Suggestions for USB-serial conversion

Hey there guys, i don't know if this question has been raised previously and is just buried in the mass of postings this forum recives but heres my question:

As you know most (if not all) new computers and laptops now come without a RS-232 serial port, but most PLCs still have not updated to having USB ports (with the exception of some new omron models) the question i have is this, do any of you have any suggestions as to what brand of USB-serial converter i should buy?

I used to work as a inside technical support and application engineer for Omron in Toronto, and that was a common issue that people would contact me for, that their store-baught USB converts could not connect to the plcs. Now i know that Omron markets their own USB converter thats designed to work with all omron brand products, but as far as i know allen bradley has not done the same.

So does anyone out there have a list of USB converters that you know work for Allen bradley series plcs and HMIs - and siemens plcs and HMIs???? or maybe a list of USB-serial converters to avoide because they dont work?

Its always been my understanding that the problem with these converters is that theres no standardized comm protical, different manufactures use different comm proticals, this creates a "hit or miss" result when buying these things.

Allen Bradley has had one for at least two years: 9300-USBS for USB to RS-232 DF1. For USB to DH-485, it would be 1747-UIC.

Hey thanks for the speedy answer!
wouldnt you know it - i was TALKING to Allen Bradley themselves about this issue not more then 6 months ago - and the tech i was speaking to was completely clueless - claiming there was no such device made by Allen Bradley

Does anyone know if seimens has followed suit?

Do you mean to tell us that we would need to purchase a seperate USB/serial adapter for every different PLC, that sucks but doesn't surprise me. I usually try to stick with an Ethernet connection.

Well ya ethernets great - if the PLC your working with supports it - but if your dealing with a stand alone system - or a micro plc - or an older model that needs program modification thats just not an option.

You don't need an adapter for every different plc - just every maker

so you could get away with 3 1)omron 2) allen bradley 3) siemens

I wonder when Allen Bradley and siemens are going to follow omrons lead and start making plcs with UBS ports on them?

Siemens has had a USB adapter for going on a couple of years now. I know it works for the S7-300 and 400, not so sure about 200.

Roy Matson said:

Do you mean to tell us that we would need to purchase a seperate USB/serial adapter for every different PLC, that sucks but doesn't surprise me.

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I have tried two different store-bought usb to serial converters (don't ask me what type) with Mitsubishi products (E-Designer and GX-developer) and they both worked fine. More than that, I could only communicate with an A-series PLC while connected to an E-series HMI in transparent mode using the converter. A regular serial port didn't work with the latest software.

You'd think with something as basic and required as communication to hardware - that someone somewhere would have decided to standardize all this **** by now!

wow you can't say "*******"? too funny

In the last 7 years I have not found anything that the keyspan cable will not work with http://www.tripplite.com/en/products/model.cfm?txtSeriesID=518&EID=14863&txtModelID=3914

I have tested on almost all Ab, Automation Direct and Omron products.

I also used to work for one of the top 3 Automation suppliers and got this question alot.The keyspan is what I recommended before we had our own.

The only USB-RS232 converter I have found working for all PLCs I'm using (Siemens S5 and S7-200, Allen-Bradley CompactLogix and SLC5/03, Omron CQM1 and Mitsubishi FX2N) is the Keyspan converter I've got trough GeniusInTraining, a member here. I have other converters too, but these don't work with all the listed PLCs.

Edit: that's exactly the one plc_noob is referring to. Makes us at least two happy customers.

Edit 2: besides this converter I also use USB to MPI (for S7-300/400) and USB to PPI (for S7-200) converters from Siemens.

Kind regards,

I can speak specifically and authoritatively on the subject of USB interfaces for Allen-Bradley products.

Most Allen-Bradley controllers over the past 18 years or so have had an RS-232 asynchronous serial port that supports the DF1 protocol. This includes PLC-5 Enhanced/Ethernet/ControlNet processors, the SLC-5/03,/04, and /05 models, all MicroLogix family and all ControlLogix family controllers. DF1 Full Duplex is the default protocol on all of these serial ports and is virtually always the method used to communicate between the controller and a personal computer's serial port.

Rockwell Automation does sell a general-purpose USB/RS-232 converter, the 9300-USBS, but it is not special nor specific to Allen-Bradley products. They just wanted to sell one that they could support instead of attempting to support the hundreds of models customers call about.

I actually recommend a different model, the Keyspan HS-19. I have had excellent results with the HS-19 with DF1, Modbus, and ASCII applications. It is compact, uses a universal USB cable, comes with a very useful serial viewing utility, and has worked perfectly with the RSLinx DF1 Full Duplex Autoconfigure feature. The Keyspan HS-19 retails for $40 and is a worthy addition to your toolbox.

I also like that the Keyspan device has a USB identifier that allows it to enumerate as the same COM port no matter which USB plug it is connected to on my PC. Some cheaper devices will enumerate as a different COM port depending on which port you plug it into, which not only hogs serial enumeration numbers but also makes it hard to remember which port you are supposed to select in software.

There is one serial protocol that A-B uses which cannot run on any general-purpose USB/RS232 converter, and that is Data Highway 485. For DH-485 applications, Rockwell Automation sells a product called the 1747-UIC, which provides USB DF1 Full Duplex conversion to DH485 protocol on both RS232 and RS485 physical interfaces. The 1747-UIC does only this function; it does not support DF1 or Modbus or ASCII or any other general-purpose protocol.

Rockwell Automation is also offering a line of USB interfaces for other legacy and automation-specific protocols, including DH+, ControlNet, and DeviceNet.

The high-performance ControlLogix network cards (1756-EN2T/EN2F, 1756-CN2/CN2R Series B and 1756-DNB Series C) have a USB port onboard.

I expect the 1756-L7x family of controllers to have an onboard USB port.

Keyspan. Buy it here http://www.plctrainer.net/

Thankyou for your help guys - its amasing how when i tried to talk to the plc makers themselves - they all played dumb (or maybe it wasnt playing with some of the staff there haha) about this issue

given as i need to replace my ageing laptop i was having serious concerns about this issue!

Ken Roach said:

I expect the 1756-L7x family of controllers to have an onboard USB port.

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Nooooooooooooooooooooooooooooooooooooooooo

Please please tell me that they get an onboard ethernet port !
It is too painful to think of, if an onboard ethernet port is sacrificed for a USB port. Dump serial, and dump USB too ! A plain ethernet port (not Ethernet/IP) doesnt cost more than a USB port and is unendingly much better.