fire alarm circuit with temperature

Posted on Feb 4, 2014

Fires can occur for several reasons, for example, forgot to turn off equipment that could cause such as irons, fire alarm circuit with a temperature sensor may be one option in an effort to secure our homes from fire hazards. Actually there is also a fire alarm circuits that use LDR, but I think it is less effective because it is basically a light

fire alarm circuit with temperature
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sensor, that is the presence of smoke then the intensity of light falling into the LDR will decrease and the triggering circuit. But as as I said seems less effective. This fire alarm circuit use IC LM35 as temperature sensor. Wherein when the temperature in a room setting has been reached it will be triggering the circuit to sound an alarm. One that I like from the LM35 sensor is its sensitivity to temperature so as suitable for the temperature sensor, it is also easy to obtain. The LM35 output is fed to pin IC LM339 comparator IC is negative with a positive setting with a value input through the VR1 10K. VR is what will the temperature sensor sensitivity setting used. While the LM 339 is a comparator IC that has a 4 in it. Output on the comparator IC LM339 is fed to the transistor T1 BC547, how it works when output low / low, T1 in a state that serves as a cut-off switch is open, so it will work like a switch T2 is closed and the resulting pin 4 (reset) on the IC 555 to be low. And because the reset input 555 is low, the alarm does not work. and so if there is a trigger that caused the LM35 IC temperature which gives a chance has been reached. As for the installation of fire alarms can be placed around flammable materials or places where the potential occurrence of fire, and it seems like if we use multiple sensors to a circuit (diparalel) will work well for this LM IC impedance is low,

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