Selection of PLC hardware

Hi All,

I have dim and distant experience of building PLC systems 10+ years ago (when I did some work with siemens hardware), but nothing recent so I'm not up on the current offerings from manufacturers. I now have a requirement to replace an old hardware based control system (mainly relay logic) which has a reasonable amount of I/O. the system I am looking at has :

46 x digital inputs
45 x digital outputs
12 x Analogue input
12 x Analogue output.

Id like to keep all the I/O within the same enclosure which is a 19" 6U unit. All I/O is presently connected to the old unit via 8 D-sub connectors.

The system is used to switch on / off and monitor some power supplies as part of a larger system and applies some very simple logic and sequencing to them. It has a front panel of illuminated buttons, which I would seek to replace with a HMI panel.

Id rather avoid using distributed I/O if at all possible

Would anyone recommend any particular manufacturer and product family.
 
Judging by the description of the project I would recommend a nano PLC system. Just about every manufacture out there has a version and the cost is quite reasonable. If you are already familiar with the Siemens platform then maybe a S7-1200 would work. There is lots of expandable IO capability and lots of communication options, it can even interface with remote IO if necessary. I would steer clear of the Siemens Logo. The programming on the Logo doesn't offer much for sequencing and mid-size projects. If you are looking at something from Allen Bradley the Micro850 or 870 has lots of room for IO, and the programming software is free but is not capable of remote IO. If you need a little more processing power an entry-level compactlogix would work well too. If you are using the compactlogix it's cheaper to use the "Point IO rack" than the IO cards. I'm sure Omron has a similar PLC package as well I'm just not familiar with their product line.
 
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