Important Questions and Answers: Mechatronics - PLC

1.     What is a PLC?

A Programmable logic controller is a microprocessor based controller that uses a programmable memory to store instruction and to implement functions such as logic , sequencing , timing, counting, and arithmetic in order to control machines and process.

2.Write short notes on the basic arrangement of a PLC system.

1.central processing unit

2.programmer/monitor

3.input and output modules

3.What is an internal relay in PLC?

Most PLCs have an area of memory allocated for internal storage that are used to hold data, which behave like relays. It can able to switch ON and Off . But this is for only internal purpose. This will not exist in the real world

4.Define adaptive control.

The control system which can adapt changes and it can change its parameters depending on the situation .it is known as adaptive control system

5.What is Shift register? What is the data required for a shift register?

Shift register can be used where sequence of operation is required or movement or track the flow of parts and information

It requires three inputs and the following information is to be provided 1.file-address of the bit array

2.control- addresss of control structure

3.bit address-address of source bit

4.length -number of bits in bit  array

6.State the purpose of shift registers.

Shift register can be used where sequence of operation is required or movement or track the flow of parts and information

7.What are shift register ?

The no of internal relays is grouped together that allows the shifting of bits serially through an array in an orderly fashion called shift register. shift register are used where sequence of operation is required or movement or track the flow of parts and information

8. What is main advantage of PLC?

PLC’s have great advantage that it is possible to modify a control system without having to rewire the connections to the input and output devices.

9. What are the features of PLC as a controller?

The features of PLC as a controller are,

a.     They are rugged and designed to withstand vibrations, temperature, humidity and noise.

b.The interfacing for inputs and outputs is inside the controller.

c. They are easily programmed and have an easily understood programming language.

10.            Write about the architecture of a PLC?

It consists essentially of a central processing unit (CPU), memory and input/output circuitry. The CPU controls and processes all the operations within the PLC. It is supplied with a clock with a frequency between 1 and 8 MHz. It also has a bus system, memory and input/output units, a system ROM for permanent storage, RAM for the users program and temporary buffers.

11. What is ladder programming?

The ladder programming involves each program task being specified as though a rung of a ladder. Thus such a rung could specify that the state of switches A and B, the inputs, be examined and if A and B are both closed then a solenoid, the output is energized .

12.List down the different types of timers .

1.on delay

2.off delay

3. retentive timer (RTO )

13.What is mean Retentive timer ?

Retentive on delay timer (RTO) will hold its accumulated value when timer rung goes false and will continue timing where it left off when timer rungs goes true again

14.            List  down the general application of PLC for control.

1.control of a process motor , vibrating machine

2.Control of a two pneumatic piston

3.Detecting , sorting and packing unit

15.            What are the factor to be considered for selecting plc .

1.system definition

2.choosing the input and output hardware

3.Analog input / output module

4.input and output timing consideration