Flip Flop flashing of many LEDs with NE555

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A flip flop circuit, here, flashes two sets of LEDs ON ad OFF in a flip flop manner. the circuit includes IC NE555 for the time triggering switching. Also, the circuit uses both the NPN and PNP transistors to achieve the required transition of lighting of LEDs.

ne555-timer-ic

Hardware Components

The following components are required to make Flip Flop flashing Circuit

S.noComponentValueQty
1.IC NE555 Timer1
2.Transistor BD139, BD1401
3.Electrolytic Capacitor10µF1
4.Battery 12V1
5.LEDs 36
6.Variable Resistor100KΩ2
7.Resistor 62Ω, 1KΩ, 4.7KΩ12, 2, 2
8.Ceramic Capacitor10nF1

NE555 IC Pinout

555 timer ic pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

BD139 Pinout

BD139-Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of BD139

Flip Flop flashing Circuit

555-flip-flop-with-many-leds-Circuit-Diagram-Schematic

Working Explanation

IC NE555 is a timer IC with which the ON and OFF time duration of the LEDs is achievable. Since the output of the NE555 timer IC is just 200mA, therefore, the IC is capable of driving only a few LEDs. Hence, two powerful transistors help increase the number of LEDs connected in the circuit. The transistors used in the circuit are NPN BD139 and PNP transistor BD140 which are able to drive a maximum of 140 LEDs altogether. This is because, the output current of both the transistor is 1.5A, enough to drive more than 120 LEDs. While connecting the LEDs with the transistors, it is necessary to connect a current limiting resistor as well.

If more than 18 LEDs are used in the circuit then a heatsink is also required with each of the transistors in order to prevent them from burning. The two 100KΩ variable resistors adjust the switching rate of the two sets of LEDs, respectively. Furthermore, the operating voltage of the circuit is 12V.