IR Burglar

CIRCUIT IDEAS ELECTRONICS FOR YOU • JANUARY 2006 • 101 WWW.EFYMAG.COM Fig. 2: Pin configurations of UM3561 and TSOP1738 Fig. 1: Circuit for IR burglar deterrent T hwart any burglary attempt us- ing this infrared proximity de- tector that triggers an alarm when the rays falling on its sensor are interrupted. The circuit of IR burglar deterrent (shown in Fig. 1) comprises transmitter and receiver-cum-alarm sections. It works off 6V DC, 500mA uninter- rupted supply and uses low-cost T.K. HAREENDRAN IR BURGLAR DETERRENT S.C. DWIVEDI readily-available electronic compo- nents. LED2 is used for indicating power-‘on.’ The transmitter section is built around timer 555 (IC1), while the receiver-cum-alarm section con- sists of IR sensor TSOP1738, dual precision monostable multivibrator CD4538 and three-siren sound generator IC UM3561. Pin configurations of UM3561 and TSOP1738 are shown in Fig. 2. The astable multivibrator (IC1) oscillates at a frequency of around 38 kHz, which is transmitted by the infrared LED (IR LED1). Resistor R2 limits the current across the IR LED. The transmitted IR signal directly falls on IR sensor TSOP1738. When- ever the IR signal is interrupted, its output pin 3 goes low and IC2 is trig- gered at pin 5 through transistor T2. As a result, its output at pin 7 goes low (for a preset time) to forward bias siren-driver transistor T2. This condi- tion is indicated by the glowing of LED1. The time-out period can be in- creased or decreased by changing the value of capacitor C6. Now siren-sound generator IC3 is activated and its output signal is am- plified by transistor T4 to produce a sound resembling that of police siren. Resistor R14 limits the loudspeaker current. The output tone of siren-sound generator IC3 can be set by connect- ing its pin 6 to either Vcc or GND. When you connect pin 6 to Vcc IC3 produces the sound of fire-alarm siren, but when you connect it to GND it produces the sound of ambulance siren. Assemble the transmitter and receiver-cum-alarm circuits on two sepa- rate general-purpose PCBs and house in suitable cabinets. Mount the units on the opposite sides of the entrance gate such that IR rays from IR LED1 fall directly on the IR receiver module (TSOP1738).

Upload
abhinav-sharma
Category

Documents
view
7
download
3

Embed Size (px):

Transcript of IR Burglar

CIRCUITIDEAS

E L E C T R O N I C S F O R Y O U • J A N U A R Y 2 0 0 6 • 1 0 1W W W . E F Y M A G . C O M

CMYK

Fig. 2: Pin configurations of UM3561 and TSOP1738

Fig. 1: Circuit for IR burglar deterrent

Thwart any burglary attempt us-ing this infrared proximity de-tector that triggers an alarm

when the rays falling on its sensor areinterrupted.

The circuit of IR burglar deterrent(shown in Fig. 1) comprises transmit-ter and receiver-cum-alarm sections. Itworks off 6V DC, 500mA uninter-rupted supply and uses low-cost

T.K. HAREENDRAN

IR BURGLAR DETERRENT S.C. DWIVEDI

readily-available electronic compo-nents. LED2 is used for indicatingpower-‘on.’

The transmitter section is builtaround timer 555 (IC1), while the re-

ceiver-cum-alarm section con-sists of IR sensor TSOP1738,dual precision monostablemultivibrator CD4538 andthree-siren sound generator ICUM3561. Pin configurations ofUM3561 and TSOP1738 areshown in Fig. 2.

The astable multivibrator(IC1) oscillates at a frequencyof around 38 kHz, which istransmitted by the infraredLED (IR LED1). Resistor R2limits the current across the IRLED.

The transmitted IR signal directlyfalls on IR sensor TSOP1738. When-ever the IR signal is interrupted, itsoutput pin 3 goes low and IC2 is trig-gered at pin 5 through transistor T2.As a result, its output at pin 7 goeslow (for a preset time) to forward bias

siren-driver transistor T2. This condi-tion is indicated by the glowing ofLED1. The time-out period can be in-creased or decreased by changing thevalue of capacitor C6.

Now siren-sound generator IC3 isactivated and its output signal is am-plified by transistor T4 to produce asound resembling that of police siren.Resistor R14 limits the loudspeakercurrent.

The output tone of siren-soundgenerator IC3 can be set by connect-ing its pin 6 to either Vcc or GND.When you connect pin 6 to Vcc IC3produces the sound of fire-alarm si-ren, but when you connect it to GNDit produces the sound of ambulancesiren.

Assemble the transmitter and re-ceiver-cum-alarm circuits on two sepa-rate general-purpose PCBs and housein suitable cabinets. Mount the unitson the opposite sides of the entrancegate such that IR rays from IR LED1fall directly on the IR receiver module(TSOP1738).