Pir sensor based security alarm system using um 3561 (2)
PIR SENSOR BASED SECURITY ALARM
SYSTEM USING UM 3561
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.
UM 3561 siren IC
Speaker 8 ohms
PIR sensor is a passive sensor abbrevated as pyroelectric
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
It is important to note that PIR sensors don't detect or measure
"heat" instead they detect the radiation from an object.
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
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
Thus oscillations along with selected tone are sent to the
address counter. The address counter then sends the data to the
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.
This can be used in the museums to protect the valuable
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.