Police Car Strobe Lights using a 555 Timer and a 4017 Decade Counter

Introduction

Today, we will solve the mystery behind police cars strobe lights! Seriously, I was looking at a way to simulate those lights using simple LEDs and without any rotating components.

Here’s the result on a breadboard:

Solution

The solution to that problem was pretty simple.
I used a 555 timer to trigger a 4017 decade counter.

I used 4 red and 4 blue LEDs to mimic the strobe lights.
They are all connected to the same 4017 chip, so only one LED is turned on at any moment in time.

The 555 timer in used in astable mode to generate a square wave signal.
That square signal is fed to the 4017 integrated circuit.
Each time the square signal changes from high to low, it triggers the 4017 that then switches to the next output pin.

police-flashers_4017-555-astable

Notes:
The 2 resistors near the 555 chip are 220 KOhms.
The 2 resistors on LED grounds are 220 Ohms.
The red capacitor is of 0.1uF.
The blue capacitor is of 330nF.

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