programing cable

marsu1821 · Apr 12, 2005

I am just starting to work about S7 200 PLC of Siemens.
Anybody can explain me What the encoder, in the cable between PC (RS232 or USB) and the PLC (RS485), makes exactly (the principle with details) ?
Is it possible to get electrical scheme in order to understand better ?

thank you for advance to help me !!!!

walters · Apr 12, 2005

seems to me the encoder transforms the data coming from the PC into readable data for the PLC and the other way back. but why is that such intersting info?? all i do with that cable is program my s7-200 and test the program by going online and check in the program what happens if i make an inuput high and that sort of stuff.

so why the interest for that sort of things.
other possibilitie is that im just so stupid by not nessicarily wanting to know that.

regards walters

rsdoran · Apr 12, 2005

I see there is a language translation problem. Encoder is usually a electro-mechanical device used to measure "motion".

In many cases the programming communication port on a plc uses RS485...NOTE this is an electrical wiring standard, here is a tutorial on RS485: http://www.arcelect.com/RS485_info_Tutorial.htm

Most PCs use RS232 connections: http://www.arcelect.com/rs232.htm

So the adapter converts a physical connection but it isnt always that simple, the trick is that the protocol decides HOW they communicate. The protocol can be proprietary or open bus.

Walters if noone had ever taken the time to learn how to build an adapter how would the first one have been built?

walters · Apr 12, 2005

ok i must admid that you are wright rsdaron and i think i understand what you mean

if noone has ever thought about building it i wasn't able to use it these days wright??

i admid my that i may have said it wrong but i also must say i never had a problem with such cable that i couldn't fix without the knowhow of that specific cable

rsdoran · Apr 12, 2005

walters said:
i admid my that i may have said it wrong but i also must say i never had a problem with such cable that i couldn't fix without the knowhow of that specific cable

First note that we are using English but its not his or your native language so the translation may not be complete.

You are looking at the fact the cable connects to the plc and allows you to program/view etc. The poster has "stepped out of that box" and wanted to understand HOW it communicates.

If you dont understand/learn some of this then later you may have problems using network(s).

walters · Apr 12, 2005

youre probably wright about that and i must say that i looked on the site yuo posted and there wore interesting things on it so im learning a bit bout the cable allready but thanx for pointing me on the fact that in the future i might not be able to fix it
i appreciate that

regards walters

marsu1821 · Apr 13, 2005

Sorry

I am sorry for my english.
I am French and I am just arriving in England last week.
I am student and I have to develop this type of cable for an internship.
I just want to understand Which solutions have been choosen by manufacturers.
I think that I have some ideas. So I'd like to know if I am in a good way...that's all !!!

thank you for web links above !!!!

Unregistered · Apr 13, 2005

that is a nice task i hope it works

good luck

marsu1821 · Apr 17, 2005

that's ok

thank you
I think I will succeed to do it.
In fact, it is not so difficult.
There is only a conversion from RS232 to RS485 signals and a MAXIM component already do it.

khalil · Apr 17, 2005

pc/ppi cable is relatevly cheap, so why build your own ? just curious,

its an rs232 ---> rs485 convertor.

best regards.

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