Digitally Controlled Precision Amplifier
This is a circuit for a precision amplifier with digital control that can provide a gain upto 100.
Stabilized Power Supply for Prototyping
This stabalised power supply circuit may be directly connected to 230V AC mains to derive output voltages of 3V to 12V DC for connection to the prototyping board.
Mains Failure/Resumption Alarm
This mains indicator sounds an alarm whenever AC mains fails or resumes. It is very useful in industrial installations, cinema halls, hospitals, etc. The...
Visual AC Mains Voltage Indicator
You should not be surprised if someone tells you that the mains voltage fluctuation could be anywhere from 160 volts to 270 volts. Although...
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...
Smart Battery Protector Using a Shunt Regulator
The life expectancy of a battery dramatically reduces when it is discharged below the minimum recommended battery voltage. You must disconnect the load before...
Simple HF Power Amplifier
Here is an inexpensive but powerful high frequency power amplifier for the 40m (7MHz) band. The circuit accepts only 20-30mW RF power and amplifies...
Teleconferencing System
This is a circuit for teleconferencing system that can be used to conference two telephone calls on two separate telephone lines.
Infrared Bug
This infrared bug circuit can be used to detect the presence of modulated infrared signals in its vicinity from any electronic source, for instance,...
Electronic Ludo
In this electronic version, the players need to press a push-to-on switch instead of throwing the six-surface dice. When the switch is pressed momentarily, the 7-segment digital counter displays a number immediately.
Easy Transistor Tester
Using this easy transistor tester circuit, find out whether a given transistor is good or bad before soldering it. You can also identify npn...
USB Power Booster
The USB serial bus can be configured for connecting several peripheral devices to a single PC. It is more complex than RS232, but faster...
Accurate 1Hz Signal Generator
Accurate 1Hz squarewave pulses are required in stopwatches and other digital circuits. Here is a low-cost, general-purpose 1Hz signal generator without using a crystal oscillator.
Low-cost Night Lamp
This simple, low-cost night lamp automatically activates at night and deactivates in the daytime. It incorporates battery charging circuit with protection against over-charging and deep-discharge.
Current Sensor
The circuit presented here senses the flow of electricity through the appliances and generate an audible beep after every fifteen minutes to indicate the ON state of device.
Remote Emergency Alarm for Unmanned Lifts
In unmanned lifts or elevators, sudden power failure cannot be detected from the remote operating room, and this can prove dangerous for the lift...
Electronic Dice
This electronic dice has no chance of wear and tear but all the features of a wooden or plastic dice used for Ludo game.
Electronic...
Versatile Power Supply
Using this versatile power supply circuit, you can obtain the following voltages (approx.) at a current limited to one ampere: 3.3V, 5V, 6V, 9V,...