Hello, Try www.idec.com , I found that IDEC is easiest one to get tech support from. They are world wide supplier of relays, hmi and plc. They offer techinical literature and training. If you can read electrical schematics and understand what happens, the plc is a joy for controlling devices and reducing relay logic that otherwise may become confusing. Good Luck
The site listed by the other posts are great site to use, I have used them all at one point in time. Another one to help you out is www.mrplc.com. It has lots of info on all makes & models of PLC's. But the biggest thing that helped me out was just getting hip deep into it and learning from experience. You can purchase emulator programs for AB PLC's and play with programming them and the program acts like a processor.
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I have never failed, only had sucess finding what doesn't work.
Thanks for asking the question, Ron Nombri. My knowledge of PLC's is limited and I shall study the links shared by all who have answered your question. Perhaps we can learn together so we are certain to know what is important and apply what we have learned.
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WARNING! All suggestions are informative only. It is the prerogative of the user to implement under his sole responsibility. This commentator will not be liable for any damages or injuries incurred.