Alarm Circuits

Mains AC Power Supply Failure Buzzer(Alarm) Circuit is small device. It makes sound (buzzer) when AC power goes OFF. It helps us to know power gone and is useful if we have important machine to know power goes at night. It uses one switch called relay. When power is there the relay works and stops […]

Touch metal part and buzzer makes sound. This uses IC 555 in monostable mode. IC 555 is good for learning in simple circuits. In this Touch Alarm Circuit using IC 555 when someone touches the metal plate then buzzer makes loud alarm. Circuit Working: Parts List: Component Type Description Quantity Resistors 1M 1/4 watt 1 […]

Using popular IC 555 we can make Electronic Horn Circuit for cycle, alarm or fun use. This Electronic Horn Circuit using IC 555 and one 8Ω speaker makes loud horn sound for car or alarm. One 555 work as astable multivibrator which means it make square wave by switching high and low voltage again and […]

Simple Door Open Alarm Circuit using Reed Switch uses reed switch which makes alarm sound when door opens. This simple circuit help protect door from people not allowed. It have reed switch, transistors, resistors, buzzer, diode and LED. Reed switch control power to alarm. Circuit Working: Parts List: Category Description Quantity Resistors 1k 1/4 watt […]

A Wailing Siren Circuit using IC 555 is simple to make sound like real siren, going up and down in pitch. The sound come from 555 IC making pulses at certain speed (frequency). Circuit Working: Parts List: Category Description Quantity Resistors 390Ω, 1k, 220k, 100k, 33k, 22k 1/4 watt 1 each Capacitors Ceramic 10nF 2 […]