Long Range IR Transimmiter

Long Range IR Transimmiter
Most of the IR remotes work reliably within a range of 5 metres The circuit complexity
increases if you design the IR transmitter for reliable operation over a longer range, say, 10 metres. To double the range from 5 metres to 10 metres, you need to increase the transmitted power four times. Here is a simple circuit that will give you a pretty long range. It uses
three infrared transmitting LEDs (IR1 through IR3) in series to increase the radiated power. Further, to increase the directivity and so also the power density, you may assemble the IR LEDs inside the reflector of a torch. For increasing the circuit efficiency, a MOSFET (BS170) has been used, which acts as a switch and thus reduces the power loss that would result if a transistor were used. To avoid any dip during its ‘on’/‘off’ operations, a 100μF reservoir capacitor C2 is used across the battery supply. Its advantage will be more obvious when the
IR transmitter is powered by ordinary batteries. Capacitor C2 supplies extra charge during ‘switching on’ operations. As the MOSFET exhibits large capacitance across gate-source terminals, a special drive arrangement has been made using npn-pnp Darlington pair of
BC547 and BC557 (as emitter followers), to avoid distortion of the gate drive input. Data
(CMOS-compatible) to be transmitted is used for modulating the 38 kHz frequency generated
by CD4047 (IC1). However, in the circuit shown here, tactile switch S1 has been used for modulating and transmitting the IR signal. Use switch S2 for power ‘on’/‘off’ control. commercially available IR receiver modules (e.g., TSOP1738) could be used for efficient reception of the transmitted IR signals.

Circuit Diagram


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Pin Configuration

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