Neil Mula


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  • Warning/Hazard Siren System

  • Created: Aug 29, 2014

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The people are aware of a siren sound which means a signal to be grasped without any word/s. This circuit is a design of a siren that is commonly used by police patrol car. It is fully functional with pushbutton as the control switch.

The system runs with two NE555 devices which are an astable multivibrators. The NE555 device generates the pulse that is supplied to the BD139 device or NPN Epitaxial Silicon Transistor. Its output pulse is approximately 1Hz from the first NE555 device but it is situated by the resistors and capacitors. As it pass through the second NE555 device, the frequency is already around 440Hz to 550Hz because of the voltage divider circuit. The 1N4007 device is a general purpose rectifier that is used to prevent reverse current.

This simple project is practical. It can be used in different applications by just simple modification. It can be a residential alarm system, ambulance siren, industrial siren and other applications that used to give signal through sound.



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