On Thu, Jun 4, 2009 at 6:48 PM, Gerhard Fiedler wrote: > Thanks a lot, that is helpful. The only downside to PLCs is that it > seems that most IO is based on 24V. That is kind of the standard in the automation world. There are 5V TTL options for some I/Os, but not so common. The DC input typically follows IEC61131 standard (Type 1 or Type 3). -- Xiaofan http://mcuee.blogspot.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist