Here is a simple circuit called earth quake alarm. This circuit is divided into two sections.
- Geo mechanical detector (Earth quake sensor)
- Alarm circuit
The alarm is based on the principle that earth quake create slow and suddenly vibration. In order to detect this vibration geo mechanical detector is used. The construction of geo mechanical detector is shown in figure 2.
The alarm circuit is built around dual input, 4 NAND IC (CD4011) and a NPN transistor. Input of NAND gate 1 (pin 1) is connected to sensor through probe 1, where NAND gate 2 configured in monostable multivibrator mode. NAND gate 3 and 4 is used as audio oscillator. The output form NAND gate 4 (pin 11) is given to base of speaker driver transistor T1 through coupling resistor R4.
The complete circuit can be kept in cabinet with 9V power supply. The geo mechanical detector where non on can disturb.
PARTS LIST OF EARTH QUAKE ALARM
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1 = 100 KΩ
R2 = 2.2 MΩ
R3 = 10 KΩ
R4 = 680 Ω
|C1 = 100 µF/10V
C2 = 10 KPF
|IC1 = CD4011
T1 = BC147
D1 = 1N4148
|LS1 = 8 Ω speaker
B1 = 9V PP3 battery
PCB, screw, nuts, metal rod etc.