IC 555 APPLICATIONS
January 10, 2022
01/10/2022
January 10, 2022
VISHWAKARMA INSTITUTE OF TECHNOLOGY
IC 555 APPLICATIONS
Group Members:
(48)sneha powar, (54) Prathamesh Ingale , (62) Rohan Mahajan, (63) Tejas mahajan
Guide – PROF. MEDHA WYAWAHARE
IC 555 APPLICATIONS
Ic 555 timer
The IC 555 is very useful and popular IC.
The IC 555 basically a timer IC. The IC 555 is consists of a timer circuit and
the timer circuit contains three five kilo Ohm resistors, for this reason, the
name of the IC is IC555.
·
Pin Diagram of IC 555:
The IC 555 is
available in so many packages. Here the block diagram of 8 pin DIP package IC
555 is given below.
The function of Each Pin
of IC 555:
Pin no.1: The pin 1
provides the ground terminal for the IC to give the power supply.
Pin no.2: The pin 2 is called Trigger. It is connected
to the inverting terminal of the second Op Amp or Comparator. As the
non-inverting terminal of the second comparator is connected to the 1/3Vcc
point so if we decrease the voltage of the trigger pin below the 1/3 Vcc then
the output of the comparator will be high and the circuit will be triggered.
Usually, we connect the trigger pin with the Vcc
and when we want to change the current state of the comparator we should
decrease the voltage of the trigger pin.
Pin no.3: The Pin 3 is called output. The pin 3 is to be
connected to the load that means the IC can drive the load through the output
pin. The IC can deliver up to 200mA of current through this pin.
Pin no.4: The pin no.4 is used to reset the flip-flop
circuit.
Pin no.5: The pin no.5 is directly connected to the
inverting terminal of the first comparator. This pin is used to control the
input voltage of the first comparator by applying external voltage.
Pin no.6: As the inverting terminal of the first comparator
is connected to the 2/3 Vcc point so when the voltage of the non-inverting
terminal is greater than2/3 Vcc the output of the first comparator will be
high. The pin no.6 or threshold pin is used to give the threshold voltage which
is greater than 2/3 Vcc.
Actually, the pin no.2 or Trigger and pin no.6 or
Threshold pin are used to control the output of the comparators.
Pin no.7: The pin no.7 is called discharge pin. It is
connected to the collector pin of the transistor.
Pin no.8: The pin no.8 or Vcc is used to give power supply
to the IC555. The voltage from 4.5V to 15V can be given to the IC555.
·
The internal block diagram of
IC 555:
You can see in the below figure the internal circuit has no.
of blocks. The first block is the voltage divider circuit. The voltage
divider circuit is made by three five kilo Ohm resistors connected in
series. The next block is comparators. Here the comparator using Op Amp is
used. There are two comparators in the circuit. The next block is the RS
Flip-flop circuit.
The outputs of the comparators are given to the flip-flop circuit. Then the
output of the flip-flop circuit is going to the output inverter circuit. The
function of the inverter circuit is that it inverse the output of the flip-flop
that means if the output of the flip-flop is high then the output of the
inverter will be low. The pin no.3 or output pin of the IC is connected to the
output of the inverter circuit. A discharge circuit using NPN transistor also
connected to the output of the flip-flop circuit.
·
Applications of IC 555:
The IC 555 is mainly used for timing related applications.
Like,
1.
The
IC 555 is used for Tone generation.
2.
It
is used to make an alarm circuit.
3.
They
also used for frequency division applications.
4.
The
IC 555 is used as a relaxation oscillator.
5.
They
are also used in digital counter circuits.
6.
IC
555 is widely used for electronics projects.
555 Timer and Its Applications
The 555 timer is
a linear IC, which works as a monostable multivibrator, an astable
multivibrator, a Schmitt trigger, a function generator with output waveforms
(such as square waves), time delay pulses, and pulse-width modulation (PWM) and
pulse position modulation (PPM) circuits have various electronic control
applications. Every year, millions of 555 IC units are being produced by
various manufacturers to meet the industrial and commercial applications.
The
555 IC is used mostly for timer functions in commercial electronic circuits. In
the timer applications, the duration or length of the output pulses is
determined by charging and discharging a capacitor through resistors connected
externally to a 555 timer. The duty cycle of the output pulse is adjustable by
timing circuit components R and C. The 555 timers to operate on supply voltages
ranging from +5 V to +18 V. They are compatible with TTL (Transistor-Transistor
Logic) and CMOS (Complementary Metal Oxide Semiconductor) logic circuits.
Applications of 555 IC Timer
1. Monostable multivibrator: It works as a one-shot pulse generator.
2. Astable
multivibrator: It
works as a free-running pulse generator (oscillator).
3. Bistable
multivibrator: It
works as a flip-flop (Schmitt trigger).
·
Monostable Mode:
This configuration consists of one stable and
unstable state. If the stable output is set at high then the output of timer is
high.
Working Of 555 Timer In
Mono-Stable Mode:-
The trigger input is held high
by connecting it to VCC through resistor. Threshold pin is low
making the threshold comparator out 0. IN result, voltage coming from source is
going to ground through the transistor. Press the pushbutton on trigger to
change the 555 timer output to high. At the same time, capacitor C1 will
start charging through resistor R1. The 555 timer will
remain in this position until
the voltage across capacitor reaches 2/3 of the supplied voltage. Comparator
will output 1 to R input of the flip flop bringing the circuit into initial
state. The amount of time the timer output will remain high; depend entirely on
value of both the capacitor C1 and resistor R1.
Given
below is 555 Timer circuit in a monostable mode.
Fig 555 Timer in Monostable Mode
Initially
the Timer output is LOW and the transistor Q2 is in saturation
mode, i.e. Fully ON. As a negative trigger pulse, more negative than -1/3
VCC, is applied to the second comparator, the Flip Flop sets to
HIGH, turning the Timer output to HIGH state and the Transistor τ is
turned OFF.
The output remains HIGH
for time
Tout i.e τ = 1.1 RC, i.e. the time
taken for Capacitor C to charge (Also known as Time Constant RC).
As Capacitor voltage exceeds 2/3 VCC, output from the upper
comparator resets the Flip-Flop to zero and the discharge transistor Q2 gets
again saturated, providing a discharge path to the capacitor. As the capacitor
voltage comes back to zero volts, the circuit comes back to its normal state.
·
Astable Mode:
In this mode, there will be no
stable level at the output and the output will keep swinging between high and
low. i.e.- It doesn’t have any stable state and keeps switching between high
and low without application of any external trigger.
Working of 555 timer in
A-stable mode:
The trigger and threshold pin
are connected together so, there is no need of external trigger pulse. The
comparator will output 1 while charging the trigger because the input voltage
at trigger pin is still lower than 1/3 of supplied voltage. This time, the
output of timer is high. Once the voltage across reaches 1/3 of the supplied
voltage, the trigger comparator will output 0,keeping the situation unchanged
as both R and S input of flip flop are 0.Once the voltage across the capacitor
reaches 3/7 of applied voltage, the threshold comparator will output 1 to R
input of the flip-flop. Now, the capacitor will start discharging through resistor
R2 and discharging transistor. The output of 555 Timer is low
at this point. Once the voltage across capacitor drops to 1/3 of the supplied
voltage, the trigger comparator will
output 1.
You can easily calculate the
output of this configuration using the below mentioned formula. The high time
depend on resistors R1, R2 and capacitor. On the
other hand, low time depends only on resistor R2 and capacitor.
High Time:
TH =
0.693 x (R1 x R2) XC1
Low
Time:
TL =
0.693 x (R2) X (C1)
Period
for one cycle:
T = TH
+TL x (R1+ 2R2) C1
Frequency:
f
=1.44 / (R1 + R2) C1) HZ
It
is also known as self-triggering mode, the Timer is used in this mode as clock
pulse generator or oscillator. The Timer switches between
two quasi stable states and without any external trigger input.
Given
below is 555 Timer circuit in Astable mode.
As the Timer is switched ON,
i.e. the output is HIGH, the transistor Q2 will be in cut off
region on receiving a LOW input signal. The capacitor
charges through both the resistors R1 and R2 toward
VCC. The capacitor charging time being
τ1 = 0.693 (R1 + R2)*C.
This capacitor voltage is the
threshold voltage to the upper comparator.
As the voltage exceeds 2/3 VCC,
the upper comparator output resets the Flip-Flop, which turns the Timer output
to OFF state (provided reset pin is in LOW state) The transistor τ will
in saturation region, i.e. will be turned ON, providing a discharge path for
the capacitor through resistor R2, the discharge time being – 0.693 R2*C.
As the capacitor voltage
falls below -1/3VCC, the second comparator output
sets the Flip-Flop, which makes the Timer output LOW and the whole process
starts again. Thus the Timer output oscillates between HIGH and LOW state,
generating oscillations.
·
Bi-Stable Mode:
In this configuration, both the output states
are stable. At each interrupt, the output changes from low to high and
vice-versa If we have a high output, it will go low once it receives an
interrupt and stays low until the next interrupts changes the status.
Working of 555 Timer in
Bi-stable mode:
The Trigger and the Reset pins of the 555 Timer IC are connected to VCC through the two resistors. To keep the input state low while holding them pushed, connect the two pushbuttons between these pins and ground.
After pressing the trigger
button, the trigger input state will become low. Consequently the comparator
will output High and that will make flip-flip Q-bar output go Low. The final
state of the timer state will be high .The output will remain high even when
the trigger pushbutton is not pushed because in that case the R and S input of
flip-flop will be 0 which means that the flip-flop won’t change the initial
state. To make the output low, we need to reset the pushbutton which eventually
Resets the entire 555 Timer IC.
This is also known as Flip-Flop
mode and the Timer remains in two stable states in this mode. It does not
require any external timing circuit as the time delay between two states
depends upon the timing of application of external pulses.
Given
below is 555 Timer circuit in Bi-Stable mode.
Fig 555 Timer Bistable Mode
Two switches are connected as such that while Switch S1 is
connected to reset pin with VCC, switch S2 is
connected to trigger pin with ground. A negative going pulse, at the trigger
input, at voltage more negative than -1/3VCC, triggers
the lower comparator output to set the Flip-Flop and thus the Timer output to
be HIGH. As the threshold pin is grounded, a positive going pulse at the reset
pin triggers the
Since
the Timer remains in one stable state until an external pulse is applied and
then changes to another stable state, this mode is termed as Bi-stable mode. An
important application is the Schmitt Trigger circuit.
· Other applications of 555 IC
timer are found in:
1. DC-DC converters and digital logic probes
2. Waveform generators (ramp and square wave generator)
3. Converts an analog voltage to a pulse length in analog to
digital conversion
4. Analog frequency meters and tachometers
5. Accurate clock signals
6. De-bounce switches
7. PWM (Pulse Width Modulation) and PPM (Pulse Position
Modulation) circuits
8. Traffic signal light control circuits
9. Temperature measurement and control devices
Good info
ReplyDeleteGreat info
ReplyDeleteWow!
ReplyDeleteNice work guys keep it up!
ReplyDeletenice info
ReplyDeleteVery good 👍
ReplyDeletegreat
ReplyDeletenice
ReplyDeleteVery good
ReplyDeleteGreat info
ReplyDeleteSuper
ReplyDeleteGREAT WORK
ReplyDeleteAmazing !!!
ReplyDelete