I wanted to design a LOW COST PLC ..So last night TV programing was BORING .and HEAVY SNOW was falling .While waiting for answers to SOME questions that I POSTED at ELEKTRODA .. I discovered the OLIMEX AVR-IO board going for $25 bucks.
Ok .. To be really a PLC .. You have to programme it in some kind of LADDER scheme ..
Well i have ladderworks a great compiler of LADDER designs The only problem is that the output is Binary 51 code ..(Hex)
Well if there was a possibility of changing the AVR chip for a 8051 .. I will be in heaven .The AVR-IO board cames with a AT90S2313 chip .But it turns out that that 20 pin chip is PIN TO PIN compatible with another CHEAP CHIP($3.00) from also ATMEL ..the AT89C4051 with 4k flash code!
Now i'm in heaven $30 dollar PLC that i can programme ( JUST FOR TEACHING PURPOSES for me )
The only PROBLEM is that i can't use a BOOT LOADER .. this chip doesn't support on board programming .. It's Ok to remove the chip for that
PRICE .. i won't be that demanding .
I will change the quartz clock to run it at full speed 24 Mhz!
I love snowy day ... and cognac...(the cheap one)!
There is a new small PLC from the chinese factory Array, it cost me only 35 US dollars and has many interesting characteristics such as real time clock, function block programming.
Using any search engine the array´s webpage could be located.
Try with FESTO FEC PLC line.
It is very cheap, and have some powerfull capabilities:
- ethernet port integrated
- rs232 master messaging
- DOS system operating
- 256 Kb of retentive memory
- 2 msec scan time for 1k instructions
- don't have battery (no manteninance)
- can be directly connected to a analog/digital converter also very cheap
Also if you want to design a cheap PLC try with the IPC integrated circuit from BECK: www.beck-ipc.com
They have a powerful integrated circuit that can handle directly a ethernet port for example.