This document describes a PIR sensor-based security alarm system that uses a PIR sensor and UM3561 siren IC. The system detects infrared radiation emitted from humans using a PIR sensor and triggers the UM3561 IC to produce an alarm siren. It uses low-power, inexpensive components like a PIR sensor, UM3561 siren IC, transistors, resistors, speaker and battery. When the PIR sensor detects human infrared radiation within its 5m range, it sends a signal to the UM3561 IC to generate an alarm siren through the speaker. This provides a low-cost solution for security and other applications.

1. PIR SENSOR BASED SECURITY ALARM
SYSTEM USING UM 3561
By
Ushaswini chowdary.M
14204115

2.  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.

3. 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.

4. Circuit diagram

5. Circuit components
 PIR sensor
 UM 3561 siren IC
 Transistor NPN
 Resistors R1,R2,R3,R4
 Speaker 8 ohms
 Battery

6. 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.

7. 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.

8. 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.

9. 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.

10.  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.

11. 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.