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Diploma in Electronics - CP04
Instructors’ Practical Manual
V semester
Industrial Electronics-I
LIST OF EXPERIMENTS
PAGE NO
1. FAMILIARISATION OF DIGITAL STORAGE OSCILLOSCOPE 01
2. FAMILIARISATION OF CURRENT PROBE AND AMPLIFIER 05
3. TRANSISTER SWITCHING CHARACTERISTICS 08
4. MOSFET SWITCHING CHARECTERISTICS 13
5. MAGNTISATION OF RL LOAD & DEMAGNETISATION USING
i. DIODE 19
ii. DIODE&RESISTER 23
iii. DIODE&ZENER 27
6. MAGNETISATION OF L LOAD & DEMAGNETISATION USING
a. DIODE 31
b. DIODE & RESISTOR 35
c. DIODE & ZENER 39
7. FAMILIARISATION OF PWM IC SG3524 43
8. INDUCTOR DESIGN 47
9. BUCK CONVERTER 53
10. FAMILIARISATION OF IC TCA785 60
FAMILIARIZATION OF DIGITAL
STORAGE OSCILLOSCOPE
OBJECTIVES
To get familiarized with DSO and its front panel controls.
EQUIPMENTS REQUIRED
SlNo Equipment Model Specification Quantity
01 DSO Tektronix 60MHz 1
02 Probe Tektronix 7A 1
HOW TO USE IT?
Tektronix TDS 350 two channel oscilloscope are digital signal processors and are
superb tools for displaying and measuring and measuring waveforms.
Two input channels, each with a record length of 1000 samples an 8-bit vertical
resolution .both channels acquire wave forms simultaneously.
1 Giga samples/second maximum sample rate (TDS500):500 Mega
samples/second maximum sample rate: 200 Mega samples/second (TDS320).
200 MHz analog band width and fastest time base setting of 2.5ns/div (TDS350).
A full compliment of advanced functions including on-screen read out.
Auto set cursors and continuously updated automatic measurements
Wave form averaging, wave form enveloping and hardware peak detection
A unique graphical user interface (GUI) and a logical front panel layout which combine
to deliver the standard in usability pioneered by the TDS family of oscilloscopes.
COMPENSATING A PROBE
Use the following procedure:
Attach the probe BNC connector to channel and attach the probe HP to the probe
comp output signal. Press auto reset.
Check that wave form indicates correct compensation. If the wave form indicates over or
under compensation, use alignment tool provided with the probe to adjust the
compensation.
FRONT PANEL
AUTOSET
Feature produces a stable triggered display of almost any signal .Two use auto
set; connect a signal to either ch1 or ch2.
CLEAR MANU
This button clears all menus from the screen.
VERTICAL CONTROL
The vertical knob controls the vertical position of the presently selected
waveforms.
The vertical menu button calls up the vertical operation menu.
The vertical volts/div knob controls the vertical scale of the presently
selected waveform.
The waveform OFF button turns off the presently selected waveforms.
HORIZONTAL CONTROL
The horizontal position knob controls the horizontal position of all
waveforms.
The sec/div knob controls the horizontal scale of active waveforms.
TRIGGER
The trigger level knob controls the trigger.
The force trigger button forces the oscilloscope to start acquiring a
waveform regardless of whether a trigger event occurs. The button has no
effect if the acquisition system is stopped.
The set level to 50 % button sets the trigger level at the half way point
between the peaks of the trigger signal.
The trigger status lights indicate the status of the triggering system.
The ready light illuminates when the instrument can accept a valid trigger
and is waiting for the event to occur.
MISCELLANEOUS CONTROLS
The general purpose knob controls the many side menu functions
including the cursor. The toggle button switches control from cursor to
cursor.
The rum/stop button starts and stops acquisition.
The Measure button calls up the automated measurement menu.
The acquire button calls up the acquisition menu.
The save/recall setup button calls up the save/recall setup.
LOGIC CONVENTIONS
This refers to digital logic circuits with standard logic symbols and
terms. Unless otherwise started all logic functions are described using the
positive logic convention. The more positive of two logic levels is the high
(1) state and more negative level is the low (0) state signal states may also
be described as “true” meaning their active state or “false” meaning their
non active state. The specific voltages that constitute a high or low state
vary among the electronic devices.
FAMILIARISATION OF
CURRENT PROBE AND CURRENT AMPLIFIER
OBJECTIVES
To familiarize with current probe amplifier and its front panel controls.
EQUIPMENTS REQUIRED:
Slno Equipment Model Specification Quantity
01 Current probe Tektronix 20 A AC/ DC 1
02 Current probe amplifier Tektronix 50Mhz 1
03 DSO Tektronix 50Mhz 1
HOW TO USE IT?
The A6302 is DC to 50Mhz current probe designed for use with AM503 family
of current probe amplifier .The A6302 can measure current up to 20A(DC+ peak AC)
and up to 50A peak current.
The slide must be locked to accurately measure current or degauss the probe. If a probe is
unlocked; the probe open indicator on the amplifier will light.
DEGAUSSING AND AUTOBALANCING OF CURRENT PROBE
Verify that current probe is connected to the amplifier.
Remove the current probe from the conductor under test.
Lock the probe slide closed.
Press the amplifier probe degauss auto balance button.
NOTE: The degauss procedure will fail if the amplifier is not properly connected to a 50
ohm termination impedance.
Why degauss the current probes:
Degaussing the probe removes any residual magnetization from the probe core such
residual magnetization can induce measurement error. Auto balancing removes unwanted
dc offset in the amplifier circuitry. Failure to degauss the probe is a leading cause of
measurement error.
MAXIMUM CURRENT LIMITS
Exceeding any of these rating can saturate the probe core and cause measurement error.
Maximum continuous current error refers to the maximum current that can be
continuously measured at DC or at a specified AC frequency the maximum
continuous current value is de rated with frequency. As the frequency increase
maximum continuous current value or rating decreases.
Maximum pulsed current refers to the maximum peak value of pulsed current the
probe can accurately measured, regardless of how short the pulse duration is.
Ampere-second product defines the maximum width of pulsed current that you
can measure when the pulse amplitude is between the maximum continuous and
maximum pulsed current specifications. The maximum continuous specifications
it itself varies by frequency.
To determine if your measurement exceeds the ampere-second
Product, perform either procedure A or B.
PROCEDURE A
To determine the maximum allowable pulse width, measure the peak current of the
pulse divide the ampere-second specification of your probe by the measured peak current
of the pulse. The quotient is the maximum allowable pulse width; the pulse width at the
50% point of the measured signal must be less than this value.
PROCEDURE B
To determine the maximum allowable pulse amplitude measures the pulse width at
50% points. Divide the ampere-second (or ampere-microsecond) specification of your
probe by the pulse width .The quotient is the maximum allowable current: the peak
amplitude of the measured pulse must be less than this value.
After degaussing the probe connect the probe to current amplifier. Set the DSO volts
per division to 10mV. Adjust the reference of the current amplifier by keeping the
coupling in reference position. Lock the probe and change the coupling to either dc or
ac depending on the current flow in the conductor. Adjust the ampere per division of
current probe amplifier. Measure the current on the DSO.
SWITCHING CHARACTERSTICS OF A TRANSISTOR
OBJECTIVE
To design a switch using a transistor.
Find rise time, fall time, delay time and storage time.
BILL OF MATERIALS
Sl no: Component Specification Value Quantity
1 Transistor BD139 Ic=1.5A,60v 1
2 Resistor R1 ½W CFR 200 ohm 1
3 R2 2W CFR 20 ohm 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement
systems
0-30v,2A
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
CIRCUIT THEORY
The above circuit is a base bias circuit, which is designed to operate transistor
in saturation and cut off. This is used in switching application.
When base drive is zero, the switch is open. There is no drop across collector
resistor and the entire supply voltage drop across collector-emitter terminals. Since the
beta of the transistor varies commonly to make sure that the circuit will work in the
saturation it is designed in the hard saturation. Even if the beta changes for a long range
the circuit will remain in the hard saturation.
On time of the transistor= Rise time + Delay Time
Off time of the transistor= Fall time + Storage time
DESIGN
To design the transistor as a switch for a current of 0.5A.
Icsat =0.5A
Icsat = Vcc / Rc
Let Vcc = 10V
Then Rc = 10/0.5A
= 20 Ohms
Since the circuit should work in the hard saturation the ratio of the Rb verses Rc
should be 10:1
Therefore Rb = 200 Ohms
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 100µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the Current and Voltage waveforms.
Measure rise time, fall time, delay time and storage time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
Rise time=
Fall time=
Delay time=
Storage time =
SWITCHING CHARACTERISTICS OF MOSFET
OBJECTIVE:
To study the switching characteristics of MOSFET.
To measure On time (Ton ) and Off time (Toff ) of the MOSFET.
BILL OF MATERIALS
Slno Component Specification Value Quantity
01 MOSFET IRF 640 18 A,200V 1
02 Resistor R1 ½w CFR 50 ohm 1
03 R2 2w CFR 10 ohm 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement
systems
0-30v,2A
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
CIRCUIT THEORY
With gate current Ig gate source capacitor is charged , once this capacitor is charged
to some extend the mosfet will start conducting , even with Ig , Cgs is getting charged Vgs
remains constant , because Cgd is getting discharged , after this Vgs starts increasing.
The above mentioned properties can be seen in the current wave forms using CPA.
Characteristics of MOSFET:
The MOSFET is preferred in most of the switching circuits because of it’s very
less gate current.
It is a voltage controlled device.
The driving circuit is easy to design.
Switching time is faster.
All these characteristics of the MOSFET make it more useful for the high
frequency switching applications.
The working of the MOSFET is mainly related to the capacitors between Cgs and Cgd.
They are available in two types they are enhancement mode and depletion mode, the
enhancement mode is more preferred because of the very less reverse current. In this
type when the switch is off there is no channel existing between drain and source.
Main disadvantage is
It is sensitive to the Electro static discharges and may get damaged easily
The Rds (on) (on state drain to source resistance) is high.
NOTE: The MOSFET can be checked using the multimeter by the following steps
Short all the three pins in order to discharge both capacitors.
Check the drain source resistance it should be infinity if the
MOSFET is working.
Keep the multimeter in diode checking mode
Charge the gate - source capacitance by connecting the probes to
gate and source of the MOSFET.
Check for the channel formation between drain and the source.
If the channel is present the resistance will be very less and the
MOSFET is OK
DESIGN:
To design the switch for a current of 1A.
Assume Idsat =1A
Vcc =10V
Calculate Rd
Rd = Vdd / Id
= 10V / 1A
= 10 Ohms
Gate current is Ig+= Qc / Ton
Consider Ton= 1us
Ig+= 63nC / 1 uS
= 63mA
Ig = 2 Ig+
= 2 * 63mA
= 126mA
Rg= Vg- Vgsth / Ig
= 10V – 4V / 126mA
= 47.619 Ohms
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 50us with a frequency of 200 Hz.
Apply the signal to gate of the switch.
Observe the wave form across the switch.
Measure the on time and off time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The On time of the MOSFET is 900ns and Off time is 700 ns.
MAGNETIZATION AND DEMAGNETISATION
OF RL LOADS USING DIODE
OBJECTIVES:
To use a diode for demagnetizing the RL loads.
Study the property of current & voltage through & across the inductor.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core 540µH,0.5A 1
2 Resistor 2w CFR
1/2w
20 ohm,
200ohm
1
1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO TEKTRONIX 50Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement 0-30v,2A
systems
4 Current probe and amplifier Tektronics 50Mhz,20A
CIRCUIT THEORY
In this circuit the inductor is demagnetized by a freewheeling diode. In most of the
commonly used circuits we can see this type of demagnetization. When the inductor
produces the back EMF then the diode gets forward biased and the inductor will be
demagnetized. This diode is commonly known as the free wheeling diode because of it’s
free wheeling action in the circuit. This diode suppresses the huge Back EMF and
protects the switch from damaging.
The inductor is magnetized with a series resistor; the current in the circuit is limited
through series resistor even if the inductor is allowed to go saturation by increasing the
pulse width. The current and voltage change is exponential. At 5T the inductor losses the
property of opposing the changes in current and goes to saturation. When the switch is
turned OFF the inductor reverses its polarity and demagnetizes through diode.
Voltage across inductor is equal to diode voltage plus resistor drop.
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 135µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch and inductor.
Take current probe and see the wave form (current waveform) through all the
components.
Find the demagnetization time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 122µs.
The nature of current waveform is Exponential.
MAGNETIZATION AND DEMAGNETISATION OF RL
LOADS USING DIODE AND RESISTOR
OBJECTIVES:
To use a diode and resistor for demagnetizing the RL loads.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core 540µH,0.5A 1
2 Resistor 2w CFR
1/2w
20 ohm,
200ohm
2
1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement 0-30v,2A
systems
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
CIRCUIT THEORY
In this circuit the inductor in series with the resister is demagnetized through
diode and a series resistor. At 5T the inductor goes to saturation, but due to presence of a
series resistor the current is limited to the finite value.
When the inductor produces the back EMF then the diode gets forward
biased and the inductor will be demagnetized. When the inductor gets demagnetized then
the voltage across the inductor will be diode voltage plus the drop across the resistor (r1)
and resistor (r2). Thus by connecting resistor in series with the diode will reduce the
demagnetization time. The maximum value of the series resistor that can be connected
depends on the breakdown voltage of the switch.
CALCULATIONS
T=L/R
=540µH / 20ohm
=27µs
So, 5T=135µs
Demagnetizing voltage across inductor is
VL=Vd+Vr1+Vr2
= 1 + 10 + 10
= 21v
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 135µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch.
Take current probe and see the current waveform through all the components.
Find the demagnetization time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 64µs.
DEMAGNETISATION OF RL LOADS
USING DIODE AND ZENER DIODE
OBJECTIVES
To use a diode and zener diode for demagnetizing the RL loads.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core 540µH,0.5A 1
2 Resistor 2W,CFR 20 ohm,
200ohm
1
1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
5 Zener diode 15v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement 0-30v,2A
systems
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
CIRCUIT THEORY
In this circuit the inductor in series with the resister is demagnetized by using diode
and zener diode. At 5T the inductor goes to saturation, but due to presence of a series
resistor the current is limited to the finite value i.e. 1A.
When the inductor gets demagnetized then the voltage across the inductor will be
diode voltage plus the drop across the resistor (r1) and break down voltage (Vz) of the
zener. Thus by connecting zener diode in series with the diode will reduce the
demagnetization time.
CALCULATIONS
T=L/R
=540µH/20ohm
=27µs
So, 5T=135µs
Demagnetizing voltage across inductor is
VL=Vd+Vr1+Vz
= 1 + 10 + 15
= 26v
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 135µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch.
Take current probe and see the current waveform through all the components.
Find the demagnetization time from the waveform.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 51µs.
MAGNETIZATION AND DEMAGNETIZATION
OF INDUCTOR USING DIODE
OBJECTIVES
To use a diode for demagnetizing the inductor.
To study the property of current & voltage, through & across the inductor.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core 540µH,0.5A 1
2 Resistor ½ W,CFR 200ohm 1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 Digital Storage Oscilloscope Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement 0-30v,2A
systems
4 Current probe and amplifier Tektronics 0-20A DC/AC,
60Mhz
CIRCUIT THEORY
In this circuit the inductor is magnetized by turning on the switch for a short
period of time. Here the inductor is not allowed to go to saturation since there is no
resistance to limit the current. The only resistance in the circuit is coil resistance which is
less than 1ohm.If the magnetizing time is increased the current shoots up to a very high
value and burns the inductor.
When the inductor produces the back EMF then the diode gets forward
biased and the inductor will be demagnetized. This diode suppresses the huge Back EMF
and protects the switch from damaging. In this the demagnetizing time of the inductor
will be more. When the inductor gets demagnetized then the voltage across the inductor
will be 0.7V which makes the demagnetizing time more. The magnetizing and
demagnetizing current is linear.
Since the pulse width is less the voltage across the inductor will be constant.
CALCULATION
E= L I / Ton
10v = 540µh X 0.5A / Ton
Ton=27µs
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 27µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch.
Take current probe and see the current waveform through all the components.
Find the demagnetization time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 270µs.
The nature of current waveform is linear.
MAGNETIZATION AND DEMAGNETIZATION
OF INDUCTOR USING DIODE AND RESISTOR
OBJECTIVES
To reduce demagnetization time by using resistor in series with diode.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core, 540µH,0.5A 1
2 Resistor ½ w,CFR
1 w
200ohm
20ohm
1
1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 Digital Storage Oscilloscope Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement
systems
0-30v,2A
4 Current probe and amplifier Tektronics 0-20A DC/AC,
60Mhz
CIRCUIT THEORY
In this circuit the inductor is magnetized by turning on the switch for a short
period of time. Here the inductor is not allowed to go to saturation since there is no
resistance to limit the current.
When the inductor produces the back EMF then the diode gets forward
biased and the inductor will be demagnetized. This diode suppresses the huge Back EMF
and protects the switch from damaging. In this the demagnetizing time of the inductor is
reduced due to the addition of series resistor. When the inductor gets demagnetized then
the voltage across the inductor will be equal to diode drop plus the drop across the
resistor. The magnetizing current is linear and the demagnetizing current is exponential
decay due to the addition of resistor.
CALCULATION
E= L I / Ton
10v = 540µh X 0.5A / Ton
Ton=27µs
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 27µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch.
Take current probe and see the current waveform through all the components.
Find the demagnetization time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 20µs.
DEMAGNATISATION OF INDUCTOR
USING TRANSIENT VOLTAGE SUPRESSOR AND DIODE
OBJECTIVES
To reduce demagnetization time by using transient voltage suppressor.
BILL OF MATERIALS
Sl
No:
Component Specification Value Quantity`
1 Inductor Ferrite core 540µH,0.5A 1
2 Resistor ½w 200ohm 1
3 Diode KHF812 2A 1
4 Transistor BD139 1.5A,60v 1
5 Zener diode 15v 1
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement
systems
0-30v,2A
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
CIRCUIT THEORY
Here demagnetization time is reduced using zener diode. This is one of the most
efficient method of demagnetizing the inductor in a very less time. This suppresses the
transients across the inductor when it is getting demagnetized and thus protects the other
components in the circuit.
Here the inductor voltage will be equal to diode voltage plus the breakdown voltage of
the zener. The magnetizing and demagnetizing current is linear and voltage across the
inductor is constant.
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per circuit diagram.
Set the pulse width to 27µs with a frequency of 200 Hz.
Apply the signal to base of the switch.
Observe the wave form across the switch.
Take current probe and see the current waveform through all the components.
Find the demagnetization time.
NOTE:
TYPICAL RESULT FOR THE CIRCUIT USED
The demagnetization time is 18µs.
FAMILIARISATION OF
PULSE-WIDTH MODULATOR IC SG3524
OBJECTIVES:
To familiarize with pulse width modulator IC SG3524.
BILL OF MATERIALS
SLNO Components Specification Value Quantity
1 Capacitors Ceramic disc 0.01µF,.1µF 1,1
2 PWM IC SG3524 40v(max) 1
3 Resistors Carbon film 100Ω 2
4 Trim pot 1K 1
10K 2
EQUIMENTS REQUIRED
Slno: Equipment Model Specification
01 DC supply Measurement
systems
0-30V,2A
02 CRO Scientific 30MHz
CIRCUIT THEORY
The IC 3524 is a PWM generator which can vary the output pulse width according to
the output of an error amplifier. It operates at a fixed frequency that is programmed by
the resistor Rt and one timing capacitor Ct . Rt establishes a constant current for charging
of Ct. we can vary the frequency by varying any of these two components.
The output of the 3524 is given by two transistors which can be connected in any
fashion.
Frequency = 1.3 / Rt * Ct
Rt is in Kohms
Ct is in uF
And the frequency will be in Khz
Rt = 600ohm
Ct = 0.1uF
F = 1.30 / 520 * 0.1 uF
= 25 Khz
The 3524 is having the feature of current limiting in the output through the pins current
sense and current limit.
This IC is having a pin known shut down pin in which if we give a voltage more than
0.8V the IC will shut down by stopping it’s output to zero. This can be used to give a
thermal or short circuit protection.
CIRCUIT DIAGRAM
PROCEDURE
Set the circuit as per the circuit diagram.
Provide required input as Vcc.
Observe the output wave form.
Vary the potential at the pin 2 and observe the variation in the pulse width.
Draw the waveforms.
INDUCTOR DESIGN
OBJECTIVE:
To design an inductor of L= 1mH and current of 1A.
To compare the practical value & theoretical inductance value.
BILL OF MATERIALS
Slno: Components Specification Quantity
01 Ferrite Core RM-8 1
02 Copper wire gauge SWG-24
DESIGN:-
L = 1mh, Irms = 1A, Ip = 1.1A.
Winding factor ( Kw ) = 0.6
Flux Density ( Bmax ) = 0.25
Current Density ( J ) = 4 X 106
Area Product
AcAw = ( L X Ip X Irms ) / (Kw X Bm X J)
= 1mh X 1.1A X 1A X 108
0.6 X 4 X 106 X 0.25
Ap = 0.175cm4
From the core table, selected core is RM - 8
Ac = 0.630
Aw = 0.320
AP = 0.195
Number of turns
N = ( L X Ip ) / ( Bm X Ac )
= 1mH X 1.1 X104
0.25 X 0.630
=70
Length of air gap
lg = 4 X pi X 10 -7 X 70 X 1.1
0.25
= 0.387 mm
Wire guage
Area of the wire = Current / Current density
a = Irms / J
= 1 / 4 X 106
= 0.25 mm2
From the wire guage table 24 SWG is selected.
DESIGN STEPS
Compute the Area product from the given input
Select the core from the core table with the required Ac and Aw.
For the selected core, find Ac and Aw.
Compute the number of turns.
Calculate area of the wire required.
Select the wire guage from the wire table.
Finally calculate the required air gap.
DESCRIPTION:
Inductor designing is a very important task in power electronics
while designing the inductor the value ,max current are the important factor.
Inductor is having the characteristics that it opposes the changes in the current through it.
This opposing characteristic is given by the name reactance. The reactance increases with
the frequency, it’s given by the formula
Reactance = 2*pi* frequency * L
Thus the reactance increases also with the increase in the inductor. The
core of the inductor is also selected by the frequency of operation. When the operating
frequency increases then the size of the inductor comes down. The SWG of the winding
wire is selected by the current carrying capacity of the inductor. As the number of the
turns increases then the inductor value also increases. So according to the inductor value
the number of turns will be designed.
PROCEDURE:-
Get the specification ,and design the inductor using
given the formula.
Collect the material, and start winding the inductor.
After winding measure the value.
Adjust the value of inductance by reducing or increasing
or decreasing the air gap.
RESULT
The Practical value of the inductor is 1.02mH.
BUCK CONVERTER
OBJECTIVES:
To study about the basic DC-DC converter.
To construct a buck regulator for 5V & 1A.
BILL OF MATERIALS
SLNO COMPONENTS SPECIFICATION VALUE Quantity
1. Diode BY 229 10A 1
2. Inductor 1mh 1A rms 1
3. Transistor BD140 60v 1
4. Capacitors Electrolytic 100µF 1
Electrolytic 220µF 1
Ceramic disc 0.01µF,.1µF 1,1
5. PWM IC SG3524 40v(max) 1
6. Resistors Carbon film 100Ω 2
Carbon film 5Ω/5W 1
7. Trim pot 1K 1
10K 2
EQUIPMENTS REQUIRED
Sl
No:
Equipment Model Specification
1 DSO Tektronics 60Mhz
2 Pulse Generator Scientific 20MHz
3 Power Supply Measurement
systems
0-30v,2A
4 Current probe and amplifier Tektronics 0-20A DC/AC,
50Mhz
SPECIFICATIONS:
Input voltage = 10v
Output voltage = 5v
Output current = 1A
Duty cycle = 50%
Ripple voltage = 0.1% of the output voltage
Ripple current = 10 % of the output current
Frequency = 25Khz
CIRCUIT THEORY
Buck converter is a DC to DC converter which can
step down the input voltage given and thus regulates it for the required voltage. It consists an
inductor ,capacitor and a switch as main components. The inductor and the capacitor acts like the
filtering components which stores and supplies the energy to the load. The switch is p-channel
MOSFET.
When the switch is on the inductor and the capacitor gets charged from the supply
and also the load is connected to the input supply. During this time the diode will be reverse biased
and does not conduct any current. When the switch is off then the inductor reverses it’s polarity
and starts discharging this turns the diode to forward bias. When switch is off then the current and
the voltage required for the load will be supplied by the inductor. So when the switch is on the
inductor is getting charged and when it is off the inductor gets discharged. The charging current
and the discharging current of the inductor is the same ,this prevents the inductor going to
saturation. Here the output capacitor is not having so much of importance because no time the load
is driven only by the capacitor.
The main disadvantage of the buck converter is not having isolation between the input
and the output. The buck converter is only used for low power applications.
The output voltage of the buck converter is given by the duty cycle. This is given by the
equation
Vout = Vin * dutycycle
In the given circuit the buck converter is connected with the feedback . For this a
PWM IC3524 is used and the feedback is given through a divider network. As the load varies the
feedback voltage changes and this adjusts the duty cycle and the output voltage is always constant
for all the loads. The supply voltage of the 3524 is the input voltage of the buck converter itself.
The inductor and the capacitor of the buck converter is designed according to the specifications
given. The core of the inductor is selected according to the frequency of operation, and the SWG
of the winding wire is selected by the current carrying capacity of the inductor.
CIRCUIT DIAGRAM
FORMULA’S:
L = [ ( Vin -Vo)Vo *T ] / Vi ∆I
Ton = (∆I *L) / (Vin-Vo)
Toff = (∆I *L) / Vo
∆Vc = ∆I /8 Fc
C=((Vin-Vo)Vo) / (8Vin*F^2*L*C)
DESIGN:
L=1mH, Vin=10V , Vo= 5V, ∆I=0.1A , Irms =1A , ∆Vc =0.1V
T = (Vin*∆I*L) / ( (Vin-Vo)*Vo)
= (10*0.1*1mH) / (5*5)
= 40 μ sec
Ton = (∆I *L) / (Vin-Vo)
= (0.1 * 1mH) / 5
=20 μ sec
Toff = (∆I * L) / Vo
= 20 μ sec
∆Vc = ∆I / 8*F*C
0.1 = 0.1 / (8 * 25Khz *C)
C = 100uF
PROCEDURE:
Set the circuit as per the circuit diagram.
Provide required input.
Check the pulse width and amplitude of the pulse.
Power all the circuits.
Observe the output and measure with DMM.
Observe the waveform on the DSO and plot the waveform.
Calculate line regulation and load regulation.
RESULT
Output voltage = 5.02V
Output current = 1A
Line Regulation = 1%
Load Regulation = 0.5%
FAMILIARISATION OF IC TCA 785
OBJECTIVE
To understand the operation IC TCA 785 for driving SCR’s and
TRAIC’s.
To observe the different waveforms of voltage at various outputs
of TCA 785.
BILL OF MATERIALS
Slno: Components Specification Value Quantity
01. TCA 785 Vs 8-18V 1
02. Resistor Carbon film 1/4W,10K 4
03. Capacitor Ceramic 1nF,47nF 1,1
04. Variable resistor 100K,10K 1,1
EQUIPMENTS REQUIRED
Sl no: Equipment Model Specification
01. Dc supply Measurement systems 0-30v
02. DSO Tektronix 200Ms/S
DESCRIPTION
The synchronization signal is obtained via a high-ohmic resistance from the line
voltage. A zero voltage detector evaluates the zero passages and transfers them to the
synchronization register.
This synchronization register controls a ramp generator, the capacitor C10 of
which is charged by a constant current (determined by R9).If the ramp voltage V 10
exceeds the control voltage V11, a signal is processed to the logic. Dependent on the
magnitude of the control voltage V11, the triggering angle can be shifted within a phase
angle of 0° to 180°.
For every half wave, a positive pulse of approx. 30uS duration appears at the outputs Q1
and Q2.The pulse duration can be prolonged up to 180 ° via a capacitor C12.If pin 12 is
connected to ground, pulses with a duration between ǿ and 180° will result.
Outputs Q1 and Q2 supply the inverse signals of Q1 and Q2.
A signal which corresponds to the NOR link of Q1 and Q2 is available at output QZ (pin
7).
The inhibit input can be used to disable outputs Q1 ,Q2 and q1,q2.Pin 13 can be used to
extent the outputs q1 and q2 to full pulse length(180° -ǿ).
CIRCUIT DIAGRAM
PROCEDURE:
Set the circuit as per the circuit diagram.
Provide required input as Vcc and control voltage.
Observe the output wave form.
Adjust the pot to get the desired output.
RESULT:
Obtained the trigger pulses for triggering the triac circuitry, triggering angle
varying from 0º to 180º with a pulse width of 30µsec.