Category «Security»

Loud 10-W Car Alarm Siren

By generating square-wave output that sweeps down and up in frequency, this circuit can produce force field of high-intensity sound inside car. This circuit can make a car thieve panics and decide to run before anyone catch his action. D1, C1 and R1 produce triangle waveform by shaping a square wave output of IC1.  If …

Black Light (UV Tube Lamp) Inverter

The voltage boosting in this circuit enable its operation to be powered by 2.5 V rechargeable battery (two cells 1.2V rechargeable batteries),  supplying 400 mA current at 26 V which is needed by the gas arc tube for portable ultraviolet lamp. This inverter circuit has a good efficiency as well, about 80%. Ultraviolet (UV)  light …

555-IC Timed Beeper/Alarm

This is a simple circuit of beeper using 555 timer. This circuit can be employed to energize lights, horn, or other signaling device at any desired interval when the mercury switch is triggered. Since the current handling capability of mercury switch is not so high, an SCR is used to handle current drawn by the …

Simple Code Lock

This is Simple Code Lock circuit. This circuit will turn on a relay when the 8-way DIP switches receives the correct code.  Here is the schematic diagram of the  circuit: There are two different types of DIP, they are piano-key DIP sw and 8-way DIP sw. This circuit will not draw the current if …

Siren Driver Circuit

Siren Driver Circuit

This is a driver circuit for siren. This circuit usually used for car alarms. To build this circuit, we use VD-MOS FETs. This circuit receives 12 v supply from battery. A microprocessor sends complementary pulse waveforms to the driver circuit as inputs.  Here is the circuit : This circuit uses two PHC21025 which each …

Provide Remote Alarm for Smoke Detector

Provide Remote Alarm for Smoke Detector

Ionization-based smoke detectors are efficient and cheap, so they are often installed in the house, other outbuildings, and  the garage. The Locations of the device is far from house, so we need to transmit the alarm signals back into central home-security system or the house. This is a simple circuit that sense a supply current …