MAHARASHTRA STATE BOARD OF TECHNICAL · PDF file2Marks . MAHARASHTRA STATE ... Mechatronics is...

MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)

(ISO/IEC - 27001 - 2005 Certified)

----------------------------------------------------------------------------------------------------------------------- WINTER – 13 EXAMINATION Subject Code: 17302 Model Answer

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Important Instructions to examiners: 1) The answers should be examined by key words and not as word-to-word as given in the

model answer scheme.

2) The model answer and the answer written by candidate may vary but the examiner may try

to assess the understanding level of the candidate.

3) The language errors such as grammatical, spelling errors should not be given more

Importance (Not applicable for subject English and Communication Skills.

4) While assessing figures, examiner may give credit for principal components indicated in the

figure. The figures drawn by candidate and model answer may vary. The examiner may give credit for

any

equivalent figure drawn.

5) Credits may be given step wise for numerical problems. In some cases, the assumed constant

values may vary and there may be some difference in the candidate’s answers and model answer.

6) In case of some questions credit may be given by judgement on part of examiner of relevant answer

based on candidate’s understanding.

7) For programming language papers, credit may be given to any other program based on equivalent

concept.

Que-01 i) Attempt any Six 12

1) Symbol of photo diode:- 1-Mark

2) Symbol of UJT:- 1- Mark

ii) The rectifier is an electronics device which converts AC voltage or current into pulsating DC voltage or current. 2-Marks

iii) Symbol of

1) PNP transistor 1-Mark

2) NPN transistor 1-Mark

iv) Pin diagram of IC 741 2Marks




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v) Applications of Multiplexer 1-Mark

1) Data Transmission system.

2) Used in DAC

Or similar

Applications of Demultiplexer 1-Mark

1) Used in microprocessor system

2) In designing combinational circuits

Or similar

vi) The transducer is a device which converts one form of energy into another 1-Mark

The transducers are classified on the basis of 1) Operating principle, 2)size,3) active/passive 4) Analog/digital etc any two classification points 1-Mark

vii) Mechatronics is the branch of engineering which deals with control of mechanical devices with the help of electronics, to enhance the efficiency and to save time, money, Minimize wastage with increase in quality of product. 1-Mark

Applications of Mechatronics:- any two like

1) in Robotics 2) In Automobile 1-Mark

viii) The advantages of FMS (Any four) 1/2 mark each

1) Capable of performing various operations 2) Quick tooling is possible

3) Instruction changeover is fast. 4) provides various types of flexibilities.

Qu 1 b) Solve any TWO 08

i) Circuit diagram of full wave rectifier - 2 Marks Waveforms 2- marks




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ii) Gain of Inverting amplifier

Formula :- 1-Mark

Calculations 1-Mark

Gain of Non inverting amplifier

Formula:- 1-Mark

Calculations 1-Mark

iii) Advantages of CNC machine (any four) 2-Marks

1)Higher flexibility

2) Increased Productivity.

3) Improved Quality

4) Reliable and safe operation.

Applications of CNC machine (any four) 2-Marks

1) Various machining operations

2) Combined machining operations

3) In milling machine

4) In drilling, boring operations




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Qu- 2) Attempt any Four 16

a) Thermal runaway is defined as the self destruction of an unbiased transistor due to increase in temperature. The temperature of transistor increases due to increase in collector current. This causes increase in collector leakage current. This process is cumulative because IC=βIb+(β+1)Iceo. 2-Marks

Thermal runaway can be avoided by biasing the transistor properly and it can also be avoided with the help of Heat-sink.[Stabilization Circuit]

If the Temperature of the collector base junction increases, the leakage current of transistor increases also increases collector current. The increase in collector current produces an increase in power dissipation at the collector base junction, causing the collector current increases .This process become cumulative due to that ratings of transistor exceeded. If it happens the device gets burn out. 2-Marks

b) The transistor can be used as switch. When collector current flows through transistor the transistor is called as closed switch. As load is connected at collector, current flows through load. When no collector current flows from transistor the transistor is called as open switch. 2-Marks

Circuit diagram 1- mark waveform- 1-Mark

c) Circuit diagram 2-Marks Waveforms 1-Each for sine and square wave




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d) Circuit Diagram 2-Marks Waveform- 2 Marks

1.44 F= ------------------------ Hz

(RA+2RB) x C

e) Compare RC and LC oscillator 1 mark each point

parameters RC Oscillator LC oscillator

Voltage gain More Less

Oscillator frequency LOW HIGH

Components used Resistors and Capacitors Inductors and Capacitors

Applications Function generators Radio receivers, TV




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f) Full adder is the circuit which adds two binary bits along with carry generated from previous stage of adder. -1 Mark

Logic diagram 2 Marks

Truth Table of full adder 1-Mark

Cn-1 B A Sum Carry Out

0 0 0 0 0

0 0 1 1 0

0 1 0 1 0

0 1 1 0 1

1 0 0 1 0

1 0 1 0 1

1 1 0 0 1

1 1 1 1 1

Q. 3 a) Comparison of RC coupling and transformer coupling (1 mark for each point)

Point RC coupling Transformer coupling

Coupling element Resistor (R) & Capacitor (C) Transformer

Distortion Low Frequency distortion is present

Voltage gain Low High

Application AF amplifier, PA system, RF amplifier, Power Amp




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b) Logic symbol ( 1 mark each) Truth table (1 mark each)

2 input NAND gate

Logic symbol

Truth table

2 input EXOR logic gate

Logic symbol

Truth table

Input Output

A B Y

0 0 0

0 1 1

1 0 1

1 1 0

Input Output

A B Y

0 0 1

0 1 1

1 0 1

1 1 0




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C) JK flip flop[ using NAND gate (2 marks)

Race around condition : ( 2 marks)

- Race around condition occurs when all inputs of J-K flip flop are 1 ( J=K=CLK=1).

- J-K flip flop keep toggling indefinitely as long as J=K=CLK=1 and that condition is known as race around condition.

d) Logic circuit for 4:1 multiplexer (2marks)




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Truth Table ( 2 Marks)

Select Input Output

S1 S0 Y

0 0 d [0]

0 1 d [1]

1 0 d [2]

1 1 d [3]

e) Comparison of electrical & mechanical transducer (1 mark for each point)

Point Electrical Transducer Mechanical Transducer

Power supply requirement Required Not required

Reliability High Low

Life time More Less

Example LDR, PHOTODIODE, Solar cell

Mechanical flow meter, Bourdon tube, galvanometer

f) Functions robotics system: ( 2 marks)

- It is used to perform variety of task like moving material, parts, tools etc .

- It can also be used to perform a dedicated task through variable programming.

Applications robotics system ( any 2)

- Pick and place robots

- Mobile robot

- Industrial robot ( Manipulating)

- Android




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Q . 4) Attempt any four of the following

a) Advance vehicle condition system (AVCS): ( 1 mark for each point)

- AVCS technology combines various technologies like ABS, collision warning, automatic cruise control etc to provide full vehicle automation.

- It significantly enhances the transportation safety and capacity of highway.

- It also improves the driver behavior in risky situations by providing warnings, speed controls, intelligent cruise control etc.

- In AVCS driver is replaced by full automatic steering of vehicles which helps to reduce accident and increase traffic flow.

Advance vehicle control system

b) Circuit diagram of single stage transistor amplifier (2 marks)

Requirements ( ½ marks for each point)

1) Biasing resistors (R1,R2) are required to biased the transistor in active region

2) Input & output Coupling capacitor ( C1 & C2) are used to couple the AC signal to input terminal & to load respectively.

3) Emitter bypass Capacitor ( CE) used to bypass emitter resistor for AC condition.




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4) High value Emitter resister RE for high Q point stability under DC operating condition.

c) Block diagram of PLC (2 Marks)

Functions: (1/2 marks each)

1) Input Module: Input can be digital or analog depends on process required. This module converts input quantity into CPU compatible signal.

2) CPU: It performs the function of controlling all operation of PLC like execution of operating system, memory management, monitoring input and output. It contains microprocessor which can be programmed as per requirement.

3) Memory: It is the part of CPU which stores both the program and data from equipment connected to PLC. ROM is used to store operating system and Ram is used to store user’s data/program.

4) Output Module: Various output modules are connected to output device depending upon the process. It can be actuator which can be ON or OFF based on input situations. Example: motor, timer, solenoid etc.

d) Data Logger : (2 marks)

- It automatically records the readings of instruments that are located at different parts of plant.

- It measures the output of transducer and logs that reading automatically.




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- It also perform the various functions like scanning, signal conditioning, recording.

- It perform the recording more quickly & accurately.

Applications: ( any 4 applications, 1 mark each)

- Refrigeration and Freezer (including Food & Medical Storage and Transportation) - Agriculture, Horticulture, Environmental Studies - Server Room Monitoring - Industrial Processes

e) Block diagram of multichannel DAS (4 marks)

f) Comparison of PN junction diode and Zener diode ( 1 mark for each point)

Point PN junction diode Zener diode

Direction of conduction Forward Reverse

Application Rectifier Voltage regulator

Reverse breakdown Occur Does not occur

Symbol




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5 a. AC signal Conditioning: It is the process used in instrumentation and measurement

system to modify or improve output of the various transducers. Improvement of signal

is necessary so as to make them useful and compatible with the measuring system. It

consists of number of circuits or blocks.

Types of circuits used in AC signal Conditioning

a) Calibration and zeroing network (offset nullifying circuit)

b) AC amplifier

c) Phase detector

d) Low pass filter

e) Power supply

2

2

b. Selection Criteria for transducers: (Any eight points)

a) Nature and range of the physical parameter to be measured.

b) Type of the physical quantity.

c) Transducer should be compatible with measuring system.

d) Performance of the transducer should be linear.

e) Performance of the transducer should be stable under operating conditions.

f) Transducer should have high sensitivity

g) Transducer should have high accuracy

h) Transducer should have better repeatability.

i) It should have high input impedance and low output impedance to avoid the

loading effect.

j) Transducer should be free from drift, noise and offset problems.

k) Transducer should have flat frequency response.

l) Transducer should be easily available at low cost in the market with essential

accessories for its installation.

m) Transducer should be portable and light in weight.

n) Any other relevant and accurate criteria may be considered.

½ * 8




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Q.N

o

Model Answer/Solution Mark

s

5 c. Comparison of BJT and FET

Parameter BJT FET

Terminals It has three terminals Emitter,

Base and Collector

It has four terminals

Drain ,Gate, Source

and Substrate {Body}

Type’s Two types NPN and PNP Two Types JFET and

MOSFET and/or N-

channel and P-channel

Input impedance Input junction is forward biased

so input impedance is very

low.

Input junction is reverse

biased so input

impedance is very high.

Controlling factor Output current is controlled by

input current so current

controlled device

Output current is

controlled by input [gate]

voltage so Voltage

controlled device

01

01

01

01

d

.

Optocoupler: It is a combination of photo (light) source and photo sensor

(detector) in a same package. They are used to couple the signal from one point

to other point optically with electrical isolation.

Advantages: [minimum 4]

a) No electrical connection between input and output.

b) Optical section controls output signal and ultimately the load.

c) No effect of electromagnetic interference.

d) No possibility of feedback voltage

e) It provides more stability

f) High reliability

g) Output is TTL compatible

h) Large bandwidth

i) Good frequency response

02

½ * 4

e. Comparison of microprocessor and microcontroller

Parameter Microprocessor Microcontroller

Components It is a CPU It consists of CPU, RAM,

ROM, I/O ports, timer,

Converters

Access time High Less

Number of opcodes Less More

Hardware required RAM, ROM, I/O ports, timer,

converters externally.

In built

01

01

01

01




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Q.No Model Answer/Solution Marks

5 f. Doping:- A process of adding impurity to a pure semiconductor is known

as

Doping.

For forming p-type semiconductor trivalent impurity such as Gallium is

added. And

For forming n-type semiconductor pentavalent impurity such as is Arsenic

added.

02

01

01

6 Attempt any FOUR of the Following 16

a. Block diagram of regulated power supply

vin

ac

04 M

waveforms

are also

shown to

each

block

b. Load Regulation:-

It is the rate of change of output voltage with respect to

change in load resistance. It shows the change in output voltage with

change in value of load resistance or load current. It is always calculated

in percentage.

Line Regulation :- It is the rate of change of output voltage with respect to

change in input voltage{line voltage}. It shows the change in output

voltage with change in input ac voltage. It is also calculated in percentage.

02

02

c. Barkhausen’s Criteria :-

Barkhausen’s criterion is applicable for oscillators.

02

Step down

Transformer

Rectifier

RECTIFIER

FILTER

Voltage

Regulator

REGULATOR

DC

output




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According to this criteria the circuit has to satisfy two conditions

First:- the total phase shift given by the circuit should be 3600 or 0

0. And

Second :- The factor A should be less than equal to one.

Positive type feedback is used in osciilator’s.

Oscillators

Sinusoidal Non

sinusoidal

Low frequency High frequency

Wein bridge oscillator Hartley oscillator

RC phase shift oscillator Colpitts oscillator

Crystal oscillator

01

01

Q.No Model Answer/Solution Marks

6 d. Different triggering methods.

There are two types of triggering methods

I] Level trigger II] Edge trigger

Level triggering is of two types

A] positive level triggering B] Negative level triggering

clk Clk

clk

o/p clk o/p

o/p changes on logic’1’ level of clk o/p changes on logic’0’

level of clk

Edge trigger are also of two types

A] Positive edge trigger{Rising Edge} B] Negative edge

trigger{falling/tralling}

clk

clk o/p

o/p

o/p changes when clk goes from 0 to1 o/p changes when clk goes

from 1 to0

1/2 for

each

method

and

1/2 for

each

waveform

½*4=2M

for

methods

and

½*4=2M

for

waveforms

FF

FF

FF FF




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e. Selection factors for PLC

a) Type of PLC: Analog or Digital

b) Number of inputs and outputs to PLC

c) Operating voltage and operating current range

d) Scan time of PLC

e) Memory size of PLC

f) Type of memory of PLC

g) Type of programming

h) Reliability of PLC

i) Flexibility of PLC

j) Any other relevant and accurate point

½*8=4M

6 f. Decade Counter

For decade counter number of Flipflops required are 2N

>= count

So 24 > 10{decade} so for decade counter 4 flipflops are required but 4

flopflops will count total 16 clock pulses so 6 clock pulses are eliminated

by using external logic.

Synchronous Counter

LOGIC ‘1’

J0 Q0 J1 Q1 J2 Q2 J3 Q3

Clk K0 K1 K2 K3

cl cl cl cl

Q0 Q1 Q2 Q3

Input connection-

J0= K0=1 , J1= Q0 Q3

K1= Q0

J2 =K2= Q0Q1

J3= Q0Q1Q2

K3= Q0

02

Q0Q1Q2 Q0Q1 Q0

Q1 Q2




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OR

Asynchronous Counter

Logic’1’

T0 Q0 T1 Q1 T2 Q2 T3

Q3

Clk

Q0 Q1 Q2

Instead of active low clear control signal one may show active high

clear and AND gate is used.

Truth Table for decade counter

Clk Q3 Q2 Q1 Q0

0 0 0 0 0

1 0 0 0 1

2 0 0 1 0

3 0 0 1 1

4 0 1 0 0

5 0 1 0 1

6 0 1 1 0

7 0 1 1 1

8 1 0 0 0

9 1 0 0 1

02

Q3

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