What cable to use to connect to SLC 5/04 via rs232?

[tetcie]

Hi All,
I have a SLC 5/04 plc that I need to communicate to - however we don't have any null modem rs232 cables on site. I am very new to Allen bradley plcs (I have mainly used Siemens s7) so I am unsure which way to go about it.

In RSlinx the driver the plc uses is AB_DF1-1 and the channel 0 configuration on the plc is DF1 Full duplex.

What cable should I use? Google mentions using a 1747-CP3 cable but I dont have a rs232 port only USB, would a null modem DB9 to usb adapter work with a 1747-CP3?

 

[dwoodlock]

Have used this adapter with a null modem cable and was able to auto-configure the serial settings succesfully.

https://tripplite.eaton.com/keyspan-high-speed-usb-to-serial-adapter~usa19hs

if you don't have a null modem cable, you will need to make one.

 

[geniusintraining]

would a null modem DB9 to usb adapter work with a 1747-CP3?

No this would be a straight through cable... the CP3 is a null modem

Just a USB rs232 with a null modem OR a 1747-CP3

Do you have a DB9 cable? make your own if you cant wait, cross 2 and 3

 

[joseph_e2]

If you don't already have the 1747-CP3 cable, I would not try to buy one. It'll be seriously overpriced.

When I connect to the 9-pin COM port of a SLC 5/04 (or 5/03...), I use a standard off-the-shelf RS232 cable with a null modem adapter. The datasheet for the -CP3 cable shows that it's just a null modem cable with all conductors straight through except for pins 2 & 3 which are swapped:
https://literature.rockwellautomation.com/idc/groups/literature/documents/in/1747-in518_-en-p.pdf
A standard RS232 cable with a null modem adapter is the same thing.

Not sure what you'll have available locally, but here's what I use:
For the USB-RS232 adapter, I use a Keyspan USA-19HS:
https://tripplite.eaton.com/keyspan-high-speed-usb-to-serial-adapter~usa19hs

For the Serial cable, this should work:
https://www.l-com.com/d-sub-reversible-hardware-molded-d-sub-cable-db9-male-female-100-f

I use this null modem:
https://www.l-com.com/d-sub-slimline-null-modem-adapter-db9-male-female

You can also use one of these that combines the USB-RS232 and null modem:
https://www.plccable.com/allen-bradley-slc-500-usb-1747-cp3-1756-cp3-aftermarket-9300-usbcbl-cp3/
They're a solid company with good products.

 

[tetcie]

No this would be a straight through cable... the CP3 is a null modem

Just a USB rs232 with a null modem OR a 1747-CP3

Do you have a DB9 cable? make your own if you cant wait, cross 2 and 3

Hi sorry I don't quite understand what you mean by "No this would be a straight through cable... the CP3 is a null modem. Just a USB rs232 with a null modem OR a 1747-CP3". This is the first time I think I have never used serial comms for connecting to a PLC so I'm a bit of noob to serial comms and I don't really understand how it all works. The PLC I need to connect to is older than I am lol .

So are you saying I just need a standard rs232 to usb adapter to go with my 1747-CP3 cable, and that I don't need get a null modem to usb adapter?

 

[joseph_e2]

I have to be able to connect to a lot of stuff via serial port, so I try to stay flexible. For a 5/04, I would use this arrangement:
PC USB port
Keyspan USB to RS232 adapter
Null Modem adapter
Straight thru RS232 cable
SLC 5/04 COM port


Use DF1 driver, select COM port number that corresponds to the Keyspan and autoconfigure. It almost always "just works".

 

[tetcie]

I have to be able to connect to a lot of stuff via serial port, so I try to stay flexible. For a 5/04, I would use this arrangement:
PC USB port
Keyspan USB to RS232 adapter
Null Modem adapter
Straight thru RS232 cable
SLC 5/04 COM port


Use DF1 driver, select COM port number that corresponds to the Keyspan and autoconfigure. It almost always "just works".

Thanks I do have a CP3 cable but I also have a normal straight through cable so I will get those adapters ordered and try it out

 

[geniusintraining]

Hi sorry I don't quite understand what you mean by "No this would be a straight through cable...

Since the CP3 is a null modem you dont need to add a null modem... if you have two null modems its straight through as they will cancel each other out

So are you saying I just need a standard rs232 to usb adapter to go with my 1747-CP3 cable, and that I don't need get a null modem to usb adapter?

Yes as joseph_e2 has also pointed out, just a RS232 adapter and either a null modem cable/adapter OR CP3 (same as a null) will do the trick for the DB9

You can also use one of these that combines the USB-RS232 and null modem:
https://www.plccable.com/allen-bradl...00-usbcbl-cp3/
They're a solid company with good products.

Thank you!

 

[Operaghost]

With serial communications there are two standard types of cables. Those are null modem and straight-thru cables.

Straight-thru cables used to be very common and were typically used for devices where the communications all went one direction only at any given time. Think downloading or uploading to and from a device.

Null modem cables were commonly used when you needed communications to be possible in both directions at the same time. Imagine you want to go online to a PLC and view what is happening and change a timer or setpoint value.

You can add a null modem adapter to a straight-thru type cable and you then have a null modem cable. This used to be really common so you didn't need to carry two types of cables. Less commonly, you could add a null modem adapter to a null modem cable and you then have a straight-thru cable. I can't say that I have ever actually tried that though.

The 1747-CP3 is a null modem cable Rockwell sells (assuming they still sell it). But any null modem cable will do the same thing. So don't feel obligated to buy that cable from Rockwell. The one thing I do like about that cable is that it has a right-angle connector so you can close the front door on the SLC controller. Unfortunately when Rockwell came out with the newer Logix style controllers this cable was too big to allow the door to close. So Rockwell came out with the 1756-CP3 cable which was shallower and permitted the door on the ControlLogix controllers to close with the cable attached. Same cable as the 1747-CP3, just a smaller connector body.

So if you do want to buy from Rockwell, look and see if thy have a price difference between the 1747 and 1756-CP3 cables. They both work exactly the same.

The big issue today is the lack of a serial port on our computers. That is where he USB adapters come in. Of course Rockwell is happy to sell you theirs. And I have one and have used it without any issues for years. But I worked for them at the time and didn't have to pay for it. If I am spending my own money or my company's money, I am going with the link previously posted above which I will repeat here

https://www.plccable.com/allen-bradley-slc-500-usb-1747-cp3-1756-cp3-aftermarket-9300-usbcbl-cp3/

Forum member geniusintraining won't promote himself here, but he is the man, the myth, the legend behind PLC Cables. Forum members here have been raving about his products for years.

OG