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Wednesday, 26 October 2016

Fire Alarm Using Thermistor.



Fire Alarm Using Thermistor.
Numerous fire caution circuit is distributed in various site. Be that as it may, here in this site is a straightforward and reasonable venture of flame caution utilizing thermistor. where thermistor is utilized as temperature sensor of flame alarm.Working guideline of thermistor is same as LDR (change their resistance with change in warmth where LDR change their resistance with change in light fall on it. Circuit Description of flame alert utilizing thermistor The entire circuit of flame alert utilizing thermistor is assemble and created around thermistor (TH1) furthermore, clock IC (IC1) with its driver transistor.


 The clock IC (IC1) utilized as a part of this circuit is as astable multivibrator oscillator used to waver in sound recurrence band. The two transistor T1 and T2 used to drive the clock IC (IC1). The yield from stick 3 of IC1 is encouraged to amplifier through transistor T3 to create sound. The estimation of resistor (R5 and R6) and capacitor (C2) decides the recurrence of IC2. The low resistance way of stretch out positive voltage to the base of transistor is given when the thermistor TH1 get to be hot. Encourage authority of transistor T1 is associated with base of transistor T2 gives positive voltage to reset stick 4 of IC1 for reset. Fire caution utilizing thermistor circuit chips away at extensive variety of information power supply voltage i.e. 6v to 12V. 

  
PARTS LIST
Resistors (all ¼-watt, ± 5% Carbon)
VR1 = 10 Kohms Variable Resistor for changing the affectability of the circuit.
R3, R7, R8 = 470 Ω; R2 = 33 K Ω ; R4 = 560 Ω; R5 = 47 Kω; R6 = 2.2 Kω
Capacitors
C1 = 10 μF/16V; C2 = 0.04 μF; C3 = 0.01 μF
Semiconductors
IC1 = NE555 (clock IC); T1 = BC548; T2 = BC558
T3 = SL100B or any Medium power broadly useful NPN transistor like: 2N4922 , 2N4921,2N4238, FCX1053A D1 = 1N4001
Various TH1 = Thermistor 10 Kω LS1 = 8 Ω, 1W speaker

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