June 28, 2009

IR Bug

Infra Red Bug
This circuit can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for instance, an IR handheld remote controller. It can also be used for testing IR burglar alarm systems.

Besides the power supply (one 9V PP3/6F22 compact battery
pack), it consists of an infrared signal detector-cum-preamplifier followed by a melody generator
and a tiny audio amplifier. The amplified signal is fed to the melody generator via resistor R5. The output of the melody generator is fed to LM386 low-power audio amplifier (IC2) via variable resistor VR1, which works as the volume control. The loudspeaker sounds to indicate
the presence of IR signal near the circuit. IC LM386 is wired as a minimum-parts amplifier with
a voltage gain of ‘20,’ which is sufficient for this application. Capacitor C3 is used for decoupling of the positive rail and the R-C combination network comprising C4 and R7 bypasses high frequency to ground. The circuit can be easily wired on a general-purpose PCB. Pin configurations of IC LM386, transistor BC547 and melody generator UM66 are shown. principle, converts the IR signal pulse trains into noticeable aural notes. S1 is used to switch on/off mains power and LED1 indicates power ‘on.’ Resistor R4 and zener diode ZD2 form a low-current voltage stabiliser for providing steady 5.1V DC to the small signal preamplifier circuit. IR LED1 is the main sensing element. The IR signal detected by IR LED1 is amplified by npn transistors T1.

Circuit Diagram

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Pin Configuration


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Electronics is the study and use of electrical that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves. and semiconductors. The pure study of such devices is considered as a branch of physics, while the design and construction electronic circuits to solve practical problems is called electronic engineering.

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