Design of a Clap Activated Switch ANNAMACHARYA INSTITUTE OF TECHNOLOGY AND SCIENCES, TIRUPATI. DEPARTMENT OF ELECTRICAL &ELECTRONIC ENGINEERING MINI PROJECT ON : DESIGN OF CLAP ACTIVATED SWITCH PROJECT GUIDE : Mr. Jakeer Hussain, B.TECH, M.E ASSOCIATE PROFESSOR, Department Of E.E.E, A.I.T.S,TIRUPATHI. PROJECT MEMBERS : 1) K.SENTHIL KUMAR : 07AK1A0245 2) R.NARENDRA : 07AK1A0228 3) Y.SANDEEP KUMAR : 07AK1A0242 1
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Design of a Clap Activated Switch
ANNAMACHARYA INSTITUTE OF TECHNOLOGY AND
SCIENCES,
TIRUPATI.DEPARTMENT OF ELECTRICAL &ELECTRONIC
ENGINEERING
MINI PROJECT ON: DESIGN OF CLAP ACTIVATED SWITCH
PROJECT GUIDE : Mr. Jakeer Hussain, B.TECH, M.E
ASSOCIATE PROFESSOR, Department Of E.E.E, A.I.T.S,TIRUPATHI.
commonly used as an amplifier or an electrically controlled
switch. The transistor is the fundamental building block of the
14
Design of a Clap Activated Switch
circuitry in computers, cellular phones, and all other modern
electronic devices.
Because of its fast response and accuracy, the transistor is used in a wide variety of digital and analog functions, including amplification, switching, voltage regulation, signal modulation, and oscillators. Transistors may be packaged individually or as part of an integrated circuit, some with over a billion transistors in a very small area. TRANSISTORS USED:
Q1,2,3,4 BC 149
7.1 TRANSFORMER:
INTRODCTION OF TRANSFORMER
A device used to transfer electric energy from one
circuit to another, especially a pair of multiply wound, inductively coupled
In the vast majority of transformers, the windings are coils wound
around a ferromagnetic core, air-core transformers being a notable
exception.
Transformers range in size from a thumbnail-sized
coupling transformer hidden inside a stage microphone to huge units
weighing hundreds of tons used to interconnect portions of power grids. All
operate with the same basic principles, although the range of designs is
wide. While new technologies have eliminated the need for transformers in
some electronic circuits, transformers are still found in nearly all electronic
devices designed for household ("mains") voltage. Transformers are
essential for high voltage power transmission, which makes long distance
transmission economically practical.
Step down transformers are designed to reduce electrical voltage. Their primary voltage is greater than their secondary voltage. This kind of transformer "steps down" the voltage applied to it. For instance, a step down transformer is needed to use a 110v product in a country with a 220v supply.
Step down transformers convert electrical voltage from one level
or phase configuration usually down to a lower level. They can include
features for electrical isolation, power distribution, and control and
instrumentation applications. Step down transformers typically rely on the
principle of magnetic induction between coils to convert voltage and/or
current levels.
Step down transformers are made from two or more coils of
insulated wire wound around a core made of iron. When voltage is applied to
one coil (frequently called the primary or input) it magnetizes the iron core,
which induces a voltage in the other coil, (frequently called the secondary or
output). The turns ratio of the two sets of windings determines the amount of
voltage transformation.
An example of this would be: 100 turns on the primary and 50 turns on the
secondary, a ratio of 2 to 1.
Step down transformers can be considered nothing more than a voltage ratio
device.
With step down transformers the voltage ratio between primary and
secondary will mirror the "turns ratio" (except for single phase smaller than 1
kva which have compensated secondaries). A practical application of this 2
to 1 turns ratio would be a 480 to 240 voltage step down. Note that if the
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Design of a Clap Activated Switch
input were 440 volts then the output would be 220 volts. The ratio between
input and output voltage will stay constant. Transformers should not be
operated at voltages higher than the nameplate rating, but may be operated
at lower voltages than rated. Because of this it is possible to do some non-
standard applications using standard transformers.
Single phase step down transformers 1 kva and larger may also be reverse
connected to step-down or step-up voltages. (Note: single phase step up or
step down transformers sized less than 1 KVA should not be reverse
connected because the secondary windings have additional turns to
overcome a voltage drop when the load is applied. If reverse connected, the
output voltage will be less than desired.)
8.1 RELAY:
INTRODCTION OF RELAYS
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Design of a Clap Activated Switch
A relay is an electrical switch that opens and closes under
the control of another electrical circuit. In the original form, the switch is
operated by an electromagnet to open or close one or many sets of contacts.
It was invented by Joseph Henry in 1835. Because a relay is able to control
an output circuit of higher power than the input circuit, it can be considered,
in a broad sense, to be a form of an electrical amplifier.
8.2 RELAY OPERATION :
All relays operate using the same basic principle. Our example will use a commonly used 4 - pin relay. Relays have two circuits: A control circuit (shown in GREEN) and a load circuit (shown in RED). The control circuit has a small control coil while the load circuit has a switch. The coil controls the operation of the switch.
8.3 RELAY ENERGIZED (ON) :
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Design of a Clap Activated Switch
Current flowing through the control circuit coil (pins 1 and 3) creates a small magnetic field which causes the switch to close, pins 2 and 4. The switch, which is part of the load circuit, is used to control an electrical circuit that may connect to it. Current now flows through pins 2 and 4 shown in RED, when the relay is energized.
8.4 RELAY DE-ENERGIZED (OFF) : When current
stops flowing through the control circuit, pins 1 and 3, the relay becomes de-
energized. Without the magnetic field, the switch opens and current is
prevented from flowing through pins 2 and 4. The relay is now OFF
.
9.1 CONDENSER MIC:
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Design of a Clap Activated Switch
INTRODUCTION OF CONDENSER MICROPHONE
Condenser means capacitor, an
electrCondenonic component which stores energy in the form of
an electrostatic field. The term condenser is actually obsolete but
has stuck as the name for this type of microphone, which uses a
capacitor to convert acoustical energy into electrical energy.
Condenser microphones require power from a
battery or external source. The resulting audio signal is stronger
signal than that from a dynamic. Condensers also tend to be more
sensitive and responsive than dynamics, making them well-suited
to capturing subtle nuances in a sound. They are not ideal for
high-volume work, as their sensitivity makes them prone to
distort.
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Design of a Clap Activated Switch
4.9.1 CONDENSER MICROPHONE
9.2 Mic Level and Line Level :
The current generated by a microphone is very
small and this current is referred
to as mic level and typically measured in milli-volts. Before it is
usable, the signal must be amplified, usually to line level, with
typical value within (0.5 – 2) volts, which is stronger and more
robust signal. The line level is the standard signal strength used
by audio processing equipment
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Design of a Clap Activated Switch
10 CIRCUIT DIAGRAM
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Design of a Clap Activated Switch
11.1 OPERATION:
Here is a circuit that can switch on & off a light, Fan, Radio etc.
by the sound of clap .The sound of clap is received by a small microphone
that is shown biased by resistor R1 in the circuit. The microphone changes
sound wave in to electrical wave which is further amplified by Q1. Transistor
Q1 is used as common emitter circuit to amplify weak signals received by
the microphone. Amplified output from the collector of transistor Q1 is then
feed to the Bistable Multivibrator circuit also known as flip-flop.
Flip flop circuit is made by using 2 Transistor, in our circuit Q2&Q3. In a flip-flop circuit, at a time only one transistor conduct and other cut off and when it gets a trigger pulse from outside source then first transistor is cutoff and 2nd transistor conducts.
Thus output of transistor is either logic-0 or logic-1
and it remains in one state 0 or 1 until it gets trigger pulse from
outer source.
The pulse of clap which is trigger for flip-flop makes
changes to the output which is complementary (reverse). Decision of flip-flop
which is in the low current form is unable to drive relay directly so we have
used a current amplifier circuit by using Q4 which is a common emitter
circuit. Output of Q4 is connected to a Relay (Electromagnetic switch), works
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Design of a Clap Activated Switch
like a mechanical switch. With the help of a relay it is easy for connecting
other electrical appliance.
The relay contact is connected to the power line and hence turns on/off
any electrical appliance connected all the way through relay.
For power supply, we have made 12Volt eliminator with the help of
Transformer T1, Diode D1 and capacitor C1.It is a half wave rectifier.
11.2 AMPLIFIER:
A transistor stage, biased near cut-off (that is, almost no current with no
signal) amplifies the signal from the microphone. The output of the
microphone is coupled to the base of the transistor using an electrolytic
capacitor (note: using a better capacitor here will not work). The top of the
electret microphone is at a few volts, the base conducts at around half a volt,
so the leakage current of the capacitor (all electrolytic capacitors leak at
least a little bit) will eventually cause the steady state condition in which the
leakage of the capacitor goes into the base terminal of the transistor. So the
collector will have Hfe times this leakage, which can usually be ignored.
The first time the microphone output goes positive, however, (because
somebody clapped) this change gets coupled to the base entirely due to the
action of the capacitor. This causes the current through the transistor to
increase, and this increase in current causes the voltage at the collector, 26
Design of a Clap Activated Switch
which was sitting near the supply voltage, to fall to nearly zero. If you
clapped loudly enough, of course.
This is not a high fidelity audio amplifier. Its function is to produce no output
for small sounds and large output for (slightly) bigger sounds, so the
customary biasing network can be omitted. The 4.7 Megohm resistor in the
previous version was as good as an open circuit, and its omission does not
affect the operation of the clap switch in any way. Provided, of course, that
you use that 10 microfarad electrolytic capacitor.
11.3 Memory:
Two cross connected transistors in a bistable multivibrator arrangement
make up a circuit that remembers. You can set it to one of two possible
states, and it will stay in that state until the end of time. When one transistor
conducts, its collector is near ground, and a resistor from this collector feeds
the base of the other. Since this resistor sees ground at the collector end the
base at the other end receives no current, so that transistor is off. Since this
transistor is off, its collector is near supply potential and a resistor connects
from this to the base of the other transistor. Since this resistor sees voltage,
it supplies the base with current, ensuring that the transistor remains on.
Thus this state is stable. By symmetry, the other state is, too.
11.4 Changing state:
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Design of a Clap Activated Switch
On a clap, the state of the bistable changes. The output of the amplifier is
converted to a sharp pulse by passing it through a (relatively) low valued
capacitor, of 0.1 microfarads (100 nanofarads). This is connected through
"steering" diodes to the base of the transistor which is conducting. This
transistor stops conducting, and the other transistor was not conducting
anyway. So at a clap, both transistors become off.
Then, those two capacitors across the base resistors come into action. The
capacitor connecting to the base of the transistor which was ON has voltage
across it. The capacitor connecting to the base of the transistor which was
OFF has no voltage across it.
As the sound of the clap dies away, both bases rise towards the supply voltage. But, due to the difference in the charges of the two capacitors, the base of the transistor which was previously not conducting reaches the magic value of half a volt first, and it gets on, and stays on. Until the next clap.
Two red Light Emitting Diodes have been placed in the two collector circuits so that this circuit can be made to work by itself. If you cover up one LED, and display the other prominently, you have it there - a clap operated light.
11.5 Output Stage:
In order to have a decent amount of light from this circuit, I propose to use six white LEDs in three groups of two each. Each series connected string of
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Design of a Clap Activated Switch
two LEDs is arranged to draw around fifteen milliamperes or so by using a series resistor of 330 ohms. Two LEDs in series will drop about five or six volts, and the remaining battery voltage drop across this resistor determines the current through the LEDs. You can get more brightness from the LEDs by reducing the value to 220 ohms or even 150 ohms, provided you keep within the ratings of the LEDs. Do so at your own risk.
Thus the output stage has to handle around fifty or sixty milliamperes. This will give you fairly long time of claplighting with a PP3 battery. The 100mA filament lamp seems to be somewhat hard to find, and people were using torch bulbs, which run at much higher current, and killing their batteries in a few minutes.
A transistor gets its base driven from the collector of one of the transistors in the bistable. With this connection, due to the base current through it, one red LED in the bistable switches between half bright and full, and the other switches between fully off and on. This is normal.
Because the LEDs do not draw as much current as a filament lamp, the output transistor, too, can be of the common small signal variety. All four could be any small signal n-p-n transistor and the circuit should work. So would it with four p-n-p transistors, provided you switch the polarity of every (polarised) component.
12.0.1Design Calculations
12.1 For transistor Switch :
Using general purpose transistor BC 337
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Design of a Clap Activated Switch
Supply voltage, Vs = 9V The load driven by the transistor is the relay Rl Load resistance Rl = 150 ohm
Load current I1 = Supply Voltage, Vs Load Resistance, Rl = 9/150 = 60 mA
Since Il (max) must be greater than Il and from the date sheet Ic(max) = 100mA
Ic > Il To calculate for Base Resistor, R2
R2 = Vc×hfe (4.2) 5×Ic
Where Vc = Chip supply voltage
But since Vc = Vs Then
R14 = (Vs×hfe) (4.3) 5×Ic = 9×400
5×100 = 7.2 KΩ
Where the typical hfe value = 400 from the date sheet, and Ic = 100 mA.
Therefore, R14 is selected to be 10 KΩ
12.2 For light Emitting Diode (LED) :
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Design of a Clap Activated Switch
To determine the value of the voltage dropper resistor, the voltage supply value must be known. From this value, the characteristic voltage drop of an LED can then be subtracted, and the value of drop across an LED depending on the desired brightness and colour will range from 1.2 V to 3.0 V.
If(max) = 20mA Vcc = 9V Vf = 2V
Required current I(req) = 5mA. RLED = Vcc–Vf (4.4) If (max) = 9-2
5×10-3 = 1.4 KΩ (4.5)
But choosing IR (LED) = 10mA R(LED) = 9–2
10×10-3 (4.6) = 0.7 KΩ
Where VF = the maximum forward voltage drop Vcc = the supply voltage RLED = the LED current limiting resistor
Considering equations (4.5) and (4.6)
R9 and R13 are chosen to be 1KΩ
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Design of a Clap Activated Switch
12.3 Design calculation for condenser microphone: From the data sheet, the electrets condenser microphone has the following specifications:
Rated Voltage = 2V Operating Voltage = 1–10 V Sensitivity = -44+/-3dB S/N = 55dB
The microphone – biasing resistor, R1 is given by
R1 = Vs–V(rated) (4.7) 2mA R1 = 3.5 KΩ
Therefore, R1 was chosen to be 3.3KΩ.
12.4 Design calculation for Transistor Amplifier :An audio low noise transistor is used for the audio signal amplifier circuit in this design, and this is wired in a common-emitter mode. At the saturation level, maximum collector current for an emitter-base design can be determined by applying a short circuit between the collector-emitter terminals. At this point, the voltage across the collector-emitter junction is almost zero.
From data sheet, Vce(sat) = 0.3 V Ic (sat) = Vs-Vce (sat) (4.12) Rc + RE
Where Ic = 2mA 2mA=9–0.3
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Design of a Clap Activated Switch
Rc+RE Rc +RE=9 – 0.3/ 2×10-3
=4.34KΩ
For linear amplification and maximum output purpose, the operating point
should lie around the dc load-line. The quiescent point normally takes a
value of about half the supply voltage.
The quiescent, Vce = 9/2 (4.13)
= 4.5 V
the emitter terminal is made to be a little above ground level. Therefore,
voltage from emitter to ground, VE is usually arranged to be one tenth of
supply voltage, VS.
VE = VS/10 (4.14)
= 9.0/ 10
= 0.9 V
Hence the emitter resistor
R6 = VE/IE 4.15)
R6 = VE /IE
= VE/ IC
= 0.9/2×10-3
= 450 Ω
The voltage drop across R4 is given by
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Design of a Clap Activated Switch
VB = R4/ R3+R4×VS (4.16)
IB–IBRTH – VBE – IERE=0 (4.17)
Substituting IE = (β + 1) IB into equation 4.17, we have
IB–IBRTH–VBE-(β+1) IBRE=0
IB=VB–VBE/ [RTH+ (β+1) RE] 4.18)
VB = VE–VBE (4.19)
= 0.9 – 0.7
= 0.2 V
From equation 4.16, we have
VB(R1 +R4)=R2VCC (4.20)
0.2 (R1+R4) =9R2
0.2R1 + 0.2R4 = 9R4
R1 = 44R4 (4.21)
And 10R4≤βRE
Where RE=450 Ω and
β = 650 From data sheet R4 ≤650×450 /10 =29,250Ω hence R4 = 30 KΩ then, from equation 4.21, we have R3=44×40 KΩ =1320 KΩ
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Design of a Clap Activated Switch
=1.3 MΩ VCE = 4.5V from equation 4.13 Then RS + RE = Vs – VCE / IC =9.0 – 4.5 / 2×10-3 RS + RE = 2.25 KΩ RE=2.25 KΩ – 450 Ω
=1.75 KΩ
13.1 :DIFFERENCE BETWEEN CONDENSER MICROPHONE AND DYNAMIC MICROPHONE :
Table1: Comparison Between Dynamic And Condenser
Microphone Dynamic Microphone
Condenser Microphone
Do not have flat frequency response but rather tend to have
tailed frequency response for particular applications
Have a flat frequency
response
Operate with the principle of Electromagnetism as it does
not require voltage supply.
Employs the principle of
electrostatics and
consequently, require
voltage supply across the
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Design of a Clap Activated Switch
capacitor for it to work.
They are suitable for handling high volume level, such as
from certain musical instruments.
They are not ideal for
high volume work as their
sensitivity makes them
prone to distortion.
The signal produced are strong therefore making them
sensitive
The resulting audio signal
is stronger than that from
a dynamic. It also tends to
be more sensitive and
responsive than dynamic.
15.1 APPLICATIONS
This circuit can be used to switch on and off a light, a fan, a radio
or a t.v. by the sound of a clap.
14.2 ADVANTAGES AND DISADVANTAGES OF
CLAPSWITCH:
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Design of a Clap Activated Switch
The major advantage of a clap switch is that you can turn
something (e.g. a lamp) on and off from any location in the room (e.g. while
lying in bed) simply by clapping your hands.
The major disadvantage is that it's generally cumbersome to
have to clap one's hands to turn something on or off and it's generally seen
as simpler for most use cases to use a traditional light switch. The primary
application involves an elderly or mobility-impaired person. A clap switch is
generally used for a light, television, radio, or similar electronic device that
the person will want to turn on/off from bed.
CONCLUSION:
Hereby we would like to conclude that this circuit is very much
useful to switch ON and OFF the household appliances just by clapping
hand .This circuit functions on using the sound energy provided by the clap
which is converted into electrical energy by condenser mic .This circuit turns
on and off a light, a fan, a radio, a t.v. etc using this converted electrical
energy which is used to turn on relay (an electronic switch).
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Design of a Clap Activated Switch
References:
1. Edward Hughes, Hughes Electrical technology, Addition Wesley Longman
(Singapore) plc Ltd, India, Seventh Edition, (pp 395-399). (2001)
2. Paul Horonitz and Weinbeild Hill, the Art of Electronics, second Edition,
Cambridge University Ulc.(1995)
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Design of a Clap Activated Switch
3. Ray Marston, “Relay Output Circuits”, Electronics Now Magazine, July
1994
4. http://www.kpsec.com : Country circuits, the Electronics club
5. Alex Pounds, “Electronics Tutorial” Denenberg University,