Connecting RS485 from PLC to RS232 (9 pin port) on PC (laptop) is simple. But the evolution of computers has made the conversion not quite so simple now days. Most computers (laptops) now days do not have a 9 pin RS232 serial port, but utilize USB ports.



As shown in the video about Allen Bradley PLC Cables (AB PLC cable Demo on youtube), you can not use the AB PIC box (RS485 to RS232 converter cable)with a USB to RS232 converter cable. You must get a single cable designed to convert RS485 to USB. As there are electronics involved, it is not just straight wiring. Then with some PLC vendors, they might slightly modify the protocol so you have to buy the RS485 to USB converter directly from the PLC vendor. Like AB uses what they call "DH485" and sells a 1747-UIC converter to do the job with one cable.



But there may be a work around as pointed out by Brian in reply to this post. You can use a Belkin USB-RS232 converter cable. (The Blue USB to RS232 cable in our video).



When using a USB to RS232 converter cable with the PLC vendor's RS485 to RS232 cable, like the AB PLC cable, you not only have the electronics (needs power from com port), but com 1-4 dependency; but also driver for the USB converter cable, drivers for the RS485 cable and drivers for the PLC software like RSlinks.



All the drivers, software and hardware leave a lot of room for conflicts, incompatibility and headaches. So save your self some headaches and use the 1747-UIC ($300+) or the much less exspensive plccables.com non-oem replacement cable (about $40).

This advice about using a PCMCIA Serial Convertor rather than a USB is basically solid but beware that PCMCIA is also changing.

What was traditionally known as PCMCIA is now referred to as "PC CARD" while the present PCMCIA Evolution is referred to as "EXPRESS CARD".

While this will affect the function very little other than you must have the proper generation card for your machine, be advised that RA has not yet made EXPRESS CARD versions of several of it's popular PCMCIA Cards {1784-PCMK, etc}.

HMMMM?
Allen Bradley says the 1747-PIC will not work with a PCMCIA card ( see pic below). Have you actually done this?
And if so, whats the brand of your PCMCIA card?

Thanks Micky for the heads up. One of my instructors mentioned success with the port replicator and one student agreed. In theory, it sound like it would work, so I trusted the tip. I will test it personaly myself and get back to this forum. I still beleave as long as the PIC box sees the port as com 1 and gets standard power, it should work. But we'll see.

The PIC box is not the problem. It's the timing requirements of DH485. These requirements have been met, so far, only by a CPU with DIRECT access to the COM UART chip. The indirect access through Windows isn't enough. Most adapters do create a COM1 but it's a Windows software replication. The PIC is only an electrical translator.

Even the 1747-UIC USB to RS485 adapter takes the non time critical DF1 protocol and translates it, by means of an on board computer and UART, to the DH485 protocol.



I'm betting that the PCMCIA port replicator suggested will fail to drive DH485 througha PIC box.

I have a serial port pcmcia card. I made a test with PIC module and it doesn't work. I assign COM 1 to pcmcia serial port. This card is from http://www.quatech.com/, work well for all plc and HMI exept for Siemens S5 series and AB PIC module. They also built a express card to native serial port card, I didn't test it.

Hope I help a bit

Ok, this is what my AB rep. told me. The PIC box is powered off of the serial port, it powers the opto isolators.
The problem hearin lies that usb to rs-232 adapters do not power devices in the same way a physical ports due. He stated that you have to have the right adapter such and a 1747-uic or Belkin USB to RS-232 converter. He even went as far as to say that Belkin manufactued these for AB, he thought. He however did not know of any other adapter that were this way and stated that he has done this. Personally I just dug out my old laptop cuz I could not find a Belkin in the time frame required and AB's usb adapter is too pricey.

hope this helps.
-Brian

Thanks Brian: I agree with the others who posted here. After extensive testing, I found the PIC Box not to work with the PCMCIA card type RS232 port replicator. I spent a lot of time just getting the PIC driver to talk to the RS232 port replicator driver. In the past I might have lucked out, becuase I bought a USB to RS232 converter cable which happened to be a Belkin and we recomend Belkin or PLCCables.com USB converter to everyone.

How do you like the Keyspan (USA-HS19) ???

Mark

It's silly that modern PLCs don't support Ethernet or USB local configuration. This problem has existed for years and will probably continue into the foreseeable future. I think AB's planning on riding the custom cable cash cow as long as they can.

We should collectively build a knowledge base for what converters/adapters work with which AB devices.

Hey Nathan,

Mitsubishi Q Series PLC's uses a standard USB cable... I still sell the RS232 to people (not a lot)

As far as the knowledge base.... look at my website (I am up to 17 different AB cables) or look at Chris's (click on the Shop link above) I think we have them covered

So do the new Telemecanique\Modicon M340's, no more panicking when you get to site and realise you have left your cable at the offoce, just drop into any shop and buy a USB camera lead !!

Actually I think AB agreed with you about the proprietary cables years back, and their current PLC (Contrologix) uses Ethernet. The dilemma is that they built their products so good, they last for 20+ years, so SLC 500 is still the most used, PLC 5 too. There are still many SLC 500 brick units (fixed i/o) still out there ticking away.



There are even PLC 2 out there. (Because people won't replace until they break.)

There is good news though. AB has upgrade solutions for all their products so you can place them on the Ethernet. You can even put a micrologix 1000 on the Ethernet.

I assure you that serial cables are hardly a "cash cow", especially when you consider that many of them include locking plugs and hard-to-fabricate right-angle connectors that you don't find on a cable from a local electronics store.

The new-generation ControlLogix network modules (1756-DNB/C, 1756-CN2/B, and 1756-EN2T) all include a USB connection that allows access to the network and the backplane.

I use the Keyspan HS-19 extensively, and have given away many of them to customers who complain about their $10 USB converters being "flaky".

The reason I asked this question was that someone purchased a Keyspan last week from me.... It was shipped to Bin95... it may have been one of your employees, but just wondering how it did in comparison to the Belkin ?

I have used them on every PLC (that I have) and other applications, even set one to Jean (across the pond) to test it on Siemens CPU's... they have never failed, not to say that the Belkin would.

I started selling them because Ken spoke of them highly, like the old TV commercial "when EF Hutton talks people listen" remove EF Hutton and insert Ken

I stand corrected. However, I have been charged > $100 for short serial cables with "secret" pinouts - mostly missing pins with a few switched. It's the kind of thing that leaves you bitter for a long time. Also - I said AB, but meant to refer to all the vendors out there who are producing new equipment and deliberately playing that game.




Lol - good point!



GIT - I should have guessed...

Actually I requested that we get a keyspan and run through our real world test, based on group comments. The other two I mentioned above are still at 100% reliability. I can tell you one we had each of our students using years back, that failed our test. Radio Shack. Many students had to keep reloading the driver mid day, but intermittently. (Because when EF Hutton speaks, we listen. ha ha)



I actually prefer PLCCables.com because you only need their cable for 503 and 504. The Belkin, you and Keyspan you need two cables, the USB converter and the Null modem cable. Greater number of connections, increase risk to reliability, and increase bulge in your cable bag. :>) The cost is a factor too, I believe we got the Belkins for under $20 each delivered. When you add the cost of Keyspan and null modem cable, I think you are in the range of the PLCCables.com solution, just a bit bulkier package, when said and done.

If the only thing I hooked my laptop up to was a PLC then I would agree... but there are so many other things besides PLC's that have to be programmed or viewed... having one cable for a 503 or 504 is out of the question.

I know the Belkins are less expensive, this was the reasoning that I asked you how they did, I am not married to the Keyspan... so if my customers would prefer the Belkin then I would offer that model as well. I feel that in our industry we need to stay on top of things or you will be passed by others, flexibility is one thing that you have to be able to do, so reading this and other forums helps me stay focused in the direction that I need to go.

The majority of my customers don't buy the Keyspan for programming PLC's if they need a USB cable for a PLC then they buy a USB cable for that PLC.