We made this as our digital lab project. It is just an idea.

1. Power saver using IR sensor
Pinaki Ranjan Sarkar & Mustafa Shahid
May 13, 2015
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 1 / 16

2. Overview
Introduction
Motivation
Concept
State Diagram
State Table
Components
Circuit
Code
Simulation
Discussion
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3. Introduction
Our project is a mechanism which detects the presence of a person in the
room and maintains the power input. If the signal goes low, a buzzer (or a
notification light) will be switched ON. The signal might go low if :
1 There is no one in the room
2 The sensor has malfunctioned
In the first case, the power input to the room will be turned OFF
after 8second (time is adjustable)
In the second case, the person in the room will have to manually
override the input within 8 seconds to make the alarm stop
The IR sensor has to be of wide field view and located in the centre of the
room.
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 3 / 16

4. Motivation
Most of us leave our room lights ON despite of having a main switch
outside the room. Our batchmates had done a project on Power
Consumption in IIST during the last semester and the figures are very bad.
We decided to make this mechanism so that as soon as a person leaves
the room, the lights will go out.
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 4 / 16

5. Concept
A Mealy machine sequential circuit is made with 4 states. If the input
is 1, i.e. the sensor senses heat signature in the room, power input
will continue
If the input goes low, the circuit will pass through two states and
ultimately cut-off the input power unless manually overridden (forced
input 1).
A 555 timer is used for the clock. Time period is 2 seconds.
Therefore, without input power will sustain for 8 seconds.
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6. State Diagram
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7. State Table
Present State Input Next State Output Flip Flop A Flip Flop B
A B x A+ B+ y DA DB
00 0 01 1 0 1
00 1 00 1 0 0
01 0 10 1 1 0
01 1 00 1 0 0
10 0 11 0 1 1
10 1 00 1 0 0
11 0 11 0 1 1
11 1 00 1 0 0
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8. K-Map Reduction
DA = ¯x(A + B) (1)
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 8 / 16

9. K-Map Reduction
DB = ¯x(A + ¯B) (2)
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 9 / 16

10. K-Map Reduction
y = x + ¯A (3)
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11. Components
IC 7474 - D flip flop
IC 7404 - Inverter
IC 7408 - AND gate
IC 7432 - OR gate
555 Timer
IR sensor
Resistor - 14.7kΩ
Capacitors - 100µF and 10nF
Breadboard
Connecting wires
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 11 / 16

12. Working of IR sensor
An IR sensor is basically a device which consists of a pair of an IR LED
and a photodiode which are collectively called a photo-coupler or an
opto-coupler. The IR LED emits IR radiation, reception and/or intensity of
reception of which by the photodiode dictates the output of the sensor.
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13. Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 13 / 16

14. Circuit Diagram
Pinaki Ranjan Sarkar & Mustafa Shahid Power saver using IR sensor May 13, 2015 13 / 16

15. Code
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16. Simulation
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17. Discussions
The time period can be increased by increasing the time period or by
adding more states
The IR sensor can be installed on the door instead of roof to keep
track of people entering the room and monitoring the input power
Optimisation can be done using two IR sensors instead of one to
avoid over or under counting
Other possible sensor candidates are:
Temperature/Heat sensor
Ultrasonic sensor
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