Monday, May 03, 2010
This is a simple fire alarm circuit, which can help the user's color interested against fire accidents based on a LDR and lamp pairs an alarm for sensing the fire.The works by sensing the smoke Produced During fire.The circuit produces an audible alarm the fire breaks Pls out with smoke.
When a number of smoke passes Between a bulb and an LDR, the amount of light falling on the LDR decreases. This Causes the resistance of the LDR to Increase and the voltage at the base of the transistor is pulled high due to Which the supply to the COB (chip-on-board) is completed. Different cobs are available in the market to generate Different Musical. The choice of the COB depends on the user. The signal generated by COB is amplified by an audio amplifier. In this circuit, the audio power amplifier is wired around TDA2002. The sensitivity of the circuit depends on the distance Between bulb and LDR as well as the setting of preset VR1. Thus by placing the bulb and the LDR at appropriate distances, one May Vary preset VR1 to get optimum sensitivity. An ON / OFF switch is suggested to turn the circuit on and off as Desirable.