PLC

Question 1

Name 3 types of counters

Answer 1

Count up
Count down
Count up and down (Bi directional)

Question 2

Why is the program Ina plc not lost when mains is lost

Answer 2

The program is always stored in non volatile memory

Question 3

Where is a photo transistor used

Answer 3

Ina opto coupler

Question 4

How do you prevent damage To a PLC in the event of back emf in a AC coil

Answer 4

Add a snubber circuit in parallel with the coil capacitor and resistor

Question 5

How do you prevent damage To a PLC in the event of back emf in a DC coil

Answer 5

Add a snubber circuit in parallel to the coil diode and a resistor

Question 6

What is the function of an internal relay in a plc

Answer 6

Tidy up the plc program

Question 7

Name the 5 main parts that make up a plc

Answer 7

Input interface
Memory
Micro processor
Power supply
Output interface

Question 8

What is the function of an opto coupler

Answer 8

Provides electrical isolation

Question 9

Name 3 advantages why PLCs are better then hard wiring

Answer 9

A plc can be re programmed rather then rewired

PLCs are reliable as they have no moving parts

PLCs have built in times and relays saves having to buy relays and external timers

Question 10

What dose a traic switch

Answer 10

Ac supply