Course Content
To fault find a system you need to know EXACTLY how it works HOW EXACTLY DOES A PLC WORK? -
Am I getting the input to the PLC? -
The Led on the output card means i am getting voltage out right? does it? -
What exactly happens in between? ,theres more than just a program in the CPU -
How exactly does it scan the program? -
What is this Watchdog Timer? Is it that important? -
Can I use the same output twice? That's bad programming isn't it? -
A PLC is a logic controller, so use a logical approach to fault find it. -
What are the 8 simple test points to check? -
The PLC is in RUN, that means theres a program right? does it? -
FORCING a bit and toggling a bit is pretty much the same yeah? depends on which PLC Then you need to Know the specifics HOW DO I DO THE FOLLOWING? (some straight forward some not so) - How do I check power is ON and PLC is in right mode (RUN or Program)
- Check for a fault condition
- Establish a link between PC and PLC (can be a major issue nowadays)
- If comms problem check interface
- Create a blank project and take a backup (just in case I mess up)
- Open project for PLC and go OnLine
- Interrogate Diagnostics
- Identify if it is a hardware or software fault?
- Change the battery
- Change modules if necessary, (with spares and without spares)
- Identify if it is a PLC or Comms fault
- Check all settings against a template etc.
- Check Hardware ( What voltage should be where)
- Clear Memory and Download program
- Check software against latest copy
- Monitor program effectively
- Searching for specific operands and instructions
- Changing timer, counter values On Line
- Making minor mods Off Line and On line
- Check or create a monitor table to establish parameter status
- Force a parameter if required
- Call up reference data to assist with software diagnostics
- Display Documentation (Symbols, Comments)
- Reassign an I/O address and change software addresses
- Printing Cross Reference / Program Listings etc.
Background information required Understanding of the following: - Number formats, bits, bytes, words, double words
- Binary, HEX,octal,floating point, integer
- Data types and parameter types, Bool etc.
- On Line and Off Line modes
- Basic Instructions, contacts, Set, reset etc.
- Timers, Counters
- Comparators, Maths
- How to make minor mods
- Altering values in a monitor table
- Using Device Monitor function
- Using Force function
- Back tracking through a program to establish where power flow stops
- Reset procedure
- Fault finding tips
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