Hiya-
is a *GREAT* text on plc's on the web.
There are several low cost PLC and programmable logic
relay controllers on the market. Watch for the ones that
include the development software for free. Usually, the
"name brand" PLCs charge for the development software.
I am working on a low cost PLC that is geared for students
hobbiests, and large numbers of systems that would benefit
from ladder logic programming with a very low unit cost.
It is open source (i.e. free).
It uses the low cost PIC microcontrollers. It will require
that you build/buy a programmer for the PICs. It will
also require:
* Opencontroller on sourceforge.net.
* ActivePerl™ or other Perl package
* Microchip PIC™ assembler.
* plc2pic.pl and config files tar format
* plc2pic.pl and config files zip format
All the software is free or open source. I typically run
the platform on windows operating systems. The tradeoff
for this approach is the assembly and configuration of
the toolchain vs. the "package" from a for profit PLC
vendor. For an instructor that has a group of students,
then the it's no big thing. OR for a guy that wants to
use the software in a lot of different applications then
setting up the platform can be leveraged.
I am in the process of building up a set of kits for the
PLC to be used as evaluation/educational systems. However,
the kits are not ready yet.
However, a training version is only the chip, a power supply
a couple of LEDs and switches. It's enough to get you
going.
You can review the site at it's temporary home at:
Hope this helps.
Cheers,
Rich S.