RS232 cable length

[needsOLTPadvice]

Hi,
I am working on a WIP and assembly line material tracking system. I would like to use two serial scanners at each location, attached to one computer. The cable length is my main concern at the moment. Below is a reference, stating "several hundred feet" for RS232.

http://www.barcodehq.com/primer.html#WDR

Can you advise me about the maximum cable length? Do you know any other solution for extending the length, except wireless scanners (e.g. using repeaters, other active devices, etc.)?
Thanks in advance

 

[jdeane]

I have done what your are trying to do in the past using Master BB+ decoders with KB wedge and although it worked the delay between scanning the barcode and it being displayed on the PC was unacceptable. I could walk the 40 meters back to the computer and reach it before the barcode was displayed.

What kind of scanning are you needing to do?

Jonathan

 

[needsOLTPadvice]

I want to scan the components, coming into the assembly line and the assemblies as they leave the line. The scanning will be performed manually with hand-held scanners. The terminal PC will just record the numbers and forward them to a server for database operations. Speed is not crucial (the items are in cases, packages, etc. with barcodes on them). Did you encounter problems like buffer overflows, overruns, etc?
What is the interface between the BB+ decoder and the PC?

George

 

[jdeane]

I was using a TTL handheld scanner into the 9 pin side of the Master BB, the 25 pin output was configured for serial using pins 2,3 & 7. The far end went into another BB this time the 9 pin side (using 2,3 & 5, I can't remember if I needed to swap pins 2 & 3 over) and thenon the 25 pin side I used a keyboard wedge into the PC, the best thing about the Master BB is that it will connect into just about any terminal or computer with the correct lead.

Very little setup required as most of this will work with the default settings of the device.

The Master BB was made by a French company called STI ( I think) then made by Percon now PSC.

http://www.pscnet.com/html/master_bb_decoders.htm

Hope this is of some help.

 

[daverr]

To solve your problem your could do the following.
Get a KVM switch like Avocent Longview 200 KVM (

http://www.avocent.com).

This device allows the transmission of Keyboard/Monitor/Mouse/Serial port signals from a transmitter box to a receiver box over standard Cat5e UTP cabel up to 500 feet.
You basically just plug the receiver into the remote PC and the scanner into the transmitter. There is no timing issues as the signal is transmitted instantly.

 

[tech217]

You could convert the RS232 to RS485 which has a maximum
length of about 1200m. Black Box has converters available.

 

[gomemphis]

tech217 has a good solution. RS485 and RS422 are current driven protocols and are designed for an industrial environment. They are much less sensitive to noise and have incredible distance limits. RS232 to RS485 adapters are fairly easy to find and easy to use but require an external AC power adapter on each end. I know from expeirence that RS232 gets pretty iffy at 9600 baud running 100 ft. Especially in an electrically noisy environment. This can cause some intermitten problems that can challenge the sanity of most project engineers.

Good Luck,
Gomemphis