Voice controlled flash LED light circuit diagram

The circuit is mainly composed of a pickup (electret condenser microphone), a transistor amplifier and a light-emitting diode.

Circuit principle

When static, VT1 is in a critical saturation state, causing VT2 to cut off. LED1 and LED2 do not emit light. R1 provides a bias current to the condenser microphone MIC. After the microphone picks up the acoustic signal in the indoor environment, it converts it into a corresponding electrical signal, which is passed through the capacitor. C1 is sent to the base of VT1 for amplification. VT1 and VT2 form a two-stage direct coupling amplifier circuit. As long as the appropriate R2 and R3 are selected, there will be no sound wave signal. VT1 is in a critical saturation state, so that VT is in a cut-off state, no current flows through the two LEDs and they do not emit light. When the MIC picks up the sound wave signal, an audio signal is injected into the base of VT1, and the negative half cycle of the signal causes VT1 exits the saturation state, and the collector voltage of VT1 rises. VT2 is turned on, and LED1 and LED2 light up. When the input audio signal is weak, it is not enough to make VT1 exit the saturation state. LED1 and LED2 remain off. Only when a strong signal is input, the photodiode lights up. Therefore, LED1 and LED2 can flash and light up and down with the intensity of environmental sound (such as music, speech) signals.

Parts list

VT1, VT2 9014(BT200) microphone

R1 4.7K R2 1M

R3 10K C1 1uF/16V

C2 100uF/10V LED1, LED2 light-emitting diodes

Assembly and debugging:

1. Draw the assembly drawing according to the schematic diagram, and then assemble according to the assembly drawing.

2. Pay attention to the wrong polarity of the triode, and the components should be arranged neatly and beautifully.

3. After powering on, first measure the collector voltage of VT to make it between 0.2 and 0.4. If the voltage is too low, after applying the sound signal, VT1 cannot exit the saturation state and VT2 cannot conduct. If the voltage exceeds VT2 If the dead zone voltage is low, VT2 will be turned on when it is static, causing LED1 and LED2 to light up, so. For condenser microphones with different sensitivities and transistors with different β values, the size of the collector resistor R3 of VT1 must be determined through debugging.

4. At a distance of about 0.5 meters from the microphone, when speaking with a normal voice (moderate volume), LED1 and LED2 should flash with the sound. If you need to speak loudly, the light-emitting tube will flash. You can appropriately reduce the resistance of R3, or replace the transistor with a larger β value.