Rs232 Extension Cord

Hi,

Has anyone ever made an RS232 extension cord work? I have 2 converters (RS422-RS232 and vice versa) on both ends but I can't establish communication. Is there something thst I should be doing or not doing? Can anyone let me know the pinouts and which pins should I connect or disconnect?

Thanks,
Fyodor

What RS232/RS422 converter ?

There must be a manual with the pinouts for 9-pin/9-pin, 9-pin/25-pin or 25-pin/25-pin.

In a 9-pin/9-pin connection you would only have to worry about pins 2, 3 and 5.

Also, depending on your application, the devices that you want to communicate with each other may or may not need to have the Tx and Rx signal wires straight or crossed.

A straight 9-pin/9-pin connection would be: 2-2, 3-3, 5-5.
A crossed 9-pin/9-pin connection would be: 2-3 , 3-2 , 5-5.

In a 9-pin/9-pin connection you would only have to worry about pins 2, 3 and 5.

Click to expand...

Not really, Some RS422 devices use CTS-RTS, DTR-DCD-DCE signals in addition to RX,TX.
Example - A-series PLC from Mitsubishi (RX-TX, RTS-CTS)

Normally if you make just an extension on RS232 side-make it straight 9F-9M with all wires connected.
Like JesperMP said, it is possioble you may need a crossed cable - give us more details.
RS232 crossed cable (null modem): 2-3,3-2,5-5, 7-8,8-7, 4-6+1, 6+1-4.

I need to convert the RS232 signal to RS422 as it needs to travel a very long distance (50 meters). The unit at the other end talks only by RS232 so I needed to convert the RS422 back to RS232. Theoretically it should work and I have read some articles over the net that it does work and they call this conversion thing (having 2 RS232-RS422 and vice versa converters on both ends) RS232 extension cord. On the net they only discussed that it does work but no other technical information was supplied. The problem I'm having is in converting it back to RS232 as I have tested that I have successfully converted the signal to RS422 at the other end.

Thanks.

I need to convert the RS232 signal to RS422 as it needs to travel a very long distance (50 meters). The unit at the other end talks only by RS232 so I needed to convert the RS422 back to RS232. Theoretically it should work and I have read some articles over the net that it does work and they call this conversion thing (having 2 RS232-RS422 and vice versa converters on both ends) RS232 extension cord. On the net they only discussed that it does work but no other technical information was supplied. The problem I'm having is in converting it back to RS232 as I have tested that I have successfully converted the signal to RS422 at the other end.

Thanks.

I've done this before with success. Not sure why you're having problems? Could be that the 422 doesn't support ALL of the 232 signal?

The pin outs on 232/485 converters are usually manufacturer specific. That's why the other responese asked for specific models.

You need to connect the TX (Transmit) of the 232 device to the RX (Receive) of the converter. You may also need to have a control wire such as CTS (Clear To Send) connected. In most cases this is jumpered to the TX wire, so the 232 is always enabled. If you have 4-wire on the RS 485 end you need to connect the TX+ and TX- to the RX+ and RX- on the other end. If you have 2-wire you need to connect the + to + and - to -.

The manufacturer of the device almost certainly has the connection diagrams available. Contact them for the diagrams.

Would you mind letting everyone here know exactly what your end devices are? A computer going to a controller or a serial mouse going to a computer 50 meters away? Please provide the specific make and model so that we don't have to guess.

Don

I was running 50m RS232 at speeds 9600 and 19200 without converters - just a straight through cable (with braid and foil shield).

I was running 50m RS232 at speeds 9600 and 19200 without converters - just a straight through cable (with braid and foil shield).

Click to expand...

RS232 spec calls for 15 meters maximum.
Normally RS232 will work on much higher distances in industrial enviroment. I have built a few machines, with HMI on RS232 (modbus) at 75-120 ft and they are running for years without any problems.
The benefits of RS485 I see are that you can put multiple devices (software addressable) on the same net, higher speeds and much higher noise imunity.

I've run a RS232 signal to 80M in an industrial enviroment using a specific cable from BlackBox. Over these distances a shielded cable will not just do, the capacitacne of the cable and the pairings of the signals is imopotant. But it does work well.

That being said though I would generrally use the convertors as u so pointed out. Once again depending on the quality of the cable u can strech this network out to 1.2 kM !!!

The convertors that I have used in the past extensively are the ADAM4520 convertors. They convert from RS232 to RS422/485.

The problem I'm having is in converting it back to RS232 as I have tested that I have successfully converted the signal to RS422 at the other end.

Click to expand...

How have u tested this at the other end if u are having troubles converting it back to RS232 ??? (If you put your note book on the other end and run Hyperterminal u could probaly see what has been sent through.)

The equipment at the other end might i suggest tying DTR to DSR and CTS and RTS respectively. Make sure that the RXD and TXD and SG are going to their corresponding signals, Ie RXD to TXD visa versa and SG to SG.

Thanks for all the information, I am still not finish playing with this and hopefully I could get it to work sometime this week.

The unit I have at the other end is a struthers dunn director 6001 PLC. I have heaps of other equipment here that talks either RS422 or RS232 so I have ways of testing if I'm getting RS422 on the other end. I have work a lot with HMI's and PMD's and I have heaps of them in my workshop which I have been using to talk to. I have been successful converting the signal from RS232 to RS422 but converting it back to RS232 really is a problem, I'll gather all the information you have all provided and see what outcome I'll have.

Many thanks to all.