ELECTRONIC COMPONENTS
1
An easy to use Guide
D.MohanKumar
Circuit designing and assembling is an interesting hobby. A large number of electronic components are now
available in the market. For a beginner, it is very difficult to identify the components through its value and more
difficult task is identification of pin outs. To get an idea about the components we have to search for the data
sheets and books. To overcome such a time consuming task, a ready to use guide is given here. It will guide you
to select the appropriate components and you can easily design a circuit without much effort.
Resistors
As you know the resistor is an inevitable part of a circuit. It is meant for reducing the current and voltage in the
circuit parts. Resistors are identified using the standard colour code chart. A simple trick can be used to identify
the resistor value range. The third colour band on the body of the resistor represents the multiplier value. So by
identifying the third colour, it easy to know the value in range.
Standard colour code
0
1
2
3
4
5
6
7
8
9
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
Third Colour
Gold
Black
Brown
Red
Orange
Yellow
Green
Blue
Value in range
1 Ohm to 9.9 Ohms
10 Ohms to 99 Ohms
100 Ohms to 990 Ohms
1 K To 9.9 K
10 K To 99 K
100 K To 999 K
1 M To 9.9 M
10 M To 99 M
Capacitors
Electrolytic capacitors have value printed on its body. Pins can be easily identified. Large pin is positive.
Moreover a black band is printed near the negative terminal to identify the polarity. Do not change the polarity.
Capacitor will explode. In Disc capacitors, only a number is printed on its body so it is very difficult to
determine its value in Pf, KPF, UF, N etc. In some capacitor, its value is printed in UF eg.0.1 in some others
EIA code is used e.g. 104. The following tricks can solve the problem.
1. One or two numbers on the capacitor represents value in PF e.g. 8 = 8PF
2. If the third number is zero, then the value is in P e.g. 100 = 100PF
3. If the capacitor has three numbers and the third number is not a zero, it represents the number of zeros
after the first and second digits e.g. 104 = 10 – 0000 PF
4. If the value is obtained in PF, it is easy to convert it into KPF or UF
PF / 1000 = KPF or N
PF / 10, 00000 = UF
For example, if the capacitor is 104, then it is 10-0000 PF or 100 KPF or N or 0.1 UF
5. Conversion formula
N X 1000 = PF
PF/1000 = N PF/1,000,000 = UF UF X 1,000,000 = PF UF X 1,000,000/1000
= N N=1/1,000,000,000F UF = 1/ 1000,000 F
6. English letter below the value represents tolerance e.g. 473 = 473 K
K
If the capacitor has four digits and the fourth digit is a zero, then the value is in PF. E.g. 1500 = 1500PF
2
7. If a number is represented with a decimal, the value is in UF. E.g. 0.1 = 0.1 UF
8. If an alphabet is given below the digits, it represents a decimal and the value is in KPF or N
E.g. 2K2 = 2.2 KPF
9. If the values are given with slashes, the first digit represents value in UF, second its tolerance and third
its maximum voltage rating E.g. 0.1/5/800 = 0.01 UF / 5 Percent / 800 Volt.
Some common disc capacitors are
EIA Code
PF
KPF/N
UF
102
103
104
202
203
223
224
1
10
100
2
20
-
1
10
100
2
20
22
220
0.001
0.01
0.1
0.002
0.02
0.022
0.22
EIA
Code
403
471
472
473
442
443
444
KPF/N
UF
40
0.47
4.7
47
4.4
44
440
0.4
0.00047
0.0047
0.047
0.0044
0.044
0.44
Polyester capacitors have five colour bands similar to the resistor colour code value.
Band 1
Temperature tolerance
Band 2,3, 4 Value in PF as per colour code used in resistors
Band 5
Tolerance
Transistors
Transistors may be in plastic or metal can packages. Value of the transistor is printed on its body. Pin numbers
are generally assigned as 1,2 and 3 from the facing side. General purpose NPN transistors have pins 1-Collector,
2-Base, 3- Emitter. That is CBE. In PNP types the pins are reversed. 1-Emitter, 2-Base and 3- Collector. That is
EBC. Metal can transistors have a small projection in the rim of the body. The pin close to it is the emitter. Pin
opposite to the emitter is Collector and the middle pin is base. Pin assignment of some common transistors is
given below.
Transistor Types
PNP
NPN
1
C
Transistor
BC546,547,548,549
550, BC 337,AC 187
TIP 120,121,122
BD139
BF494,495
C2570
C1730
BD677
D882 / 2SD882
D313/MJE 13005
2
B
3
E
1
E
2
B
3
C
Type
NPN
Pins 1 2 3
CBE
Transistor
2N 2222A,2N 3904
Type
PNP
Pins 1 2 3
EBC
NPN
NPN
NPN
NPN
NPN
NPN
NPN
NPN
BCE
ECB
CEB
BEC
ECB
BCE
ECB
BCE
TIP 125,126,127
BD140
MPSA 92,42,44
BC636
SK/CK/BEL100P
AC188
BC557
BC558
PNP
PNP
PNP
PNP
PNP
PNP
PNP
PNP
EBC
ECB
EBC
BCE
EBC
EBC
EBC
EBC
3
Pin outs of more components
Component
C1906/1730
Pins
ECB
Type
VHF/UHF Transistor
Component
7805,06,08,09,12
BF200/C1393 BEC
VHF/UHF Transistor
LM 317
Ad/G, Op, VIN
VIN
Pins
G VOUT
C2570
BEC
VHF/UHF Transistor
YS 414/415
Op coil Gn
BF245A
BC170
BS170P
GSD
DGS
SGD
FET
MOSFET
MOSFET
LM 34/35
UM66
2N5777
GN OP VIN
Op VIN Op
ECB
IRF540
GDS
MOSFET
L14F1
CBE
Type
Regulator
IC
Variable
Reg. IC
MW
receiver IC
TempSensor
Melody IC
Phototransis
tor
Phototransis
tor
D- Drain S-Source G - Gate
Component
2P4M
SN104
TIC206D
TYN604
8T44
Pins
KAG
AGK
AKG
KAG
A1A2G
K-Cathode A-Anode G-Gate
Type
SCR
SCR
SCR
SCR
SCR
Component
BT169
SN102
BT136
BT138
ST44B
Pins
KAG
AGK
MI M2 G
MI M2 G
MI M2 G
Type
SCR
SCR
Triac
Triac
Triac
M1- Main terminal 1 M2- Main terminal 2 G-Gate
Infrared Sensors
Remote operation of TV is based on Infrared transmission and reception. Infrared is a form invisible light with a
wavelength of 950 nano meters. Human eye cannot sense this wavelength so that infrared rays cannot be
detected visually. The remote handset is used to emit modulated infrared light using an infrared diode. This
diode emits pulsed infrared waves in a coded form at a frequency of 38 kHz By pressing each button in the
remote handset, it is possible to emit infrared rays at a particular coded form. This helps to control the functions
of the TV precisely. Inside the TV there is an Infrared receiver circuit. It consists of an infrared sensor- TSOP
1738. This sensor is sensitive only to pulsed infrared rays at the 38 kHz frequency and not other forms of light.
The infrared sensor has a black covering which filter visible light and allow only the infrared to enter. It has an
FET bas signal amplifier. The modulated infrared rays from the handset are received by the sensor and it
amplifies the signal. These signals are used for controlling different functions of the TV.
4
TSOP
1738
1
GN
Type
TK 1836
SFH 5110-38
SFH 505A
TK 19-904
TSOP 1738,
SFH 506-38
Pin 1
OP
OP
VCC
GN
GN
GN
Pin 2
GN
GN
GN
VCC
VCC
VCC
Pin 3
VCC
VCC
OP
OP
OP
OP
2
3
VCC OUT
Type
SHARP GPIU 561X
TK 19931
ISIV 60
ISIU 60
TSOP 1736
TSOP 1838
Pin 1
VCC
GN
OP
OP
GN
GN
Pin 2
OP
VCC
GN
GN
VCC
VCC
Pin 3
GN
OP
VCC
VCC
OP
OP
Pin numbers 1, 2, 3 assigned from the facing side
Infrared Sensors require 5volt maximum. Do not give more than 5 volt Vcc
Optocouplers and Melody generators
MELODY GENERATORS
8
IC UM66
6
5
4
OPTOCOUPLER
4N34/MCT2E
1
PINS
1
2
3
4
5
6
7
8
2
3
NE555
Timer
GN
Trigger
OP
Reset
Control
Threshold
Discharge
Vcc
1VIN
2GND
3.NC
4.Emitter of Phototransistor
5.Collector of Phototransistor
6.NC
UA 741/CA 3130/CA3140/TLO 71
Op Amps
Inverting input
Non inverting input
GN
OP
Vcc
1
1. Output
2. 3V in
3. Ground
7
6
5
IC UM 3561
2 3
1
1. NC
2. Ground
3. Output
4.NC
TLO 72/LM358/LF353/TLO82
Dual Op Amp
OP1
Inverting input 1
Non inverting input 1
GN
Non inverting input 2
Inverting input 2
OP 2
VCC
2
3
4
5.3V IN
6. Tone Selector
7,8, Oscillator resistor
5
6
5
4
OPTOCOUPLER
4N34/MCT2E
1
2
3
1VIN
2GND
3.NC
4.Emitter of Phototransistor
5.Collector of Phototransistor
6.NC
Batteries
Batteries can be divided into two categories. The primary type is intended for one time use only and
is disposed after the charge has dropped to a level that cannot be used. Primary type should not be
discharged as heat will be generated within sealed cells. It will also damage the equipment as a
consequent of fluid leakage. The storage or secondary type can be recharged many times and is
reusable.
The rating of its capacity is ampere hours (Ah) which is a product of current drain and time.
Primary Batteries
Carbon zinc is the most common primary cell in which the chemical oxidation converts the zinc into
salts and electricity. When there is no current flowing, the oxidtion stops. If keep for a long period of
time, the stored batteries will degrade and dry out where it will no longer able to supply the desired
current. The time taken for the degradation without being used is called shelf life. It has a nominal
voltage of 1.5V.
Alkaline types have longer capacity at low temperatures. Lithium type have nominal voltage of
3V/cell and has the best capacity, discharge, shelf life and temperature characteristics. Its setback is
the high cost.
Silver Oxide and Mercury has voltages of 1.5 V and 1.4 V respectively and are used where constant
voltage is desired at low currents over a long period of time. Their main used and applications are in
hearing aids.
Storage Batteries
The most common type is nickel-cadmium (Ni-Cd) type with a nominal voltage of 1.2V/cell. If used
carefully, it can be rechargeable up to 500 times compared to alkaline type which is 50 times or so.
The most widely used storage type is the lead-acid type in automobile. The Lead Acid battery is
made up of plates, lead, and lead oxide with a 35% sulfuric acid and 65% water solution.
Gas escaping from it may be explosive and always keep flame away. It should not be subjected to
unnecessary heat, vibration or physical shock. Frequent inspections for leak are recommended. The
electrolyte is chemically active and conductive and may ruin electrical equipment if leaks occurred.
Its acidity may be neutralized with sodium bicarbonate or baking soda.
In order to ensure that all the cells in NiCd reach a fully charged condition, it should be charged by a
constant current of 0.1 C current levels. It is around 50 mA for a AA size cells. Charging should be
terminated after 15 hours at the slow rate. A built in circuit that will stop charging when 1.43V/cell is
reached will enhance the life of the battery.
Capacitors
A capacitor is a body which can store an electrical charge. It consists of 2 conducting plates facing
each other and separated by an insulating material. This insulating material is also called dielectric
material. When a charge is stored in one plate, an equal and opposite charge is inducted on the other
plate and thus a potential difference is set up between the plates.
6
The unit of measurement for capacitance is Farad but this unit is much too large for practical work.
It is usually measured in microfarads (uF) or picofarads (pF). The formula of calculating capacitance
is
C= [(0.224 KA) (n-1)]/d where
C = capacitance in pF
K = dielectric constant of material between plates
A = area of one side of the plates square inches
d = separation of plate in inches
n = number of plates
The potential difference V developed when a charge Q is stored depends directly on the value of Q
and inversely with the capacitance C of the cap.
V = Q/C
They are used in timing circuits as it takes time for a cap. to be charged up. They are used to smooth
varying DC power supplies by acting as a reservoir of charge. They are also used in filter circuits
because they easily pass AC signals but they block DC signals.
DC Voltage Rating
The DC working voltage of a cap. is the maximum voltage which may be applied continuously on the
electrodes of the cap. at the upper limits of the working temperature range. The peak value of an
alternating voltage should not exceed this rating and have to be derated according the the FMEA as
recommended in FMEA.
Leakage Resistance
The dielectric of a practical cap. introduces power losses which can be represented by a small
resistance connected in series with the cap. The insulating resistance is often greater than 3,000 Meg
ohm.
Types of Capacitors
There are many different types of cap. that are used for different types of applications. They are
electrolytic cap., ceramic cap., tantalum cap., polyester cap., polystyrene cap. and safety cap.(namely
X and Y types of cap.).
Electrolytic Type
Electrolytic cap. have leads that are marked with + or - signs. They have polarity and must be
connected with the correct polarity. The values of the capacitance and voltage rating are printed with
on its body. The voltage rating can range from 5V up to 440V DC. Generally this type of capacitor is
used as smoothing cap. in power supply regulation. The bigger the value of the cap. is, the less ripple
the DC supply that has been rectified will be.
DIODES
Types of Commercially Available Diodes
In small signal application of which the current requirement is less than 100mA, 1N4148 is a typical
choice. It has a forward voltage drop of 0.7V and is made from Silicon type.
In rectifier circuit applications, the typical ones used are 1N4001 to 1N4007 for current rating of 1A
and 1N5401-1N5408 for current rating up to 3A. The table below shows the devices and their
maximum reverse voltage ratings.
Diode
Maximum Current Maximum Reverse Voltage
1N4001
1A
50V
1N4007
1A
1000V
1N5401
3A
100V
1N5408
3A
1000V
Applications
7
There are various applications for diodes. Among the popular use of them are as highlighted below.
Diodes as Switches
They can be used in series switching or shunt switching in place of relays or mechanical switches.
They can be used in applications from DC up to audio frequencies. Its recovery time must be taken
into account when chosen for the frequency of operation. The higher the operating frequency is, the
faster the switching speed is required. In audio and DC applications, normal power supply rectifier
types can be used.
Diodes as Voltage References
Zener diodes can be used as voltage regulators.
When used as voltage regulators in power supplies, they provide a near constant DC output voltage
even though there are changes in load impedance or the input voltage. They use the reverse
breakdown voltage characteristics of the devices to maintain a fixed voltage across them. One
example of the circuit as voltage reference is as shown below. The various zener ratings ranges from
2.4 V to 200 V. Its power ratings range from 0.25W to 50W.
Diodes as back EMF Protection
When relay coil is switched off by a transistor, the inductance of the coil will create a back EMF that
may be high enough to damage the transistor. In most circuits, one can see a diode connected across
the relay coil to conduct when this happens. In this way, the relay coil is protected from the high
voltage that is induced by the switching off of the coil. In normal operation, it will not conduct.
Without it, no current could flow and the coil will create a high voltage pulse to keep the coil current
flowing.
LED
The primary component in optoelectronics is the LEDs. Light emitting diode is a diode with PN
junction of crystal material that produces luminescence around the junction when forward bias
current is applied. The junctions of this light emitting diode are made from Gallium Arsenide (GaAs),
Gallium Phosphide(GaP) or a combination of both(GaAsP).
The available colors are red, white, yellow, green and blue. Some are housed in plastic affixed to the
base header of a transistor package. Others are contained in plastic packages that have a dome
shaped head at the light emitting end. Two wires protrude from the opposite end for applying
forward bias to the device.
8
These days, surface mount types are commonly used.
The forward bias current of a typical LED ranges between 10 and 20 mA for maximum
brilliance. A 1 Kohm resistor in series with a 12 V DC source will caused it to operate at 12 mA. In
order to ensure the lifetime of it is preserved, do not exceed the maximum rating of the current. The
voltage drop across it is typically 1.8 to 2.0 V DC.
Definition and Terminology
Incident Flux Density
This is defined as the amount of radiation per unit area expressed as lumens/cm2 or watts/cm2. This
is the measurement of the amount of flux received by a detector measuring its output.
Emitted Flux Density
This is defined as radiation per unit area and is used to describe light reflected from a surface. This
measure of reflectance determines the total radiant luminous emittance.
Source Intensity
This is the flux density that will appear at a distant surface and is expressed as lumens/steradian or
watts/steradian.
Luminance
This is a measure of photometric brightness and is obtained by dividing the luminous intensity at a
given point by projected area of the source at the same point.
LED is glowing
As the name implies light emitting diodes exploit the property of the pn junction to emit photons
when it is biased. LEDs are specially made to emit light and there was a revolution in the LED
industry during the past few years. LEDs form an inevitable part in the modern electronics as simple
indicators to optical communication devices. The history of LED date backs to 1907 when Captain
Henry Joseph observed the property of electro-luminescence in Silicon Carbide. The first LED was
born in 1962. It was developed by Holonyak worked at General Electric (GE). It was a GaAsP device.
The first commercial version of LED came on 1960s. LED industry made a boom during 1970s with
the introduction of Gallium Aluminium Arsenide (GaAlAs). These LEDs are high bright types and
are ten times brighter than the diffused varieties. Blue and White LEDs born in 1990 and used Indium
Gallium Nitride (InGaN) as the semiconductor. White LED contains a blue chip with white inorganic
Phosphor. When blue light strikes the phosphor, it emits white light.
9
Secrets behind LEDs
Brightness is an important aspect of LED. Human eye has maximum sensitivity to light near 550 nm
region of yellow – green part of the spectrum. That is why a Green LED looks brighter than a Red
LED even though both use same current. Three parameters of LED are responsible for its
performance.
a. Luminous flux – It is the light energy radiating from the LED. It is
measured in terms of Lumen ( lm ) or Milli lumen ( mlm )
b. Luminous intensity – is the luminous flux covering a large area. It is measured as Candela ( cd ) or
milli candela ( mcd ) Brightness of LED is directly related to its luminous intensity.
a. Luminous efficacy - is the emitted light energy relative to the input power. It is measured in
terms of lumen per watt (lm w).
Forward current, forward voltage, Viewing angle and Speed of response are the factors affecting the
brightness and performance of LEDs. Forward current ( IF) is the current flowing through the LED
when it is forward biases and it should be restricted to 10 to 30 milli amperes other wise LED will die.
Viewing angle is the off – axis angle at which the luminous intensity fall to half its axial value. This is
why the LED becomes brighter in full on condition. High bright LEDs have narrow viewing angle so
that light is focused into a beam. Forward voltage ( VF ) is the voltage drop across the LED when it
conducts. The forward voltage drop range from 1.8 V to 2.6 Volts in ordinary LEDs and in Blue and
White it will go up to 5 volts. Speed of response denotes how fast an LED switch on and off. This is
an important factor if LEDs are used in communication systems.
Table 2 shows some of the properties of the typical Red and Green LEDs.
Why a ballast resistor accompany each LED?
LED always has a series resistor along with it. This is” Ballast resistor”, the life saving device of LED.
It controls the forward current to the LED to a safer limit and protects it from burning. Value of the
resistor if the factor that determines the forward current and hence the brightness. The simple
equation Vs – Vf / If solves the problem of resistor value. Vs represents input voltage, Vf the forward
voltage and If the allowable current through the LED. The resulting value will be in Ohms. It is better
to restrict the current to a safer limit of 20 mA.
LED along with the limiting resistor R4 is the power on status indicator. A significant voltage drop
(about 2 volts) occurs across the LED when it passes forward current. The forward voltage drops of
various LEDs are shown in Table 2.
Table 2
Red
1.8 V
Orange
2V
Yellow
2.1 V
Green
2.2 V
Blue
3.6 V
White
3.6 V
A typical LED can pass 30 –40 mA current without destroying the device. Normal current that gives
sufficient brightness to a standard Red LED is 20 mA. But this may be 40 mA for Blue and White
LEDs. Current limiting resistor R4 protects LED from excess current that is flowing through it. The
value of R4 should be carefully selected to prevent damage to LED and also to get sufficient
brightness at 20 mA current. The current limiting resistor can be selected using the formula
R=V/I
Where R is the value of resistor in ohms, V is the supply voltage and I is the allowable current in
Amps. For a typical Red LED, the voltage drop is 1.8 volts. So if the supply voltage is 12 V ( Vs ) ,
10
voltage drop across the LED is 1.8 V ( Vf ) and the allowable current is 20 mA ( If ) then the value of
R4 will be
Vs – Vf / If = 12 – 1.8 / 20 mA = 10.2 / 0.02 A = 510 Ohms.
A suitable available value of resistor is 470 Ohms. But is advisable to use 1 K resistor to increase the
life of the LED even though there will be a slight reduction in the brightness. Since the LED takes 1.8
volts , the output voltage will be around 10 volts. So if the circuit requires 12 volts, it is necessary to
increase the value of Zener slightly. Table 3 is a ready reckoner for selecting limiting resistor for
various versions of LEDs at different voltages.
Table 3
Supply Red
Orange
Yellow
voltage
12 V
470 E
470 E
470 E
9V
330 E
330 E
330 E
6V
180 E
180 E
180 E
5V
180 E
150 E
150 E
3V
56 E
47 E
47 E
* Available resistor values in ohms
Green
Blue
White
470 E
330 E
180 E
150 E
33 E
390 E
270 E
120 E
68 E
-
390 E
270 E
120 E
68 E
-
Infra Red diode – The Silent LED
Usually an LED makes its presence through its beautiful colour light. But there are LEDs performing
their functions without emitting visible light. Infrared diode is such a kind of LED. Infra red actually
is normal light with a particular colour. Human eye is not sensitive to its light because its wave
length is 950 nm which is below the visible spectrum. Many sources like sun, bulbs, even the human
body emit infra red rays. So it is necessary to modulate the emission from IR diode to use it in
electronic application to prevent spurious triggering. Modulation makes the signal from IR LED
stand out above the noise. Infra red diodes have a package that is opaque to visible light but
transparent to infra red. The massive use of IR LEDs at TV / VCR remote controls and safety alarm
systems brought IR diodes at very low cost at the market.
LASER Diode
A laser diode is similar to LED but it produces a narrow beam of high intensity. A laser is a device in
which a number of atoms vibrate in such a fashion that all the emitted radiation of a single wave
length is in phase with each other. Laser light is monochromatic and can be focused into a narrow
pencil beam. The beam of typical laser diode is 4 mm x 0.6 mm widening only to 120 mm at a
distance of 15 m. Laser diode can be switched on and off at higher frequencies even as high as 1 GHz.
So it is highly useful in telecommunication systems. Since the laser generates heat on hitting the body
tissues, it is used in surgery to heal lesions in highly sensitive parts like retina, brain etc. Laser diodes
form important components in CD players to read the recorded memory.
11
Add on Circuits
D.MohanKumar
These simple circuits can be used as add on circuits along with various electronic circuits
Transformerless power supply
To make the circuit light weight, power supply based on resistor or capacitor is used. Two power supply are shown
Caution. Since the circuit uses 230 Volt AC most points are at mains lethal potential. Do not touch any parts while the circuit is powered to avoid
shock.
Resistor based Power supply
R1 10W
D1 IN4007
R2 1K
C1
PHASE
230V AC
C2
POSITIVE
ZD 12V 1W
DC V
NEURTAL
NEGATIVE
LED RED
C1 0.1 C2 1000
25V
Output voltage depends on the values of R1 and ZD
Volt
3
6
9
R1
15K
12K
10K
ZD
3V
6.2V
9.1V
Volt
12
15
18
R1
10K
10K
10K
ZD
12V
15V
18
Capacitor Type
R1 100R 1W
C1 105K
400V AC
D1 IN4007
230V AC
Positive
R3 1K
Phase
12V DC
R2 470K
Neutral
D2 IN4007
LED
C2 1000
UF 25V
Negative
ZD 12V 1W
C1 Must be X rated AC capacitor R2 is must to dischage C1. Output depends on the value of ZD
Capacitor pass only low current. Useful only in low current circuits
Output current depends on the value of C1. To get the required current, divide the current in mA by 75 to get the Capacitor value in UF C = mA /
75.Some of the common AC capacitors and their current are shown below
Current in
mA
10
15
25
35
50
75
Value in
uF
0.13
0.2
0.33
0.47
0.6
1
Capacitor
uF
0.33
0.1
0.47
105K
225K
684K
Output
Voltage
10
4
12
24
50V
18V
Current
mA
22
8
100
100
100
100
12
POWERSUPPLY WITH BATTER BACKUP
D1 IN4007
T1 SK100
R1 470R
PHASE
R2 1K
230V AC
NEUTRAL
9V DC
0-9 500MA
D2 IN4007
BRIDGE
4 X IN 4007
R310K
ZD 6.1V
C1 1000UF 9V RE CHARGE
25V
BATTERY
When Ac is available, battery charges via D1 and R1. T1 conducts to give 9v output.
When power fails, D1 reverse biases and D2 forward biases and Battery will take up the load.
Zener diode ZD stops T1 conducting when the battery voltage drops below 6.7 volts
preventing battery deep discharge.
POWER SUPPLY WITH SHORT CIRCUIT INDICATION
D1 IN4007
R2 47K
R1 47K
PB
PHASE
T1 BC547
POSITIVE
230V AC
9V OUT
NEUTRAL
C1
0-9 500MA
NEGATIVE
BRIDGE
4 X IN 4007
LED
T2 BC547
C1 1000UF
25V
As long as the output is above 1 volt, current through R2 bias T2 and it conducts
T1 remains off since its base at ground potential. Buzzer remains silent. When
there is a short circuit at the output, current through R2 drops, T2 turns off and
T1 turns on to activate the buzzer. Beeps continue till short circuit is removed.
Delay on Relay
D1 IN4007
RELAY
6V 100R
R1 470K
SCR BT169
Power s aving LED
9V DC
R2 1K
C1 1000UF
25V
R2 1K
R1 1M
ZD 4.7V
TO CIRCUIT
Protect electrical appliances like TV from
instant voltage spike at power on or power
resumption after a power failure. At power on,
C1 charges slowly and SCR conducts only after
C1 gets full charge. SCR then turns on to connect
the load through the N/o contacts. With 1000 UF
1 minute delay will be obtained.
T1 BC 557
C1 100UF
C2 100UF
LED RED
If an LED pilot lamp is used in battery powered circuits, it will unnecessarily consume power. This circuit lights an LED at power on and after one
minute it will turns off.
13
TONE GENERATOR UM 3561
R2 220K
SP
R1 1K
7
MELODY GENERATOR CIRCUIT
5
6 NC
R2 100R
9V
Pin 6 is the tone selector
Pin6 not connected - Police siren
Pin6 connected to Pin5 - Fire engine siren
Pin6 connected to ground - Ambulence siren
T1 AC 187
LOGIC PROBE
R2 5.6K
R1 4.7K
R3 5.6K
T1 BC547
T2 BC 547
9V BATT
BICOLOUR LED
RED PROBE
BLACK PROBE
R3 100R
T1 AC 187
UM66
2
1
3
ZD 4.5V
3
2
ZD 4.7V
SP
R1 1K
8
IC UM3561
GREEN
RED
Sim ple logic s tate tes ter to indicate the pres ence of pos itive
output from ICs and other com ponents . Green part of the LED
lights when the input s ignal is pos itive and Red LED indicates
a negative s ignal.When T1 s witches on by getting a pos itive
s ignal through R1, Green LED lights . At the s am e tim e bas e
of T2 is grounded . T2 and Red LED then turns off.
9V