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kratmel

MVP 2023
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Posts posted by kratmel

  1. In general, the main problem in your case is to calculate the position of the crane.

    I'm afraid that it is almost impossible to do this clearly with the help of one sensor.

    Therefore, I recommend reading the information about the quadrature signal and using two sensors on the crane to distinguish the direction of movement and count the positions as a number. Accordingly, you will avoid vibrations and false readings of the position counter.

    In the PLC, it is possible to use two high-speed inputs as an encoder input and automatically count the positions of the crane, which must be marked by the corresponding mechanical fixed parts from which the two sensors can read the signal.

    Another problem is to set the zero position after switching on. But in general, the main thing is to calculate the positions correctly - and with the help of only one sensor, it can be unstable.

  2. I think this crane

    5 hours ago, Deyan Tenev said:

     stop on different positions , which are selected before switching in automatic mode.

    is the same task as elevator PLC control.

    Please read this info about ladder logic idea

    https://instrumentationtools.com/elevator-plc-ladder-logic/

    https://www.theseus.fi/bitstream/handle/10024/338304/PLC Controlling Program of an Elevator_Thai_Nguyen.pdf?sequence=5

    https://www.ijser.org/researchpaper/Implementation-of-a-Four-Floor-Programmable-Logic-Controlled-Elevator-System.pdf

    You can find different control strategy for elevator ("vertical crane") and try to build your own code.

  3. Analyzing what you said and that piece of code, I came to the conclusion that the set from the scan time of the code, the setting of the timer and the way of handling the rising edge from the timer make it so that the variable that should toggle on the display screen does so just after the screen refresh is complete.

    That is, the process of changing the variable took place, but the OS did not receive the command to update the display with the variable. After some time, analyzing the state of the variables on the screen and seeing that there is a problem, OS starts a full refresh.

    I think that the solution to the problem lies in moving the location of the subprogram where the display is updated in the main program.

    That is, it should be before the subroutine where your MB 3141 is set.

    But this is just my hypothesis.

  4. Then you probably need to experiment with the size of the file with firmware and without firmware in the SD file.

    It may turn out that the files are the same and the firmware is still stored in the file, but its download is not activated if the firmware is equal to the needs of the program.

    But these are only guesses. As I said above, the developers probably could not provide a version check in the firmware when updating the software from the SD.

  5. I think that only the creators of the controller's firmware can provide a reliable answer.

    However, analyzing the SD function you mentioned, it can be assumed that when creating such a controller, the creators could not imagine how long the platform would be updated. I mean both the software environment and the firmware of the PLC itself.

    I can only be surprised that some other companies (I won't mention the names :) ) during the year for the same controller model, there were 4 incompatible firmware updates in sequentially provided PLCs that cannot be changed. That is, I converted the program 4 times to load it into the next PLC during the year.

    PS.... I remember the time when I installed WIN 3.1 on a 286 machine. It was a joke to prove that everything will work even on such slow machine. I just increased the memory to 4MB and I succeeded. One problem that was insurmountable was that almost 15 seconds passed from pressing the keyboard to the appearance of the symbol on the screen.

    Therefore, I think that the performance reserve built into the design of the Vision series will allow us to improve the capabilities of this PLC several times in future.

  6. You must connect power to Jazz PLC power connector.

    If powered PLC do not connect - please check USB cable also. Some cable have only two conductor for USB device charging.

    If no connect with tested cable - please go to Info mode (via "i" button  long press and 1111 pasword) - search for communication settings and try to switch PLC to STOP mode.

  7. On 2/18/2023 at 3:24 AM, John_R said:

    Anybody done something like this who can provide some guidance?

    I have experimented with different ways of controlling synchronous motors. The use of hard switching and PWM modulation requires a specialized controller. The simplest PWM from a PLC requires quite a large number of components to implement frequency control. This is due to the fact that you have high-voltage motor circuits and need to isolate the control circuits (upper and lower transistors in the H-bridge).

    In my opinion, the cheapest way to implement your task is to use a specialized IC - a set for implementing frequency control. Below are two manuals about a IC and a ready-made board for implementing a sine wave with an adjustable frequency for your motor.

    5-389_EGS002_manual_en.pdfeg8010_datasheet_en.pdf

    I installed such a circuit board in a UPS with burned-out MCU and got a good inverter with the ability to adjust the frequency and voltage, similar to a frequency converter, but in a single-phase version.

     

  8. After reading the need described in the author's post, I can state that the proposed solution has an 1 contact SS button that, through the PLC, simulates the operation of the original switch.

    The main problem of this decision is non-compliance with safety requirements. The switch

    2 hours ago, Jeff164 said:

    Many of our panels use a single mechanical switch housing that we call a "Push / Pull".   It combines the function of a momentary NO Start button and momentary NC stop button, and pilot light, into one physical housing.  You pull it to engage the NO start and push it to engate the NC stop.   

    that you once used had a clearly defined state. In the event of an accident, the User has the skills and understanding that pressing the button will stop the machine.

    In your SS button case, it is impossible to predict whether the user will press the button only 1 time and not allow the machine to continue working in a dangerous situation.

    At the same time, modern equipment safety requirements require that the production device must have separate on-off buttons and a separate emergency stop button. Simplification is allowed only in household appliances.

    I don't know where your solution applies. However, I advise you to familiarize yourself with the safety requirements for this type of equipment.

    A possible solution through the PLC is to turn on the system by pressing the button for a longer time - for example, 2s and turn it off immediately when the button is pressed in the working state of the machine. But it still does not meet the safety requirements.

    • Upvote 1
  9. On 2/14/2023 at 9:15 PM, Jhav said:

    my question is will the values refresh after after the allotted ms are up?

    Yes, it will refresh, this number only indicates with which period the average frequency will be determined.

    The frequency will be determined by the number of pulses received per time unit selected by you.

    The only remark is that if you have chosen encoder x2 or encoder x4 as a source, the frequency will be 2 and 4 times higher, respectively. And it will have to be divided by 2 and 4 to get the correct value.

  10. I would divide your task into two parts:

    1) setting of VFD;

    2) development of a code for interaction with VFD.

    Considering control via Modbus, I would like to say that turning on and off the VFD must meet the safety requirements.

    If the VFD does not have an external Safe stop input, then controlling it via the network causes a problem - what will happen when the network is interrupted or the PLC fails.

    Therefore, taking into account the fact that in a standard VFD it is possible to separately define the source of control and the source of the setpoint.

    Then I would use the VFD logic inputs of the START-STOP and the network as the source of the speed setpoint, write parameters, reading the status, errors and resetting them.

    In this case, there is no need to constantly monitor the network and configure network control timeouts in the VFD (sometimes they cannot be disabled in the VFD converter even for a test).

    If the above-mentioned control method is not possible, then for the network it is necessary to determine the polling period of each parameter and each VFD in the network (timer controlled send command) to ensure constant control and accordingly adjust the VFD to stop or other reaction in case of network loss.

    1 hour ago, roghenr said:

    I also noticed that I have timing problems because I need to press key several times to turn it on or off.

    In order to speed up the reaction to pressing the control buttons, it is necessary to take into account that, in addition to the data sending command (and transmission times), there are other parts of the program that must be executed. Therefore, before the Modbus start-stop command, you should put a label in the program, and at the end of the program rung, where there is a button-click, place a jump to this label.

    Main idea - do not send something if it not needed at this time.

  11. The linearization block does not work with floating point numbers.

    Therefore, it is probably advisable to multiply the desired number by 10, 100 or 1000, converting it into a integer number and carry out linearization for the integer number. Then convert the obtained result into a number with a comma. Some "how to" advice in the topics below.

     

  12. I noticed that in some PLCs, the fastening bolts are tightened so tightly that the body is deformed and, as a result, there is a problem with the touch screen.

    However, I think that the main issue of sensitivity is the distance between the sensor itself and the main sticker film (this is not about the removable film that comes with the new screen as protection against damage during transportation).

    • Upvote 1
  13. 4 hours ago, Fernando Castro said:

    I mean, you are not wrong but after doing that, I don't see the point on using Modbus.

    The main idea proposed by me is to use the standard SCADA Modbus protocol for connection.

    That is, by making your own limited  Modbus protocol in the PLC, you can allow users to read or write something via SCADA without worrying about the possibility of messing up the settings.

    In my case user can only set setpoint and read statistic via free  SCADA.

  14. It is clear that the direct use of Slave Modbus mode does not have any protection against reading or writing to PLC memory.

    I haven't tried to do something like password protection, but I think it's possible to run your own exchange Modbus commands using the Protocol FB when starting the PLC.

    Here are the possible options:

    - set the password that must be set (writed) by master (using an address that does not exist in the PLC and own "Simulated Modbus" protocol) and put the PLC in full access Slave mode via standard Modbus (and disable "Simulated Modbus" protocol until the next restart of the PLC or the programmed standard modbus write command action - reset the password);

    - create your "Local simulated Modbus" with a set of available cells for writing or only reading via Protocol FB.

    I was building "My Modbus"  to read a record of User defined Modbus codes in the range 65-72 (Not implemented in PLC). Everything worked without problems, so I think it's easy to create something like this to give write and read access to only specified cells using standard modbus codes or User defined Modbus codes.

  15. Is it  CPU-for-Panel present?

    Panel cannot operate independently. CPU-for-Panel must be plugged
    into the back of a UniStream® HMI panel. The panel provides the CPU’s
    power source. The CPU-for-Panel comprises:
    1 IO/COM Bus connector for interfacing Uni-I/O™ & Uni-COM™ modules
    2 Isolated RS485 and CANbus ports
    3 Backup battery

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