24 LED Police Flasher

Dual color (4 line x 3 column) led, 12 white and 12 blue are intermittently switched controlled by two NPN transistors BC337.
The speed and duty/cycle timing of lighting duration is determined by NE555 oscilator. The number of repetition of sequential
lighting of each group of led is determined by 5-stage divide-by-10 Johnson counter with 10 decoded outputs and carry out bit (CD4017).
The intermittent lights from two group of led imitate the police car strobe lights.
The speed of switching off and on of led are continuously regulated by variable trimmer resistor.
Only two integer circuits, two transistors, 12 resistors and 24 led diodes is needed to build this very interestingly light toy.
Never ever use it to avoid the fuss of city cars, simulating the police car. 🙂
The instruction for built of this project you can find on:


author: writer to magazine Emiter, D-r Petar Avramovski.

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