructions, "trigger" logic is not necessary, however, if you wish, you could "monitor for change" (EQU, NEQ, GRT, etc) the relevant data and enable the MSG instructions depending of the result of the "compare logic".

I have to warn you though that this is a pretty complicated task; I'd personally try installing the 1761-NET-ENI modules and use Ethernet as the "electrical layer" (transport)of your proposed networking.

 

[mjggjm12]

Thank you.

 

[ELake20]

I hope the ML's scan time is fast enough to catch your spikes.

I really like to use the measurement computing USB DAQ boards for this type of application. They are extremely low cost.

I've seen/used 'isolators' to be as minimally invasive as possible, with these you could put your DAQ wiring in parallel of the PLC analog inputs so no rescaling necessary....

Some food for thought anyway.

 

[mjggjm12]

Can I daisy chain the serial cable from 1 plc-5 to the other and then to my 1761-net-aic module or do I need 1 module for each plc-5?

 

[mjggjm12]

I looked at the diagrams but they don't show the pintouts just a line going to the controllers.

 

[dmargineau]

You will need one 1761-NET-xxx module for each CPU; one NET-xxx module port will be connected to the CPU Serial Port and the other one to the implemented networking (RS485 for AIC modules or Ethernet for the ENI ones).
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1761-um004_-en-p.pdf

 

[mjggjm12]

You will need one 1761-NET-xxx module for each CPU; one NET-xxx module port will be connected to the CPU Serial Port and the other one to the implemented networking (RS485 for AIC modules or Ethernet for the ENI ones).
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1761-um004_-en-p.pdf

Thank you very much. I am going to try this on a DF1 half-duplex master slave setup.