1 Government Polytechnic, Muzaffarpur ELECTRONIC CONSTRUCTION AND REPAIR LAB Subject Code: 1620407 Experiment:1& 3 Aim of experiment:Construction of a Battery Eliminator Apparatus required AC Plug 15-18V Transformer Full Wave Bridge Rectifier LM317 Voltage Regulator Heat Sink 2200μF electrolytic capacitor 100μF electrolytic capacitor Rotary Switch 240Ω Resistor 48Ω Resistor 336Ω Resistor 624Ω Resistor 912Ω Resistor 1488Ω Resistor (1.5KΩ is fine) 2064Ω Resistor (2KΩ is fine)
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1
Government Polytechnic, Muzaffarpur
ELECTRONIC CONSTRUCTION AND REPAIR LAB
Subject Code: 1620407
Experiment:1& 3
Aim of experiment:Construction of a Battery Eliminator
Apparatus required
AC Plug
15-18V Transformer
Full Wave Bridge Rectifier
LM317 Voltage Regulator
Heat Sink
2200μF electrolytic capacitor
100μF electrolytic capacitor
Rotary Switch
240Ω Resistor
48Ω Resistor
336Ω Resistor
624Ω Resistor
912Ω Resistor
1488Ω Resistor (1.5KΩ is fine)
2064Ω Resistor (2KΩ is fine)
2
Theory of experiment
A battery eliminator is any device which supplies the necessary DC power to a device,
replacing the need for batteries.
For example, say if we have a device that is normally powered by batteries, such as a
calculator. It may receive 4 'AA' or 'AAA' batteries, depending on the calculator. In this
case, the DC voltage that the calculator needs is 6 volts, since 4 'AA' batteries in series adds
up to 6VDC. We can power the calculator without batteries if we supply it with the 6VDC.
So any device which allows us to bypass the use of batteries and power the device still is a
battery eliminator.
Now , we will build a simple, effective battery eliminator which supplies many of the typical
voltages that batteries would, only without the need for batteries.
Resistors Connected to Rotary Switch- We attach resistors to the rotary switch, S1, to create
different voltage outputs at each of the terminals of the switch. We use 48Ω, 336Ω, 624Ω, 912Ω,
1488Ω, and 2064Ω resistors. The reason we use these resistors is because the output voltage
created by the LM317 voltage regulator is produced according to the formula, VOUT= 1.25V (1
+ R2/R1). The recommended resistor value to use for R1 by the manufacturer is 240Ω. So this
resistor value is fixed. To create different output voltages, we vary the value of resistor R2. By
making R2 48Ω, we create 1.5V as output. By making the value 336Ω, we create 3V as output.
By making the value 624Ω, we create 4.5V as output. By making the value 912Ω, we create 6V
as output. By making the value 1488Ω, we create 9V as output. By making the value 2064Ω, we
create 12V as output.
We realize that getting resistors of value 1488Ω and 2064Ω is difficult, so you can get use
1.5KΩ and 2KΩ as replacements to simplify the value.
Again, these resistance values are what create the various output voltages.
Heat sink- One thing we must do to the voltage regulator is attach a heat sink to it. This is vital
for this application.
This is because when we use a regulator, we input a voltage into it and it outputs the voltage,
based on the values of resistor R1 and the resistance value which the rotary switch is connected
to. When the rotary switch is connected to its highest resistance, it doesn't dissipate that much
heat. Since our transformer outputs 15-18V, when the rotary is set to 2.6KΩ, the regulator
outputs 12V. 15-12V=3V. Thus, not that much wasted voltage is created. However, if the
potentiometer is set to 48Ω, the regulator outputs approximately 1.5. 15V-1.5V= 13.5V of
wasted, dissipated energy. This creates a lot of heat, since the voltage difference between input
and output voltage is so great. Any difference appears as heat. So the greater the difference, the
greater the heat. This is the r reason it is vital to attach a heat sink to the regulator. When the
difference between input and output voltage is great, it appears as heat. We must have a way to
dissipate this heat, or else it can damage or destroy the circuitry of the battery eliminator. The
way to do this is to use a heat sink.
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C2 Capacitor- The C2 capacitor acts again as a load balancer. It helps to smooth out any
fluctuations that may exist on the output of the regulator.
And this is how a simple battery eliminator can be built that allows for voltage adjustment.
Conclusion:
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Government Polytechnic, Muzaffarpur
ELECTRONIC CONSTRUCTION AND REPAIR LAB
Subject Code: 1620407
Experiment:1 & 3
Aim of experiment: Construction Assembling of a Stabilizer
Apparatus required
Resistor R1 & R2 = 10KΩ
Resistor R3 = 470KΩ
Variable Resistor = 10KΩ
Capacitor C1 = 1000 µF/25 V
Diode D1 & D2 = 1N 4007
Zener Diode Z1 & Z2 = 4.7 V/ 400mW
Transformer TR1 = 0V - 12 V , 500mA
Transformer TR2 = 9V-0V-9V, 5A.
Op-Amp = LM 741
Transistor = BC 547
Relay = DPDT, 12V, 200Ω.
LED = Red (1)
Voltmeter = 1 Pcs.
Theory of experiment
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A voltage stabilizer is a device which is used to sense inappropriate voltage levels and correct
them to produce a reasonably stable output at the output where the load is connected. Here we
will study the design of a simple automatic mains AC voltage stabilizer which can be applied for
the above purpose. Referring to the figure we find that the whole circuit is configured with the
single op amp IC 741. It becomes the control section of the whole design. The IC is wired as a
comparator, we all know how well this mode suits the IC 741 and other op amps. It's two inputs
are suitable rigged for the said operations. Pin #2 of the IC is clamped to a reference level,
created by the resistor R1 and the zener diode, while pin #3 is applied with the sample voltage
from the transformer or the supply source. This voltage becomes the sensing voltage for the IC
and is directly proportional to the varying AC input of our mains supply. The preset is used to set
the triggering point or the threshold point at which the voltage may be assumed to be dangerous
or inappropriate. We will discuss this in the setting up procedure section. The pin #6 which is the
output of the IC, goes high as soon as pin #3 reaches the set point and activates the
transistor/relay stage. In case the mains voltage crosses a predetermined threshold, the ICs non
inverting detects it and its output immediately goes high, switching ON the transistor and the
relay for the desired actions. The relay, which is a DPDT type of relay, has its contacts wired up
to a transformer, which is an ordinary transformer modified to perform the function of a
stabilizer transformer. It’s primary and secondary windings are interconnected in such a manner
that through appropriate switching of its taps, the transformer is able to add or deduct a certain
magnitude of AC mains voltage and produce the resultant to the output connected load.
The relay contacts are appropriately integrated to the transformer taps for executing the
above actions as per the commands given by the op amp output. So if the input AC voltage tends
to increase a set threshold value, the transformer deducts some voltage and tries to stop the
voltage from reaching dangerous levels and vice versa during low voltage situations.
Circuit Diagram:
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Operation:The proposed simple automatic voltage stabilizer circuit may be set up with the
following steps: Initially do not connect the transformers to the circuit. Using a variable power
supply, power the circuit across C1, the positive goes to the terminal of R1 while the negative
goes to the line of 39 D2’s cathode. Set the voltage to about 12.5 voltage and adjust the preset so
that the output of the IC just becomes high and triggers the relay. Now lowering the voltage to
about 12 volts should make the op amp trip the relay to its original state or make it de-energized.
Repeat and check the relay action by altering the voltage from 12 to 13 volts, which should make
the relay flip flop correspondingly. Your setting up procedure is over. Now you may connect
both the transformer to its appropriate positions with the circuit. Our simple home made mains
voltage stabilizer circuit is ready. When installed, the relay trips whenever the input voltage
crosses 230 volts, bringing the output to 218 volts and keeps this distance continuously as the
voltage reaches higher levels. When the voltage drops back to 225, the relay gets de-energized
pulling the voltage to 238 volts and maintains the difference as the voltage further goes down.
The above action keeps the output to the appliance well between 200 to 250 volts with
fluctuations ranging from 180 to 265 volts.
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Limitation:
When installed, the relay trips whenever the input voltage crosses 230 volts, bringing the
output to 218 volts and keeps this distance continuously as the voltage reaches higher
levels.
When the voltage drops back to 225, the relay gets de-energized pulling the voltage to
238 volts and maintains the difference as the voltage further goes down.
The above action keeps the output to the appliance well between 200 to 250 volts with
fluctuations ranging from 180 to 265 volts.
11
Government Polytechnic, Muzaffarpur
ELECTRONIC CONSTRUCTION AND REPAIR LAB
Subject Code: 1620407
Experiment:2
Aim of experiment: Soldering Practice: Connecting circuit components
Apparatus required
The basic tools that are used for this purpose are
Soldering Iron
Solder Wire [Alloy]
Flux
PCB and the components that are to be soldered
The soldering iron is the heat source tool for the process. It should be of high quality. Of course
the price may increase with the quality, but the soldering will be perfect. Usually a 25 Watt
soldering iron is adequate for the process. A higher watt device may bring too much heat to the
PCB and will surely damage the sensitive components. A lesser watt device may not have
adequate heat and thus is prone to be extensively used. This may also cause extensive heat
damage.
The solder wire is used to fix the components like resistors, capacitors and so on to the PCB in
the given fields. The leads of the devices are connected to the track of the PCB by melting the
soldering wire to the junction. When the heat from the soldering iron touches the soldering wire
it starts melting and this melted wire when introduced to the junction, joins the components to
the track firmly.
The soldering wire is actually an alloy of tin and lead in the ratio 60:40. This is the best ratio that
is considered for soldering in PCB’s. There are other proportions of this alloy and they are
considered low quality as the tin content with respect to lead will be lower.
A high quality solder wire will have a melting point of about 250 degree Celsius and will have a
very high conductivity along with a shiny appearance. When a high quality solder wire is used
to connect the components to the PCB, there is to be no fear of corrosion in future.
Flux is another important component that is used in soldering purposes. It is sealed to the core of
the solder wire before soldering. The flux is used to reduce the surface tension of the solder wire
in its melting point. Thus, it acts as a wetting agent and wets the parts that are to be joined to the
PCB. This also helps in the proper heat transfer from the solder iron to the solder wire.
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Another main use of the flux is to prevent oxidation of both the solder wire and the components
that are added to the PCB. The Tin-Lead alloy that is used as solder wire may have no problem
when attached to copper. But they do not attach so well, when in contact with the oxides of
copper. The oxides of copper mostly form when the temperature is increased for soldering. The
flux can prevent the formation of metal oxide as they are nearly inert at room temperature and
become strongly reduced when the temperature increases. The use of flux causes the rise of
smoke when the soldering process continues. During this time the flux acts as a catalyst and
helps in removing the oxidants and thus cause a better solder joint.
Soldering Technique
Here is the step by step procedure for soldering.
1. By that time the solder iron may get heated to the optimum temperature [250 degree Celsius].
2. Bend the leads of the different devices that are to be connected to the PCB. For a clean bend, the
approximate distance of bend is about 2mm from its body ends.
3. If you are connecting a resistor to the PCB, find its spot and place it into the hole of the PCB.
4. After placing the resistor flip the PCB in such a way that the inserted leads looks towards you.
5. Take the soldering iron in the right hand and the solder wire in the left hand. The solder wire
must be placed on your finger tips with about 3 inches extending from your finger grip.
6. Bring both the solder iron tip and the solder wire tip close to the base of the lead of the resistor
and copper track of the PCB. Make them come in contact at the same instant at the junction.
7. You will notice that the solder wire starts to melt as soon as the contact is made.
8. When the wire starts melting keep pushing it till the joint has been filled up with the molten
alloy.
9. Move away the solder wire and the solder iron simultaneously and allow the molten wire to
solidify. Thus one lead of the resistor has been connected to the PCB. Do the same step for the
other lead and also for all other components.
The setp by step procedure is also shown in the figures given below.
10. Soldering Techniques
11.
13
Precautions to be taken while Soldering
For a good heat transfer, the solder wire and the solder iron must be well cleaned before starting.
It must also be pre-tinned with solder. In order to avoid the overheating of PCB, the components
are usually elevated above the PCB. After the component is inserted in the PCB hole, the excess
lead is cut off, thus leaving a length of about the radius of the pad.
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After soldering, the soldered joints must also be cleaned after it has been solidified.
Some components that are to be soldered may be heat sensitive. For such components a heat sink
may be used on the leads which will reduce the heat transfer to the components. The only
problem is that for such components more heat will be required from the solder iron to complete
the joint.
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Government Polytechnic, Muzaffarpur
ELECTRONIC CONSTRUCTION AND REPAIR LAB
Subject Code: 1620407
Experiment:4
Aim: Assembling Inverter
Theory:
An inverter is a device that changes D.C. voltage into A.C. voltage. A direct current (D.C) is a
current that flows in only one direction, while an alternating current (A.C.) is that which flows in
both positive and negative directions.
The inverter performs the opposite function of a rectifier formed in the late nineteenth century
through the middle of the twentieth century; DC to AC power conversion was accomplished
using rotary converters or motor-generator sets (M-G set).
The origins of electromechanical inverters explain the source of the term inverter. Early A.C to
D.C converters used an induction or synchronous AC motor direct – connected to a generator
(dynamo) so that the generators commutator reversed its connections at exactly the right
moments to produce DC. A later development is the synchronous converter, in which the motor
and generator windings are combined into one armature, with slip rings at one end and a
commutator at the other end only one field frame.
Transformer:
It is an inductively coupled circuit used for transmitting alternating current energy. It is also used
for matching impedance between the generator and the load. It makes use of mutual inductance
in which a current flowing in a coil produces a varying electromagnetic wound over the primary
coil.
Most transformers are used to step-up or step down voltage or current. The number of turns on
the primary winding is usually different form that of Secondary. However, an isolation
transformer provides secondary voltage and current that is same as that of primary voltage and
current, because both winding have the same number of turns, (Expect for resistive losses).
These transformers prevent the transfer of unwanted electrical noise from the primary to the
secondary winding.
The primary and secondary windings of conventional transformer for electronic application are
wound on tubular bobbin (insulated spool that serves as a support for the coil) made of plastic
and other insulated materials. The wound bobbins are then enclosed by iron or steel cores in the
shape of figure start of “E” and “I” shaped laminated metal sheets, assembled through and round
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the wound bobbins. The laminations are then clamped down to form a rigid assembly; some
transformers have plastic shrouds to insulate the windings from the core. Both primary and
secondary windings can be wound on the same bobbin, but it is now common practice, to wind
the primary and secondary windings separately on a split bobbin, to improve electrical isolation.
The primary and secondary terminals may be connected to rigid pins on the bobbin that also
functions as printed circuit board mounting pins.
Mosfet:
Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is a three terminal device they
can be used either as an amplifier or as a switch. MOSFETs are classified as enhancement a
depletion types.
Battery:
It is a d.c. power source to electrical or electronic equipment or devices that make use of it.
Battery is being made available as direct source of energy. It is therefore necessary to select a
reliable battery for optimum performance.
Light Emitting Diode:
It radiates optical energy when forward biased. LED is divided into base on the type of optical
energy it radiates. The visible LED provides a useful means of indicating the state of a circuit
and is therefore used as an indicator. In order to use visible LED as an indicating there is a need for the
use of a protective resistor, which serves as a potential divider as shown below. The invisible/infrared
LED radiates infrared light when forward biased. It is used in conjunction with the photodiode
phototransistor to form a sensing system as in the remote control circuit.
2. INVERTER DESIGN AND CONSTRUCTION
The inverter is a two operation modes device, the inverting and the charging modes. The
inverting mode comprises of the oscillator, the driver, the output (MOSFET) section, the PWM
section, low battery / overload protection circuit, and the transformer. The charging mode
implements the transformer, the FET‟s (internal diodes) and the charging control circuit. A third
operation mode is the changeover modes for switching between the two aforementioned modes
at times of auto-back up for power failure and power restoration for the charging process. This
mode implements a delay circuit, electromagnetic relays and power supply circuit.
3. TRANSFORMER DESIGN
A transformer is a device that couples two AC circuits magnetically and provides electrical isolation
between the circuits while allowing a transformation of voltage and current from one circuit to another i.e.
it is mainly used for voltage and current transformation .
The Generated E.M.F in a Wounded Transformer
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In observing an ideal transformer with secondary opened and the primary connected to a
sinusoidal alternating voltage V1, the potential different causes an alternating current to flow in
the primary since primary coil is purely inductive and has no output but draw the magnetizing
current I only .And this I will function as to magnetized the core in the secondary .It is small in
and lag voltage V1 by 900. It therefore produces an alternating flux that is proportional to the
current inputs. This flux is linked by both primary and secondary windings .Thus; this leakage(s)
produced a mutually induced e.m.f E2 in secondary winding that anti-phase with V1 and has
magnitude proportional to rate of change of flux and the number of secondary turns.
Let N1=Number of turns in primary, N2=number of turns in secondary
The transformation ratio, K= N1/N2
The equation for the voltage and current transformation of a transformer is given by K= V2/V1= I1/I2
F=Frequency of A.C input (Hz)
Maximum flux in core (Webbers) =B*A
Average rate of change of flux =maximum. Flux divided by 1/4F. (Wb/s or Volt.)
Now rate of change of flux per turn means induced e .m .f in Volt
Thus Average e.m. f /turn =4*F*max. Flux
Since the flux is sinusoidal
r.m.s =form factor*Average e.m.f /turn
But form factor =r.m.s value /Average value=1.11,
Then r.m.s value of E.m.f =1.11*4F*max. Flux =4.44F*max. Flux ,
But max .flux =Bm*A r.m.s value of E.m .f in primary turn (Tp) =4.44F*Bm*A*Tp
NOTE: Bm is assumed to be 15000Wb/m. F=50 Hz By introducing stacking factor (10-8) and Tp
factor (0.9) then we have Number of turns per volt, NT.V-1= 7/A
But form factor =r.m.s value /Average value=1.11, Then r.m.s value of E.m.f =1.11*4F*max. Flux
=4.44F*max. Flux , But max .flux =Bm*A r.m.s value of E.m .f in primary turn (Tp)
=4.44F*Bm*A*Tp NOTE: Bm is assumed to be 15000Wb/m. F=50 Hz By introducing stacking
factor (10-8) and Tp factor (0.9) then we have Number of turns per volt, NT.V-1= 7/A
4. CHOICE OF TRANSFORMER’S COMPONENTS
The power Rating for the Inverter transformer (KVA) =1.0KA , E2=12V
Assuming the efficiency of transformer =85%
Then Input rating =output /Efficiency=1000VA/0.85=1176VA
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Ip = PI / VP VP = 260V
Ip = 1176 / 260 = 4.5A
Is = Po / Vs Vs = 12V
Ip = 1000 / 12 = 83.3A
5. 50 Hz FREQUENCY OSCILLATOR SECTION
The generation of 50 Hz frequency by the oscillator section is based on the application of a
PWM controller IC SG3524
6. SG3524 DESCRIPTION
7. THEORY OF OPERATION
Voltage Reference
An internal series regulator provides a nominal 5V output which is used both to generate a
reference voltage and is the regulated source for all the internal timing and control circuitry. This
reference regulator may be used as a 5V source for other circuitry. It provide up to 50mA of
current itself and can easily be expanded to higher current with an external PNP
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Oscillator
The oscillator in the SG3524 uses an external resistor (RT) to establish a constant charging
current into an external capacitor (CT). While this uses more current than a series-connected RC,
it provides a linear ramp voltage on the capacitor which is also used as a reference for the
comparator.
8. THE OSCILLATOR SECTION
The schematic diagram of the oscillatory section is as shown in fig. 2. IC1 SG3524 is used to
generate the 50 Hz frequency required to generate AC supply by the inverter. Battery supply is
connected to the pin-15. Pin-8 of the IC1 is connected to negative terminal of the battery. Pin-6
and 7 of IC1 are oscillator section pins.
9. DRIVER SECTION
MOS drive signal from pin-11 and 14 of IC1 are coupled to base of transistors T1 and T2. This
result in the separation of the signal into two different channels and an amplification of the signal
to a sufficient level output from the transistors emitter. The resulting MOS drive signal at emitter
of T1 and T2 is coupled to the gate of each MOSFET in the first and second MOSFET channels
respectively. The driver section made up of T1 and T2 circuit is incorporated into the oscillator
Fig 2. Oscillator Circuit Diagram
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10. OUTPUT SECTION
The 50Hz alternating MOS drive signal reaching the MOSFET channel separately results in the
channels being alternatively ON and OFF. Drain (D) of all the MOSFET of one channel is
connected together and one end of the inverter bifilar winding is connected to this connection.
The same is done to the second channel and the other end of the inverters winding. Positive
terminal of the battery is connected to the centre tapping of the bifilar winding. Source (S)
terminal of each MOSFET is connected to the negative terminal of the battery. Because polarity
of the 50Hz MOS drive signal at pin-11 and 14 are alternatively different, current flows through
the first half and second half of the transformer‟s bifilar winding alternatively.
Fig.3. Output Section Change Over Circuit
The alternating current flowing will induce an AC current of 50Hz in the 260V tapping of the
transformer. This tapping is connected to N/O-2 terminal of relay. When the AC mains is not available,
pole P-2 of the relay is connected to N/O-2 terminal and thus the AC voltage produced by the inverter
reaches the inverter output socket. The output section changeover circuit is as shown in fig. (3).
11. PULSE WIDTH MODULATION PWM SECTION
PWM is used to keep the inverter output to a constant 220V AC irrespective of a change in the load value
connected to the inverter output socket. PWM is realized by feeding back the AC supply generated by the
inverter to the PWM IC1 to keep the pulse width output from pin-11 and 14 constant. To provide
feedback to the PWM controller IC, a bridge rectifier circuit made of four diodes (D2, D3, D4 and D5) is
21
connected to the drain of the MOSFET channels. The DC voltage from the bridge rectifier is filtered by a
10μF capacitor and given to pin-1 of PWM IC through a potential divider circuit made of 10k and PWM
adjustment preset VR2. The PWM circuit has also been incorporated into the oscillator schematic
diagram as shown in fig. (2). Pin-1, 2 and 9 are three pins of an internal Op-Amp, pin-1 and 2 are input
pins and pin-9 is the output pin. Pin-1 is given the feedback signal; pin-2 is given 2.5V regulated supply
as reference voltage through voltage divider circuit of two 10K resistors. The reference voltage is taken
from pin-16 of the PWM IC1. Pin-9 is internally connected to the section that controls the width of the
oscillating frequency. Change in signal at pin-9 will result in a change in the width of the output
frequency and this will always bring back the inverter output to its original 220V.
12. LOW BATTERY / OVERLOAD PROTECTION CIRCUIT
The low battery and overload protection circuit is a protection circuitry that protects the
battery from being over drain and inverter‟s transformer and MOSFET from being damaged
respectively. The low battery and overload shutdown circuit are built upon Op-Amp
comparator application.
Overload Protection Circuit
The overload protection circuit uses two Op-Amps A and C made of pin-6, 7, 1 and pin-10,
11 13 of IC2 (LM339) respectively
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Battery Charging Control Section
In this mode, the inverter transformer works as a step-down transformer and output 12V at
its secondary winding. During charging, MOSFET at the output section works as rectifier
(due to internal diodes), the drain being the cathode and the source as anode. The center
tapping of the transformer is connected to the positive terminal of the battery and the
MOSFET source is connected to negative terminal of the battery. When the inverter receives
AC mains supply, inverter transformer and MOSFET together works as a charger and
charge the battery.
The battery charging control circuit is as shown in fig. 7. In other to protect the battery from
being over charge and the MOSFET from sudden surge current at the start of charging when
power is restored, two other circuits are incorporated; the soft start section and charging
voltage sensing sections.
13. CHARGING VOLTAGE SENSING SECTION
The charging voltage sensing section makes use of Op-Amp A and B of IC3 (LM393), SCR Q2,
transistors T6 and T7. Pin-2 and 6 of IC3 is given a constant reference voltage of 5.6V through 47k
resistor. Pin-3 is given positive supply from the battery through divider circuit of 5k and 7k resistor.
When the charging battery voltage is below 12V, pin-2 voltage is higher than pin-3 voltage and thus
Op-Amp A of IC3 ramps low which biases transistor T6. The voltage at the collector of T6 provides
the trigger current IT for SCR Q2 through 1k resistor. Q2 switches ON (conduct) and 8V battery
charging signal is available at cathode used for the following;
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Once Q2 is fired, charging continues until the voltage at pin-5 of IC3 passes a voltage level
of 5.6V when the battery is charged beyond 14.5V. At charging battery Volt of 14.5V, pin-5
of IC3 becomes more positive than pin-6 thus op-amp B ramps high to bias transistor T7.
The switching of T7 reduces the holding current IH of Q2 to zero and Q2 stops conducting.
Q2 remains in the off state until battery voltage fall below 12V when charging starts again.
Charging continues till 14.5V is reached. In this way, the battery charge is topped at interval
to keep the battery voltage level before power failure. This is incorporated in fig. 6 battery
charging control circuit.
14. CHANGEOVER POWER SUPPLY SECTION
The circuit diagram of the changeover power supply circuit for the relays is shown in fig 7.
The transformer steps the 220Vac voltage down to 12Vac that is rectified by the bridge
rectifier and filtered by the 1000μf capacitor. The supply increases to 16V after filtration.
The supply is regulated by LM7812 to keep the voltage for relay switching constant at 12V.
15. COMPONENTS SELECTION
T2 – 220V/12V 500mA: The 12V transformer in conjunction with the filter capacitor
(1000uf/25V) and regulator (LM7812) guaranteed that 12V was available to switch the relays
when the mains voltage is restored.
Full Wave Rectifier: Four diodes, D1 – D4 (IN4007) were used to convert the ac voltage
available at the secondary of the power supply circuit to dc. The IN4007 diodes are suitable for
the circuit because of its rating (PIV - 1000V, Average Rectified output current for resistive load
– 1A, and Non repetitive peak surge current for one cycle – 30A)
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Filter Capacitor: the 1000μf /25 capacitor is used to filter the ripple levels present in the
rectifier voltage. The values of the capacitor used with a 50Hz supply may range from 100uf –
30,000uf depending on the load current and the degree of smoothening required. In selecting
capacitors, the ripple voltage required is 10% of the peak value. The selection of this capacitor is
based on the following calculation.
17. PERFORMANCE EVALUATION
Table 4.1. Settings on the Inverter
Inverter output voltage
Inverter frequency
Minimum battery voltage
Maximum loading capacity
Minimum A.C. input voltage
Maximum A.C. input voltage
Table 4.2. Load Test
Power (watt)
Voltage (v)
16. MAINTENANCE, SAFETY AND PRECAUTION
1. Dead batteries should not be used with the inverter
2. The battery terminals should not be removed too often. When it is removed, replacement of
correct polarity must be ensured.
3. The inverter must be put in a moderate temperature environment.
4. The inverter should always be shut down when not in use
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5. The inverter should always be partially loaded (not more than 80% of its maximum capacity
will be enough).
6. The use if inductive loads like refrigerator, induction machine e.t.c. on the inverter should be
avoided.
7. The input plug of the inverter should be plugged to a three-pin, properly earthed socked.
18. CONCLUSION
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Government Polytechnic, Muzaffarpur
ELECTRONIC CONSTRUCTION AND REPAIR LAB
Subject Code: 1620407
Experiment:5
Aim:
AC Adapter Troubleshooting and Repair
AC Adapter Testing
AC adapters can easily be tested with a VOM or DMM. The voltage we measure (AC or DC)
will probably be 10-25% higher than the label specification. If we get no reading, wiggle,
squeeze, squish, and otherwise abuse the cord both at the wall wart end and at the device end.
We may be able to get it to make momentary contact and confirm that the adapter itself is
functioning.
The most common problem is one or both conductors breaking internally at one of the ends due
to continuous bending and stretching.
Make sure the outlet is live - check with a lamp.
Make sure any voltage selector switch is set to the correct position. Move it back and forth a
couple of times to make sure the contacts are clean.
If the voltage readings check out for now, then wiggle the cord as above in any case to make sure
the internal wiring is intact - it may be intermittent.
Although it is possible for the adapter to fail in peculiar ways, a satisfactory voltage test should
indicate that the adapter is functioning correctly.
It's also possible that the power jack on the device itself is damaged from use or abuse. If
possible, confirm proper operation with a COMPATIBLE adapter. With battery operated
devices, there is usually a set of contacts that should close when the adapter is removed to
connect the internal battery to the circuitry. If these don't operate properly, the device may not
work off batteries (they may appear to not be charged), the AC adapter, or both. Check the jack
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for obvious signs of damage (cracked, loose, etc.). A squirt of contact cleaner into the jack may
clear up intermittent contact problems not due to actual damage.
AC Adapter Repair
Although the cost of a new adapter is usually modest, repair is often so easy that it makes sense
in any case.
The most common problem (and the only one we will deal with here) is the case of a broken wire
internal to the cable at either the wall wart or device end due to excessive flexing of the cable.
Usually, the point of the break is just at the end of the rubber cable guard. If we flex the cable,
we will probably see that it bends more easily here than elsewhere due to the broken inner conductor. If we are reasonably dextrous, we can cut the cable at this point, strip the wires back
far enough to get to the good copper, and solder the ends together. Insulate completely with
several layers of electrical tape. Make sure we do not interchange the two wires for DC output
adapters! (They are usually marked somehow either with a stripe on the insulator, a thread inside
with one of the conductors, or copper and silver colored conductors. Before you cut, make a note
of the proper hookup just to be sure. Verify polarity after the repair with a voltmeter.
The same procedure can be followed if the break is at the device plug end but we may be able to
buy a replacement plug which has solder or screw terminals rather than attempting to salvage the
old one.
Once the repair is complete, test for correct voltage and polarity before connecting the powered
equipment.
This repair may not be pretty, but it will work fine, is safe, and will last a long time if done
carefully.
If the adapter can be opened - it is assembled with screws rather than being glued together - then
we can run the good part of the cable inside and solder directly to the internal terminals. Again,
verify the polarity before we plug in our expensive equipment.
FAULTS IN RADIO RECEIVER
Aim :
Mension the faults in Radio Receiver and observe the effects on voltage data and performence of the radio receiver.
Equipment needed :
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AC multimeter, radio receiver kit, power supply and connecting wires.
Theory & Procedure :
General faults identified in radio receiver as follows
1. low sound of Radio Band
2. Shortwave working but MW is not working
3. Disturbed and booming sound of radio band
4. Normal sound at low volume level, but distorted output when volume increases.
5. AM band is not working
1. Low Sound of Radio Band :
Due to misalignment of IFTs and related stages components detection diode (OA79) and related
components loose contact or dry solder, check print.
2. SW working but MW is not working :
This problems occurs when band switch point open at MW band position. Properly contact
position should be adjusted to switch position, MW oscillator, MW antenna coil open, moisture
on MW oscillator coil, loose contact or dry solder, check print of PCB.
3. Disturbed and booming sound of Radio Band :
This problem comes when gang capacitor is connected loosly, trimmer loose, band switch loose,
oscillator crip or IFT instable or loose contact or dry solder, check print of PCB.
4. Normal sound at low volume level, but distorted output when volume increases :
Low supply voltage or low current, check for excess to motor, high tension in pinch roller, belt is
Defects in coils and gang capacitor, select switch S1 defective band switch, loose contact or dry
solder, check print of PCB.
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Results :
Stage wise voltages are measured and found the kit is in working condition.
FAULTS IN INVERTER
Aim :
Mension the faults in Radio Receiver and observe the effects on voltage data and performence of the radio receiver.
Equipment needed :
AC multimeter, inverter kit, power supply and connecting wires.
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Inverter
Theory & Procedure :
If the inverter appear to be malfunction following procedure should be followed to eliminate any
external problems.
1.Turn the Inverter “OFF” via the circuit breaker switch on the front panel.
1. Disconnect all AC wiring from the Inverter.
2. Disconnect DC Battery leads from Battery.
3. Clean Terminals (remove all grease and or corrosion on both DC leads and battery terminals
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4. Ensure we have sufficient battery capacity at the nominal voltage (specified on the
compliance label at the rear of our Inverter). Please note: Use minimum 60AH battery or the
size of a substantial car battery.
5. Make connection direct to battery terminals and insure all connections are tight.
6. Ensure battery voltage is within the correct limits as outlined in the section ELECTRICAL &
MECHANICAL SPECIFICATIONS of this manual. If we do not have a DC voltmeter or
multimeter check the front panel for overvolts and undervolts LED’S.
7. Turn the Inverter “ON” via the circuit breaker switch on the front panel. Observe the lights
on the front left of your Inverter. Refer to sections INVERTER OPERATION for
explanation of lights and / or section FAULT FINDING CHART.
8. Plug in various appliances and monitor the Inverters operation.
Important must be remembered
• Remember that it has automatic start with load.
• Make sure leads and terminals are not corroded or faulty in any way.
• Make sure the Inverter goes into Standby with no load switched on.
• Make sure the circuit breaker is reset properly. If unsure switch “OFF” and “ON” again.
• When measuring the AC output of Modified Squarewave Inverters use a TRUE RMS VOLT
METER. Average reading meters will not give an accurate measurement. (240V RMS =
210V average) depending on Battery voltage and load
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Symptom Cause a
Action
No LED on. Is Circuit Breaker switched on? Switch OFF and ON.
No output power. Is input voltage present? Check battery connections.
Was too high DC Voltage left on Inverter ie. from PV If voltage exceeds more than triple the Inverter input voltage, damage
Modules or battery charger may have occurred.
Inverter does not go back to Stand by Inverter senses load present.
Disconnect all loads. Disconnect leads on junction box on back of
mode Green LED does not Inverter.
flash. Auto Start set too low. Turn Auto Start clockwise.
Inverter overloads constantly. Inverter overheated due to a large load being run. Check if case is hot, allow 5 minutes to cool down, reset Inverter via
circuit breaker.
Current draw from battery is excessive due to a short Disconnect all AC 240V wiring from Inverter, check if Green LED
circuit on 240V AC side or load to be started is too flashes .
large.
Fluorescent Lights are used with power factor Remove capacitors (MSW only)
correction capacitors
If any lightning has occurred unit might be damaged. Return to supplier.
Inverter constantly shuts down in Battery voltage below specified limit. Check battery connections and state of charge (should be above SG
undervolts. level of 1220)
Battery voltage drops below limit only when load is Check size of load, might be too large for battery to handle. Check
being connected. connections! Check DC wiring between Inverter and battery for any
defects!
Inverter constantly shuts down in Battery voltage above specified limit. Battery might be overcharged.
This is a circuit of FETVM-FET Volmeter. The function of the VTVM is replaced by the FTEVM while at the same time ridding the usual line cord instrument. This circuit can allow a 0.5 volt scale range because drift rate of FETVM are superior to vacuum tube circuits. Here is the circuit:
The 2N4340 are implemented on this circuit because it has low noise and low leakage.
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v
Vacuum Tube Volt Meter (VTVM)
These types of instruments handle DC voltage, AC voltage, and resistance measurements. In this
type of voltage measuring device electronic amplifier is used in between the input and the meter.
Due to this arrangement the current drawn from the circuit under test is reduced. The range of
resistances used at the input side in range of 1-20 mega ohms. By these resistances variation we
can select the range to be measured. If this instrument uses the vacuum tube in the amplifier then
it is called as vacuum tube voltmeter. These are used in high power AC measurements. As the
invention of solid state devices used in the amplifiers, these type of voltmeters are called FET-
Reset circuit breaker: We need to turn the switch off first and then move it back into the
"On" position. The circuit breaker generally turns off when a circuit has overloaded or short
circuited. Check for loose wires: Often problems such as flickering of lights are caused due to faulty
wiring. Check for any loose wires and replace them. Check the load: In case of a circuit overload, before resetting the circuit breaker, check all
appliances connected into the circuit. If there are too many, shift some to another circuit.
To Replace:
1. Remove fuse or trip circuit breaker to off for the lab or outlet you are replacing.
Test to be sure we have correct circuit by plugging a lamp that we know works into
the receptacle.
2. Unscrew and remove face the plate.
3. Unscrew the mounting screws at top and bottom and pull the unit out.
4. Notice how wires are connected and connect them to the new unit the same way.
All white wires are connected to the side with a silvery color and the black wires to the
brassy terminals.
5. A green grounding wire is connected on newer systems so be sure to reconnect
this wire also. If not and a loose ground wire is present, connect it to the grounding
screw attached to the top of the metal support plate.
6. Reassemble the outlet doing steps above in reverse order.
7. Wrap electrical tape around the entire top, bottom and sides of the outlet so that
when removing it in the future, we have less of a chance of touching wires.
If one of sockets has been scorched, it's usually been caused by overloading or loose
connections in a plug. Don't plug circuit back in without dealing with the problem first or it will
happen again.
1. Safety first
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Never take risks with electrical safety. Modifications to any circuit must comply with the latest IEE Wiring Regulations. New or replacement cables or sockets may need RCD protection.
Zoom: [i mage descripti on]
Step 1
Start by isolating the circuit. Use a socket tester to double-check that it's dead. Unscrew the socket faceplate and pull it away from the wall, but keep the screws in case the new ones don't fit.
Zoom: [i mage descripti on]
Step 2
Loosen the terminal screws and free the cable cores. If the insulation has been heat damaged, cut back the cores and strip the ends. Run green/yellow sleeving over the earth core if it's exposed. As the metal back boxes must be earthed, run a short length of earth cable between the earth terminals of the back box and the faceplate.
Connect the live core or cores to the live terminal (L) of the new faceplate, the neutral to the neutral terminal (N) and the earth to the earth terminal (E or (Earth symbol)). Fully tighten the terminal screws, and fit the new faceplate. If the new screws don't fit the lugs of the old box, just re-use the original screws. Finally, use the socket tester to check you've wired everything correctly.
Precaution:
Use electrical cords only if they are in good condition. Cords must not be cracked, frayed, or
have corroded prongs.
Do not use 3-to-2 prong adapters unless other grounding provisions have been made. Plug 3-
prong plugs into 3-prong outlets.
Use power strips that have circuit breakers or fuses. Do not link power strips in series.
Do not leave cables and cords unsecured and hanging in areas where they can pose a trip and
movement hazard. Place cords so that they are not subjected to mechanical stress or
temperatures that could damage the insulation.
Do not conceal cords behind or attach electrical cords to building surfaces.
Do not leave electrical circuits exposed. Use electrical tape to insulate wires or use a guard as
cover to prevent accidental contact.
Do not block access to electrical panels.
Do not install standard electrical equipment in locations where flammable gases, vapors,
dusts, or other easily ignitable materials are present. If electrical equipment is used in a
chemical fume hood, elevate it to allow efficient air flow.