Real RS-232 Cable Length Limit

Question

Real RS-232 Cable Length Limit

danielthb (Electrical)

(OP)

16 Jan 08 09:35

175 cable feet of STP between a PC comm port and the DCE--think it'll work at 9600, at 19.2k? I'm not looking for what the specs say but what your experiences are. Cut sheet for the cable says 40pF/ft @ 1.0 MHz.

Dan B

itsmoked (Electrical) · Answer 1 · 2008-01-16 16:10:30

Sure.

Oh..
40pF/foot... That sucks.

Maybe not. If it doesn't, it's your crummy cable.

It's a hard call really as it also depends on your electrical environment. I would imagine 9600 would be dependable. Maybe 19.2k with good cable. In a benign place.

Hopefully you are driving the cable with nice levels not some laptop with +/- 3V levels.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

danw2 (Industrial) · Answer 2 · 2008-01-16 17:22:54

I doubt there's a commercial cable for this service, so your're talking custom cable. That'll cost ? ?

If it's a dollar a foot plus connectors and labor, $200?

What about a couple 232/485 converters, one for each end, and 200' of twisted pair that you've already got lying around, instead? Far higher probability of it working.

Dan

controlsdude (Electrical) · Answer 3 · 2008-01-21 15:17:11

If you use this cable spec you can get 500 ft distance. experienced it myself.

Black Box EDDC

but on the - side it is expensive.

itsmoked (Electrical) · Answer 4 · 2008-01-21 15:54:46

controlsdude; You experienced it at what speed?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

controlsdude (Electrical) · Answer 5 · 2008-01-22 08:35:02

I believe most of interfaces were at 9600, some were 19200, and never above that speed. bar code scanners usually char length= 20 to 50. sometimes scales, conv speed up to 550 fpm, gap between cases 12-15 inches.

MikeHalloran (Mechanical) · Answer 6 · 2008-01-22 19:48:23

I don't think you'll do 9600 at 175' over STP.

Current loop should work okay.

Mike Halloran
Pembroke Pines, FL, USA

itsmoked (Electrical) · Answer 7 · 2008-01-22 20:42:10

Well Black box said 500ft.

http://www.blackbox.com/Catalog/Category.aspx?cid=45,85,790

They don't say at what baud rate. Might be 300. But I think 175ft is possible. I had about 120 feet that we used all the time for various serial endeavors at speeds up to 34,5k and I don't remember having any problems.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

controlsdude (Electrical) · Answer 8 · 2008-01-23 09:01:45

some applications that I did were up to 400 feet and at 9600 baud as far as I remember. It all depended on main panel location and scanner locations. This was with the black box eddc cable.

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Real RS-232 Cable Length Limit