Voice controlled delay LED light control circuit diagram

The circuit of this device is shown in the figure. It is mainly composed of a single-supply low-power operational amplifier integrated circuit IC 1, two low-power transistors, a microphone and a high-brightness light-emitting diode. When the microphone MIC receives a certain intensity of external sound (including various noises), it generates an output voltage of corresponding intensity and adds it to the comparator IC1c. When this voltage exceeds the comparator threshold, its output is at a high potential, turning on V1. Its output voltage is added to comparator IC1b. Similarly, this voltage is higher than the threshold value of IC1b. IC1b outputs a high potential to excite the power amplifier composed of IC1a and V2, thereby driving the LED to emit light. The preset delay length. It is determined by the time constant of the charge and discharge circuit composed of C2 and R6, as well as R7 and R8.

On this kind of lighting device, a push button switch can also be added to make the LED light up and continue to shine at a predetermined time. The power supply of the circuit is also very convenient, using 4 cells of nickel metal hydride (MiMH). The entire device works intermittently, and the battery can be used for 2 months. The entire circuit is in standby mode, consuming 400μA, and 24mA when the LED is lit.

From the circuit structure, the microphone MIC is connected between the input terminal and the ground wire through a wire. And it is connected to the positive terminal of the power supply through R1, and the signal AC component is coupled to the non-inverting pin of the op amp IC through the capacitor C1. The adjustment of microphone sensitivity depends largely on the value of R1. It is recommended that the R1 value be 15kΩ. Depending on the microphone brand and model used, the R1 value should be changed accordingly to achieve the desired sensitivity. When the maximum sensitivity is adjusted, when the door is opened and the air flow exerts pressure on the microphone diaphragm, the LED should be triggered to light up. IC 1 uses TLC274, its pin diagram is shown in the figure.