The simple and reliable Vibration alarm circuit designed by using Vibration sensor switch SW – 18020P and timer IC555 and few easily available components. The SW – 18020P sensor has two terminals and there is no contact between terminals in idle condition.
When Vibration or External force applied on sensor two contact pins of sensor are closed. This sensor is suitable for producing trigger signal to the timer ICs and as well as microcontrollers.
You can see the physical view of vibration sensor SW – 18020P and internal view. This sensor works in maximum voltage range of 12V and maximum current value < 5mA. It creates < 10MΩ during idle condition (no vibration detected) and produce < 5Ω during vibration detection. It has fast response time as 2ms, and has ambient temperature range < 100°C. It is suitable for different applications that needs vibration detection.
Circuit diagram for Vibration alarm
Construction and Working
This circuit has timer IC 555 configured in monostable mode. It produce buzzer sound and light indication upto two minuets during the vibration detection. You can change this alarm sound duration by changing the timer elements R3 and C2.
T = 1.1 * R * C
for given circuit
Tmono = 1.1 * R3 * C2
= 1.1 * 1MΩ * 100µF
= 1.1 * 1000000 * 0.0001
Tmono = 110 Seconds.
When the vibration detected by the sensor, it will produce trigger signal and it triggers the timer IC 555 hence it produce Mono timing pulse upto 110 Sec. The output pulse taken from pin 3 is applied to the NPN transistor BC547, here the Q1 reacts as switching device and makes contact between buzzer, LED to ground supply it lasts upto monopulse end. So the buzzer produce alarm sound. If the circuit deserves fixed place means you can connect +5V DC adapter to the alarm circuit.