10-04-2017, 08:00 PM
KNOCK/VIBERATION ACTIVATED ALARM
This inexpensive project can be used as knock / vibration activated burglar alarm. Piezo electric sensor plate can be fixed on table, door, cupboard, window etc using cello tape or adhesive.
When an intruder knocks on them, piezo electric sensor converts mechanical vibrations into electrical vibration.
Electrical pulses are undergone amplification by transistor amplifier stages. Final transistor drives a piezo buzzer.
Time delay can be changed by adjusting value of capacitor connected across 220k resistors. TO activate AC loads buzzer may be replaced with a relay. Load to controlled can be connected via normally opened contacts of the relay.
For demonstration a 9 volts battery can be used.
For continuous use, alarm may be powered using 9 volts or 12 volts AC adaptor. Simple unregulated supply is enough. This alarm can be used to protect car and other vehicles. Other application of this project is an earthquake warning alarm.
Reference: http://seminarsprojects.in/showthread.ph...z4Fsx4CJNe