Pulse-Frequency Modulated Receiver

Description: This receiver utilizes an IR-sensitive phototransistor (such as those from Clairex or HP) housed within a light-tight enclosure that features an aperture for the incoming infrared beam. An optical system may be integrated with this receiver to enhance its operational range. A 741 operational amplifier is employed to amplify the pulsed infrared signal, while a 565 phase-locked loop (PLL) frequency modulation demodulator is used to recover the audio. This audio signal is then processed by an LM386 audio amplifier, which drives a speaker.

The described infrared (IR) receiver circuit is designed for applications requiring the detection and processing of IR signals. The core component, an IR-sensitive phototransistor, is sensitive to modulated infrared light, enabling it to detect signals transmitted from IR remote controls or similar devices. The use of a light-tight enclosure minimizes interference from ambient light, ensuring that only the intended IR signals are processed.

To enhance the effective range of the receiver, an optical system can be incorporated. This system may consist of lenses or mirrors that focus the incoming IR beam onto the phototransistor, effectively increasing the sensitivity and range of the receiver.

The operational amplifier (741) plays a crucial role in the circuit by boosting the weak pulsed IR signal detected by the phototransistor. The amplification is necessary to ensure that the signal is strong enough for further processing. The amplified signal is then fed into the 565 PLL FM demodulator, which is designed to extract the audio information encoded in the modulated IR signal.

The output from the 565 demodulator is an audio signal that is subsequently amplified by the LM386 audio amplifier. This amplifier is well-suited for driving small speakers, providing sufficient power to reproduce the audio signal clearly. The final stage of the circuit involves the speaker, which converts the amplified audio signal into sound, completing the signal processing chain.

This IR receiver circuit can be applied in various applications, including remote control systems, wireless audio transmission, and other IR communication systems, offering a reliable method for receiving and processing infrared signals. This receiver uses an IR-sensitive phototransistor (Clairex, HP, etc.) mounted in a light-tight enclosur e with an aperture for the incoming IR beam. An optical system can be used with this receiver for increased range. A 741 amplifies the pulsed IR signal and a 565 PLL FM demodulator recovers the audio, which drives an LM386 audio amplifier and speaker.