On Sat, Nov 29, 2008 at 4:20 PM, Jinx wrote: > I guess the material costs, not including sensors, using a PIC may be around > NZ$70 (US$35-$40), and software perhaps a little less (@ Q = 300), then > there's markup on that > > Can anyone with practical experience of PLCs give me any advice as to > whether the cost of a PLC system is even worth considering ? And, if so, > how do prices compare ? There are a few Sub US$100 PLCs. But not US$40. And most of the US$100 PLC will not have analog input points. Eg: http://www.ab.com Allen-Bradley Microclogix ML1000 1761-L10BXB 10 digital points only, about US$99, free software No expansion available for ML1000. Pico controller is another option. http://www.ab.com/programmablecontrol/plc/pico/controller.html Automation Direct D0-05DD + D0-05DD 10 digital points only, US$99, 4ch analog expansion I/O will cost another US$79 The good thing about PLC is the shorter development time and the good system reliability. Xiaofan -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist