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Explain the principle stereo channel selector

2017-01-03 04:20  
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This article is to explain the principles of the stereo channel selector. Want more quickly grasp the principles, please carefully read schematics combine text. The circuit has been connected to provide stereo output from the four different sources / channels as input, only one of them is selected / connected to the output at any one time. When power is "on", the channel (AR and AL) is selected. If you do not appear in the audio channel one, the circuit waits for some time and then select the second channel (channel B). The search operation has been continued, until it detects an audio signal channels. Reactor wait or delay time can be preset according to the help of VR1. If you still takes a long time to replace the capacitor C1 and the capacitor can be a higher value. Assuming the channel is connected to a tape recorder and channel B is connected to a wireless receiver. If the initial channel one is selected, the audio output from the recorder will be present. In the recording playback completely, or if there is sufficient pause recording, the circuit automatically switches to continuously between the output of the radio receiver. Manually skip from one (selected) active channel to another (remove) active channel, simply skip switch (S1) once or more until the desired channel input transient was selected. Selected channel (A, B, C, or D) to said corresponding light emitting LED (LED11, LED12, LED13, LED14, or separately). IC CD4066 contains four analog switches. These switches are connected to four separate channels. For the three-dimensional operation, the use of two similar CD4066 ICs circuit shown in Figure. These analog switch control IC CD4017 outputs.  CD4017  is a 10 ring counter IC. Because only one of its outputs are high at any instant, only one switch will be closed at a time. IC is configured as a 4-bit ring counter CD4017 fifth output connection Q4 (pin 10) to the reset pin. Capacitor C5 in conjunction with resistor R6 forms a power-on reset circuit, IC2, so that the initial switch "" Power, output Q0 (pin 3) is always "high." The clock signal is generated by IC1 CD4017 (NE555), as an astable multivibrator when transistor T1 is cut - off. IC5 (KA2281) is used here not only to display the audio level of the selected stereo channel, but also for forward biasing transistor T1. When a certain threshold value is detected audio level on a selected channel, the pin 7 and / or pin 10 IC5 go "low." This is coupled to a low level, the transistor T1, the diode resistor combination d2 r1 / d3 r22. Therefore, the transistor T1 and the output of IC1 causes remain "low" (disabled) as long as the selected audio channel output exceeds a preset threshold level. VR2 and VR3 preset adjustments already included personal audio threshold level of the left and right stereo channels, as expected. Once the multivibrator action is disabled IC1, IC2's output does not change further. Therefore, the search channels continue indefinitely, until it receives the audio signal exceeds a predetermined threshold. skip switch S1 is used to skip a channel even if the audio in the selected channel. The number of channels can be easily extended to ten, by using additional 4066 ICs.
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Stereo Channel Selector

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