Beginer

Jacobplctalk · Apr 21, 2008

Hello,
Could anybody tell me if RS232(9-pin From a PC) network can be connected directly to a RS485 device without the help of a converter.
Sorry for the silly question.

randylud · Apr 21, 2008

The short answer is NO! The two protocols are different. You can configure a PLC processor for RS232 communication through RSLinx if the processor has an RS232 port and connector, also 9 pin. To use the DH485 connector you must configure your link for DH485 and use a converter that will handle USB to 485, as the old PIC module no longer functions with the latest versions of Windows, you have to use the UIC converter.

krk · Apr 21, 2008

Hi,

Yes..it's possible to have a RS232 to RS485 without a converter...I've used it before on Siemens MM3 drives, drawing is attached.

Note though that this shouldn't be used as a permanent solution.

John Soltesz · Apr 21, 2008

Once again no. Besides protocol differences found in comm products like RSLinx, there is a big difference in signal voltages and how each responds, 232 is single ended and 422/485 is differential. There are impedance differences as well. The cost of a simple converter can be as low as US$50. Don't waste time trying to get around this difference.

Jacobplctalk · Apr 21, 2008

Beginner

Thanks a lot for the reply.
But even now there is a twist to the PDF that was attached. So should I finally come to a conclusion that the answer is No? As the PDF too states that it’s only for Demo purpose and not a permanent solution. So I guess I will come to a conclusion that it is possible but is not the feasible solution.

rdrast · Apr 21, 2008

Absolutely NO. That PDF is a quick and dirty hack, that only works at all because of an oddball configuration of the port on the MicroMaster drive. Honestly, it's just plain stupid that a company like Siemens even demonstrates nonsense like that.

krk · Apr 21, 2008

rdrast said:
That PDF is a quick and dirty hack

I think that's made clear both in my post and in the PDF itself.

Jacobplctalk · Apr 21, 2008

Beginner

Once again I would like to thank you for the reply.
now I Have got the right answer finally as a simple "NO".
Thanks to all

krk · Apr 22, 2008

rdrast said:
That PDF is a quick and dirty hack

While I agree with this sentiment, I must disagree with your following statement:

rdrast said:
...that only works at all because of an oddball configuration of the port on the Micromaster drive.

This is incorrect and was obviously pure supposition on your part.

This afternoon, as a more generic test (than connecting to a Micromaster 3), I connected this lead to the RS485 side of a RS485/RS232 converter and used the finished assembly to connect 2 PC's together via their serial ports. I ran a terminal program on both PC's and established bi-directional communication immediately.

Jacobplctalk · Apr 24, 2008

Beginner

Thanks KRK for the answer. I can understand that you have performed a test on this matter.

So I thank you so much for the answer. I also would thank all the others for the answers that you have provided.

krk · Apr 24, 2008

Jacobplctalk said:
I can understand that you have performed a test on this matter.

Yes, I was curious as to whether rdrast was correct when he said it was just a peculiarity of the Micromaster RS485 port.

But I'd like to re-iterate that it's just a (handy?) trick and not an engineered solution...you were correct when you said:

Jacobplctalk said:
So I guess I will come to a conclusion that it is possible but is not the feasible solution

mordred · Apr 24, 2008

This afternoon, as a more generic test (than connecting to a Micromaster 3), I connected this lead to the RS485 side of a RS485/RS232 converter and used the finished assembly to connect 2 PC's together via their serial ports. I ran a terminal program on both PC's and established bi-directional communication immediately

probably up to 50' seriously doubt it will work up 1000' yes it will work because it still has a differential voltage change but the rs 232 port does not have the driving current for long distances

rdrast · Apr 24, 2008

The problem is with the signal levels. RS-485/422 are well defined line-driver signal levels. RS-232 is just about completely random, with potentials of up to 25 volts, positive and negative, for a potential 50 volt differential.

I'm just not going to trust mixing signals like that. The devices cost much more than a proper converter.

mordred · Apr 24, 2008

Trust me Rdrast neither do I reminds me of simplex networks

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