An array is a storage area for a group of common data type tags. They usually have some relationship to each other and need to be manipulated as a group. Last time we defined an array and use this in an indirect addressing program. It sequenced bits in an output card indirectly. In this second part we will be looking at the following instructions: Array Statistics (STA) – This will perform operations such as Summing, Averaging, Minimum Value and Median Value on an Array. Copy Array (CPA) – Copy a block of 1 or 2 dimensional arrays into a destination array. Fill Array (FLA) – Copy a value to a block of array elements Shift / Rotate Array (SRA) – Concurrently Shift or Rotate values in an Array.
Let’s get started with the Productivity 1000 Series PLC arrays part 2. Continue Reading!
An array is a storage area for a group of common data type tags. They usually have some relationship to each other and need to be manipulated as a group. We can use arrays for motion control, recipe management, sequencing (indirect addressing), math, etc. The Productivity 1000 Series PLC uses arrays which are programmed using the Productivity Suite Software.
We will be defining an array and use this in an indirect addressing program. This will sequence bits in an output card indirectly.
Let’s get started with the Productivity 1000 Series PLC arrays. Continue Reading!
Data handling instructions are used to perform movement and manipulations of the memory in the programmable logic controller. The Productivity 1000 Series PLC has fifteen different data handling instructions that can be used in a wide variety of applications. In this first part we will be looking at the following instructions: Absolute Encoder (ABSE) – Encoder input using Gray Code or Binary Code Compare Values (CMPV) – Compare two different tags and determine if equal, greater than or less than. Copy Data (CPD) – Copy tags from one location and place in another. FIFO / LIFO (FILI) – First in first out / Last in first out First Bit On/Off (FIB) – Determines first bit on in a series of bit tags. Inc / Dec (INC) – Increment or decrement a tag by a number. Logical Bits (LOG) – Perform logical operations on Boolean input tags. Logical Words (LOGW) – Perform logical operations on tags.
In part 2 of data handling we will continue with additional data handling instructions.
Let’s get started with the Productivity 1000 Series PLC data handling instructions. Continue Reading!
Just about every programmable logic controller (PLC) program will include a timer instruction. The Productivity 1000 Series PLC has several different timer instructions for your program. We discussed the timed coil (TMC) and flasher coil (FLS) last time as part of the contacts and coil discussion. (Contact and Coil Instructions – Video)
We will now look at using the Simple Timer (STMR) and the Timer (TMR) instructions in the productivity suite software. Let’s get started. Continue Reading!
The Productivity Suite Software consists of more than 82 instructions divided into 13 categories for the PLC. Contacts and Coils are two of the categories of instructions. Contact instructions include NO / NC, NO Edge / NC Edge and Compare. Coil instructions include Out, Set, Reset, OR Out, Flasher, Debounce, Timed, Toggle, Program End and No Operation.
We will be looking at these instructions in the Productivity 1000 series PLC. Adding to our favorite instructions helps us to organize the instructions. We will also look at organizing your favorite instructions. Let’s get started. Continue Reading!
The Productivity Suite Software allows us to modify our existing program and execute the new code without stopping the scanning of the PLC. This is referred to as online editing. We change the ladder logic code and when we save it to the PLC, the current scan of the PLC is held until the new code is written into the unit. It then releases the scan and our new program start to execute. This happens in milliseconds so our process can continue to operate.
Troubleshooting the logic in our PLC sometimes can be difficult. The Productivity Suite Software has a Debug Mode. This will allow us to control the scan cycle of the PLC, decide on the rungs to execute and control the physical outputs during this time. This ability of control helps to fix errors or understand existing code in our programmable logic controller.
We will be taking our existing Start / Stop circuit from last time and add a Jog input using online editing. We will then use the debug mode in the Productivity Suite software to understand the scan and the jog function that we added.
Let’s get started. Continue Reading!
The Productivity Suite Software provides tools for us to monitor and test our programs. Last time we used Tag Names and Details, Task Names and Descriptions, Rung Comments and Instruction comments to document our first program and transferred this to our connected Productivity 1000 Series PLC. We will be monitoring our ladder using the ladder editor window and display the information two different ways. Data View is a powerful tool to help us to test and view our program. We will be forcing the IO, toggling the IO view and graphing our tags to test our PLC logic circuit.
Let’s get started. Continue Reading!
We will be connecting the Productivity 1000 Series PLC with our computer running the Productivity Suite Software. A micro USB and an Ethernet (RJ45) communication link will be made to our programmable logic controller.
The latest Productivity Suite software version is 126.96.36.199. This is the programming software that we will be using to create our logic for control.
Let’s get started. Continue Reading!
Your control system does not work. Where do you start? Lets walk through a series of questions in order to determine where the problem lies.
Is this a new installation or previous installation that was running fine? Determine if system has been running well in the past and has currently stop working correctly. This is the indication that the problem relies inside the system.
Is there anything that has happened outside of the system? Has there been a lightening strike, blown drives on other systems, etc. This can point to the original cause of the malfunction.
What is the system doing now and what should it be doing? Gather all of the information you can from every resource you can.
Supervisors – machine, location, time of error, other happenings in the plant, etc
Operators – What is it currently doing? What should it be doing? What do you think is wrong?
Operators of the equipment are your key resource in finding, correcting and ensuring the error does not happen again. They know the equipment from an operational point of view which can assist you greatly in troubleshooting.
PLC fatal and non-fatal errors:
If the machine is still running partially then this is an indication of a non-fatal error. Cannot run at all is usually a fatal error.
Take a look at the PLC indicator lights on the CPU. Refer to the operation manual for the PLC for troubleshooting specific lights on the CPU. The following are general tips:
If no lights are on then the possible cause is a power supply. This is usually the most common of errors on a PLC system. Mean time before failure (MTBF) is rated on the lowest rating of components which is usually the power supply.
If the run light is on and an error light flashing this usually indicates internal errors such as batteries, scan time, etc. It is usually not the reason for the lack of operation.
If the run light is on and no other errors are seen on the CPU we can put the PLC program on the bottom of the list of items that could be the cause.
Check the input cards of the PLC. You should see the individual sensors lighting up the inputs. If not then check the power supply to the input card / cards.
Ask the operator what is happening and what is suppose to happen. Try to follow the sequence of events in the PLC to determine either and input or output device not working.
Some items to watch:
Leakage current on two wire sensors (False triggering the input)
If this is a new PLC program that you are doing start with a logic flow diagram. This will determine the procedure to start programming.
Every program can be done in several ways. The best method is the most documented one.
Documentation is the mark of a good program.
Some trouble with new programs can be racing conditions. This is usually a case of not understanding how the PLC scans logic. In general the PLC will scan from left to right, top to bottom. The output bits / words are available to the inputs of the next rung of logic. (Modicon PLC’s will scan differently.) Actual outputs and inputs are not read until the end of the scan of the PLC. Racing conditions happen when the output is set on multiple rungs, but will not get actually set until the end of the scan. Think of it as the last action will always win. So if this happens move the logic to the end of the program and see if it works. Then go back and see where the output was also set. Cross reference guides are ideal for this purpose. (Refer to your programming software on how to get cross references.)
We have discussed just a few troubleshooting techniques. Hopefully now you know how to start looking for the errors on your system. Let me know how you make out.
Do you know of additional tips or methods to share?
If you have any questions or need further information please contact me.
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