Monday, February 14, 2011

1.5V LED flasher


The circuit to light LED with single 1.5V battery is usually based on a blocking oscillator or a charge-pumped voltage doubler.
This is another (but similar to charge pump) way to flash LED with 1.5V battery. The base-R voltage becomes nearly double the Vcc while making oscillation timing of astable multivibrator. LED can be flashed if it is attached aside. Since the LED discharges the C electricity, oscillator timing is shortened.

Figure 1:  1.5V LED flasher

        Normal astable multivibrator ( without LED )

        LED attatched timing

        LED discharged electricity

Figure 2:  LTspice simulation

You can see the light at the marked points.

Figure 3:  Implementation


The circuit above is not enough to light blue or white LEDs which need more than 3V voltage. This version boosts the voltage by a charge-pump extension. It produces about 2.8V momentary, with 0.8 sec intervals. Try other LEDs if the lighting is dim, since some LEDs may require the higher voltage.

Figure 4:  1.5V flasher for Blue/White LED


The V(vl) is the LED's cathode voltage, and the V(vh) is the anode.

Figure 5:  LTspice simulation (blue/white)


Figure 6:  Implementation (blue/white)

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