Custom PLC

Daniels_here

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Join Date
Jun 2007
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hey,
I am interested in building a custom PLC for a project i have. i have very little knowledge in PLC so i need some help, what i want to know is if i get a simple Atmel ATMEGA128, than setup the communication on RS232.

how hard is it to convert the digital signal into orthogonal frequency-division multiplexing, than place it on a 24V line and convert it back at the other end, or is there a simpler method that is cheap?
cya
daniel
 
Sorry to sound negative, but how do you know you need a custom plc if, as you say, you have very little knowledge of plc ?
 
What is "orthogonal frequency-division multiplexing" ????
If you put it in laymans terms, then maybe we can have a guess at if it is possible or not.

It sounds more like an "embedded controller" than a PLC to me.
There are forums for embedded controllers that can help you if this is the way for you.

If it absolutely must be a "PLC" then 3S (CoDeSys) makes a PLC runtime that will run on very modest hardware, an 8051 for example. Dont know what processor family that Atmel belongs to.
 
JesperMP said:
What is "orthogonal frequency-division multiplexing" ????
Click to expand...
Google yields this
http://en.wikipedia.org/wiki/OFDM
I hope this explains everything and makes it clear. ;)

If you put it in laymans terms, then maybe we can have a guess at if it is possible or not.
Click to expand...
I don't think it can be expressed in layman terms.

It sounds more like an "embedded controller" than a PLC to me.
There are forums for embedded controllers that can help you if this is the way for you.
Click to expand...
I think a DSP is required. Certainly not a PLC.

If it absolutely must be a "PLC" then 3S (CoDeSys) makes a PLC runtime that will run on very modest hardware, an 8051 for example. Dont know what processor family that Atmel belongs to.
Click to expand...
The Atmel group. :) Actually Atmel does support the 8051 but the ATMEGA 128 is specific to Atmel.
 
Maybe Daniel found this site because one of the communication categories that is mentioned to use OFDM is "PLC" !
Only problem is that PLC with OFDM is Power Line Communication.
 
hey,
yeah i did want to communicate the flow rates and control solinodes.
i wanted custom to make it as cheap as possible.
i think i have worked it out by using the st7538 for the communication and the control part should be very easy.

thanks alot
Daniel
 
sapoleon said:
well, they does... if you don't take into account time and labor. It's just a small shopping list.
Click to expand...

I have to laugh. A smaller shopping list doesn't make it cheaper.
I have to agree with Crocop on this one.
I have NEVER done a custom job that has been cheaper!

I also have a question; at what stage does time and labor stop being accounted for ? In my experience, it is one of the first things that HAVE to be accounted for.
 
sapoleon said:
well, they does... if you don't take into account time and labor. It's just a small shopping list.
Click to expand...
So, using this reasoning, I can conceivably build BOTH the Great Wall of China AND the Great Pyramid, IF I'm willing to spring for the rocks. (How much could that be?)
 

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