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 NXP Semiconductors


  • Police Lights

  • Created: Dec 08, 2014

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Description

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Summary

This project describes a set of warning lights fitted to a police vehicle when the officer wants to convey to other road users compelling them to pull to the side of the road using NXP Semiconductor's 74HC4017N decade counter. Moreover, it helps law enforcers to provide a means of signaling another driver to stop so the police car may proceed through unimpeded. The police lights can be used along with a siren in order to increase their effectiveness.


This circuit uses 555 timer and a decade counter. Here, 555 timer runs in astable mode. It produces continuous pulses via Pin3. For every incoming pulse, the output state of the decade gets incremented. That is, the first pulse at Q0 becomes HIGH and the second pulse at Q1 becomes HIGH and so on again until the 10th pulse when Q0 state becomes HIGH. Based on the outputs of the 4017 IC, the two transistors (NPN) switches the LED's ON and OFF. Resistors R10, R11, R14, R15 are used to protect the LED's from high voltage. The circuit is powered by a 12V supply.


Police lights are generally used to clear the right of way for emergency purposes, or to warn approaching motorists of potential hazards, such as a vehicle that is stopped or moving slower than the rate of traffic, or a car that has been pulled over.