AUTOMATIC NIGHT LIGHT
The
circuit will automatically switch on the AC lamp when night falls and
the lamp will be automatically switched off after a preset time.
CIRCUIT DIAGRAM:
WORKING:
The
working of this night light circuit very simple. An ldr is used as
the sensor here. At day time the resistance of the ldr will be low
and so do the voltage drop across it, the transistor q1 will be in
the conducting mode. When darkness falls the resistance of ldr
increases and so do the voltage across it. This makes the transistor
q1 off. Base of q2 is connected to the emitter of q1 and so q2 is
biased on which in turn powers the ic1. Ne555 is wired as monostable
multivibrator that is automatically triggered at power on. This
automatic triggering is achieved with the help of capacitor c2. The
output of ic1 remains high for a time determined by resistor r5 and
capacitor c4. When output of ic1 goes high transistor q3 is switched
on which triggers triac t1 and the lamp glows. A 9v battery is
included in the circuit in order to power the timer circuit during
power failures. Resistor r1, diode d1, capacitor c1 and zener d3
forms the power supply section of the circuit. R7 and r8 are current
limiting resistors.
Notes.
1]
the circuit can be assembled on a vero board.
2]
preset r2 can be used to adjust the sensitivity of the circuit.
3]
preset r5 can be used to adjust the on time of the lamp.
4]
with r5 @ 4.7m the on time will be around three hours.
5]
the wattage of l1 must not exceed 200w.
6]
heat sink is recommended for bt136.
COMPONENT
USED:
R1=10K
R2=50K
R3=1K
R6=10K
R7=200OHM
R8=150OHM
C1=100uF
C2=0.1uF
C3=.03uF
C4=2200uF
D1,D2=1N40007
D3
=ZENER DIODE
Q1=BC558
Q2=BC558
Q3=BC548
MODIFICATIONS:
As
the above circuit is buid by using the 555timer ic now we can buid
this circuit by using the LDR and EMOS.
APPLICATIONS:
- HOME APPLIANCES
DANCING
LIGHT
Here
is a simple dancing light circuit based on ne555 (ic1) & cd4017
(ic2) . The ic1 is wired as an astable multivibrator to provide the
clock pulses for the cd4017. For each clock pulse receiving at the
clock input (pin14) of ic cd4017, the outputs q0 to q9 (refer pin
diagram of cd 4017) becomes high one by one alternatively. The leds
connected to these pins glow in the same fashion to give a dancing
effect. The speed of the dancing leds depend on the frequency of the
clock pulses generated by the ic1.
CIRCUIT
DIAGRAM:
COMPONENT
USED:
RESISTOR:
R1=10K
R2=100K
R3=1K
R4=1K
R5=1K
R6=1K
R7=1K
R8=1K
R9=1K
555
TIMER
IC
CD 4017:
10V
POWER SUPPLY
CAPACITORS:
C1=10uF
LED
1-9
MODIFICATIONS:
AS
IN THE ABOVE CIRCUIT WE ARE USING 555TIMER AND IC CD4017 ,WE CAN USE
THE TWO TRANSISTORS T1 AND T2 (BC 548).
APPLCATIONS:
- HOME APPLIANCES
- DISCO
FM TRANSMITTER:
FM
transmitter is a portable device that plugs into the headphone jack
of a portable audio or video device, such as a portable media player,
CD player, or satellite radio system. The sound is then broadcast
through the transmitter, and plays through an FM broadcast band
frequency. In this case the frequency of a carrier signal is
modulated in accordance with that of frequency of modulating signal.
FM frequency is from 76.0 to
108.0 MHz. FM transmitter have a range of about 30 feet (about 9
meters). A good radio can increase that range to upwards of 75 feet
(about 23 meters).
CIRCUIT
DIAGRAM:
This
is two transistor FM transmitter circuit. The first stage of the
circuit is a preamplifier stage based on transistor Q1. This is a
collector to base biased amplifier stage where resistor R2 sets the
collector current and R1 provided the necessary collector to base
bias. C1 is the input DC decoupling capacitor which couples the input
audio signal to the Q1 base. C8 is the power supply by-pass
capacitor. Next stage is the oscillator cum modulator stage built
around transistor Q2. Electrolytic capacitor C2 couples the output of
the first stage to the second stage. R3 and R4 are the biasing
resistors of Q2. R5 is the emitter resistor of Q2. Inductor L1 and
trimmer capacitor C5 forms the tank circuit which is necessary for
creating oscillations. The modulated FM signal is available at the
collector of Q2 and it is coupled to the antenna using capacitor C9.
COMPONENTS
USED:
NPN
TRANSISTERS Q1 AND Q2
Q1
- BC108
Q2
- 2N2369
POLAR
CAPACITER:
An
electrolytic capacitor is a capacitor that uses an electrolyte(an
ionic conducting liquid) as one of its plates to achieve a larger
capacitance per unit volume than other types. The large capacitance
of electrolytic capacitors makes them particularly suitable for
passing or bypassing low-frequency signals and storing large amounts
of energy. They are widely used in power supply and interconnecting
stages of amplifiers at audio frequencies.
C1 - 1uFC2 - 1uF
C3 - 2.2nF
C4 - 4.7nF
C5 - 10pF
C6 - 10pF
C7 - 100pF
C8 - 2.2nF
RESISTERS:
R1 - 86K
R2 - 10K
R3 - 3.3K
R4 - 2.2K
R5 - 100ohm
POWER SUPPLY : 9VOLT
Antenna can be a 1m copper wire
MODIFICATIONS:
As the above FM transmitter is made up of the two transistor were as we can made the FM transmitter from one transistor, so given below the circuit diagram of the FM transmitter using only one transistor.
CIRCUIT DIAGRAM:
COMPONENTS
USED:
Q1 -
Transistor- 2N3904Capacitors - 4.7pF, 20pF, 0.001uF, 22nF
Resistors - 4.7 kilo Ohm, 470 Ohm
Inductor - 0.1uF.
Antenna: Use 15cm to 1 meter long wire for antenna. If you have a long antenna, the
signal transmission will be better.
APPLICATIONS:
- In home
- In car
- In stations
Night
security
light-Security Alarm System
Here
is a simple circuit switches on a light around 2 hours after
midnight, the time at which most of the robberies taking place.This
simple circuit is build around a cmos ic 4024 to obtain the required
timing. During day time the ldr has low resistance and keeps the pin
12 of the ic1 high, preventing the ic1 from oscillating. When it is
dark the ldr resistance becomes high and the pin 12 of ic1 becomes
low and the ic starts oscillating, which indicated by the flashing of
led d3.The Values of the timing components r1, r2, c4 are so selected
that the out put pin3 of ic1 goes high after 8 hours. That means the
high output drives the triac to switch on the lamp around 2’o
clock. At morning, the ldr resistance drops and the pin 12 of ic1
goes high and stops the oscillation, making the lamp off. The switch
s1 can be used to manually on the lamp. The capacitor c2 prevents
false triggering.
COMPONENTS USED:
The
LDR can be general purpose LDR.
The
light sensitivity can be adjusted using the preset R6.
- RESISTOR:It is a passive component and mainly employed in the circuit to direct the flow of current in the circuit. Resistors are broadly classified as fixed type and variable type.
- R5-Thermistor is a kind of temperature dependent resistor and its resistance varies depending on the temperature in its vicinity.
- R1=120k
- R2=1M
- R3=1000ohm
- R4=1000ohm
- R6=-100k
- C1 (1000uf) – Capacitors are mainly employed in the circuit to store the charges. A dielectric medium flows in it which is used to separate the two conducting plates inside it.
- c2=100uF
- C3=.1uF
- C5=1uF
- 4024 IC
- FULL WAVE RECTIFIER
- 1 TO 1 TRANSFORMER
- POWER SUPPLY OF 12 VOLT.
MODIFICATIONS:
THIS
CIRCUIT CAN BE MODIFIED BY USING THE 555TIMER IC.
APPLCATIONS:
- HOME SECURITY
PURPOSE:This model is designed for parking purposes, instead of looking at the LED display,we are using the audio for parking which make easier the parking operation.
CIRCUIT DIAGRAM:
COMPONENT USED:
R15 ---- 3K3 1/4W Resistor
R16 ---- 330K 1/4W Resistor R17 ---- 470K 1/4W Resistor R18 ---- 150K 1/4W Resistor C6 ---- 1µF 63V Electrolytic or Polyester Capacitor D8,D9,D10---- 1N4148 75V 150mA Diodes IC4 --- 555 Timer IC BZ1 ----Piezo sounder (incorporating 3KHz oscillator)CIRCUIT WORKING:
In this model the input pins of IC2B, IC2C and IC2D are reversed. LED’s D5, D6 and D7, as also resistors R12, R13 and R14 are omitted. IC2B, IC2C and IC2 outputs drive resistors R15, R16 and R17 through D8, D9 and D10 respectively, in order to change the time constant of a low frequency oscillator based on the 555 timer IC4.
This allows the Piezo sounder to start beeping at about 2 times per second when bumper-wall distance is about 20 cm., then to increase the beeps to about 3 per second when bumper-wall distance is about 10 cm. and finally to increase further the beeps frequency to more than 4 beeps per second when the distance is about 6 cm. or less.
ALTERNATIVE COMPONENTS :
Here is this model we are using 555 IC which is used to generate the high stable time delay or oscillations so instead of this IC we can use IC 4060 which is an excellent integrated circuit for timing applications. Its ten active high outputs can give time delay from few seconds to hours. With a few components, it is easy to construct a simple but reliable time delay circuit.
PHONE
DETECTOR
A cell phone typically transmits and receives signals in the frequency range of 0.9 to 3GHz. This simple circuit is used to detect the presence of an activated cell phone by detecting these signals.
CIRCUIT DIAGRAM:
DESCRIPTION:
The
basic principle behind this circuit is the idea of using a schottky
diode to detect the cell phone signal. Mobile phone signal is in the
frequency range of 0.9 to 3ghz.Schottky Diodes have a unique property
of being able to rectify low frequency signals, with low noise rate.
When an inductor is placed near the RF signal source, it receives the
signal through mutual induction. This signal is rectified by the
schottky diode. This low power signal can be amplified and used to
power any indicator like an led in this case.
WORKING:
In
normal condition, when there is no RF signal, the voltage across the
diode will be negligible. Even though this voltage is amplified by
the transistor amplifier, yet the output voltage is less than the
reference voltage, which is applied to the inverting terminal of the
comparator. Since the voltage at non inverting terminal of the OPAMP
is less than the voltage at the inverting terminal, the output of the
OPAMP is low logic signal.
Now
when a mobile phone is present near the signal, a voltage is induced
in the choke and the signal is demodulated by the diode. This input
voltage is amplified by the common emitter transistor. The output
voltage is such that it is more than the reference output voltage.
The output of the OPAMP is thus a logic high signal and the LED
starts glowing, to indicate the presence of a mobile phone. The
circuit has to be placed centimeters away from the object to be
detected.
COMPONENTS
USED:
- V1 = 12V
- L1 = 1uH
- R1 = 100Ohms
- C1 = 100nF
- R2 = 100K
- R3 = 3K
- Q1 = BC547
- R4 = 200 Ohms
- R5 = 100 Ohms
- IC1= LM339
- R6 = 10 Ohms
LED
= Blue LED
CIRCUIT
MODIFICATION:
As
in the above diagram we are using only transistors and op-amp 741IC
so we can modify the circuit by using the 555timer ic as well as the
CA3130IC.
APPLICATIONS:
- This circuit can be used at examination halls, meetings to detect presence of mobile phones and prevent the use of cell phones.
- It can be used for detecting mobile phones used for spying and unauthorized transmission of audio and video.
- 3.It can be used to detect stolen mobile phones.
POLARITY
CUM COUNTINUITY CIRCUIT
The
polarity of lots of components viz diodes, led comprises zener diode
as well as infrared led can be tested with the help of
polarity
cum continuity tester.
With the help of this circuit, we can also identify that whether the
components we are using in our circuit are good or bad before
mounting them on the PCB. Although it happens many times that people
are not being able to discovered the polarity of any component and
mount them wrong in the circuit which leads to damage of the
component or may damage the entire circuit. The content of any
circuit can also be tested with the help of this circuit.
Firstly
connects the component which you want to test with test probe.
Glowing of any led in this circuit is the indicator of cathode
terminal. Both the led in the circuit will start glowing when you
first start the circuit. Now across the probe provide for testing
connect the component. If led1 start glowing it means that the
cathode side of the component is coupled to the probe 1 and if led2
start glowing it implies that the cathode side of the component is
coupled with probe 2.
The
circuit is finished with the aid of two transistors and both the
transistors in the circuit are connected as an astable multivibrator.
The circuit output which we get from the both transistors are not in
phase with one another, it implies that if we get high output from
the first transistor then the other transistor output will be low or
if the output of the second transistor is higher than the output from
the first transistor will be low. Led 1 will start glowing when t1
transistor is in “on” state and t2 transistor is in “off”
state. In the same manner led 2 will be glowing when the t1
transistor is in the “off” state while t2 transistor is in “on”
state.
When
the component like diode or led which you want to test is put between
the probes provided for testing it bypasses to any one of the led
based on the polarity. In Place of the bypass led the test current
will start flowing via a component in the circuit. Series grouping of
led as well as diodes are connected in the circuit with the t1 and t2
transistor at the collector terminal so that it can raise the forward
voltage drop. This Will make sure that the
voltage drop across any one of the led is bigger as compared with the
forward drop of the component being examined.
The
result of the test when the component is connected.
- If LED 1 starts glowing this implies that at probe 1 of the tester cathode is coupled while at probe 2 of the tester anode is coupled.
- If LED2 starts glowing it implies that at probe 1 of the tester anode is coupled while cathode of the component is coupled with probe 2.
- If any of the LED will not glow it implies that the component coupled to the circuit is short circuit and due to that stable multivibrator of the circuit stop oscillating.
- If the components open circuit than both the LED in the circuit will start glowing.
If
you want to check the continuity of the circuit coupled the circuit
with the polarity cum continuity tester circuit with the help of
probe C1 and C2 provided in the circuit. A sound of the buzzer will
start when both the probes are attached to each other it means that
your circuit is in proper working condition. When probe C1 and C2 are
not connected with each other than at that time transistor T3 is
closed and there is no base current. At this moment voltage level of
transistor T3 at the emitter and base are of the same level.
Transistor gotten open at the time when you start the continuity test
and as compared with the emitter base of the transistor is at a
higher level so the sound started from the buzzer connected with it.
CIRCUIT
DIAGRAM:
COMPONENTS
USED:
- RESISTOR:it is a passive component and mainly employed in the circuit to direct the flow of current in the circuit. Resistors are broadly classified as fixed type and variable type.
- R1, R4 (820e) – 2
- R2, R3 (33k) – 2
- R5 (270e) – 1
- R6 (1m) – 1
- D1, D2 (1n4148) – It is a semiconductor device and it permit the current to flow merely in forward direction and block the current in backward direction.
- LED1, LED2 – LED is a semiconductor device and generally work as an indicator in any circuit and works on low voltage and current.
- C1, C2 (1uf) – Capacitors are mainly employed in the circuit to store the charges. A dielectric medium flows in it which is used to separate the two conducting plates inside it.
- T1,T2,T3 (BC547) – Transistor is a semiconductor device mainly used to amplify the current.
- BUZZER – also known as beeper and is an audio signal device.
- POWER SUPPLY OF 5 VOLT .
APPLICATIONS:
- Cables
and PCB can be checked with the help of this circuit.
- Polarity of components.
BAND PASS FILTER:
A device
that passes frequency within a certain range,and reject the
frequency outside the range. This filter can be made by combining the
low pass filter with the high pass filter. An ideal bandpass filter
would have a completely flat pass band (e.g. with no gain/attenuation
throughout) and would completely attenuate all frequencies outside
the pass band. In practice, no bandpass filter is ideal .The
bandwidth of the filter is simply the difference between the upper
and lower cutoff frequencies.
one of its type is
R.L.C band pass filter .
Here in the above circuit we are using the resister ,capacitor and inductor in series. Sin wave data is connected with having frecuency10kHz.
Resister - 8kcapacitor - 1uF
inductor - 1uH
Resonance Frequency:- AT which the simple driving force will produce large amplitude oscillation.
WO =2piFO
Q-factor:-A band-pass filter can be characterized by its q-factor higher q-factor narrow the pass band.
Q= WOLR
WAVEFORM OF R.L.C BAND PASS FILTER:
Applications:
1.
A
very frequent use of these circuits is in the tuning circuits of
analogue radios.
Adjustable
tuning is commonly achieved with a parallel plate capacitor which
allows the value of
to be changed and tune to stations on
different frequencies. For the IF stage in the radio where the tuning is preset in the
factory the more usual solution is an adjustable core in the inductor to adjust L.
2. Oscillators
3. Voltage multiplier
4. Pulse discharge circuit
BAND PASS FILTER:
A device
that passes frequency within a certain range,and reject the
frequency outside the range. This filter can be made by combining the
low pass filter with the high pass filter. An ideal bandpass filter
would have a completely flat pass band (e.g. with no gain/attenuation
throughout) and would completely attenuate all frequencies outside
the pass band. In practice, no bandpass filter is ideal .The
bandwidth of the filter is simply the difference between the upper
and lower cutoff frequencies.
one of its type is
R.L.C band pass filter .
Here in the above circuit we are using the resister ,capacitor and inductor in series. Sin wave data is connected with having frecuency10kHz.
Resister - 8kcapacitor - 1uF
inductor - 1uH
Resonance Frequency:- AT which the simple driving force will produce large amplitude oscillation.
WO =2piFO
Q-factor:-A band-pass filter can be characterized by its q-factor higher q-factor narrow the pass band.
Q= WOLR
WAVEFORM OF R.L.C BAND PASS FILTER:
Applications:
1.
A
very frequent use of these circuits is in the tuning circuits of
analogue radios.
Adjustable
tuning is commonly achieved with a parallel plate capacitor which
allows the value of
to be changed and tune to stations on
different frequencies. For the IF stage in the radio where the tuning is preset in the
factory the more usual solution is an adjustable core in the inductor to adjust L.
2. Oscillators
3. Voltage multiplier
4. Pulse discharge circuit
Fan
control is the management of the rotational speed of an electric fan.
There are many types of electric fans and many types of fan controls
.
All
fans which are used now a day are controlled manually by voltage
regulators which have different stages of speed. This process is done
manually which can be done automatically by the use of this circuit.
Here we are introducing an efficient fan speed regulation circuit, by
which the speed of a fan can be controlled depending up on the room
temperature. The circuit is highly efficient since energy loss can be
minimized by power saving as the circuit automatically adjusts the
fans speed.
CIRCUIT
DIAGRAM:
Here
is a simple circuit based on two transistors that can be used to
control the speed of a 12 V DC fan depending on the temperature. A
thermistor (R1) is used to sense the temperature. When the
temperature increases the base current of Q1 (BC 547) increases which
in turn decreases the collector voltage of the same transistor. Since
the collector of Q1 is coupled to the base of Q2 (BD 140), the
decrease in collector voltage of Q1 forward biases the Q2 more and so
do the speed of the motor. Also, the brightness of the LED will be
proportional to the speed of the motor.
COMPONENTS
USED:
- RESISTOR:It is a passive component and mainly employed in the circuit to direct the flow of current in the circuit. Resistors are broadly classified as fixed type and variable type.
- R1-Thermistor is a kind of temperature dependent resistor and its resistance varies depending on the temperature in its vicinity.
- R2,R3,R4,R5,R6,R7 – 1K
- D1 (1n4148) – It is a semiconductor device and it permit the current to flow merely in forward direction and block the current in backward direction.
- LED1– LED is a semiconductor device and generally work as an indicator in any circuit and works on low voltage and current.
- C1 (1uf) – Capacitors are mainly employed in the circuit to store the charges. A dielectric medium flows in it which is used to separate the two conducting plates inside it.
- Q1-Q2 (BC547,BD 140) – Transistor is a semiconductor device mainly used to amplify the current.
- POWER SUPPLY OF 12 VOLT .
CIRCUIT
MODIFICATIONS:
As
in the above circuit we are using the two transistors q1 and q2 ,we
can also build the circuit by using the op-amp 741IC and thermistor
as a sensor given below the circuit diagram.
CIRCUIT DIAGRAM:
APPLICATIONS:
- CONTROLLING
OF ROTATION OF FANS
BURGLAR
ALARM
This
optical burglar alarm uses two 555 timer ics (ic1 and ic2). Both the
ics are wired as astable multivibrators. The first astable
multivibrator built around ic1 produces low frequencies, while the
second astable multivibrator built around ic2 produces audio
frequencies.
General-purpose darlington photo-transistor t1 is used as the light sensor. To increase the sensitivity of the circuit, npn transistor t2 is used.
Place phototransistor t1 where light falls on it continuously. Phototransistor t1 receives light to provide base voltage to transistor t2. As a result, transistor t2 conduct to keep reset pin 4 of ic1 at low level. This disables the first multivibrator (ic1) and hence the second multivibrator (ic2) also remains reset so the alarm (ls1) does not sound.
General-purpose darlington photo-transistor t1 is used as the light sensor. To increase the sensitivity of the circuit, npn transistor t2 is used.
Place phototransistor t1 where light falls on it continuously. Phototransistor t1 receives light to provide base voltage to transistor t2. As a result, transistor t2 conduct to keep reset pin 4 of ic1 at low level. This disables the first multivibrator (ic1) and hence the second multivibrator (ic2) also remains reset so the alarm (ls1) does not sound.
CIRCUIT
DIAGRAM:
WORKING:
When
light falling on darlington phototransistor t1 is obstructed,
transistor t2 stops conducting and reset pin 4 of ic1 goes high. This
enables the first multivibrator (ic1) and hence also the second
multivibrator (ic2). As a result, a beep tone is heard from speaker
ls1. The beep rate can be varied by using preset vr1, while the
output frequency of ic2 can be varied by using another preset
vr2.
This circuit works off a simple 6v-12v dc power supply.
This circuit works off a simple 6v-12v dc power supply.
COMPONENT USED:
Resistors (all ¼-watt, ± 5% Carbon unless stated otherwise)
R1,
R5 = 1 KΩ
R2 = 100 KΩ
R3 = 4.7 KΩ
R4 = 10 KΩ
VR1 = 1 MΩ
VR2 = 100 KΩ
Capacitor:R2 = 100 KΩ
R3 = 4.7 KΩ
R4 = 10 KΩ
VR1 = 1 MΩ
VR2 = 100 KΩ
C1 = 1 µF/16V
C2 = 0.01 µF
C3 = 0.047 µF
C4 = 0.01 µF
C5 = 47 µF/25VSemiconductors:
IC1, IC2 = NE555
T1 = 2N5777 Photo Transistor
T2 = BC547
LED1 = RED LED
Miscellaneous
LS1 = 8Ω / 0.5W
MODIFICATIONS:
HERE
WE CAN USE THE ONE TRANSISTOR Q1 AND SPDT SWITCH AND WINDOW FOIL.
APPLCATIONS:
- Residential, commercial, industrial, and military properties
BATTERY
OPERATED MINI NIGHT LAMP
This
is the circuit of a low power led night lamp that will automatically
switch off at day time. The cmos timer ic ts555cn is wired as a
square wave generator operating at around 5hz.The Output voltage from
the ic1 is doubled using the combination of capacitor c2 and diode d2
in order to drive the led. The led can be a bright white led. At day
time the resistance of ldr drops to few k ohms and inhibits the ic
from producing oscillations.
CIRCUIT
DIAGRAM WITH PARTS LIST:
Notes.
Assemble
the circuit on a general purpose pcb.
The
circuit can be powered from two 1.5v cells in series.
Any
diode can be used in place of d2, but schottky diode like 1n5819 will
give more brightness.
The
ic1 must be cmos type because other types won’t operate at low
voltages like 3v.
An
optional switch can be added in series with the battery ( not shown
in circuit) to provide an manual on/off.
COMPONENTS
USED:
RESISTOR:
R2,R1=1M
R3=47K
R4=LDR
CAPACITORS:
C1=100uF
C2=220uF
DIODE:
D1,D2=1N5819
555
TIMER
MODIFICATIONS:
This
circuit can be made by using two transistors(bd 139 ,bd140) and ldr
senser with 12 v battry.
APPLCATIONS:
- HOME APPLIANCES
DARK
DETECTOR CIRCUIT
The
dark detector circuit shown here can be used to produce an audible
alarm when the light inside a room goes OFF. The circuit is build
around timer IC NE555. A general purpose LDR is used for sensing the
light. When proper light is falling on the LDR its resistance is very
low. When there is no light the LDR resistance increases. At this
time the IC is triggered and drives the buzzer to produce an alarm
sound. If a transistor and relay is connected at the output (pin3) of
IC1 instead of the buzzer, electrical appliances can be switched
according to the light.
CIRCUITR
DIAGRAM:
COMPONENT
USED:
The
LDR ,R4 can be any general purpose LDR.
The
circuit can be powered from a 9V PP3 battery.
The
POT,R3 can be sued as a volume controller.
R1=100K
R2=1M
R3=1K
R4=LDR
C1=100PF
C2=1uF
MODIFICATIONS:
As
in the above circuit we are using the 555timer , we can also buid
the circuit by using the two transistors q1 and q2 bc547 as shown
below.
Applications:
- home security
Photocell
based night light
Many
automatic night light circuits had been published here. This one uses
a photocell for detecting the light intensity. At full light the
resistance of the photocell will be few ten ohms and at darkness it
will rise to several hundred ohms. The ic1 ua741 is wired as a
comparator here. At darkness the resistance of photocell increases
and so the voltage at the inverting input of the ic1 will be less
than the reference voltage at the non inverting input. The output of
the ic1 goes to positive saturation and it switches on the transistor
to activate the relay. By this way the lamp connected through the
relay contact glows. The diode d1 works as a freewheeling diode.
CIRCUIT
DIARRAM:
COMPONENT
USED:
Use
9V DC for powering the circuit.
POT
R7 can be used to adjust the sensitivity of the circuit.
The
relay K1 can be a 9V, 200 Ohm SPDT type.
L1
can be a 230V,60W lamp.
R8
can be a ORP 12 photocel
R1=10K
R2=10K
R3=10K
R6=1K
R7=1M
D1=1N40007
Q1=BC109
L1=1uH
9V
POWER SUPPLY
MODIFICATIONS:
We
can use the transistor BC558 and LDR senser to creat this above
circuit.
APPLCATIONS:
- HOME SECURITY
- HOME APPLIANCES
BAND PASS FILTER
A device
that passes frequency within a certain range,and reject the
frequency outside the range.
This filter can be made by combining the low pass filter with the
high pass filter. An ideal bandpass filter would have a completely
flat pass band (e.g. with no gain/attenuation throughout) and would
completely attenuate all frequencies outside the pass band. In
practice, no bandpass filter is ideal .The bandwidth of the filter
is simply the difference between the upper and lower cutoff
frequencies.
One of its type is
R.C band pass filter .
RC
Bandpass Filter:
As
by connecting or “cascading” together a single Low Pass Filter
circuit with a High Pass Filter circuit, we can produce another type
of passive RC filter that passes a selected range or “band” of
frequencies that can be either narrow or wide while attenuating all
those outside of this range. This new type of passive filter
arrangement produces a frequency selective filter known commonly as a
Band Pass Filter.
Circuit
Diagram:
Here in the above circuit we are using the 2resister ,2capacitor in series and parallel. Sin wave generator is connected with having frecuency10kHz.
Resister - .2k,1kcapacitor - 2.5uF
Resonance Frequency:At which the simple driving force will produce large amplitude oscillation.
WO =2piFO
Q-factor:A band-pass filter can be characterized by its q-factor higher q-factor narrow the pass band.
Q= WOLR
CUT off Frequency: Frequency at which energy flowing through the system begins to be reduced rather than passing through.
FC= 1
2piRC
WAVEFORM OF R.C BAND PASS FILTER:
Applications:
- Many communications and sensor applications require a bandpass filter with wide bandwidth. This filter typically requires precision resistors and capacitors to obtain an accurate filter position and response.
- They are especially useful in remote areas that lack cell-signal coverage or cell towers
Sawtooth
Wave Generator
Sawtooth
waveform is a type of linear non sinusoidal waveform with a
triangular shape in which the rise time and fall time are different.
A pure triangular waveform is is also linear, non sinusoidal and have
a triangular shape but it has equal rise and fall times. The sawtooth
waveform can also be called an asymmetric triangular wave. The
graphical representation of a triangular and sawtooth waveform are
shown in the figure below. T1 is assumed to be the rise time and T2
is assumed to be the fall time.
WAVE FORM
PATTERN:
CIRCUIT DIAGRAM:
Description:
Sawtooth
waveforms can be generated by integrating square waves with unequal
rise and fall times (asymmetrical square waves). The circuit shown
above shows a setup for generating sawtooth wave. Here an NE555 timer
IC is used for generating the asymmetric square wave and op amp
integrator based on uA741 is used for integrating the asymmetric
square wave.
The
circuit diagram is shown above. When
the power supply is switched ON, capacitor C1 starts charging through
resistors R1 and R2. When the voltage across C1 is above 2/3Vcc the
upper comparator inside the NE555 swings to positive saturation and
this triggers the internal flip-flop. This makes the output (pin 3)
of the timer low. Now the capacitor C1 starts to discharge through
resistor R2 into pin 7 of the IC. When the voltage across capacitor
C1 becomes less than 1/3Vcc, the lower comparator inside the IC
switches to positive saturation and this again triggers the internal
flip-flop. As a result the output of the timer( pin 3) goes low. This
action is repeated and the result will be a square wave at pin 3 of
the NE555. The charging time period (ON time) is given by the
equation T1= 0.69(R1+R2)C1 and the discharging time period (OFF time)
is given by the equation T2=0.69R2C1. Read this article :
NE555 as astable multivibrator
for a better understanding on NE555 based astable multivibrators..
The
assymmetric square wave obtained at the output of NE555 is integrated
by the inverting active integrator based on opamp IC uA741. Resistors
R3 and R4 sets the gain of the opamp integrator. Resistor R4 in
conjunction with capacitor C3 sets the bandwidth. Since the
integrator is wired in inverting mode, the sawtooth wavform falls
when the timer output is high and rises when the timer output is low.
COMPONENT
USED:
POLAR
CAPACITER:
An
electrolytic capacitor is a capacitor that uses an electrolyte(an
ionic
conducting
liquid) as one of its plates to achieve a larger capacitance per unit
volume than other
types.
The large capacitance of electrolytic capacitors makes them
particularly suitable for
passing
or bypassing low-frequency signals and storing large amounts of
energy. They are
widely
used in power supply and interconnecting stages of amplifiers at
audio frequencies.
C1
- 1uF
C2
- 1uF
C3
- 1uF
C4
- 1uF
C5
– 1uF
RESISTERS:
R1
- 86K
R2
- 10K
R3
- 3.3K
R4
- 2.2K
R5
- 100ohm
POWER
SUPPLY : 9VOLTMODIFICATIONS:
AS IN THE ABOVE CIRCUIT WE ARE USING 555TIMER ,BUT WE CAN ALSO USE TWO 741 IC TO GENERATE SAWTOOTH WAVES.
CIRCUIT DIAGRAM:
In
this circuit a potentiometer is used (47K) . Use of the potentiometer
is when the wiper moves towards -V ,the rise tim of the sawtooth
become longer than the fall time. If the wiper moves towards +V , the
fall time becomes more than the rise time.
Reason is when comparator output is at -ve saturation. When wiper moves to -ve supply, a negative voltage is added to inverting terminal. This causes the potential difference across R1 decreases and hence the current through the resistor and capacitor decreases . Then slope of the output, I/C decreases and un tern rise time decreases. When the comparator output goes positive , due to presence of negative voltage at the inverting terminal, potential difference of across the resistor R1 increases and hence current increases. Then slope increases and fall time decreases. And obtained output as sawtooth wave.
Reason is when comparator output is at -ve saturation. When wiper moves to -ve supply, a negative voltage is added to inverting terminal. This causes the potential difference across R1 decreases and hence the current through the resistor and capacitor decreases . Then slope of the output, I/C decreases and un tern rise time decreases. When the comparator output goes positive , due to presence of negative voltage at the inverting terminal, potential difference of across the resistor R1 increases and hence current increases. Then slope increases and fall time decreases. And obtained output as sawtooth wave.
