PIR SENSOR BASED SECURITY ALARM

SYSTEM USING UM 3561

By

Ushaswini chowdary.M

14204115

Generally, in security systems, infrared or laser transmitters

and receivers are used. But these methods are cost effective.

This article explains about PIR based security system in which

PIR sensor is used instead of transmitter or receiver.

This saves the power consumption and is low cost.

PIR sensor based security system principle

The main principle of the circuit is to provide security. This is

based on PIR sensor with an IC that produces siren.

The PIR sensor detects the IR radiations emitted from the

humans and it produces a digital output.

This digital output is applied to the UM 3561 siren IC. Thus it

produces the sound when any human is detected.

Circuit diagram

Circuit components

PIR sensor

UM 3561 siren IC

Transistor NPN

Resistors R1,R2,R3,R4

Speaker 8 ohms

Battery

PIR sensor

PIR sensor is a passive sensor abbrevated as pyroelectric

infrared sensor.

A pyroelectric infrared sensor (PIR sensor) is an electronic

sensor that measures infrared (IR) light radiating from objects

in its field of view. They are most often used in PIR-based

motion detectors.

It is important to note that PIR sensors don't detect or measure

"heat" instead they detect the radiation from an object.

UM 3561

UM3561 is a low-cost, low-power CMOS LSI designed for

use in alarm and toy applications

UM 3561 is a siren IC

It is a ROM IC

It generates multi siren tones like ambulance siren, fire engine

siren, police siren, machine gun sound.

PIR sensor based security alarm system design

The proposed system mainly consists of PIR sensor, UM3561

IC, Speaker, transistors.

The UM3561 has 8 pins. Fifth and sixth pins are shorted and

are connected to the PIR sensor output through a resistor.

One end of the 220K resistor is connected to the seventh pin of

the IC and the other end is connected to the eighth pin of the

IC.

Output is taken from the third pin of the IC.

Working of PIR sensor based security system

Switch on the circuit initially.

The PIR sensor is powered and it detects the IR rays emitted

from any human.

This PIR sensor has a range of 5meters. One can adjust the pot

provided for the sensor to vary this distance.

When any human is detected, this PIR sensor outputs a logic

high value i.e. voltage of 3.5v to 5v.

This voltage is applied as input to the siren generator IC.

The siren generator has an oscillator internally, to produce the

sound.

Thus oscillations along with selected tone are sent to the

address counter. The address counter then sends the data to the

ROM.

ROM then sends the tone on the output pin 3.

The output is given to the NPN transistor to amplify the siren.

Thus sound produced can be heard from the speaker when

human is detected.

Applications

This can be used in the museums to protect the valuable

things.

This can also be used as an automatic door bell circuit that

rings the bell when human is detected.

This can be used in defense applications to detect the humans

in war field.

This can be used in toy applications that produce sound.