The TV sound infrared repeater, a simple structure, easy production, without interference, noise is low.
The transponder transmitter and receiver by the two components ( Click here to download the schematic diagram ). Figure 1 (a) for the emission part of the circuit. After the sound frequency discrimination (audio) signal amplified by the transistor VT promoting infrared emission control. Emission intensity of the launch tube and through its current proportional to the VD1, VD2 infrared light emitted will be the audio signal modulation. To prevent distortion, VD1, VD2 to set a certain bias. Figure 1 (b) is to receive part of the schematic. The circuit uses an audio amplification IC LM386. VD for the infrared receiver tube. When the audio signal is modulated infrared light shines on VD, in its both ends with the audio signal to produce a variation of the same signal, coupled via C1 to the IC, the magnification. Amplification of the IC with power, so the headphones simultaneously listening for, vice 1-4.
Selection and production of components
VT transistor power tube used in 8050, P CM = 300mW, I CM = 500mA, the power of not less than R2 1/4W, VD for the infrared receiver tube (not photodiode, or by visible light interference reception).
Debugging of the transponders is very simple. Simply adjust the R1 to launch part of the VT is about 30mA quiescent current. Just install the correct receiving part, without debugging to work.
Transmitter can be installed inside the TV, using the machine 12V power supply. Signal input A, B side, received the two ends of the volume potentiometer. The DC volume control integrated circuit telephones, can be A, B received a speaker at both ends of both ends, but to addition of a switch, the speaker off (using the headphone output jack is more convenient). Adjust the volume to make it forward distances without distortion.
Two launch tubes installed, to consider the scope of its radiation, to make them a part of the effective radiation angle of overlap.
The design of the transponder slightly lower sensitivity, the aim of increasing interference. After measurement, the effective distance of not less than forwarding 3m, fully meet the needs of ordinary families.