PLC Question

All PLCs are supplied with access to proprietary software that is compatible with them individually, as the equipment is practically useless without it. Sometimes there is no need to exercise any choice in these matters, and knowing the name of the PLC manufacturer enables one to go to the local supplier to see what is available for that particular make and model.

PWSlack is correct. The most important aspect long term will be picking a vendor who's PLC you already use in other machines in your facility. Then you may already have software needed too, which save you money. Every PLC vendor will have a PLC model with the little amount of I/O points. Especially if decide to go with PAC Controller (Programmable Automation Controller - an advanced PLC).

While PLC will be less expensive initially and in the long run, I was not sure if meant you wont be able to add this PLC/PAC controller until 10 years from now, or if you meant the next up grade wont be until 10 years later.

If purchase is now and cost is major concern, I would go with a small size category PLC (Like SLC 500), if you are planing for purchase 10 years from now, go with micro or small PAC (like FlexLogix or CompactLogix).

Control features needed would be a consideration too when deciding between a PLC and PAC, but vendor wise, they all will have something with the controller features you need. If it just 100 discrete I/O needed with a few analog, programmed in standard ladder logic, PLC will work fine and last 30 years. If you need motion control, multi-tasking processors, a lot of higher level processor control functions like PIDs, communicating with other highspeed processes, etc. a PAC is the route to go.

The software is almost all proprietary and is supplied by the PLC manufacturer to work with their specific PLCs or ranges of their specific PLCs ONLY. I am assuming this is not a DCS (distributed control system) which is more complicated but the following still apply.

If this is for existing plant PLCs, have you contacted the PLC manufacturer for options for upgrading the software or extending the licence to allow more points if your current PLCs don't have enough?

For a new plant or new PLCs most PLC manufacturers have a range of PLCs which have a range of maximum data points or IO expansion capability. You need to choose one that meets your current and future requirements.

For upgrading the hardware IO capability you need to follow the above suggestions also.

Ten years is a long time any more. Five to seven years is more the normal as hardware and software changes. The PLC you purchase today should be of the latest version and same goes with the Software.

Depending on manufacture the software is going to be the 1st to be changed as revisions are made. Why, its important to make sure your buying the latest software.