PORTABLE SIGNAL WAND
Flashing lights have varied applications. For example, travelers can use these as warning beacons on highways to catch the attention of the public in...
Remote Phone-Bell Ringer
Did you ever miss an important telephone call simply because you were away where you couldn't hear the phone ringing? This should not happen...
9V Converter Using Two AA Cells
Normally, 9V PP3 batteries last less than a couple of hours if used continuously. These cannot be used if the voltage is below 7.8V....
Electronic Water Alarm
Aburst water-supply hose of the washing machine, a bathroom tap that you forgot to close, or a broken aquarium wall may turn your house...
Door-Opening Alarm
Children are at a high risk of drowning in a swimming pool. Majority of accidents occur when children get into a pool unsupervised. Such...
USB-Powered PC Lamp
This white LED lamp lets you use your PC or laptop at night without disturbing others’ sleep. It produces a soft white light just...
Car Reverse Horn
This car reverse horn can be used with any vehicle having a 12V battery. Transistors T2 and T3 form an astable multivibrator (AMV) that...
Automatic Bathroom Lamp
This simple circuit can be used as an automatic bathroom lamp controller. It disables the bathroom lamp at daytime and enables it at night....
Door Alert
This circuit can be operated by any kind of switch. For example, it can be used in a shop to warn that a customer...
Over-Temperature Alarm
This circuit can be used as a warning device which triggers an alarm whenever the temperature exceeds a preset level. It can also be...
Simple Alert Timer
This timer is a useful device for people who often forget to turn off devices in time. Suppose you want to boil water in...
Sound Sensor Alarm
This 6V battery-operated circuit triggers an acoustic piezobuzzer when a sound is detected. It can also be used as a cheap acoustic-type glass break...
Door Ajar Alert
Have you ever accidentally left your front door ajar and had a pet or your little kid escape? Here is a smart solution to...
TELEPHONE LINE IN-USE INDICATOR
This circuit gives a visual indication of whether a telephone line is in use or not, helping two or more people sharing the line...
RADIO/AUDIO FREQUENCY GENERATOR CUM BFO
This radio-cum-audio frequency signal generator can also be used as a beat frequency oscillator (BFO) for continuous-wave and single-sideband signals.
Fig. 1 shows the circuit...
Pull-Pin Security Alarm
Here is a simple and low-cost circuit of pull-pin security alarm. While travelling, rig the alarm unit to your luggage using a home-made security...
Electronic Electroscope
An electroscope is the instrument used to detect charged bodies. Here is an electronic version of the scope that is sensitive and, unlike conventional...
LASER-BASED INTRUDER ALARM
You can use this laser-based intruder alarm conveniently at the entrance of a hall or any other similar location to protect the same from...