Fire activated alarm


Posted on Apr 2, 2012

This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This causes the resistance of 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 sounds.


Fire activated alarm
Click here to download the full size of the above Circuit.

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 IC TDA 2002. The sensitivity of the circuit depends on the distance between bulb and LDR as well as 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.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Analog counter circuit
Angle of rotation detector
Conversion Receiver For 160 To 20M Circuit
10 Note Sound Synthesizer Circuit
Circuit examples
interafce 16x2 lcd with avr
Variable inductor
Handheld Oscilloscope Oscillator Circuit
Detecting an ultrasonic beacon
Remote-controlled preamplifier
AC DIGITAL CLOCK WITH STANDBY BATTERY
Bachmann Sound Tips
TDA4866 test circuit diagram



Top