Hiya-
I have an open source PLC design site (i.e. Free).
It uses the PIC microcontrollers for use. It requires
a PERL (free) interpreter to run. It takes another
open source project which has the gui interface for the
ladder logic, then you run it through this large perl
script that I've developed, which outputs pretty readable
PIC assembler code. You then run the assembler code through
the standard microchip tools and you can simulate the
operation using their MPLAB simulator (it's also free)
and, more importantly, you can actually program a PIC
microcontroller and have the real PLC to play with.
The whole toolchain is either open source (free) or
commercial (free) software. The only cost is for a
programmer for the PIC microcontroller and a couple of
dollars for the PIC microcontroller itself.
It's at the "alpha" to "beta" stage of development.
You can review it at it's temporary home at:
if you are interested.
Cheers,
Rich S.