connecting multiple RS232's to one PC?

[sabihakber]

good evening,
i am new here at PLCs.net and have found a great many of my questions answered here.
hope u guys can help me in this:

im working on a project in which i want to process multiple analog signals.for that i have uesd DACs with built-in RS232 ports.now i want to bring this serial input from say,6 RS232 ports and view them on one PC using an HMI i designed on LABVIEW.

QUESTION:
how do i connect 6 or 7 RS232s to a PC when there are only two ports available in a standard PC?
will i have to use profibus,of which i know nothing about?

thanks
SYED SABIH AKBER

 

[tragically1969]

good evening,
i am new here at PLCs.net and have found a great many of my questions answered here.
hope u guys can help me in this:

im working on a project in which i want to process multiple analog signals.for that i have uesd DACs with built-in RS232 ports.now i want to bring this serial input from say,6 RS232 ports and view them on one PC using an HMI i designed on LABVIEW.

QUESTION:
how do i connect 6 or 7 RS232s to a PC when there are only two ports available in a standard PC?
will i have to use profibus,of which i know nothing about?

thanks
SYED SABIH AKBER

You need a Digiboard or similar:

PCI

http://www.digi.com/products/serialcards/

USB

http://www.digi.com/products/usb/edgeport.jsp

 

[nonuke]

You can use RS232 to Ethernet converters to build a network. Moxa has a few models.

 

[diat150]

black box splitter.

http://www.cdw.com/shop/products/default.aspx?edc=284749

keep in mind that you arent supposed to have longer than around 25-50 feet on serial rs232. it may be in your best interest to use some rs232 to rs485 adapters and build a rs485 network(your equipment may have a rs485 option also) if your equipment isnt right next to each other. with rs485 you wouldnt need to have multiple comm ports and you can go to like 2000 feet or something like that.

 

[OkiePC]

We found these to be trouble free even on the plant floor:

http://www.*******.com/products/family/rp_uPCI

 

[sabihakber]

good evening and thanks all for ur suggestions ,
@diat150:
if i convert the 6 RS232 inputs using this black box splitter, i will get just one output and that is an RS485...
and in an RS485 I CAN receive data from different devices on the same COMM port without any losses or the data interference?
have i understood right?

and i think if i use this technique then i would not be requiring any software for that PC?

thanks again!

 

[sapoleon]

You can also buy a serial ports card for the PC. We use it when the system is going to be fixed. Install a card with 2, 4, 6, or 8 serial ports with the driver and you have them on.

We also use Digi. It's quite reliable.

In any of the cases you need the PC drivers.

 

[sabihakber]

@ sapoleon:

thanks sir,
my only misgiving now is whether the HMI i designed on LABVIEW in the PC will be able to correctly differentiate between the incoming signals.
can anyone educate me as to how to create a virtual ports,bcus my dad mentioned that its also a solution to the problem!

 

[sapoleon]

Labview will not have any problems to differentiate the incoming signals, because each of it will be coming through a different serial port.

The creation of Virtual Serial Ports its different for each manufacturer, but all of them are created when installing the original drivers. Digi have a nice wizard that helps you with it. I think the other manufacturers also will have a wizard, or the installation instructions. You will have to acquire a product first.

In any case, depending on your PC, the option for hardware serial ports can be cheaper, specially if you don't need further expandability.

 

[diat150]

good evening and thanks all for ur suggestions ,
@diat150:
if i convert the 6 RS232 inputs using this black box splitter, i will get just one output and that is an RS485...
and in an RS485 I CAN receive data from different devices on the same COMM port without any losses or the data interference?
have i understood right?

and i think if i use this technique then i would not be requiring any software for that PC?

thanks again!

im not quite understanding. the black blox splitter doesnt convert to 485.

I gave you two options, one would be use a black box splitter, but then your devices would all have to be close enough to the black box splitter and the pc running the software to work right according to rs232 specs.

next option would be to convert each device to 485 and run a 485 network which would give you plenty of distance. you wouldnt need a black box splitter in that scenario, you just start at the pc and daisy chain each device in and use terminating resistors on both ends.

 

[sabihakber]

greetings,
for clarity sake, i'll describe the situation in detail.im working on some Practical Lab work panels for the chemical engineering department for a university in karachi. the work panels will have simple systems to test and monitor temperature changes in a boiler.
now im measuring the temperature using termocouples and sending the data to DATEXEL aquisition modules(DAT3580) which have a built in RS232 port for further communications to PCs.
the work panels are placed quite near to each other, hence no problem of distance.

@ diat150:
ok now i get it,that to make an RS232 network i need a black box splitter which doesnot convert to RS485, but this setup will have a short range(which is quite ok) here

@sapoleon:

thanks about the tips about PC board and Digi's wizard.

 

[diat150]

ok, as long as your equipment is close by you are ok with rs232. black box splitters work great and the price is right.

 

[sabihakber]

 

[panic mode]

... and as long everything is isolated (or you will have PC locking up)

 

[sabihakber]

greetings,
@ panic mode:

wat do you mean by isolation?
if u you mean that the system is placed in any harsh enviorment, then no the workpanels are simply to simulate the conditions of a boiler.namely,how to maintain a set fixed point, how to control the cooling fluid (AIR,in this case) etc.
and wat do u mean by PC locking up?

pls elaborate.

thanks in advance!