Automatic power-off circuit of the player

Working principle of the circuit : When there is sound, the LED of the vu level meter emits light (not shown in the figure ). After receiving the light from the LED
, the photoresistor LDR sends a high-potential pulse to the transistor VT, VT, to the capacitor C. to charge. The slow discharge process of the capacitor can provide a delay function, so C. The values ​​are different. The duration of the delay also varies. The charging and discharging process of the capacitor forms an exponential signal, which is converted into a digital signal suitable for completing the breaker function after being passed through the integrated circuit NE555 (Schmitt trigger) .