Standard RS323 Cable

[Steve.Briggs]

Hi,

What I am trying to do is re-create a custom RS232 cable that came along with a Cecil CE3055 Spectrophotometer.  I was able to establish connection by altering the pin connections with paper clips, but the slightest movement would short my signal.  By using two standard RS232 cables and soldering them across a pc board I will be able to eliminate the shorting problem, but I need to know the color coding for standard RS232 cables (i.e. red = pin 1, black = pin 2, and so on).

Thanks

Message Edited by Steve.Briggs on 12-15-2006 10:00 AM

[AnalogKid2DigitalMan]

There is no such standard to the best of my knowledge. If you have access to an ohmmeter, you can determine which pins on one end are wired to the pins on the other end of the existing cable. The users manual of your spectrometer may also have a wiring diagram.

[Steve.Briggs]

Ya, that's what I began to do. 

I was just wondering if some "superior" being had "advanced" knowledge on RS232 color coding

[AnalogKid2DigitalMan]

Must be Mr. Dennis Knutson you are referring to, a Proven Zealous Veteran.

The RS-232 protocol is a very 'loose' standard.

[Albert.Geven]

the real important pins are 1,2,3 and 1 is ground, 2 is either receive or send and 3 is the other one.
For the rest you can try to do without,
if not, try to find out the direction and ask again.

furthermore is it 25 or 9 pole?

[Steve.Briggs]

Just a 9-pole.  What makes this so difficult is the complexity of the custom RS232 cable I am trying to duplicate:

Pin 1 - not used (but has some sort of double back wiring, looping itself into Pin 😎

Pin 2/3 - crossed together

Pin 4/6 - crossed together

Pin 5 - ground

Pin 7/8 - crossed together

Pin 9 - not used

That bit of information does help though, I can be certain now that 2/3 are correct and wire Pin 1 to my custom Pin 5.

Message Edited by Steve.Briggs on 12-18-2006 08:29 AM

[Dennis_Knutson]

That looks like a null modem cable though there are a couple different 'standard' types of this. You could probably find one in a catalog like Newark or Digi-Key. The local Radio Shack might even have one. It should cost somewhere around U$ 5-10.

[Brian_Beal]

I don't believe that the #1 pin is used for ground.  It is the #5 pin for a DB9, and the #7 pin for a DB25

[Steve.Briggs]

Brian, you are correct.  Pin #5 is the ground, and pins #2/#3 are send/receive.  After taking apart 10 different RS232 DB9 cables and testing them with a multimeter the results are :

Pin 1 - black wire

Pin 2 - brown wire

Pin 3 - red wire or pink wire

Pin 4 - orange wire

Pin 5 - yellow wire

Pin 6 - green wire

Pin 7 - blue wire or light blue wire

Pin 8 - purple wire

Pin 9 - white wire or grey wire

Still I can't say for sure if this is some sort of protocol for the cables, but the similarity of results between these 10 different cables is good enough for me.

[Albert.Geven]

You are right pin 1 is shield in the db25
this maybe helps

            1          DCD    Data Carrier Detect    to pc

            2          RXD    Receive Data               to pc

            3          TXD     Transmit Data          from pc

            4          DTR     Data Terminal Ready  from pc

            5          SG        Signal Ground          both sides

            6          DSR     Data Set Ready          to pc

            7          RTS     Request to Send      from pc

            8          CTS     Clear to Send              to pc

            9          RI        Ring Indicator                to pc