4-in-2-out audio channel switcher

Have you ever been annoyed by having too many audio devices? When you have multiple computers, game consoles, CD players, or other audio equipment, do you need to connect audio cables one by one?
Or do you have to constantly change plugs every time you replace speakers/headphones, especially in homes with many multimedia devices?
This circuit is an audio channel selector co-designed by me and @element115mc. It supports up to 4 audio inputs and 2 audio outputs, and allows for function selection and switching via buttons.
For aesthetic purposes, the entire PCB silkscreen, audio connectors, and electrolytic capacitors are light blue. The LCD1602 uses a gray backlight
circuit. The main controller is an STC89C52RC, and an AT24C02 is used to store user settings from the previous power outage. Audio input and output are easily controlled via relay switching. The audio
circuitry is isolated from the controller circuitry to prevent signal interference.
The included program contains basic functionalities; users can add additional functions to the controller based on the circuit diagram (e.g., modifying the names of input/output devices on the LCD1602).
The side of the circuit retains serial port programming headers and short-circuit reset headers .
The included program has a self-test function; a clear relay click and the LEDs lighting up sequentially upon power-up indicate normal relay operation. (
PCB front view,
PCB back view , close-up of
buttons, indicator lights, LCD1602, programming
headers, reset headers
, power interface, electrolytic capacitors, contrast potentiometer close-up)
. Principle: The program controls the corresponding relays via a microcontroller, switching the corresponding audio connection mode to achieve audio channel switching. By reading and writing to the AT24C02 via soft I2C, a power-off data memory function is implemented (recording the user's selections at the time of the last power outage). The current channel is indicated by relay indicator lights, and the LCD1602 displays the information synchronously .
This circuit can be mounted on the casing of speakers or other equipment with screws, or it can be attached to a metal casing surface using internal magnets.
Parameters: Power supply voltage: 5V. No-load current: 0.04A, operating current: 0.13A.
Usage: The "Select" button switches the current selection (displayed as a ">" on the front of the LCD1602), the "Set" button switches the signal of the corresponding channel, and pressing the "Mute" button releases all relays; pressing it again cancels the mute mode.