USB Cable

[gendy 0]

Hi We have many types of PLC with different ports Like PLC5 (30, 20, 11) round port 8 pin PLC5 (15,10) 9 pin And we have SLC 500 5/3 RJ 5/4 I need solution for connecting all this type to USB? Also I have one old PLC (PLC2 /16) is there any new program under windows and cable USB for that type?? Please advice me with A.B part numbers

[paulengr 44]

Sorry, but this is a huge square peg/round hole situation. Serial is relatively simple in the first place, with a little understanding, but USB is definitely NOT and overcomplicated things drastically, especially because there is almost nothing "universal" or standard about it (except the name). It can be but the implementations are far from it. In terms of all of them: no, none support any sort of USB connection as-is. They all require RS-232, as do most other PLC's on the market. One of the major problems is that USB allows CODE to be shipped back and forth across the connector, and that means that you have to make assumptions about the binaries that the end points can execute, because it doesn't specify a virtual machine or anything else locking down the implementation. So in the end, there is virtually nothing "standard" about a USB port except that as long as you have Windows XP on a desktop PC, it's pretty reliable. Outside of those specifications, you are on your own with ANY device attaching to USB, never mind industrial equipment. Some relative standards (memory cards, keyboards, mice) are starting to emerge, but manufacturers quite often ignore these and just do their own thing (downloading code) and ignore the standards. So the end result is that USB is a total mess to use for anything other than Windows XP (Vista/Windows 7 isn't any better, and Mac users can tell you tons of horror stories). Now, RS-232 requires at a bare minimum, a 3 wire interface with absolute level signals referenced back to a signal ground. The signal ground is shared between both end devices so you can get ground loop trouble happening quite easily. The SPEC is that the output has to be between 3 and 15 VDC positive, or negative (depending on whether it is a mark or space signal). The inputs must be able to accept down to about 1 or 2 volts DC. The USB port itself "can" power devices. It has only 5 VDC available though, not +/-15 VDC, and PC motherboards (never mind PCI cards) these days rarely have the old +12/-12 VDC which was perfect at the time. Nowadays they are trying to get away with 3.3 VDC on motherboards in laptops and aiming to go even lower. There are perfectly good reasons for it but supporting RS-232 isn't one of them. SO, you CAN do this properly. Use a DC-DC converter which is fairly large and make the proper +/-15 VDC signals. You may run into a power problem if you attempt to draw it all off the USB port (which has standards for how much power should be available, but then again, the laptop manufacturers like to skimp on this too). Then the standard UART chips can drive a serial device with no problems. The standard for connectors is 25 pin DIN (as on the PLC-5), but a long time ago, a de facto 9 pin DIN connector became standard (from IBM PC's) came into existence. Allen Bradley also came up with their own goofy round nonstandard connector because it takes up less space. The biggest thing to remember is that PC's AND PLC's are DTE (data terminal equipment), not DCE (data communication equipment) so you need a "crossover" or "null modem" cable. Ideally this only has 3 wires in it. However, there are a bunch of extra hardware start/stop signals on the side that some devices implement (and AB PLC's at least make an attempt to support this). Some of the null modem cables have very goofy jumpers on these extra signals which cause the cable/connector not to work at all. The best solution for this seems to be either experimenting, buying AB cables, or making your own. HOWEVER, that's in the ideal world. The USB manufacturers are interested in small and cheap and realize that you can probably "fake" RS-232 simply by using a resistive divider to try to make 5 VDC look like +/-2.5 VDC. It's very, very, very illegal (by RS-232 standards) and if you cable size gets very long at all, or your connections are not very tight and clean, then you get intermittent communication problems. That's IF you get past the fun with software compatibility because although there is a standard for serial ports on USB, of course, nobody can follow that either and they either take shortcuts or do something else silly with it. So, talk to the manufacturer (such as AB) about which USB-serial converters they recommend and buy that one. Also, B&B Electronics sells some that are pretty reliable and they sell mostly to industrial customers so they have a reputation to maintain (www.bb-elec.com). There is one other thing you need to buy from B&B Electronics, a serial port "sniffer" or diagnostic device. This little dongle has a bunch of red/green LED's on top and plugs into your serial cables. By matching the LED pattern on the device, you can easily discern between DTE and DCE connections and figure out what type of cabling arrangement you need. See, pins 2 and 3 are the transmit and receive pins in RS-232. On a 9 pin DIN connector, they are opposite of the order on a 25 pin DIN connector. PLC's by default are DTE and so are PC's, so you need to reverse the pins when connecting these together. Most other devices are SUPPOSED to be DCE (data communication devices) which means that they are wired in the opposite arrangement so that a "standard" serial cable just connects everything straight through (2 to 2, 3 to 3). However, that's not always the case either. Basically, the auto MDI/MDI-X stuff on Ethernet doesn't exist so every time you try another combination one of the first things to figure out is which is which, and the little serial port diagnostic tool makes this trivially easy to do. Now, you CAN go another route. I hear that the USB ports (where available) on ControlNet cards can be used. There is also a USB to ControlNet and USB to DeviceNet adapter. This can be used in many cases if you have these types of networks, but not all. So your mileage can and will vary. That's staying with AB equipment, and assuming that you want to buy network adapters and/or have Controlnet or Devicenet already. The other alternative that I prefer is to go to Ethernet across the board. It bypasses all of these compatibility issues, even if it's just for laptop-to-PLC communications. However, you will have problems with SLC and PLC-5 (no serial port). You can either buy a NET-ENI card from Allen Bradley (expensive, has bugs), or go with a Digi One SP or IAP. The Digi One SP is a "virtual serial port". You run special software on the PC that can connect to the serial port on the PLC, no matter where the PLC is at as long as it can be reached by Ethernet. Works well but can only be used by ONE PC at a time. Alternatively, you can use the Digi One IAP. Once set up, your PLC-5's and SLC's appear on the network as if they have real (but limited by serial port speed) Ethernet ports, even models that don't have an Ethernet port. You can also upgrade SLC's to SLC-5/05, and use either a sidecar Ethernet module or upgrade your PLC-5's to Ethernet versions which is the more expensive but better way to go long term. Once done, the only time you need to fool around with the serial port ever again is if the PLC loses it's programming, since it doesn't have an Ethernet address at that point (unless it's an external card or it's a ControlLogix which has that info buried in the ENBT's). Now you are trading "serial port issues" for "network issues", but at least you don't run into so many hardware problems.

[Mickey 71]

I have a different take on the OP's question. The PLC5/30,20,11' s round 8 pin port is a DH+ port the 1784-U2DSHP ( USB to DH+ converter) will work for these controllers. The PLC5/15,10's 9 pin port is also a DH+ port there is a thread somewhere here or the other forum about someone making an adapter to fit the 1784-U2DHP. The SLC5/03's RJ port is DH485 you can use the 1747-UIC ( USB to DH485 converter). The SLC5/04 serial port can use a USB to serial adapeter ( Keyspan is a good one) The SLC5/04's round 8 pin port is a DH+ port the above 1784-U2DHP will work. I don't know the PLC2. Edited 20 Mar 2011 by Mickey

[mhowasso 5]

I have many PLC-2's (2/16, 2/17, 2/30, etc., etc) I can find many USB adapters for the cables, but their is no drivers that would allow the software to work smoothly or consistently. There are many serial 9 pin to USB adapters out there. Getting them to work with old PLC's, now that not very easy (if at all). With the older AB 6200, etc., and the newer Master PLC software for PLC-2's you might just have to find an older laptop with a serial port just for these older processors.

[gendy 0]

HI thanks for all i search about the price of the different solution found 1- use 9300-USBS and different cable for each family with low cost price and found 2- 1784-U2DHP USB TO DATA HIGHWAY PLUS CABLE but its price is about 5 times higher than the first did any one know the first solution and use it ? is it any problem if i use it? thanks

[Mickey 71]

The two diveces above are completly different for diffenent protocols. See links below for a couple of alternatives to the USB to Serial adapter ( scroll down left hand side in the first link) http://www.plctrainer.net/ http://store.mrplc.com/Allen-Bradley_c_1.html

[gendy 0]

whatever the protocol i want the solution for programming and troubleshooting the PLC is there any problems if i use any

[Mickey 71]

The solution depends on the PLC and the comm ports it has and the protocol they support. One size does not fit all. Edited 28 Mar 2011 by Mickey

[Berna 0]

By the way there´s a new Controllogix controllers the 1756-L7 it supports connectivity via USB cable. http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/360807/1837516/tab3.html Maybe in a near future you might want to consider migrating those old systems to CLX. One of this controllers may handle most of your old PLCs at once, using them as Remote I/O