Michael Lloyd

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About Michael Lloyd

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  • Birthday 06/01/58

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  • Gender Male
  • Location Texas
  • Country United States
  • Interests Photography, Long Range Shooting, Reloading, Fishing, Hunting

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  1. Comms Monitoring of SCADA

    Nope, not silly at all. There is literally a tag called Heartbeat in the PLC and the script turns it on (and then "lets go so it's not latched in the HMI software). I read the elapsed time and some other stuff but the time value can't be read if there is no comm. Our graphics turn "magenta" if the comm status from the driver is bad. I'm kind of handicapped right now. I left my laptop in New Mexico when I came home to gather up the family because of the storm. Otherwise I'd be able to tell you what the value is in Kepware. Somewhere in the driver there is a tag for stale comm.
  2. Comms Monitoring of SCADA

    There are lot of ways to do this. We use a "heartbeat" script in the SCADA software for the PLC side of things. Basically it turns a bit on every time it's run. We run it every 30 to 45s. We shut our remote stations down if comm fails for longer than 600s. For the HMI side we use the Comm fail detection parameters that are built into the driver. In our case we use Kepware for most comm services. There is a health status bit (don't think that's what they call it but I can't check the HMI right now) PLC logic looks like this:  

    If you have an IT group that is responsible for your facility network I would get them involved. They can give you a pool of addresses for the control network that are excluded from the DHCP pool. I'm assuming that your network is behind a router and properly secured from intruders.
  4. Interview Question

    I agree with the last two posters. I'd rather have a tech with troubleshooting skills than a programmer. If you hired a programmer, and it was me (not looking for a job btw), I'd want to change all of the code you listed to something that would be safe, easy to troubleshoot, and work  EVEN IF WHAT YOU WROTE WOULD WORK (it won't) I've edited a fair share of working programs to make them work "better" when they worked fine as they were and I will probably do that for as long as I work on PLC's. If you want a tech, test for a tech.
  5. You may get quite a few different answers to this question. Personally, I don't like to turn the PLC off unless it's for specific maintenance and even then I don't like to turn it off. The battery has a finite lifespan. If I remember right we change our batteries once every 3 years. I also put a Battery Fault Alarm in each program in case a battery dies before we catch it. If you power the PLC off then the only thing holding the memory up is the battery. I wouldn't trust that.. If it's set up for to do so the PLC can retrieve the latest saved image from the CF card. However, if an edit is made to the program and it isn't backed up to the CF card it will load the old version over the new program IF it's set up to do that. There are various options for when and how the backup is loaded. I stopped using the CF card since the process of backing up required a system shutdown. If the PLC "loses it's mind" a tech has to either remote in or go to the site and download the program to the PLC.
  6. I think I would use a Red Lion DSPGT <--- might not be the correct model. They have a bare bones DSP that doesn't have some of the stuff that the "deluxe" model has. The Red Lion "talks" a lot of different protocols with ease
  7. Find password from .mer or .apa

    It's been a long time since i've programmed  PV plus but if you have the APA file can't you just edit the password to be nothing and compile / upload that?
  8. Bit Shift Left BSL

    Lets say you have a 16 bit integer 12345. The bit pattern for it is 0011 1000 0011 1001. If you BSL 3 times everything shifts to the left 3 places, 0's fill in the rightmost values. 0011 1000 0011 1001 becomes 1100 0001 1100 1000 (hopefully I got that right, it's been a while since I've used BSL)   
  9. COP instruction conversion

    Why not use the COP in CLX?  It's been awhile but that looks like indirect addressing
  10. GPS time synchronisation with AB PLC

    You can log on with your laptop and synchronize it that way
  11. Preferred HMI with RSLogix 5000

    ClearSCADA would be too expensive for you then We don't use many alias tags. I map IO to tags into a tag created from a UDT. The UDT also has two strings for the HMI. Tag and Description. Like so: P1000.RunStat := Local:9:0.0; <-- not the exact format but I use a spreadsheet to build the map file so I really only need to know Rack, Slot, Tag, and Description
  12. Preferred HMI with RSLogix 5000

    Gotta agree with the Red Lion and the way it integrates with CLX. We went client / server so the HMI lives in one place and looks the same everywhere. For machine (in my case, pump, expander, compressor, etc) dependent HMI's the Red Lion works really well.
  13. Preferred HMI with RSLogix 5000

    We used to use the big Panelviews but the then client, now employer, had moved to ClearSCADA so we switched to a Nematron Panel PC running a ClearSCADA client and talking to a ClearSCADA server running Kepware. At the time the SCADA dept was very small and resources were few. One guy was particularly good with ClearSCADA programming. He and I teamed up, I tailored my UDT's to meet his needs in ClearSCADA, and he wrote scripts and created mimics that made the integration between the two systems almost seamless. We use the same tag structure (UDT's to the rescue) and I wrote the programs (52 stations, one with 12 pumps, (5) 250hp, (7) 1500 HP) and he did most of the ClearSCADA development. Eventually I had to learn the HMI said and thanks to his hard work it was very easy. We had the system down so well that we could do a decent sized station in a couple of days. That's PLC and graphics. When I FAT'd the panels, the graphics were done and waiting to he linked. I would use a cell modem to link to the server, pull the PLC database into ClearSCADA, install ClearSCADA on the HMI, have an IT guy remote in an add the license, turn on the comm in Kepware, and bingo... all done. Needless to say, I'm a fan of ClearSCADA / Kepware for AB CLX PLC's
  14. visual basic to rslogix

    Sure isn't :)  
  15. Tisoft analog alarm programming

    The analog alarm block in TiSoft (I actually use Workshop but TiSoft works) is a real handy block. Give it a Vflag address and then use Vx.x bit to trip a C bit. I map every single analog into the alarm blocks. I map them consecutively. Ie Alarm 0 is the first AI point on the card, Alarm 15 is the 1st alarm point on the second card. etc If you use 8 point cards the numbering changes. The alarm blocks may start with 1. It's been awhile. I even map the unused analogs to alarm blocks so future added analogs are easy to implement. The true value of the block is that all of the features of the alarm are in one place. Scaling, setpoint, scan time, etc. So HMI programming becomes easy (easier) and more structured and troubleshooting an alarm or shutdown is very easy. Disabling an alarm or shutdown is easier to program. There are lots of good reasons to learn to use the alarm block in the TI. I make it a habit to latch shutdowns (so if something blips i can see what shuts something down).  I liked the alarm block so much that I made one for Siemens S7 and the Control Logix PLC when we stopped using the TI (beast of a PLC though) and moved on the S7 and CLX.