Here’s a Quick Way to Connect RS232 Equipment

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Most programmable controllers will come with an RS232 communication port. This recommended standard (RS) has voltage signals between 3 to 15 volts DC concerning the ground/common pin. RS232 devices are called DTE (data terminal equipment) or DCE (data communication equipment).
The maximum cable length for the communication cable is 15m; however, depending on the environment, I have seen this as much as 50m without an issue.
Most RS232 connectors are nine pins like the diagram below, but they can also come in 25-pin or RJ45 connectors.


 

A minimum three-wire RS232 connection consists of only the transmit data, receive data, and ground. This is commonly used if full handshaking is not required.

Pin 2 RD ————————– Pin 3 TD
Pin 3 TD ————————– Pin 2 RD
Pin 5 Ground ———————- Pin 5 Ground
Pin 7 RTS                                       Pin 8 CTS
Pin 8 CTS                                       Pin 7 RTS
Cable Shield

Note: I always jump Pin 4 and 6 together on each side.
The shield on the connection cable should only be connected to one housing when making the cable. I usually connect it to the PLC end.

Five-wire RS232 connection consists of the  transmit data, receive data, ground, request to send (RTS), clear to send (CTS)

Pin 2 RD ————————– Pin 3 TD
Pin 3 TD ————————– Pin 2 RD
Pin 5 Ground ———————- Pin 5 Ground
Pin 7 RTS  ———————— Pin 8 CTS
Pin 8 CTS  ———————— Pin 7 RTS
Cable Shield

Note: The shield on the connection cable should only be connected to one housing when making the cable. I usually connect it to the PLC end.

RS232 is a one-to-one communication method. (1:1) This means it is designed to communicate with one device. If multiple devices are needed,(1: N) RS422 or RS485 should be used by converters.
RS232 must have the same settings on each end. (Port Settings)
These include the following parameters:
Bits per second:  9600 (Baud Rate)
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: None
The following connectors are great to test and connect if you are unsure of the communication pinout.


Select a DB9, DB25, or DB15 connector depending on the number of pins of your serial port.
These connectors should be part of everyone’s toolbox. You never know when they will come in handy.

If you have any questions or need further information, please contact me.
Thank you,
Garry



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