Various
Electronic Doorbell with Counter
Description
This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a “ding-dong” chiming doorbell. Additionally, the circuit includes a CMOS 4026 counter display driver IC to count your visitors. More >
Electronic Door Release
Description
The IC is a quad 2 input “AND” gate, a CMOS 4081. These gates only produce a HIGH output, when BOTH the inputs are HIGH. When the key wired to ‘E’ is pressed, current through R1 and D1 switchs Q5 on.The relay energises; and Q5 is ‘latched on’ by R8. Thus, the Alarm is set by pressing a single key,say one of the two non-numeric symbols. More >
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 >
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 >
Led-based running display
Here is a circuit that creates an eye-catching running display effect using LEDs. It can be used to light up borders of animations, pictures, etc, and also for short word displays. 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 >
Laser-guided Door Opener
This automatic door opener can be made using readily available components. The electromagnetic relay at the output of this gadget can be used to control the DC/AC door-opener motor/solenoid of an electromechanical door opener assembly, with slight intervention in its electrical wiring. More >
Remote Control for Toy Car
Make any battery-operated toy car remote-controlled using this circuit. The circuit, consisting of an infrared transmitter-receiver pair, uses IR beam transmission to switch the toy car ‘on’ or ‘off.’ To operate the toy car, More >
CCFL Tester for LCD Screens
Liquid crystal displays (LCDs) are used in a wide range of products including flat-screen computer monitors, laptop computers,tablet PCs, PDAs, digital cameras and portable instruments. More >