Bicolour LED flasher circuit

Bicolour LED flasher circuit

Basically this circuit is similar to some flasher circuits already published in www.electronicsproject.org using IC555 as a free running multivibrator. The only difference lies in the way it flash using bi-colour LEDs.

When output at pin 3 of IC 555 goes high it operates on group of LEDs. By inverting the IC’s low output by pnp transistor BC558 the other group of LEDs is made to flash.

AS shown in circuit diagram the LEDs are arranged in alternately reversed order so that a “twinkle twinkle little stars” effect is produced. The 100K preset VR1 sets the blinking rate.

The circuit diagram for the project is:

To maintain simplicity I omitted the current limiting resistor. So, the red and green LEDs may not flash with equal intensity (as they require different threshold voltage).

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R1, R2 = 1.5 KΩ

R3 = 330 Ω

VR1 = 100 KΩ

Capacitor

C1 = 10 µF/10V

Semiconductors

IC1 = NE555

T1 = BC558

LED1 – LED5 = Bi-colour LEDs

LED6 = RED LED