This article describes the use of infrared wireless headphones to close the audio signal transmitted by the transmitting and receiving part of the digital circuits, making low-cost, easier to debug for the majority of electronics enthusiasts self-imitation.
Transmitter circuit shown in Figure 1, which includes pulse modulation, current amplification and infrared emission and some other circuits. CD4O46 constituted by the phase-locked loop VCO (VCO) is the core of the transmitter; when the audio signal is applied in Figure 1, A point, VCO’s output frequency will produce a set of oscillation amplitude with the size of the audio signal synchronization change the FM signal by infrared IR LED into FM signal to send out
Figure 1 transistor VT1 and VT2 to drive the infrared LED, if not the same model can also be used instead of the common C1815 or 9014, but the tube to obtain the best value of ß larger point. The receiver by the photoelectric conversion, pulse amplification, frequency demodulation and audio amplification of four parts, the receiver circuit shown in Figure 2. The infrared signal is first modulated infrared photodiode receiver and converted to FM signals, after pre-amplification FET 2SK117, µPC1373H selected frequency, amplified and then formed by the CD4046 phase demodulation circuit and restore the audio signal.
Receiver and transmitter circuits are two CD4046’s center frequency 45kHz, so the R7 and R17, R8 and R18, C4 and C24 of the parameters must correspond exactly equal. Infrared LED driver transistor VT1 and VT2 are working in the amplification status, the Vbe of about 0.6V; VT1 and VT2 can also be replaced by 9013, but the tubes of ß should be greater than 100. Transmitter power supply circuit not shown in the figure, the production obtained after the time available LM7806 regulator. Each infrared LED’s forward voltage drop are 1.15V, transmission power less than 100mW, the three infrared tube infrared series aimed at increasing the transmit power. In addition, infrared LED radiation angle is limited, so the board is required in the design of the three sub-stagger just 45 ° arrangement. Infrared photodiode to be coupled with the right only to work the reverse voltage, so the electrical installation must be careful to check infrared photodiode is reverse in the circuit. Battery-powered receiver circuit of the bridge amplifier TDA2822M machine is to reduce power consumption. Inductor L10 in the week in the skeleton-section of enameled wire with f0.06 150 turn around after the close fitted with magnetic cap and shield in the system. Infrared LED and infrared photodiodes easily damaged, and their specific parameters such as shown in the table. Infrared wireless headphone transmitter does not need to adjust to normal work. Adjusted on the receiver, we can first TV remote control panels align the receiver and press any key at random, monitoring