PLCMentor.com

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Everything posted by PLCMentor.com

  1. Array of data

    Akkkkkk!  Dont post your email in the forum or you will get spammed to death.  Use the messaging system. 
  2. Array of data

    Sooooo what are you trying to say?  ;)  Seriously, if I understand what you are suggesting then it sounds like it would work but just say no. First, arrays are something that should be used sparingly and there are much easier ways to do things than what you propose.  Simpler is better in a PLC.  When you posted this originally, you inspired me to do a series on arrays.  Message me with your email and I will get you links to that material since you had the idea anyway.  I put together about 2 hours of material on arrays, indexes, usage and troubleshooting.  I think they should make things clearer for you.
  3. DH+ issue

    Yes the expected wiring is Clear-Shield-Blue with DH+, but as long as it is wired incorrectly on both sides it will still work.  That would be worth fixing over time.  The whole reason for the wire sequence is to differentiate it with Remote I/O which is supposed to be wired Blue-Shield-Clear.  Maybe you can get all of that worked out when you have some downtime.  It is not a good idea to be working with the network at all while the rest of your plant depends on it.  That's a good way to get some unexpected downtime. 
  4. DH+ issue

    Sorry I should have been more clear.  If you have a station connector, then you have a trunk/drop structure.  When people daisy chain DH+, they do not use station connectors.
  5. DH+ issue

    kaiser brings up many good points.  The most important is your network addressing.  I have found over the years that DH+ is pretty forgiving and have seen some pretty poorly designed/installed systems that run without issues.  Four things you have to be absolutely certain about:  you cant add duplicate addresses to the network; your wiring has to be consistent (clear, shield, blue) and proper calble (blue hose - belden) is important;  Your baud rate has to be the same (i remember 3 - 56k, 115k, and 230k but maybe that last is just RIO); the terminating resistors must be installed and correct.  They resistance is dependent on the network speed.  Total network length can be an issue but not generally as at 56k you can run 10,000 feet.  Trunk and drop are how DH+ was designed; however, I have seen maybe 2 networks installed that way over the last 25+ years.  Generally you will find that DH+ is daisy chained from one device to another.  Not saying to change now that your network is installed to spec; however, I am doubtful that how you connected the components is the issue. 
  6. PIDE Temperature Control

    Sorry that this got left out here so long.  I believe there is a function block to do that but I have not used it.  In the past I have taken the output from a PID block and turned on the SSR for a predetermined time period depending on the output of the PID.  Simple enough to do with two timers.  One timer is your period time and the other is the on time.  You determine your maximum period between evaluations and set your period timer to that value.  Lets say we pick 10 seconds.  Every ten seconds we look at our PID output to see what percent on we are going to require.  If our PID CV is set at 30%, then we set our On timer to 3 seconds (30% of our full period) and start timing.  Our SSR is on during the 3 second On time and off for the remainder of the period - in our example 7 seconds or the remainder of the 10 second period. 
  7. OTU without an OTL?

    Should not be a problem with that.  You need to confirm that the HMI is just setting the bit.  Sometimes we will add catches in the program if the HMI or SCADA system has a history or tendency to leave bits on periodically.  Looking at the wording, these appear to be disables.  It may be that the programmer is continuously unlatching the bit to disable the function and override the HMI.  If the HMI is setting the bit and leaving it or even has separate set and reset function, you should be able to get away with putting some PLC logic that will operate in a similar manner.  Keep in mind that the HMI will still be able to set and reset that bit.  If you are looking to being able to do that functionality from both places, then it looks like you have what you need.  The HMI will set the bit or your PLC will set the bit.  If you want either the PLC or HMI to be able to reset the bit, then you will want to use a oneshot in your PLC logic to insure that it does not override a reset from the HMI.  Once again - this assumes that the HMI is setting the bit and not acting as a momentary and setting the bit and resetting it after a predetermined time period.
  8. Array of data

    If you have no concept of arrays they can be tricky to understand.  Kaiser has done a good job of explaining a one dimensional array.  In such you have a tag and you set the number of elements you need - ie, setup 100 elements and you have tag[0] through tag[99].  Multi dimensional arrays get a bit more tricky.  You can then have a tag:  tag[0][0] or tag[0][1].  It helps to understand these if you think of a table or spreadsheet.  If you think of the first dimension as the columns and the second as the rows then it helps to get your head wrapped around it.  So if I have a tag that has first dimension of 100 and second of 50 then we can have a tag such as:  tag[0][0] or tag[99][49].  If you think of it as a spreadsheet then we have 100 columns and 50 rows.  This can be useful for tracking items or storing information. We use arrays for some of our more complicated programs just for this purpose.  For example we may have a sequence that has 100 different steps and 10 setpoints for each step.  We could create a Real array with first dimension of 100 and second of 10.  If we need the 3rd setpoint for the tenth step then we could just program located it in a tag:  Setpoint[9][2]   keeping in mind that our count starts at 0.  Taking it further, we can also use another tag to point to that information.  So if our sequence is on step 10 then we can use an integer tag such as STEP and point to our information with that:  Setpoint[STEP][2]    That is very similar to indirect addressing in the SLC and so is very difficult to troubleshoot and follow later on - as I am sure you are finding out!  When we program with such logic, we make sure it is necessary and that either nobody will have to go into that logic to troubleshoot or that the staff maintaining the system is sufficiently trained to understand such logic. 
  9. SCADA

    I have found that the default communication time slice in the ControlLogix processors is not sufficient for larger SCADA projects.  You can look at your current task speeds and see if you have room to increase the processors communications period.  If you decide to increase it, then recheck your tasks to make sure they still have enough time to run smoothly. 
  10. Macro Burned by the Micro 850

    I feel your pain!  I came close to purchasing one of these low priced "marvels" and after a little bit of research and posts from guys like you I ran the other direction.  Trusty Micro 1400 was priced nice and none of the pain and suffering.  Everything I read said that they are not cost effective due to the extra time required unless you are an OEM using a bunch of them.  Of course the poor guy at the plant that gets stuck with the OEM installed stuff.... well his time is free right? 
  11. 1794-IE8 RAW COUNTS FLUCTUATING

    My first inclination is that the small fluctuations you are seeing are due to noise.  That is a very small variation considering that your full scale is 30840 counts.  A change of 30 is less than .1%.  You hooked it to a 1762-IF4 which has around 25000 counts for the same range.  It also has filtering available which may be eliminating any noise.  Cant remember if the flex IE8 has such.  Also did you have the same cable run for both connections?  If it is noise you may not see it if you are trying the micro on a test stand.  Finally the raw data ranges of the two cards are very different so it doesnt surprise me that you have two different values.  The flex input of 10258 translates to 9.3 ma and the raw of 14541 on the IF4 also correlates to 9.3 ma.
  12. 1761-NET-DNI Replacement?

    I think most of us would agree that staying away from device net is best when avoidable.  Its just a pain.  I'm not even sure you could do what you wanted using device net between the two processors.  There is a device that will allow you to connect to your SLC via ethernet.  1761-net-eni (if my memory serves me).  It would require modifying the panelview to talk tot he SLC via ethernet, but it should also allow both PLC's to communicate.  Of course if you have the I/O, you could always go I/O to I/O if its just a few points.  Not sure about the DH485 port on the SLC.  Anyone know if that could be used to communicate with the 1400?
  13. Tag Scope

    While most of my tags will generally be controller scoped, I have to agree with Armadillo when it comes to duplicate program modules.  Using program scoped tags in the type of cells he refers to allows all of the tags in each cell to be named exactly the same due to their localized characteristics.  It organizes the data more effectively in those cases.  Many of the projects I do require that data be shared between different programs.  In this case it just doesn't make sense to localize your tags.  I really wish that folders were available at the controller level and then tag organization would not even be an issue.  Also, keep in mind that programming in a PLC and programming with other high level languages require a very different mindset.  In most programming compact and efficient are a big goal (unless you program for Microsoft ;).  In the PLC simpler is better.  We have to program for our audience, ie the end user. 
  14. Allen Bradley training

    You are welcome to check out our training site if you cant get away and need something online - Link is in my signature.  We have plenty of sample videos and course outlines on the site.  I agree with TW on the manufacturer training.  They lead you by the hand from a book.  The instructors are usually knowledgeable, but the 4 day cram tends to evaporate as soon as you leave the class.  Trying to buy a book on PLCs is usually fruitless.  They are usually based on a generic PLC which I would challenge anyone here to try and find a generic PLC.  The training we setup on plcmentor was designed to teach platform specific information over time.  It requires completing programs in the actual programming software and we have instructors that review the students programs.  We also have a weekly web class available that you can attend for question and answer sessions.  I have had several students attend the class in situations like yours to review their project progress and get pointers on how to move forward and to find out what might be done differently.  That all said, I really like Ron.  I have all his youtube videos on my site (with his permission) and have spent enough time talking with him on the phone to really appreciate his passion and hard work he incorporates into each class.  I thought he had already retired, but if you have a chance to get in I think it would be a great experience.  If you need help along the way maybe our web class platform would be useful also.  Good luck!
  15. RSview32

    I think you will need to install RSView32 from the original install CDs or other medium.  Sounds like you just tried to copy the files from a backup and none of the registry connections have been set. 
  16. If he is just setting the gateway he shouldn't lose comms as his ip address will still be the same.  Armadillo852's comment about having to set the BootP is interesting.  Pretty easy to try and I for one would be very interested to hear if that solves your problem.  Just make sure you turn it back off again after you make your gateway change (if it works).  
  17. Brewing station

    OK so I used to work at a place when networks were just coming out and they were a little flaky.  If it went down you lost all your work.  We would always get these messages that said, "Save often."  Two words and a habit that has saved me much grief over the years.  I would suggest you take up that mantra early! Now as to your problem with step 2 it really does not look that bad.  Your induction heater is probably controlled by an output (you have no I/O list so I am not really positive).  It sounds like your heat is supposed to stay above the low setting and that there is one input for this.   When your  input is on I interpret that as low - turn on the heater.  When the input is off the temp is high - turn off the heater.  Kinda confusing how it is written.  It actually looks like a fail safe system since a wire coming loose will cause the heater not to work.  I would have more problem with the cooling as it does not give any indication on how to determine if the material is cool enough.
  18. Well it sound more like a supply power problem than a power supply problem...
  19. Interesting and I'm sure that was fun to track down! I guess we should add that not only would they processor type be good to know, but explain exactly what you mean by "tripping."  Is it a cabinet power down, processor power down, fault, or other?
  20. Funny I had just assumed from his post that it was a SLC (you know where that usually gets you).  I think that it is the only AB I have had this problem with and it always seemed to be the power supply. 
  21. Is the panel actually tripping anything or shutting down and starting back up again?  If it is flaky with suddenly powering off, you may have a bad power supply.  That can cause strange things like that to happen.
  22. RSView32 not toggling bits in RSLogix500

    Dennis, It sounds like to me you are trying to toggle an input or "I" data type in your PLC.  That type of data should only be used for "real world" inputs and outputs wired to the PLC I/O.  Before every scan of your ladder, your inputs will be refreshed from the real world i/o and anything your HMI writes will be overwritten.  If you want to make  a soft pushbutton to be activated from an HMI then use the "B" data type.  You should already have a data file B3 that you can use to test this. 
  23. Read/Write Access DB

    I will take a bite on this.  Nobody jumped on this as there is no Logix instruction that will send data to a database as you are expecting.  Generally when inserting data in a database, you would pull the data from a PLC with some type of SCADA or HMI software and then use SQL inserts to send the information to your database.  If the HMI that you have is Factory Talk ME edition - basically a panelview - then I do not think it has the capability to do this.  I did pull data from a PLC5 into Wonderware and dump it into an access database around 15-20 years ago so it is possible; however, now days (even back then) people tend to use more capable databases.  MySql would be a step up in the number of records it can store and due to the fact that it is not a single user database as is Access.   I suspect it would also be easier to connect to these days. 
  24. Allen Bradley Integer

    I have heard of people doing this also in conjunction with a sequencer instruction.  Shift to a new sequence of bits and then just copy the resulting word to outputs.  Not something I would suggest emulating! 
  25. RSLogix 5000 Paid Project $50

    I just took a chance to look at the schematic.  Sad thing is it looks like you have a pretty good teacher that has taken the time to give you a real world situation with a drawing package that is realistic.  There are many students out there that are struggling with professors that have only read about PLCs and are taking tests on generic PLCs (which dont exist).  You might want to take a step back and struggle with this class and come out actually knowing how to program.  The struggle is the only way to learn how to do this stuff!