8.7 PRACTICE PROBLEMS

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(Note: Problem solutions are available at http://sites.google.com/site/automatedmanufacturingsystems/)

1. Does a PLC normally contain RAM, ROM, EPROM and/or batteries.

2. What are the indicator lights on a PLC used for?

3. A PLC can only go through the ladder logic a few times per second. Why?

4. What will happen if the scan time for a PLC is greater than the time for an input pulse? Why?

5. What is the difference between a PLC and a desktop computer?

6. Why do PLCs do a self check every scan?

7. Will the test time for a PLC be long compared to the time required for a simple program.

8. What is wrong with the following ladder logic? What will happen if it is used?

9. What is the address for a memory location that indicates when a PLC has just been turned on?