Download - Mini Porject
-
8/8/2019 Mini Porject
1/38
1
A
MINI PROJECT
REPORT ON
MOBILE BUG
Submitted in partial fulfillment
of the requirement for
BACHELOR DEGREEIN
ELECTRONICS & COMMUNICATION
2010-2011
Guided by:-
Md. YUSUF
SUBMITTED BY:-1. KAUSHAL KR. SINGH -0701931040
2. KHUSHBU GUPTA - 0701931041
3. KM. ARTI TEOTIA- 0701931042
-
8/8/2019 Mini Porject
2/38
2
ACKNOWLEDGEMENT
A lot of effort has gone into the report and my thanks are due to many people
without whom this report wouldnt been possible. First of all, I gratefully
acknowledge the continuous assistance and inspiration given to me by my
college faculty. I would like to thank my family for providing me monetary and
non-monetary support, as and when required. My gratitude also goes to the
IEEE website, via internet, which gave me lots of fruitful information, about the
proposed topic. . Finally I would like to thanks Md. YUSUF, in charge
withoutwhom this would not have been completed in time.
- Kaushal kr. SinghKhushbu guptaKm. Arti teotia
-
8/8/2019 Mini Porject
3/38
3
Contents
S
no.
Description Page no.
1 Introduction 4
2 Circuit description 5-13
3 Definition of pin function 14-22
4 Operating modes 23-27
5 Comparison between 555 & 7555 timer 28
6 A stable operation 29-31
7 Required parts 32-36
s8 Precautions 37
-
8/8/2019 Mini Porject
4/38
4
INTORDUCTION
Q.1:- What is mobile bug????
Th is h andy, pocket-size mobile transmission detector can sense t h e presence of an activated mobile p h one from a distance of one and a- h alf meters.
Q.2:- Where is mobile bug used????
It can be used to prevent use of mobile p h ones in examination h alls, confidential
rooms, etc. It is also useful for detecting t h e use of mobile p h one for spying and
unaut h orized video transmission.
Th e circuit can detect bot h th e incoming and outgoing calls, SMS andvideo
transmission even if t h e mobile p h one is kept in t h e silent mode.
y Th e moment t h e bug detects RF transmission signal from an activated
mobile p h one, it starts sounding a beep alarm and t h e LED blinks.
y Th e alarm continues until t h e signal transmission ceases.
y An ordinary RF detector using tuned LC circuits is not suitable for detecting
signals in t h e GHz frequency band used in mobile p h ones.
y Th e transmission frequency of mobile p h ones ranges from 0.9 to 3 GHz
wit h a wavelengt h of 3.3 to 10 cm. So a circuit detecting giga h ertz signals is
required for a mobile bug.
-
8/8/2019 Mini Porject
5/38
5
Circuit description:-
y O P-amp IC CA3130 (IC1) is used in t h e circuit as a current-to-voltageconverter wit h capacitor C3 connected between its inverting and non-
inverting inputs.
y It is a CMOS version using gate-protected p-c h annel MOSFET transistors inth e input to provide very h igh input impedance, very low input current and
very h igh speed of performance.
y Th e output CMOS transistor is capable of swinging t h e output voltage towit h in 10 mV of eit h er supply voltage terminal.
y Capacitor C3 in conjunction wit h th e lead inductance acts as a transmissionline t h at intercepts t h e signals from t h e mobile p h one.
y Th is capacitor creates a field, stores energy and transfers t h e stored energyin t h e form of minute current to t h e inputs of IC1.
y Th is will upset t h e balanced input of IC1 and convert t h e current into t h ecorresponding output voltage.
y Capacitor C4 along wit h h igh -value resistor R1 keeps t h e non-invertinginput stable for easy swing of t h e output to h igh state.
y Resistor R2 provides t h e disc h arge pat h for capacitor C4. Feedback resistor
R3 makes t h e inverting input h igh wh en t h e output becomes h igh .
y Capacitor C5 (47p F) is connected across strobe (pin 8) and null inputs
(pin 1) of IC1 for p h ase compensation and gain control to optimize t h e
frequency response.
-
8/8/2019 Mini Porject
6/38
6
y Wh en t h e mobile p h one signal is detected by C3, t h e output of IC1
becomes h igh and low alternately according to t h e frequency of t h e signal
as indicated by LED1.
y Th is triggers mono-stable timer IC2 t h roug h capacitor C7 .
y Capacitor C6 maintains t h e base bias of transistor T1 for fast switc h ing
action.
y Th e low-value timing components R6 and C9 produce very s h ort time delay
to avoid audio nuisance.
y Assemble t h e circuit on a general purpose PCB as compact as possible and
enclose in a small box like junk mobile case.
y carefully solder t h e capacitor C3 in standing position wit h equal spacing of
th e leads.
y Th e response can be optimized by trimming t h e lead lengt h of C3 for t h e
desired frequency.
y You may use a sh ort telescopic type antenna .
y U se t h e miniature 12V battery of a remote control and a small buzzer to
make t h e gadget pocket-size.
y Th e unit will give t h e warning indication if someone uses mobile p h one
wit h in a radius of 1.5 meters.
-
8/8/2019 Mini Porject
7/38
7
CIRCUIT DIAGRAM
-
8/8/2019 Mini Porject
8/38
8
y Th e 555 timer IC was first introduced around 1971 by t h e Signe
tics Corporation as t h e SE555/NE555 and was called " Th e IC Time
Mac h ine " and was also t h e very first and only commercial timer IC
available.
y Th is device was first made commercially available.
y Th e past ten years some manufacturers stopped making t h ese
timers because of competition or ot h er reasons. Yet ot h er
companies, like NTE (a subdivision of P h ilips) picked up w h ere
some left off.
y Alth oug h th ese days t h e CMOS version of t h is IC, like t h e
Motorola MC1455, is mostly used, t h e regular type is still
available.
y But all types are pin-for-pin plug compatible. Every time we can
see t h is 555 timer used in advanced and h igh -tec h electronic
circuits. It is just incredible.
y Here we will s h ow you w h at exactly t h e 555 timer is.
y Th is timer uses a maze of transistors, diodes and resistors and for
th is complex reason we will use a more simplified (but accurate)
block diagram to explain t h e internal organizations of t h e 555.
y So, let s start slowly and build it up from t h ere.
y Th e first type-number represents t h e type w h ich was/is preferred for
military applications w h ich h ave somew h at improved electrical and t h ermal
ch aracteristics, but also a bit more expensive, and usually metal-can or
ceramic casing.
-
8/8/2019 Mini Porject
9/38
9
y Th is is analogous to t h e 5400/7400 series convention for TTL integrated
circuits.
y Th e 555 come in two packages, eit h er t h e round metal-can called t h e ' T '
package or t h e more familiar 8-pin DIP ' V' package . About 20-years ago t h e
metal-can type was pretty muc h th e standard (SE/NE types).
y Th e 556 timer is a dual 555 version and comes in a 14-pin DIP package, t h e
558 is a quad version wit h four 555's also in a 14 pin DIP case.
-
8/8/2019 Mini Porject
10/38
10
I nside the 555 timer, at fig. 3, are the equivalent of over 20 transistors, 15
resistors, and 2 diodes, depending of the manufacturer.
-
8/8/2019 Mini Porject
11/38
11
y Th e Th res h old current determine t h e maximum value of Ra + R b. For 15
volt operation t h e maximum total resistance for R (Ra +Rb) is 20 Mega-
oh m.
y Th e supply current, w h en t h e output is ' h igh ', is typically 1 milli-amp (mA)
or less.
y Th e initial mono-stable timing accuracy is typically wit h in 1% of its
calculated value, and
y Exh ibits negligible (0.1%/V) drift wit h supply voltage.
y Th e temperature variation is only 50ppm/C (0.005%/C).
Some of t h e more attractive features of t h e 555 timer are :-
Supply voltage between 4.5 and 18 volt,
Supply current 3 to 6 mA,
A rise/Fall time of 100 nSec.
It can also wit h stand quite a bit of abuse.
-
8/8/2019 Mini Porject
12/38
12
y it takes a finite period of time for a capacitor (C) to c h arge or disc h arge
th roug h a resistor (R).
y Th ose times are clearly defined and can be calculatedwit h th e given values
of resistance and capacitance.T h e basic RC c h arging circuit is sh own in fig.
4.
y Assume t h at t h e capacitor is initially disc h arged. Wh en t h e switc h is closed,
th e capacitor begins to c h arge t h roug h th e resistor. T h e voltage across t h e
capacitor rises from zero up to t h e value of t h e applied DC voltage.
-
8/8/2019 Mini Porject
13/38
13
y Th e c h arge curve for t h e circuit is s h own in fig.6. T h e time t h at it takes for
th e capacitor to c h arge to 63.7% of t h e applied voltage is known as t h e
time constant (t) .
y Th at time can be calculated wit h th e simple expression :
t = R X C
Assume a resistor value of 1 MegaO h m and a capacitor value of 1uF (micro-
Farad). T h e time constant in t h at case is :
t = 1,000,000 X 0.000001 = 1 second
y Assume furt h er t h at t h e applied voltage is 6 volts. T h at means t h at it will
take one time constant for t h e voltage across t h e capacitor to reac h
63.2% of t h e applied voltage. T h erefore, t h e capacitor c h arges to
approximately 3.8 volts in one second.
F ig. 4-1, Change in the input pulse frequency allows completion of thetiming cycle.
-
8/8/2019 Mini Porject
14/38
14
As a general rule, t h e mono-stable 'ON' time is set approximately 1/3
longer t h an t h e expected time between triggering pulses. Suc h a circuit is
also known as a Missing Pulse Detector .
Looking at t h e curve in fig. 6. You can see t h at it takes approximately 5
complete time constants for t h e capacitor to c h arge to almost t h e applied
voltage. It would take about 5 seconds for t h e voltage on t h e capacitor to
rise to approximately t h e full 6-volts.
Definition of Pin Functions:
Pin 1 (Ground):Th e ground (or common) pin is t h e most-negative supplypotential of t h e device, w h ich is normally connectedto circuit common (ground)
Wh en operated from positive supply voltages.
Pin 2 (Trigger): y Triggering is accomplis h ed by taking t h e pin from above to below a
voltage
y Sensitive, allowing slow rate-of-c h ange waveforms, as well as pulses, to
be used level of 1/3 V+ (or, in general, one- h alf t h e voltage appearing at
pin 5).
y Th e action of t h is pin is t h e input to t h e lower comparator and is used to
set t h e latc h , w h ich in turn causes t h e output to go h igh . Th is is t h e
beginning of t h e timing sequence in mono-stable operation.
-
8/8/2019 Mini Porject
15/38
15
y Trigger input is level-as trigger sources. T h e trigger pulse must be of
sh orter duration t h an t h e time interval determined by t h e external R and
C.
y If th is pin is h eld low longer t h an t h at, t h e output will remain h igh until
th e trigger input is driven h igh again. One precaution t h at s h ould be
observed wit h th e trigger input signal is t h at it must not remain lower
th an 1/3 V+ for a period of time longer th an t h e timing cycle.
y If th is is allowed to h appen, t h e timer will re-trigger itself upon
termination of t h e first output pulse. T h us, w h en t h e timer is driven in
th e mono-stable mode wit h input pulses longer t h an t h e desired output
pulse widt h , t h e input trigger s h ould effectively be s h ortened by
differentiation.
y If th e minimum-allowable pulse widt h for triggering is greater t h an t h e
1uS (micro-Second), triggering will be reliable.
y In practice, t h e minimum mono-stable output pulse widt h sh ould be in
th e order of 10uS to prevent possible double triggering due to t h is effect.
Th e voltage range t h at can safely be applied to t h e trigger pin is between
V+ and ground .
y For a-stable configuration operating at V+ = 5 volts, t h is resistance is 3
Mega-o h m; it can be current, termed t h e trigger current , must also flow
from t h is terminal into t h e external circuit. T h is current is typically
500nAgreater for h igh er V+ levels.
-
8/8/2019 Mini Porject
16/38
16
Pin 3 (Output):
y Th e output of t h e 555 comes from a h igh -current totem-pole stage
made up of transistors Q20 - Q24. Transistors Q21 and Q22 provide drive
for source-type loads, and t h eir Darlington connection provides a h igh -
state output voltage about 1.7 volts less t h an t h e V+ supply level used.
y Transistor Q24 h as a low saturation voltage, w h ich allows it to interface
directly, wit h good noise margin, w h en driving current-sinking logic.
y High -state level is typically 3.3 volts at V+ = 5 volts; 13.3 volts at V+ = 15
volts. Bot h th e rise and fall times of t h e output waveform are quite fast,
typical switc h ing times being 100nS. T h e state of t h e output pin will
always reflect t h e inverse of t h e logic state of t h e latc h , and t h is fact may
be seen by examining Fig. 3.
y To trigger t h e output to a h igh condition, t h e trigger input is
momentarily taken from a h igh er to a lower level. [see "Pin 2 - Trigger"].
Th is causes t h e latc h to be set and t h e output to go h igh .
y Actuation of t h e lower comparator is t h e only manner in w h ich th e
output can be placed in t h e h igh state.
y Th e output can be returned to a low state by causing t h e t h res h old to go
from a lower to a h igh er level [see "Pin 6 - T h res h old"], w h ich resets t h e
latc h .
y Th e output can also be made to go low by taking t h e reset to a low state
near ground [see "Pin 4 - Reset"]. T h e output voltage available at t h is pin
is approximately equal to t h e Vcc applied to pin 8 minus 1.7V.
-
8/8/2019 Mini Porject
17/38
17
Pin 4 (Reset):y Th is pin is also used to reset t h e latc h and return t h e output to a low
state. T h e reset voltage t h res h old level is 0.7 volt, and a sink current of
0.1mA from t h is pin is required to reset t h e device. T h ese levels are
relatively independent of operating V+ level; t h us t h e reset input is TTL
compatible for any supply voltage.
y Th e reset input is an overriding function; t h at is, it will force t h e output to
a low state regardless of t h e state of eit h er of t h e ot h er inputs. It mayth us be used to terminate an output pulse prematurely, to gate
oscillations from "on" to "off", etc.
y Delay time from reset to output is typically on t h e order of 0.5 S, and
th e minimum reset pulse widt h is 0.5 S. Neit h er of t h ese figures is
guaranteed, h owever, and may vary from one manufacturer to anot h er.
y In s h ort, t h e reset pin is used to reset t h e flip-flop t h at controls t h e stateof output pin 3. T h e pin is activated w h en a voltage level anyw h ere
between 0 and 0.4 volt is applied to t h e pin.
y Th e reset pin will force t h e output to go low no matter w h at state t h e
ot h er inputs to t h e flip-flop are in. Wh en not used, it is recommended
th at t h e reset input be tied toV+ to avoid any possibility of false resetting.
-
8/8/2019 Mini Porject
18/38
18
Pin 5 (Control Voltage):y Th is pin allows direct access to t h e 2/3 V+ voltage-divider point, t h e
reference level for t h e upper comparator. It also allows indirect access to
th e lower comparator, as t h ere is a 2 :1 divider (R8 - R9) from t h is point to
th e lower-comparator reference input, Q13.
y U se of t h is terminal is t h e option of t h e user, but it does allow extreme
flexibility by permitting modification of t h e timing period, resetting of t h e
comparator, etc. Wh en t h e 555 timer is used in a voltage-controlled
mode, its voltage-controlled operation ranges from about 1 volt less t h an
V+ down to wit h in 2 volts of ground (alt h oug h th is is not guaranteed).
Voltages can be safely applied outside t h ese limits, but t h ey s h ould be
confined wit h in t h e limits of V+ and ground for reliability.
y By applying a voltage to t h is pin, it is possible to vary t h e timing of t h e
device independently of t h e RC network.
Mono-stable mode
y Th e control voltage may be varied from 45 to 90% of t h e Vcc, making it
possible to control t h e widt h of t h e output pulse independently of RC.
A-stable mode
y Th e control voltage can be varied from 1.7V to t h e full Vcc. Varying t h e
voltage in th
e a-stable mode will produce a frequency modulated (FM)output.
y In t h e event t h e control-voltage pin is not used, it is recommended t h at it
be bypassed, to ground, wit h a capacitor of about 0.01uF (10nF) for
immunity to noise, since it is a comparator input.
-
8/8/2019 Mini Porject
19/38
19
y Th is fact is not obvious in many 555 circuits since I h ave seen many
circuits wit h 'no-pin-5' connected to anyt h ing, but t h is is t h e proper
procedure. T h e small ceramic cap may eliminate false triggering.
Pin 6 (Threshold): y Pin 6 is one input to t h e upper comparator (t h e ot h er being pin 5) and is
used to reset t h e latc h , wh ich causes t h e output to go low. Resetting via
th is terminal is accomplis h ed by taking t h e terminal from below to above
a voltage level of 2/3 V+ (t h e normal voltage on pin 5).
y Th e action of t h e t h res h old pin is level sensitive, allowing slow rate-of-
ch ange waveforms.
y Th e voltage range t h at can safely be applied to t h e t h res h old pin is
between V+ and ground. A dc current, termed t h e threshold current,
must also flow into t h is terminal from t h e external circuit.
y Th is current is typically 0.1A, and will define t h e upper limit of total
resistance allowable from pin 6 to V+.
y For eit h er timing configuration operating at V+ = 5 volts, t h is resistance is
16 Mega-o h m.
y For 15 volt operation, t h e maximum value of resistance is 20 MegaO h ms.
Pin 7 (Discharge): y Th is pin is connected to t h e open collector of a npn transistor (Q14), t h e
emitter of w h ich goes to ground, so t h at w h en t h e transistor is turned
"on", pin 7 is effectively s h orted to ground.
-
8/8/2019 Mini Porject
20/38
20
y U sually t h e timing capacitor is connected between pin 7 and ground and
is disc h arged w h en t h e transistor turns "on".
y Th e conduction state of t h is transistor is identical in timing to t h at of t h e
output stage. It is "on" (low resistance to ground) w h en t h e output is low
and "off" ( h igh resistance to ground) w h en t h e output is h igh .
y In bot h th e mono-stable and a-stable time modes, t h is transistor switc h
is used to clamp t h e appropriate nodes of t h e timing network to ground.
Pin 8 (V +) :
y Th e V+ pin (also referred to as V cc) is t h e positive supply voltage terminal of
th e 555 timer IC.
y Supply-voltage operating range for t h e 555 is +4.5 volts (minimum) to +16
volts (maximum), and it is specified for operation between +5 volts and +
15 volts.
y Actually, t h e most significant operational difference is t h e output drivecapability, w h ich increases for bot h current and voltage range as t h e supply
voltage is increased.
y Th ere are special and military devices available t h at operate at voltages as
h igh as 18 V.
-
8/8/2019 Mini Porject
21/38
21
T he simple 555 testing-circuit is shown in F ig. 5. to test all 555 timer ic's.
y U se as a trouble shooter in 555 based circuits. T his tester will quickly tell you
if the timer is functional or not. Although not foolproof, it will tell if the 555
is shorted or oscillating.
y If both Led's are flashing the timer is most likely in good working order. If
one or both Led's are either off or on solid the timer is defective.
-
8/8/2019 Mini Porject
22/38
22
T he capacitor slows down as it charges, and in actual fact never reaches the full
supply voltage. T hat being the case, the maximum charge it receives in the timing
circuit (66.6% of the supply voltage) is a little over the charge received after a time
constant (63.2%).
-
8/8/2019 Mini Porject
23/38
23
T he capacitor slows down as it discharges, and never quite reaches the ground
potential. T hat means the minimum voltage it operates at must be greater than
zero. T iming circuit is 63.2% of the supply voltage.
T he discharge of a capacitor also takes time and we can shorten the amount of
time by decreasing resistance (R) to the flow of current.
Operating Modes:
y Th e 555 timer h as two basic operational modes :
1 .One shot mode .
2. A-stablemode .
1.one-s h ot mode -- Th e 555 acts like a mono-stable multivibrator. A mono-
stable is said to h ave a single stable state--t h at is t h e off state. Wh enever it is
-
8/8/2019 Mini Porject
24/38
24
triggered by an input pulse, t h e mono-stable switc h es to its temporary state.
It remains in t h at state for a period of time determined by an RC network.It
th en returns to its stable state.
y In ot h er words, t h e mono-stable circuit generates a single pulse of a fixed
time duration eac h time it receives and input trigger pulse. T h us th e name
one-s h ot .
y One-s h ot multivibrators are used for turning some circuit or external
component on or off for a specific lengt h of time.
y It is also used to generate delays. Wh en multiple one-s h ots are cascaded, a
variety of sequential timing pulses can be generated.
2. A-stable mode-
y A-stable multivibrator is simply and oscillator. T h e a-stable multivibrator
generates a continuous stream of rectangular off-on pulses t h at switc h
between two voltage levels. T h e frequency of t h e pulses and t h eir duty
cycle are dependent upon t h e RC network values.
O ne-S h ot O peration :
y Fig. 4 s h ows t h e basic circuit of t h e 555 connected as a mono-stable
multivibrator. An external RC network is connected between t h e supply
voltage and ground. T h e junction of t h e resistor and capacitor is connected to
th e t h res h old input w h ich is t h e input to t h e upper comparator. T h e internal
disc h arge transistor is also connected to t h e junction of t h e resistor and t h e
capacitor.
-
8/8/2019 Mini Porject
25/38
25
y An input trigger pulse is applied to t h e trigger input, w h ich is t h e input to
th e lower comparator. W ith th at circuit configuration, t h e control flip-flop is
initially reset. T h erefore, t h e output voltage is near zero volts. T h e signal from
th e control flip-flop causes T1 to conduct and act as a s h ort circuit across t h e
external capacitor.
y For t h at reason, t h e capacitor cannot c h arge. During t h at time, t h e input to
th e upper comparator is near zero volts causing t h e comparator output to
keep t h e control flip-flop reset.
Mono-stable mode:
y Th e 555 in fig. 9a is s h own h ere in its utmost basic mode of operation;
as a triggered mono-stable. One immediate observation is t h e extreme
simplicity of t h is circuit. Only two components to make up a timer, a
capacitor and a resistor.
y And for noise immunity maybe a capacitor on pin 5.
-
8/8/2019 Mini Porject
26/38
26
y Wh at 'bounce' is: bounce is a type of fast, s h ort term noise caused by a
switc h , relay, etc. and t h en picked up by t h e input pin.
y Th e trigger input is initially h igh (about 1/3 of +V). Wh en a negative-
going trigger pulse is applied to t h e trigger input (see fig. 9a), t h e
th res h old on t h e lower comparator is exceeded.
y Th e lower comparator, t h erefore, sets t h e flip-flop. T h at causes T1 to
cut off, acting as an open circuit. T h e setting of t h e flip-flop also causes
a positive-going output level w h ich is t h e beginning of t h e output
timing pulse.
y Th e capacitor now begins to c h arge t h roug h t h e external resistor. As
soon as t h e c h arge on t h e capacitor equal 2/3 of t h e supply voltage, t h e
upper comparator triggers and resets t h e control flip-flop. T h at
terminates t h e output pulse w h ich switc h es back to zero.
y At t h is time, T1 again conducts t h ereby disc h arging t h e capacitor. If a
negative-going pulse is applied to t h e reset input w h ile t h e output pulse
is h igh , it will be terminated immediately as t h at pulse will reset t h e
flip-flop.
y Wh enever a trigger pulse is applied to t h e input, t h e 555 will generate
its single-duration output pulse. Depending upon t h e values of external
resistance and capacitance used, t h e output timing pulse may be
adjusted from approximately one millisecond to as h igh as on h undred
seconds.
y IC timers are normally used w h ere long output pulses are required.
-
8/8/2019 Mini Porject
27/38
27
y In t h is application, t h e duration of t h e output pulse in seconds is
approximately equal to :
T = 1.1 x R x C (in seconds)
y Th e output pulse widt h is defined by t h e above formula. T h ere isactually no t h eoretical upper limit on T (output pulse widt h ), only
practical ones. T h e lower limit is 10uS. You may consider t h e range of T
to be 10uS to infinity.
y A reasonable lower limit for R(t) is in t h e order of about 10Kilo o h mandt h e upper limit for R(t) is in t h e order of about 15 Mega o h m
y A practical minimum for C(t) is about 95pF.
y Th ere are several different types of 555 timers.
y Th e LM555 from National is t h e most common one t h ese days.
y Th e Exar XR-L555 timer is a micro-power version of t h e standard 555
offering a direct, pin-for-pin (also called plug-compatible) substitute
device with
an advantage of a lower power operation.y Maxim's ICM7555, and Sanyo's LC7555 models are a low-power,T h e
internal sc h ematic of t h e 7555 (not s h own) is h owever totally different
from t h e normal 555 version.
y Th is very versatile version s h ould be considered w h ere a wide range of
timing is desired, as well as low power operation appears to be
important in t h e particular design.y A couple years after Intersil, Texas Instruments came on t h e market
wit h anot h er cmos variation called t h e LINCMOS (LINear CMOS) or
Turbo 555.
-
8/8/2019 Mini Porject
28/38
28
y Th e cmos version is t h e c h oice for battery powered circuits.
y However, t h e negative side for t h e cmos 555's is t h e reduced outputcurrent, bot h for sink and source, but t h is problem can be solved by
adding a amplifier transistor on t h e output if so required.
Comparison between 555 and 7555 timer -- y Th e regular 555 can easily deliver a 200mA output versus 5 to 50mA for
th e 7555. y On t h e workbenc h th e regular 555 reac h ed a limited output frequency
of 180K h z wh ile t h e 7555 easily surpassed t h e 1.1M h z mark and t h e
TLC555 stopped at about 2.4M h z.
-
8/8/2019 Mini Porject
29/38
29
A- stable operation:
y Figure 9b s h ows t h e 555 connected as an a-stable multivibrator. Bot h t h e
trigger and t h res h old inputs (pins 2 and 6) to t h e two comparators are
connected toget h er and to t h e external capacitor. T h e capacitor c h arges
toward t h e supply voltage t h roug h t h e two resistors, R1 and R2. T h e
disc h arge pin (7) connected to t h e internal transistor is connected to t h e
junction of t h ose two resistors.
y Wh en power is first applied to t h e circuit, t h e capacitor will be unc h arged,
th erefore, bot h t h e trigger and t h res h old inputs will be near zero volts (see
Fig. 10). T h e lower comparator sets t h e control flip-flop causing t h e output
to switc h h igh . Th at also turns off transistor T1.
y Th at allows t h e capacitor to begin c h arging t h roug h R1 and R2. As soon as
th e c h arge on t h e capacitor reac h es 2/3 of t h e supply voltage, t h e
-
8/8/2019 Mini Porject
30/38
-
8/8/2019 Mini Porject
31/38
31
Th e frequency of operation of t h e a-stable circuit is dependent upon t h e
values of R1, R2, and C. T h e frequency can be calculated wit h th e formula :
f = 1/(.693 x C x (R1 + 2 x R2))
y Th e Frequency f is in Hz, R1 and R2 are in o h ms, and C is in farads.
Th e time duration between pulses is known as t h e 'period', and usually
designated wit h a 't'. T h e pulse is on for t1 seconds, t h en off for t2 seconds.
Th e total period (t) is t1 + t2 (see fig. 10).T h at time interval is related to t h e
frequency by t h e familiar relations h ip:
f = 1/tort = 1/f
y Th e time intervals for t h e on and off portions of t h e output depend upon
th e values of R1 and R2. T h e ratio of t h e time duration w h en t h e output
pulse is h igh to t h e total period is known as t h e duty-cycle. T h e duty-cycle
can be calculated wit h th e formula :
D = t1/t = (R1 + R2) / (R1 + 2R2)
You can calculate t1 and t2 times wit h th e formulas below :
t1 = .693(R1+R2)Ct2 = .693 x R2 x C
y Th e 555, w h en connected as s h own in Fig. 9b, can produce duty-cycles inth e range of approximately 55 to 95%. A duty-cycle of 80% means t h at t h e
output pulse is on or h igh for 80% of t h e total period. T h e duty-cycle can
beadjusted by varying t h e values of R1 and R2.
-
8/8/2019 Mini Porject
32/38
-
8/8/2019 Mini Porject
33/38
33
CAPACITOR:--
y Capacitance is t h e property of opposition to a c h ange in voltage.
Capacitance h as t h e same reaction to voltage as t h e inductance h as to t h ecurrent. T h at is t h e voltage across circuit increases. Capacitor will resist
th e c h ange and if t h e voltage applied to a circuit is decreased and try to
maintain t h e original voltage.
y Th e property of capacitor is to store c h arge and release. T h e storing
capacity of capacitor is depend upon t h e value of capacitor as defined in
micro farad.A basic capacitor consist of two conducting metalplatesseparated by a layer of air or ot h er insulating material. T h e insulating layer
is called dielectric layer. All capacitor h ave two plates and separating layer.
y In practice t h e dielectric layer are often staked and even rolled into
compact form.
y Th e capacitor areas classified by t h e name of dielectric used in t h e
particular.
1. Paper capacitor
2. Mica capacitor
3. Ceramic capacitor
4. Electrolytic capacitor
All electrolytic capacitors are above 1 micro farad. All electrolytic capacitor
h aving two legs one is positive and second is negative , bigger leg is positive and
smaller leg is negative.
-
8/8/2019 Mini Porject
34/38
34
RESISTANCE: -
Th e unit being o h m t h e greater t h e o h mic value t h e greater is t h e opposition to
th e flow of current causes. T h e h eating effect and causes a loss of electrical
energy in t h e form of h eat energy, greater t h e o h mic value greater t h e loss.
TYPES OF RESISTANCE :-
1. F ixed value
2. Variable value
Normally fixed type of resistance are carbon resistance value of resistance in o h m
printed on t h e body of resistance in color code.
TRANSISTOR :-
y Transistor are tiny semiconductor device t h at provide current amplification.
A transistor h as t h ree leads identified as emitter Base and collector. A small
current to say 1mA flowing between base and emitter produce a large
current of 100ma or more in t h e widely used as a current amplifier circuit
transistor are also very useful in switc h ing circuit.
y W e use normally two type of transistor one is NPN and second in PNP. InPNP transistor conduction is conducting between emitter and collector wit h
th e h elp of electron flow. In PNP transistor conduction is conducting
between emitter and collector wit h th e h elp of h oles.
-
8/8/2019 Mini Porject
35/38
35
y W e normally give a forward bias to t h e emitter point and reverse bias to
th e collector point wit h t h e h elp of load resistance and for t h e base point .
W e give a very low voltage by resistance or any ot h er circuit control
devices.
SPEAKER :-
y Th e simply speaker c h anges electric audio energy into sound. T h e speaker
is a transducer.One in a family of devices w h ich converts energy from one
from into anot h er.
y Th e speaker in greatest use today is t h e permanent-magnet(pm) dynamic
speaker.
y Electromagnetic dynamic - Speakers are no longer used ,alt h oug h th ey
were very popular early in t h e development of audio systems.Dynamic
speakers are similar in operation. T h ey differ in met h od used to obtain t h e
stationary or static magnet field.
y Permanent magnet speaker - A permanent magnet concentrates a
magnetic field at t h e pole pieces of a h igh ly permeable h ousing. T h e pole
pieces are very close toget h er to obtain an intense magnetic field. A voice
coil cemented to t h e speaker cone is freely suspended between t h e
magnetic poles.
y A flexible membrane called t h e spider is attracted to t h e voice-coil form
sand cemented to t h e speaker frame. T h e spider centers t h e voice coil form
between t h e speaker poles keep it from rubbing against t h em. T h e flared
end of t h e cone is flexibly attac h ed to t h e speaker frame.
-
8/8/2019 Mini Porject
36/38
36
y Th e permanent magnet of a pm speaker is made of a mixture of aluminum,
nickel and cobalt and is called an alnico magnet.T h e audio-signal currents
led to t h e voice coil set up a moving magnetic field about t h e voice coil.
Th is interacts wit h th e fixed magnetic field and result in a vibratory motion
of t h e voice coil and h ence ossf t h e speaker cone.
y Th e rate of vibration of t h e speaker cone is determined by t h e frequency of
th e audio current. T h e amplitude of vibration i.e. h ow far t h e cone depends
on t h e amplitude of audio current. T h e speaker cone moves t h e air mass
surrounding it producing sound.
y Connections from t h e voice coil ends are broug h t to insulated solder
terminals on t h e speaker frame. Wh en output transformer are used to
matc h t h e impedance of t h e last audio amplifier to t h at of t h e speaker t h e
transformer may be mounted on t h e amplified classis .Leads from t h e
secondary of t h e output transformer are t h en connected to t h e voice coil at
th e solder terminals on t h e frame.
y A continuity c h eck may be made on t h e voice coil of a dynamic speaker.
Th e resistance is very low, usually 3 or 4o h m alt h oug h in some solid state
amplifier driven speakera it may be as 32o h m.Th e continuous motion of
th e voice coil may be cause t h e coil wire to break,resulting in an open
voice coil .T h is would c h eck as an infinite.
-
8/8/2019 Mini Porject
37/38
37
PRECAUTIONS :---
1. Mount t h e components at t h e appropriate places before soldering. Follow t h e
circuit description and components details, leads identification etc.2. Do not start soldering before making it confirm t h at all t h e component are
mounted at t h e rig h t place.
3. Do not use a spread solder on t h e board, it may cause s h ort circuit.
3. Do not sit under t h e fan w h ile soldering.
4. Position t h e board so t h at gravity tends to keep t h e solder w h ere you want it.5. Do not over h eat t h e components at t h e board. Excess h eat may damage t h e
components or board.
6. Th e board s h ould not vibrate w h ile soldering ot h erwise you h ave a dry or a
cold joint.
7. Do not put t h e kit under or over voltage source. Be sure abort t h e voltage
eit h er do or ac w h ile operating t h e gadget.8. Do spare t h e bare ends of t h e components leads ot h erwise it may s h ort circuit
wit h th e ot h er components. To prevent t h is use sleeves at t h e components
leads or use sleeved wire for connections.
9. Do not use old dark color solder. It may give dry joint. Be sure t h at all t h e joints
are clean and well s h iny.
10 . Do make loose wire connections specially wit h cell h older, speaker, probes
etc. Put knots w h ile connections to t h e circuit board, ot h erwise it may get loose.
-
8/8/2019 Mini Porject
38/38