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Pies Buzzer white LED for energy from a single battery.
Receiving single-battery-powered LED flashlight is attracted widespread attention. Lit white LED tactical flashlight generated by the low-voltage, need some kind of electronic oscillator, easiest piezoelectric buzzer. The piezoelectric transducer special for the oscillator and drive white LEDs (Figure 1). Piezoelectric die composed of the piezoelectric ceramic plate, or a curved plate with a double-sided electrode, attached to brass, stainless steel or similar material, a metal panel with a conductive adhesive. The circuit uses the three ends of the piezoelectric converter. In this converter, the die in which one electrode has a reaction marker. Resonant oscillation is between inductive and capacitive devices. The working frequency is: fOSC = 1 / (2π), where, L is the inductance value, C is the electric capacity of the piezoelectric element.
With the first of the Figure 1 circuit voltage, the transistor Q1 is turned on. When the conduction of the transistor, the current through the inductor L1 gradually increases, the voltage through the metal plate so that the piezoelectric ceramic bending. This bending produces a negative voltage to the reaction mark, which in turn is powered for the base of the transistor. Subsequently transistor turns off. When shutdown occurs, the inductor the stored energy is input into the LED. The flyback voltage is sufficient to illuminate LED tactical flashlight.