PLC's and industrial automation

Doug Harrison wrote:

> Try www.automationdirect.com and look for the DL-05 or DL-105. The 05
> starts at $99 and the 105 at $149. I got the software for an additional
> $99, though I think its now $199. AB, GE, etc are often available in the
> dumpsters but the software will kill your bank account if you have to buy it.

OK, no-one has said just what the darn things are! Just a quick overview
please. Is it just a little loop logic and input/output relays?

I'll give you a counter-example: A Scenix (now Ubicom) SX-28
programmable microcontroller chip:

http://www.ubicom.com/hardware/sx28ac.html

programmers available (~$200 range) from:
http://www.parallaxinc.com/html_files/sxtech/sxtech_home.htm

It gives you 20 I/O (dedicated or multiplexed), analog in & out,
and 50 or 75 MIPs (millions of instructions/sec). If you prefer
not to use assembly, there are C compilers (at least one is free).
I have one very complex program that is 35 pages long, and am
still only using half the ROM! The chip is only $5.


The SX-52 runs at 100 MIPs and has 40 I/O pins, and twice the
ROM storage. This chip is around $10.

- - - -

I am assuming the PLC's have no where near this sophistication,
so unless someone tells me otherwise, I am still going to assume
PLC's are 1970's technology, and it is more worthwhile to spend
time learning something new ( like high performance microcontrollers)
vs something old (like PLC's). The only two advantages to PLC's is
perhaps that they are field programmable & integrated with high current
drivers - but really that is no different than putting some relays and
programming pins on a little SX circuitboard.

...unless I'm way off base, of course.

Doug Fortune
http://www.cncKITS.com