1 of 8. I. (13pts) TRUE OR FALSE

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1 Sample PLC Final Exam Name (1pt): By signing I agree to abide by the UWA policies governing academic integrity. I. (13pts) TRUE OR FALSE 1. The user memory segment stores information needed to execute the user program. 2. Sourcing occurs when the current flows out of the PLC port and sinking occurs when the current flows into the PLC port. 3. A proximity switch uses a light-emitting diode (LED) and a phototransistor. 4 Flow switches are used to open and close contacts in response to changes in liquid level. 5. Output devices can be represented multiple times in a relay logic diagram. 6. Each input device can only be represented once in a relay logic diagram. 7. Input devices can be connected in series. 8. Only one input to an AND gate must be low to produce a low output. 9. Both inputs to a NOR gate must be high to produce a low output. 10. Inverting an OR gate will result in creating a NAND gate. 11. Both inputs to an XNOR gate must be high to produce a high output. 12. Both inputs to an AND gate must be high to produce a high output. 13. Inverting a XNOR gate will result in creating an XOR gate. II. (5pts) MATCHING 1. A timer has preset value timer instructions. 2. The format uses coils to display the timer instruction. 3. The format uses a box shape to display the timer instruction. 4. The content of the register is the preset value that the timer is initialized to hold. 5. The time that the timer has been timing is held in the register. A. accumulated B. block C. coil D. discrete E. fixed F. flag G. preset H. status I. system J. timer K. variable 1 of 8

2 III. (7pts) MULTIPLE CHOICE 1. If all the units are in one fixed enclosure, the PLC is called a PLC. A. modular B. fixed C. discrete D. None of the above. 3. A converts the digital output signals back to analog signals. A. bus B. register C. triac D. DAC 4. The segment holds the ladder logic program. A. system memory B. user memory C. ladder memory D. logic gate 5. You can only place one output device per rung; therefore, so you cannot place any output devices in A. parallel B. series C. junction D. None of the above. 6. The device that must be placed as a last device on a rung of a relay logic diagram is a(n) device. A. output B. input C. discrete D. indiscrete 7. A motor can operate in continuous run mode or in temporary run mode, also called mode. A. run B. jog C. skip D. stall 2 of 8

3 IV. (14pts) MATCHING 1. XIC is an acronym for. 2. XIO is an acronym for. 3. An Allen-Bradley SLC 500 series PLC has words addressed from N7:0 to N7: An Allen-Bradley SLC 500 series PLC has addressed from T4:0, T4: An Allen-Bradley SLC 500 series PLC has addressed from to C5:0 to C5: In order to change the program, the PLC must be in mode. 7. In an XNOR gate ladder logic diagram, when one input is closed and the other one is open, the output is. 8. Inverting an NOR gate will result in creating a(n) gate. 9. PLC program execution, or program flows from left to right on each rung, starting from the top rung and continuing to the bottom rung. 10. In a one-rung NOR gate ladder logic diagram, both inputs must be normally. 11. In a one-rung XNOR gate ladder logic diagram, the normally closed inputs are connected in. 12. In an XNOR gate ladder logic diagram, when both inputs are open, the output is. 13. In a one-rung NAND gate ladder logic diagram, the inputs must be in. 14. In a NOR gate ladder logic diagram, when one input is closed and the other one is open, the output is. A. AND B. closed C. counters D. Data Base E. de-energized F. energized G. examine if closed H. examine if open I. forced condition J. I/O Configuration K. Integer L. NAND M. NOR N. off O. offline P. on Q open R. OR S. parallel T. Report Options U. scan V. series W. timers X. XOR X. XNOR 3 of 8

4 V. (21pts) SHORT ANSWER 1. There are 9 rules for creating Relay Logic Diagrams. List 3 of those nine rules. 2. Write Gray code for 0 through Convert binary to decimal. 4. Convert hexadecimal B3 to decimal. 5. Convert BCD to decimal. 6. Convert decimal 45 to octal. 7. Subtract binary number 0101 from binary number of 8

5 VI. (20pts) SHORT ANSWER 1. Identify each of these logic gates by name, and complete their respective truth tables: 2. Identify each of these relay logic functions by name (AND, OR, NOR, etc.) and complete their respective truth tables: 5 of 8

6 VII. (9pts) SHORT ANSWER 1. Convert the following relay logic circuit into a Boolean expression, writing Boolean sub-expressions next to each relay coil and lamp in the diagram: 2. Write the Boolean expression for this TTL logic gate circuit, then reduce that expression to its simplest form: 3. Give the minimized Boolean expression for the following Karnaugh map. AB\CD of 8

7 VIII. (10pts) RELAY LOGIC DIAGRAMS 1. Design a PLC ladder logic diagram or relay diagram for the following: A red pilot light (RED_PLT) turns on when the start pushbutton (Start) is pressed. After eight seconds, motor one (M1) turns on. Twenty seconds later, the red pilot light (RED_PLT) turns off and the motor cuts off. 7 of 8

8 2. Design a relay diagram AND PLC ladder logic diagram for the following: A switch (MODE) toggles motor one (M1) between JOG and CONTINOUS operation. When in JOG mode motor one (M1) will run when pressing the yellow (NO) push button (PBY). In CONTINOUS mode motor one (M1) turns on using the (NO) green pushbutton (PBG) and off using a (NC) red push button (PBR). A yellow pilot light (Yellow_PLT) indicates JOG mode. A red pilot light (Red_PLT) indicates CONTINOUS mode. A green pilot light (Green_PLT) is on whenever the motor is running. 8 of 8