RS232 cable length

Hi,

Can anyone tell me what the cable length of the new RS232 cable for the B&W touch screen is?

From what I know the max. length for RS232 is about 10 meters, but is that true?

Problem: We have a site where we need to control some equipment via RS232 and I want to use the new touch screen's serial port for that, rather than a PCI/PAC, but is in an auditorium and the distance is exceeds 10 meters.

Suggestions?

Thanks
Brodsky

 

There are several different technologies that allow you to extend RS232 comms over vast distances, all depending on which technology you choose (and also how much you're willing to spend ).

There is simple RS232 to Cat5e and back again adaptors, which can extend the range up to around 100m safely.

There is dedicated RS232 extenders, and RS232 to RS485 (and back again) units that allow range to be extended into the hundreds of meters safely.

And then there is the serial to fibre-optic ones, which can generally extend the range into the range of tens of kilometres/miles, depending on the quality of the equipment.


I'd suggest the middle option, either using simple RS232 extenders over a good quality shielded cable, or use RS232 to RS485 adaptors, and run RS485 over the long distances.
Using these devices, you wont have very high comms speeds, but you should be able to achieve 9600 no problem, which should be more than enough for simple RS232 controls.
Also, do you need two-way comms? or is one way enough for your needs? Ie; are you simply sending commands to a device? (One way), or do you need the device to also feed back information about itself and it's state? (two way). One way comms can be extended much further much more easily, as well as being able to do so at a cheaper cost.

Let me know what technology you're interested in, and how much you can afford to spend, and I'll see what info and brochures I can find for you.

I'd also recommend keeping any cables from the units to the adaptors/extenders as short as possible, around 1 metre would be fine, as this will ensure more reliable comms.

Cheers,
Darpa

 

I run RS232 over cat5 at home using DB25-rj45 adapters (no extenders or special converters). I cover cable distances of approx 25m+ with no issues. The connection speed is about 19200.

You should be able to go anywhere within a house on cat5 with no problems as long as the speed is not getting up very high.

Mick

 

There are a lot of variables that will affect your maximum distance, including:

• Device voltage levels. (The spec calls for voltages of +/-5V to +/-15V)
• Baud rate
• Cable resistance
• Cable capacitance
• Interference

Using a device that uses 5V signal levels at 115kbps over a 20m run of cat3 will likely be unstable at best.

Using two devices with 15V signal levels at 9600kbps over cat5e may well get you as much as 50m.

Certainly the best option if you want a high speed serial over a long distance is to use rs232-rs422 converters as Ashleigh suggested, or possibly also rs232 over TCP/IP.

I've used Quatech remote serial device servers. Little black box with two RS232 DB9 and one TCP/IP RJ45. Load a device driver on my Windows box, and presto COM3 and COM4 are available over the network. Wireless versions also available.

 

Thanks for all the info guys.
I'll try it out and let you know what the outcome is.


Regards,
Brodsky