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Circuit 85 – Smoke alarm (Deaf person).
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| Submitted: Thu Oct 16 2003
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Circuit 85 - Smoke alarm (Deaf person) Function When normal smoke alarm sounds it will activate the add on circuit which in turn will switch on a vibration motor which will arouse the deaf person. Circuit diagram Components R1 = 1k ohm R2 = 470 ohm R3 = 470 ohm R4 = 47k ohm R5 = 10k ohm VR1 = 100k ohm C1 = 100?F C2 = 470 ?F IC1 = 555 Timer Transistor (TIP121) LED = 5mm Standard Smoke alarm (Commercial) Motor (12V) THY1 = Thyristor (TIC106D) RLA-1 = Relay (DPDT) D1 = D2 = 1N4001 Operation The heart of the circuit is a 555 timer chip configured in astable mode. This means the out put at pin 3 is constantly changing, i.e. the output goes high (9V) for a specified time and then low (0V) for a specified time before again switching high. The frequency is controlled by the size of R1, VR1, and C1. Formula to calculate the frequency:- From values of R1, VR1, and C1. The frequency of the output is...
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