Hello, new to VEE (and programming).
I need to connect an 8753D + PC running VEE to a PLC. The VEE program looks at the data and decides pass or fail and just shows pass/fail on the PC screen. I need to connect this system to a PLC to report pass/fail only. Can anyone offer suggestions on what hardware to use and how to send the information? Currently I'm thinking to buy GPIB to USB and hope that the PLC will be recognized by the I/O program.
PLC info:
Mitsubishi FX3U-128M7
Thanks
If by "IO Program" you mean Keysight's IO libs then almost certainly the PLC will NOT be recognized. The IO Libs are designed for instruments and do not support computer peripherals, controllers, IO cards, etc. The first two solutions that come to mind are:
(1) Find a PLC whose driver has an API then call that driver from VEE
(2) Use most any DIO card (can highly recommend the ones from accesio and they work fine with VEE) and connect the output to one of the PLC's inputs. i.e. use hardware signalling. This might seem clumsy but would be very robust!
In either case you'll be bypassing the IOLIB's. You might also look for networked PLC so that USB isn't needed, in which case you might be able to bypass the PLC driver and use sockets directly to the PLC.
Stan
Hi Stan, thanks for your help.
If the PLC driver has the API option will that allow me to connect the PC to PLC directly using USB or GPIB-to-USB (or something else)?
Also, you mention a networked PLC. If the PLC can be put on the network would I communicate from VEE using an IP address? What sockets on the PLC are you referring to?
FYI...the PLC is a Mitsubishi FX3U-128M7. Unfortunately, the PLC is oceans away so it's hard to try anything.
This is my first VEE project, I bookmarked your VEEOS.org website for later learning.
Most of the questions you have are device specific- completely depends upon which PLC you have. Fortunately you already know the PLC, and quick look at its specs shows a plethora of optional interfaces. Also looks like all sorts of nifty IO options- a pretty high-end PLC. So it looks like you could connect via USB, though you would need to look at their drivers to see if there's a API that would meet your needs. Or you could connect via ethernet with one protocol or another. Sockets would be whatever the PLC supports. Protocols would be the real issue though- you would likely have to implement one of the protocols the PLC supports or get a module that implements it. You would need to look at the docs but one promising and simple way to proceed could be via RS232 since that's an option, and VEE can talk direct to RS232 so no problem there.
HOWEVER, given the layers of programming needed in any of these options, I'm back to the really low-tech hard signalling method as my best suggestion. Simplest cheapest DIO could easily create a flag that feeds one of the analog or digital inputs on the PLC and then you are done. No PLC options, protocols, connection issues, drivers, command structures, security issues, etc. Just LVDC signal along a little copper wire and you're set to go. Back in the old days (20th century) you could even use the parallel port on your computer to do the same, but when was the last time you saw a parallel port!
This sounds like a great opportunity for a low-tech solution.
Stan
If you go the DIO route, another vendor of interest other than Acessio is Measurement Computing. They have DIO under $100 that would work fine and their "universal library" driver works great with VEE.
Another thought- even the low end DIO devices seem overkill for what you need (single line hardware signal) so maybe you should take a look at a simple relay module. For instance https://numato.com/product/1-channel-usb-powered-solid-state-relay-module is VERY cheap and has a virtual serial port driver so should be trivial to talk to from VEE.
Stan
Or for that matter, you could even get more basic and take the $zero approach: use one of the control pins on your computer's serial port as the hardware signal. Then from VEE just set the control pin's state as needed.
Hi Stan, you have provided so much helpful information thanks! I went with your suggestion to purchase the relay modules from Numato. I'm waiting for them to arrive, then I can hook them up and start messing with the VEE program. I'll post and let you know how that goes (or ask more questions).
I've received the Numato USB relay today but I'm having trouble finding it in VEE. Within my PC's device manager I can see the Numato device and installed the driver. The Relay is connected to the PC using a USB but it shows up on a COM port in both the device manager and in the Keysight connection expert. The Keysight programs don't recognize what device it is or have a driver for it. I've played around with the different add instrument settings within the instrument manager but couldn't see that it was connected. I'm not sure why it doesn't show up under USB. Any advice on how to configure the instrument within VEE to communicate?
Thanks!
You actually already have it configured. It will appear as a COM device to VEE just as it does to Connection Expert. The driver takes care of this and is otherwise invisible.
In VEE you will control the relay by instantiating a DirectIO object for that COM device and sending whatever command is needed - likely a one-liner string that looks something like "relay on x" where x is the number of the relay on your device if it has multiple relays. There will be a corresponding "relay off" command.
Check the relay programming manual for correct commands.
As for "The Keysight programs don't recognize what device it is or have a driver for it"--- that's exactly why you want a device like this that has a virtual COM driver. Keysight software won't recognize much of anything other than "instruments" and certainly not peripherals, IO devices, USB devices and so on. But since there's a VCOM driver the Keysight software (including VEE) just sees it as another COM port so is happy.
I'm trying to turn the relay on via the direct i/o but haven't been able to, so far. According to Numato the relay should turn on with the text relay on 0 (there's only 1 relay). As a check I downloaded the Numato software and was able to toggle the relay on/off so it does work.
First I tried to write the text "relay on 0", then I tried to create a text constant as an input. Neither of these worked, I also tried the 1st option with different settings from the dropdown (string, string with quote, etc..). The program says it runs and doesn't give an error but the relay doesn't come on (there is an indication light). Do I need to put the text into ASCII characters or HEX or some other format? It seems from the Numato website the module understands text. Maybe I am making a syntax error in VEE?
Thanks!
RS232 problems usually are caused by serial settings. Start by verifying that your EOL is correct for that device. Then look at baud rate and whatnot. If that doesn't help bypass VEE by using the interactive mode in connection expert. If that still doesn't work pull up a terminal (hyperterminal is fine) and try from there. Once you find a working interface you'll have known good settings and can go back to CE and then VEE. If the manual says "relay on 0" is the right syntax, then you example looks fine- basic ASCII text is pretty robust.
AND-- another reason to drill down to a terminal is that if you need to chat with the vendor's tech support they will be much more likely to help. Afterall nobody in their tech support will know about instrument software (Connection Expert) or graphical programming (VEE) but they will know standard computer software.
Wow thanks! Just as you said the read/write EOL terminator needed to be r instead of n. I can now use my relay... on to the rest of the programming. Thanks again for your help!
Hi Stan,
I have the module working with VEE but I get an error about every 10-20 cycles as described below. I ended up using the GPIO pins to output signals instead of the relay as I had multiple signals. I'm not reading from the module just writing text commands.
VEE Run Time Error
I/O error or timeout occured-VISA error vrf_ERROR_INV_PARAMETER: invalid parameter
Error #: 811
Unable to set baud rate to 9600 BAUD
This error seems to be random as it will run OK for 10-20 cycles. I'm using the direct I/0 to send GPIO on/off signals.
The PC is an old XP unit and I'm running VEE 8.2 on it (although I have the latest versions)
Do you have any experience with this?
There's generally three types of causes for intermittent but not necessarily random serial device I/O errors like you describe.
(1) timing. Asnychronous communications is, well, asynchronous. It seems possible that you are sending two signals too close together for the device to respond.
(2) buffers. If a serial buffer is filling or has leftover cruft it could indeed cause what you are seeing. May need to clear a buffer before sending new command.
(3) less likely but I have seen it multiple times: running out of resources. If you said every few thousand cases it failed this would be my first suspect, but it seems much less likely with 10-20. In this case a handle leak would explain what you are seeing or maybe hitting 32-bit limits (even if you have XP/64, VEE and IO libs are still 32 bit).
The easiest to diagnose would be (1). Simply add a delay somewhere to make sure that commands to the module are spaced temporally. If that fixes the issue then you can leave the delay (easy) or implement a poll (more robust but can be a pain to set up) to make sure that the device is ready for the next command.
You might also try using SICL instead of VISA to verify that the problem isn't related to VISA.
Failing both troubleshooting (2) (look in device docs for buffer info) and (3) (bring up a monitor and check process usage and handles as the program runs) would seem in order.
Stan
XP and VEE 8.2. What version of IOLIB's. Using 15 by any chance? If so there was known compatibility issue with VEE 8.2.
Stan
Well to complicate things I'm doing the programming on 1 machine but it needs to run on a separate machine 12 hours in-time away. I found an XP machine so they are both as close as possible but I must make a change and wait a day to get the error #. I can log onto their PC remotely.
My programming machine has IOLIB ver 16.0, and the program is opening in Agilent 8.0 runtime
The machine it runs on has has IOLIB ver 16.0, and the program is opening in Agilent 9.2 runtime
Both machines have the full HPVEE 5.0 program that has never been removed from days gone by but this isn't what either is opening in.
So, I don't seem to have IOLIB 15 & VEE8.2 problem. I also have the situation where I'm not getting the error on my machine but they are seeing it. Do you think I should load runtime 8.0 on their machine? I don't think this will conflict if I change "opens with 8.2" on the shortcut.
Thanks
If you are developing and testing in a different environment than your target, then sure, that would be bad since any testing you do would be of questionable utility. So sure, modify your machine or the target machine as needed before you do much more troubleshooting to get them as idetical as possible. Make sure that the hardware is identical if feasible. In your case you might also get as much detail as possible about the target machine and how it is being used. There may well be something in place that you aren't aware of. I for one find it VERY hard to troubleshoot problems that I can't "touch" myself. Can you have the operators there set everything up so that you can run and observe the test yourself while they are asleep? That way you could observe and see what actually happens.
Another thought- even the low end DIO devices seem overkill for what you need (single line hardware signal) so maybe you should take a look at a simple relay module. For instance https://numato.com/product/1-channel-usb-powered-solid-state-relay-module is VERY cheap and has a virtual serial port driver so should be trivial to talk to from VEE.
Stan