Deck 18: Developing a Program for a Plc

Question 1

What rules should be followed when converting a schematic?

Answer 1

There are some basic rules that should be followed when making a conversion.
-Each line of logic must end with a coil.
-Any contact labeled the same number as a coil is controlled by that coil.
-Each relay can have an infinite number of contacts and they can be assigned as normally open or normally closed.
-Any coil assigned the same number as an output will control that output.
-Any contact assigned the same number as an input is controlled by that input.
The PLC assumes inputs to be low (no power applied) when the program is loaded into
-memory. When power is applied to an input, it will cause the contact assigned to that input to change state. A normally open contact will close and a normally closed contact will open.
-Any number of contacts can be assigned to the same input.

Question 2

How are the inputs assigned in the PLC described in this chapter?

Answer 2

In this example the on-off switch is assigned to input 1, the pressure switch is assigned to input 2, the auto terminal of the selector switch is assigned to input 4, the pump 1 terminal is assigned to input 3, and the pump 2 terminal is assigned to input 5. Note that one side of each input device has been connected to the hot or ungrounded power terminal. The other side of each input device is connected to the appropriate input terminal. PLCs do not provide power to the input or output terminals. The inputs and outputs must have power provided to them. The common (C) input terminal is connected to the neutral or grounded power conductor.

Question 3

The water pump circuit will cause the pumps to alternate running each time the switch closes.

A) limit
B) pressure
C) float
D) temperature

Answer 3

B

Question 4

How is the operation of motor start coil 1M controlled in the example presented in this chapter?

Question 5

How are the overload contacts connected in the logic circuit described in this chapter?

Question 6

The input terminal is connected to the neutral or grounded power conductor.

A) common
B) L1
C) L2
D) tenth

Question 7

The simplest way to convert a ladder diagram into a is to make the changes in stages.

A) logic circuit
B) terminal diagram
C) schematic
D) coil diagram

Question 8

Before a program can be developed from a ladder diagram, it is first necessary to determine the number of .

A) differential amplifiers
B) protection schemes
C) input and output devices
D) CPUs

Question 9

Control circuits are generally drawn as standard .

A) logic diagrams
B) lines of code
C) truth tables
D) schematic or ladder diagrams

Question 10

A selector switch can be set to any of operating modes.

A) one
B) two
C) three
D) four

Question 11

A(n) occurs when it is possible for one contact to open before another closes or for one contact to close before another opens.

A) bypass
B) contact race
C) off-delay
D) on-delay

Question 12

In a logic diagram, each line of logic must end with a .

A) circuit
B) coil
C) pump
D) switch

Question 13

One advantage of PLCs is that any input can be assigned contact(s).

A) one
B) 10
C) 1000
D) any number of

Question 14

Describe the circuit considered in this chapter.

Question 15

Given that the internal clock that controls the operation of timers operates in 0.1-second intervals, what value do you have to program in order to get a one-second delay from the timer?

A) 0.1
B) 1.0
C) 10
D) 100

Question 16

In a circuit designed to operate two well pumps, what is the protection mechanism?

A) fuse
B) circuit breaker
C) ground-fault protector
D) branch-circuit protector

Question 17

A PLC assumes inputs to be when a program is loaded into memory.

A) set
B) high
C) low
D) off

Question 18

The second step in actualizing a ladder diagram is to add the logic that .

A) controls the pump one bypass circuit
B) controls motor starter coil 2M
C) controls motor starter coil 1M
D) controls the pump two bypass circuit

Question 19

When power is applied to an input, it will cause the contact assigned to that input to .

A) activate a push-button
B) close
C) open
D) change state