Fire Alarm schematic design
Posted on Dec 11, 2010 4971
Explanation Here is a simple fire alarm circuit based on an LDR fire detection sensor. Smoke generated during circuit generates an audible alarm, fire smoke in case of fire. Al
arm works and lamp pairs. When there is no smoke from the light bulb will directly LDR.The decline LDR resistance is low, the voltage across it (less than 0.6 V). Transistors will not have enough smoke happens.When shield falls LDR, LDR resistance increases, so the whole it.Now voltage transistor switching to ON.This to IC1 power, it 5V.This power output tone generator IC UM66 ( IC2) by the IC3 2002 (TDA), play music.This music will be amplified to drive speaker.Resistor R6 is R4 is open protected against low resistance value of the transistor means. resistors R1 and R2 for the TDA2002 feedback web forms, C1 couples from R1 and R2 are the same at the junction of the inverting input of IC feedback signal. Diodes D1 and D2 binding, down to 1.V rated voltage (3.5V) UM66. The UM 66 can not afford less than 4V. Circuit diagram and parts list Fire alarm circuit Precautions 32 speaker may be a tweeter. R4 potentiometer can be used to adjust the sensitivity of the alarm. Potentiometer R3 may be used for different alert volume. The first quarter may be used for any general purpose NPN transistor (such as BC548, BC148,2N222). The circuit can be from 9V battery or a 9V DC power supply. Instead bulb can use a 1K resistor series bright LED.