This multiutility flash light consists of three sections: a flasher, a sound-to-light display and a white LED-based flashlight.
The flasher circuit (Fig. 1) is built around an NE555 timer IC that is wired as an astable multivibrator. It flashes a pair of LEDs alternatively. The frequency of the astable multivibrator can be varied using preset VR1.
The working of the sound-to-light display (Fig. 2) is simple. The condenser microphone (MIC) picks up the sound in its vicinity and outputs a low voltage. The low output of the microphone is boosted by the first section (A1) of dual op-amp LM358. The output of op-amp A1 is fed to the second section (A2) of LM358 to drive transistor T1 (2N2222). The three RGB LEDs flash accordingly. (An RGB LED is actually a two-pin white LED package that glows red, green and blue sequentially when powered.)
The flashing light circuit (Fig. 3) consists of a group of four white LEDs connected in series. Resistor R13 limits the current flowing through the white LEDs (LED8 through LED11).
Assemble the entire circuit including the flasher, sound-to-light display and flashlight on a general-purpose PCB and enclose in a cabinet. Connect the flasher LEDs (LED1 through LED4) on top of the box and the condenser microphone and flashlight white LEDs (LED8-LED11) in the middle of top as shown in Fig. 4. Connect the three switches to select any one function or the combination of two or three sections.