Detector
Dark Activated Switch
This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer. More >
Frost Alarm activated switch
A simple thermistor triggered switch with adjustable threshold. It triggers with cold temperatures so may be used as a frost alarm or cold temperature switch. More >
Temperature controlled relay circuit
This temperature controlled relay circuit is a simple yet highly accurate thermal control circuit which can be used in applications where automatic temperature control is needed. The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. More >
Simple water detector circuit
This simple water detector circuit uses alternative voltage in order to prevent the corrosion of the electrodes. It is easy to build and uses N1 as a trigger Schmitt gate which generate the AC. If between the electrodes is a electricity conductor, for example an aqueous solution, then because of the rectification action of D1 and D2, the C4 capacitor is charging. More >
Vibration Sensor/Detector circuit
With the help of a simple ceramic piezo-electric detector it is possible to assemble an interesting and useful Impact sensor unit,which can be used to detect impact and vibration on doors, showcases, windows etc. More >
Invisible Broken Wire Detector
Portable loads such as video cameras, halogen flood lights, electrical irons, hand drillers, grinders, and cutters are powered by connecting long 2- or 3-core cables to the mains plug. More >
Gas Leakage Alarm
Here is a circuit that detects the leakage of LPG gas and alerts the user through audio-visual indications. More >
Single-Zone Automatic Burglar Alarm System
The circuit was designed to provide an alarm system against any form of burglary based on the operation of CMOS 4011 where a high output would only result when any of the input is low. More >
Dew-Point Sensor
Dew-point sensors are widely used in sensitive electronic equipment like cameras and copiers etc, to protect them from moisture failure by fast detection of dew. You can easily build one yourself using the readily-available dew sensor element as described here. Alternatively, you can use the tiny dew sensor element of your old VCR or video camera. More >
Infrared alarm security
This infrared alarm security can be used to detect persons passing through doorways, corridors and small gates. The transmitter emits a beam of infrared light which is invisible to the human eye. The buzzer at the output of the receiver is activated when the light beam is interrupted by a person passing through it. More >