1.3 PRACTICE PROBLEMS
1. Write the mnemonic program for the Ladder Logic below.
(ans. XIC 100, XIC 101, OR, OTE 201)
2. A PLC can be used effectively to,
a) replace a few relays.
b) replace customized electronics.
c) replace a highly skilled human operator.
d) control a well understood process.
5. Why would relays be used in place of PLCs?
(ans. for simple designs)
6. Give an example of where a PLC could be used.
(ans. to control a conveyor system)
7. Give a concise description of a PLC.
8. List the advantages of a PLC over relays.
9. Explain the trade-offs between relays and PLCs for control applications.
10. In the figure below, if a limit switch is NO, the power the power flow to the output will normally be___________________.
11. In the figure above, if a limit switch input is NC, the power indicator in the input module should be __________________.
12. TRUE or FALSE - The left-most side of the PLC’s ladder diagram simulates the power line.
13. In ladder diagram programs, all outputs are represented by:
a) Contact symbols
b) Coil symbols
c) a or b
d) None of the above
14. List the advantages of PLCs over relay logic.