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Police Light Circuit Design

Paper Type: Free Essay Subject: Engineering
Wordcount: 915 words Published: 30th Aug 2017

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Police light have been around for years, since then they have developed drastically, with technology moving forward so have aspects of police light and how they are made, developed and manufactured nowadays. In the 1940s authorities used single beacon lights, which was placed on top of their cars. Early 1990s the single beacon lights became less common as light bars where introduced, they became popular and replaced the single beacon light.

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Police lights are a significant aspect of many emergency vehicles, as its one of their most recognisable features, which informs the public that indeed the given vehicles is an emergency vehicle. This system is controlled by in system controls within the vehicle itself, which allow the user to have full control of the lights system, determine how and when the lights come on or go off, and even how the police light behave in terms of how they flash.

This system is used in the case of an emergency, the user will turn it on whenever there is an emergency, as a result the public will be aware that that given vehicle is an emergency vehicle, this allows the public to respond with necessary action, in that given situation.

Principle behind the circuit

Circuit diagram

Required components


  • NE555 Bipolar Timer
  • 4017 Decade Counter
  • 1N4148 Diode
  • 1.2K Resistor
  • 10K Resistor
  • 470 Resistor
  • 4.7uF Electrolytic Capacitor (50V)
  • BC547 NPN Transistor
  • LED
  • 10K POT
  • Switch


  • Proteus 8 professional
  • Windows 10

Components used


When trying to resist the flow of alternating or direct electric circuit a resistor can be used in order to perform that action, this piece of component is placed in the electric circuit, depending on the circuit and how it functions the location of where the resisters are placed will vary. In electronic circuits a resistor is typically used to either limit or divide the current, protect an electric circuit or reduce voltage. When the charged particles(electrons) move from one region to another it is known as electric current. the shape of a resistor is cylindrical. There are many different types of resistors that have different values, when using resistors, you can identify the value of the resistor by looking at colour coding, resistors have something known as a colour band, a resistor can have 3,4 or 5 colour bands, depending on the resistor value. When the temperature is constant the current density is directly proportional to the electric field, which obeys ohms’ law.


A component such as a capacitor can be used when needing to store an electric charge. When electrical energy is added to the capacitor it is known as charging, however when energy is release from the capacitor it is known as discharging. A capacitor has two metal plates, which are separated by a non-touching layer which is called a dielectric. Electricity from a direct current or an electrostatic source charges one of the plates. When power is supplied through a circuit electrical charge will gradually build up in the plates. While one plate gains a positive charge, the will gain a negative charge. When you integrated a capacitor within a circuit that might contain a lamp or motor, the charge of the capacitor flow through the lamp or motor, until there is no charge remaining gin the plates. The capacitance of a capacitor is the amount of electrical energy the capacitor can store, the bigger the capacitance the more electrical energy it can store. There are a wide range of capacitors available on the market, such as Air, Mica and Paper, depending on the intended purpose, different capacitors are used.


A component such as a transistor is a device which is used to transforms current flow from a low resistance to al high resistance path. A transistor is a solid-state device which contains a piece semi conducting material, which can usually be silicon or germanium. When negatively charged, electrons are present we call a transistor an n-type transistor, because it contains donor impurity atoms. However, when positively charged electrons are present we call a transistor an p-type transistor, because it contains acceptor impurity atoms.

Flow chart


  • User control
  • Ease of use
  • No mercury in LED
  • Cheap
  • Light up quckly


  • Colour shift
  • Constant flow of voltage and current


  • future enchancments
  • Light patterns – changing how thy flash



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