Tcp/ip communications

[Guest Gary Young]

We are trying to get our PLC guru to communicate to other devices on our IP network (ie scanners printers etc). Up till now we have used AB Basic units with serial ports. Now our devices are more sophisticated we are looking to connect them using IP. We have ordered ethernet interfaces for our PLCS (Micrologix 1000, 1500 and SL/5's). I hope this non plc expert waffle makes some sense. Can anyone point me at a reference source, sample codes etc etc.? Regards, Gary Young IT Manager Precision Valve Australia ???

[Ken Roach 194]

Welcome to the PLC Ethernet quagmire, where Marketing drowns out the protesting cries of the engineers. Typically, PLCs just have to communicate with other PLCs of the same brand, so their implementations of Ethernet and TCP/IP are very application-specific.    Allen-Bradley controllers will only talk to Allen-Bradley software and other Allen-Bradley controllers.  Similarly, Siemens or Modicon or Koyo controllers only talk to their brethren. Things you take for granted in computers with TCP/IP, like FTP or HTTP or Telnet or SNMP.... aren't part of a PLC's job as a machine or system controller so they typically aren't built into the implementation. About the closest thing to a "lingua franca" for PLCs on Ethernet and TCP/IP is Modbus/TCP, a version of the classic Modbus serial protocol.   Catching up to it is EtherNet/IP, a Rockwell-sponsored alternative. But still those are optimized for industrial use with I/O blocks and operator interfaces.   You won't find a way to use a PLC equipped with Modbus/TCP to control a H-P laser printer. You said "printers and scanners" which makes me think about office equipment.   If you mean "barcode printer and scanners" there might be something to be done with "terminal servers" but probably not directly over IP.

[poncho 0]

another option if you needed to get plc information accross TCP/IP would be to use RSLinx OEM or PRO on a computer to grab information from a PLC and serve it up via OPC/DDE to an application on the computer that can send it where ever it needs to go or manipulate it in any desired way. this would require either VB knowledge or a pre-made app that can act as a OPC client to do what you needed.

[Guest Russ]

you could definitely hook up the processors to a "server" pc. Then run software to interface the processors to the devices in question. Of if the functions you are looking for are specific and repetitive you could use micro-controllers triggering/being triggered by discrete i/o. (i.e. voice recognition for security access using a microcontrollers output to initiate a discrete input based upon specific commands, which would then enable/disable locks/alarms/camera's/whatever your heart desires). You could automatically export data from processors to an excel spreadsheet and periodically "dump" it (maybe print out 1x per shift). Possibilities are endless. Regards, Russ