Time Controlled DC Power Supply Using 555 Timer

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 06 | June 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 385
Time Controlled DC Power Supply Using 555 Timer
Shrihari. S1, Venkateshan. R2
1,2Department of ECE, PSG College of Technology, Coimbatore-641004, India.
------------------------------------------------------------------------***--------------------------------------------------------------------
Abstract—In today’s world, the need for electronic
gadgets has increased significantly. In a lithium-ion
battery, overcharging can create unstable conditions
inside the battery, increase pressure and cause
thermal runaway. Most phone manufacturers preach
“Do not leave your phone connected to the charger for
long periods or overnight” and “Keeping your battery
level as close to the middle (30% to 70%) as possible
can effectively prolong the battery life”. So, to solve
this problem, we should have a timing mechanism that
automatically shuts the power after the desired time.
To make this timing mechanism we used a 555 Timer
IC as a monostable multivibrator which has one stable
state and a quasi-stable state. The output of the power
supply is given to the 555 timer and whenever the
trigger pulse is given the timer is activated, which in
turn gives power to the load only for that desired time.
The time delay of the circuit is determined by the
resistor and capacitor value. The potentiometer is
used here to vary the resistor value and in turn the
time delay. The 16 x 2 LCD will display the time delay
at the current instant for the corresponding
potentiometer value.
Keywords—555 Timer, power supply, 16 x 2 LCD
In today’s world, we are very much dependent on
electronic gadgets like mobile phones and laptops, which
have become a significant part of our life. So it is essential
to know how we can effectively utilize these devices to
have a longer life. The one main reason a device ages is its
battery and to sustain good battery health we need to
avoid overcharging it as overcharging decreases the
battery health significantly. Many phone manufacturers
have said that overcharging your phone overnight can
significantly reduce battery life, and also keeping the
battery percentage between 30 - 70 % results in good
battery health. To solve this problem, we have a solution.
The basic idea is to control the output of a power supply
using a 555 timer and making the electronic device charge
to a specific set time by the user, by doing this the power
supply terminates to charge the device after a specific
amount of time, which eventually prevents overcharging
and improves the battery life of the electronic devices.
II. METHODOLOGY
The system consists of two blocks namely
A. Power supply
This block contains a transformer that steps down
230V AC to 5V DC, followed by which we have a rectifier
section that removes the ripples from the input signal, the
next section has a capacitor filter to reduce the voltage
fluctuations, and the last section of power supply block is a
voltage regulator which gives a constant voltage of 5V in
the output despite the variations in the input voltage.
Figure 1: Power supply-Circuit diagram
B. Timer Block
The 555 timer used here is in monostable multivibrator
mode with one stable and quasi-stable state. The input
voltage to the timer is 5V DC which is taken from the
power supply block. Whenever a trigger pulse is applied to
the trigger pin of the 555 timer, the timer produces the
output voltage to the load circuit with a specific time delay
based on the potentiometer value and the capacitor value.
Figure 2: 555 timer (Monostable mode) Circuit diagram
I. INTRODUCTION

A. 555 Timer
555 Timer is an IC that is used to introduce various
types of time delays in the circuit based on our needs.
Figure 3: Pin Diagram
• Ground (Pin 1) – Connected to the ground (0V).
• Trigger (Pin 2) – trigger pin is an active low pin which
means whenever the trigger pin goes below 1/3 of the
main supply voltage it gets activated and the output is set
to High.
• Output (Pin 3) – It goes to a High state only when the
trigger pin is triggered based on its condition. It can
supply/source a maximum of 200 mA to the load.
• Reset (Pin 4) – It is an active low pin, when we need to
use the 555 timer it needs to be connected to Vcc and
when we ground that pin the timer resets its timing
operation and waits until we get another trigger input
from pin 2.
• Control Voltage (Pin 5) – This pin is mostly connected to
the ground via a small capacitor which is used to eliminate
any fluctuations in the voltage to save the timer from its
operation.
• Threshold (Pin 6) – This pin is used to check the voltage
discharged by the capacitor in pin 7, so when the voltage
reaches above 2/3 of the main supply voltage the timing
cycle ends and goes to a stable state.
• Discharge (Pin 7) – It is mostly connected with a
capacitor that is connected to supply voltage via a resistor
and another end is connected to the ground. This helps
control the time interval of the 555 timer.
• Vcc (Pin 8) – Connected to the power supply (5V), which
can also be in the range of 4.5 V to 15 V.
B. Modes of Operation
● Astable multivibrator:
In this mode of operation, the timer has no stable
state, it keeps on fluctuating between Low and High states.
● Monostable multivibrator:
In this mode of operation, the timer has only one
stable state and another quasi-stable state, whenever the
trigger pulse is applied there is a transition from one state
to another state and after the specified time delay it
returns to the stable state.
● Bi-stable multivibrator:
In this mode of operation, the timer has two stable
states and whenever there is a trigger pulse, the current
state is changed and it moves to another stable state until
we get another trigger pulse.
C. Equations
The equation used to calculate the time delay of the
circuit is given below:
The circuit starts with a 230V AC supply which is given
to the step-down transformer, after the transformer it is
given to a rectifier which removes ripples in the wave.
After this part, it is given to a filter circuit which removes
the remaining AC components from the wave which is then
given to a voltage regulator (LM7805) so that the output
voltage from the power supply block will be constant even
when there are any fluctuations in input voltage. In the
circuit, we used the voltage after the voltage regulator as
5V.
III. DESCRIPTION
IV. WORKING

Figure 4: Power supply block (with value)
After giving the output from the power supply block to
the 555 timer, we have to give an appropriate connection
to make the 555 timer run in a monostable multivibrator
mode. To vary the time delay of the circuit dynamically, we
need to use a potentiometer in place of a fixed resistor, by
tuning the potentiometer the time delay of the circuit is
changed, and on applying a trigger pulse to the 555 timer
the circuit is on (quasi-stable state) for a desired amount of
time which can be found out by the formula mentioned in
the above section.
Figure 5: 555 Timer block (with value)
In addition to this block, we have introduced one
more block where we use an Arduino UNO and a 16 x 2
LCD display which helps in displaying the time delay
value based on the potentiometer value dynamically. So,
whenever the user changes the potentiometer value, we
then calculate the time delay using a formula and display
the exact time delay produced by the circuit.
Figure 6: LCD interfacing with Arduino
REFERENCES
[1] Roy Choudhury and Shail Jain " Linear
Integrated Circuits & quot; Wiley Eastern, New
Delhi, 2014.
[2] Jacob Millman, Christos C Halkais, Satyabrata Jit.
Electronic Devices and Circuits, Fourth Edition,
McGraw Hill Education,2015.
[3] https://www.allaboutcircuits.com/tools/555-timer-
monostable-circuit.
[4] https://www.555-timer-circuits.com/operating-
modes.html
[5] https://store-usa.arduino.cc/products/arduino-
uno-rev3
[6] http://www.learningaboutelectronics.com/Articles/
555-timer-pinout.php
AUTHORS PROFILE
Shrihari S is a student of the
department of Electronics and
Communication Engineering in PSG
College of Technology, Coimbatore
He is interested in Embedded
Systems and programming
microcontrollers. He has completed
numerous projects pertaining to
Embedded systems and IoT.
Venkateshan R is a student of the
department of Electronics and
Communication Engineering in PSG
College of Technology, Coimbatore.
His interests include Digital
electronics and programming
microcontrollers. He has completed
projects pertaining to Embedded
systems and IoT.
Thus, with the help of this model users can dynamically
control the time in which the circuit should be turned off,
by tuning the potentiometer value and the user can see
the updated time for the updated potentiometer value in
the LCD display (interfaced with Arduino). Therefore,
using this model we can prevent overcharging and
increase the battery longevity of our electronic gadgets.
V. CONCLUSION

Time Controlled DC Power Supply Using 555 Timer

More Related Content

Similar to Time Controlled DC Power Supply Using 555 Timer (20)

More from IRJET Journal (20)

Recently uploaded (20)

Time Controlled DC Power Supply Using 555 Timer