To each their own.....
The Logo is probably the easiest PLC one can buy and use and there are more powerful versions. I stand by my sugestion this would be the simplest thing to use. You don't need analog inputs with a Lister high speed counters, and some simple logic will work fine.
If you must get more complicated the AB Micrologics are very common and popular in the US, SLC 500s if you can find them. But RS logics is expensive programing software.
The Modicon A120 series offer a more flexable programing language (that means its more complicated to learn) and the Demo software package lets you program up to 25 networks (that 7*25 rungs of logic more than any Old Listeroid will need).
Mr.Lister (Ken), your dead on the money keep it simple.
QuinnF, your absolutely right and I'll tell you something a few years back I began building an automated home brewery because I got in a pissing contest with another brewer/electrcian in California. I now have a 90% completed gizmo with a big Modicon 800 series machine to run it and TCP touch screan set the parameters variable speed drives RTDs auto vavles ect to and it will never brew beer how Rube Goldberg is that.....
Bruce.M, Micro controllers are fine if thats what you comfortable with. I used to be able to program 6800, and Z80s (8085 too by extention) but I gave up my wire wrapping tool when Inco handed me blunt instruments like cable spikers and rachet cutters. I'm sure you can build your own very good controller but I have a Modicon Micro 612 that can do all the same things, I salvaged it from a scrap electric train. After 2years hard use a mile down and 3 years of snow sun and rain out in the bone yard I cleaned out the bugs and rust and it worked (so did a second I salvaged from a another train. Heres irony for you I installed them 3 years earlier when I rebuilt these trains at another company)
I don't believe any home built controller would survive such abuse.
Shipcheif (Scott), If you have access to RS Logics I'd say go for it and buy a used PLC on Ebay, Pitty I traded one for two empty Corny Kegs a while back it would have been just right for you. What ABB lacks in sophistication they make up for in ease of use and programing.
Fanuc
SYMAX
Texas Instruments
Toshiba
Foxboro
ABB
Avoid these, some are orphans now no longer suported, or just so plain wierd you have to ask what they were thinking. The ABB PLCs are probably the most flexable and powerful machines you can get, but you will end up a freaking out trying to use them. I run in small circles waving my hands in the air screaming bad words more than a mile underground because of an ABB machine in an electric truck I am convinced was designed by Swedish engineers on the wrong meds in mental hospital far north of 60