Deck 39: Programming a Plc

Question 1

Figure 38-11


The circuit shown in the above figure contains two control relay coils. A normally closed contact, controlled by the opposite relay, is connected in series with each coil. When the switch is closed, which relay will turn on and which will be locked out of the circuit?

Answer 1

The relay that is turned on depends on which one managed to open its normally closed contact first and break the circuit to the other coil. There is no way to really know which relay will turn on and which will remain off. There is not even a guarantee that the same relay will turn on each time the switch is closed.

Question 2

As a general rule, for programmable logic controllers, coils can be connected in a series.

Answer 2

False

Question 3

Programmable logic controllers are all programmed the same way.

Answer 3

False

Question 4

Programmable logic controllers operate by scanning the program that has been entered into memory.

Question 5

Figure 39-1


In the accompanying figure, when the tank is empty, the ____________________ de-energizes solenoid C.

Question 6

Most programmable logic controllers (PLCs) contain a timer that runs continually when the PLC is in the RUN mode. What is the function of this timer?

Question 7

Figure 39-1


In the accompanying figure, what happens when the tank is filled?

Question 8

Programmable logic controllers know what device is connected to which input.

Question 9

Figure 39-2


When the START button is pushed in the accompanying figure, relay coil CR is energized. This causes all CR contacts to close. Contact CR-1 is a(n) ____________________ used to maintain the circuit to coil CR when the START button is released.

Question 10

Figure 39-12


In the accompanying figure, when contact 1 closes, coil 100 will always be the ____________________ that turns on because it is scanned before coil 101.

Question 11

As far as programmable logic controllers are concerned, the program will scan in the order that it is entered.

Question 12

With programmable logic controllers, each line of logic must end with a(n) ____________________.

Question 13

Figure 39-1


In the accompanying figure, what happens when the motor turns off?

Question 14

How do programmable logic controllers scan a program?

Question 15

Contacts that exist in the logic of the program only are ____________________.