Here is five burglar alarm circuits for you can look as idea To protect their property from thieves. simple switching, vibration systems, touch-sensitive.
This is Simple Solar light alarm circuit with the special edition, that improve this circuit whole new to higher efficiency. use solar cell instead of LDR
The Mouse and Rat repellent circuit using astable multivibrator which use sound waves or ultrasonic so it escaped away. Use transistor and piezoelectric.
This AC 220V siren circuit is a simple siren that use 220V AC as power supply. It is small size and use a piezo speaker cause use low power and saving.
This is four siren sound generator circuit using UM3561,VR1 to take to control the frequency of oscillator circuit the internal IC, 8 ohms speaker output [....]