In this project, I will guide you through the construction of a straightforward IR Audio Link circuit capable of wirelessly transmitting audio signals. This infrared audio link is designed for short-distance transmission of audio signals. In the transmitter section, the audio signal intended for transmission is fed into the base of a transistor. To receive and listen to the transmitted signal, an 8-ohm speaker or headphones can be connected to the receiving part of the circuit.
Outline
- Introduction
- Simple IR Audio Transmitter and Receiver Circuit Principle
- IR Audio Transmitter and Receiver Circuit Diagram
- Components Required
- Transmitter Section
- Receiver Section
- Simple IR Audio Link Circuit Design
- How to Operate IR Audio Transmitter and Receiver Circuit?
- Simple IR Audio Link Circuit Applications
- Simple IR Audio Link Circuit Limitations
Introduction
Bluetooth and RF communications are the predominant technologies in the realm of wireless audio, which is already a highly advanced field, with most commercial audio equipment relying on Bluetooth. Creating a basic IR Audio Link Circuit may not offer the same advantages as established technologies, but it can provide valuable insights into wireless audio transmission.
This is because, unlike Bluetooth, IR operates as a line-of-sight communication system, necessitating that both the transmitter and receiver maintain an unobstructed view of each other at all times. Additionally, the range of IR may be more limited compared to that of a standard Bluetooth wireless audio device.
Nevertheless, for the sake of learning and comprehension, let’s proceed with designing a simple IR Audio Link circuit using readily available components.
Simple IR Audio Transmitter and Receiver Circuit Principle
This circuit is primarily built around the concept of IR communication. Infrared (IR) is exclusively employed for short-range line-of-sight communications. In the electromagnetic spectrum, infrared rays have longer wavelengths than visible light. While these IR rays are invisible to the human eye, they can be detected using a digital camera.
Most IR communication systems utilize infrared sources like IR lasers or LEDs with specific wavelengths. The transmission of IR signals can occur through various mediums, including vacuum, atmosphere, and optical fibers. Finally, in IR communication, photodiodes or phototransistors are used to detect IR rays.
The output signal from this detector is relatively weak and may not be sufficient to drive speakers. Consequently, we incorporate a basic amplifier to amplify the signal, enabling it to drive the speakers effectively.
IR Audio Transmitter and Receiver Circuit Diagram
Components Required
Transmitter Section
- 9V Battery
- Resistor – 1KΩ X 2
- IR Transmitters (IR LEDs) – 2
- BC548 NPN Transistor
- Connecting wires
- Breadboard
Receiver Section
- Photo Diode
- Resistor – 100KΩ
- POT – 100KΩ
- Capacitors – 0.1µF X 2, 10µF, 47µF
- LM386 Audio Amplifier
- Connecting wires
- 8Ω Speaker
- 9V Battery
- Breadboard
Simple IR Audio Link Circuit Design
The IR audio link circuit comprises two distinct sections: one for the transmitter and another for the receiver. The transmitter section is powered by a 9V battery, and it involves feeding the audio signal to the base of Q1 via a 1K resistor.
Transistor Q1 drives the IR LEDs, D1 and D2, resulting in the modulation of the incoming audio signal into infrared signals.
The photodiode receives these transmitted infrared signals and converts them back into an electrical signal before routing it to the LM386.
The LM386 is a fundamental Audio Power Amplifier IC capable of delivering a maximum output power of 1W. It can drive both 4- and 8-ohm speakers, and for this circuit, an 8-ohm speaker was employed.
In my setup, I used 9V batteries to supply power to both the transmitter and receiver sections. Alternatively, in the receiver portion, you can use a Photo Transistor such as the BPW77NA, BPW85, PNA1605F, or PNZ154 instead of a Photodiode.
NOTE: In case you are using a Photo Transistor, the circuit at the receiver end changes to the following.
How to Operate IR Audio Transmitter and Receiver Circuit?
- As shown in the circuit diagram, connect the transmitter and receiver individually at first.
- Using two 9V batteries, power both the transmitter and receiver portions.
- Connect an 8-speaker to the LM386 Audio Amplifier IC’s output.
- Make sure the distance between the transmitter and the receiver is less than 30cm.
- Using a mobile phone or a music player, apply the audio signal to the transmitter part. You can now listen to the sound from the speaker.
- Disconnect the transmitter and receiver batteries.
Simple IR Audio Link Circuit Applications
- Used in audio communications to transfer the audio signal from one place to other.
- Used in short range communications.
Simple IR Audio Link Circuit Limitations
- This IR audio link circuit works only for short distances
- This circuit is not very practical in the sense that there exists a lot of noise and may require some changes to implement it more efficiently.
