SOLID STATE AUTO POWER-OFF ON MAINS FAILURE
A good number of circuits which turn off the power to the load on mains failure have already appeared in EFY. This circuit is...
AUTOMATIC SPEED-CONTROLLER FOR FANS AND COOLERS
During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic...
FREQUENCY MEASUREMENTS USING PC
PROBIR GOYAL
Here is a simple technique for measuring frequencies over quite a wide frequency range and with acceptable accuracy limits using a PC. It...
A Hierarchial Priority Encoder
Anormal priority encoder encodes only the highest-order data line. But in many situations, not only the highest but the second-highest priority information is also...
DIGITAL SWITCHING SYSTEM
This circuit can control any one out of 16 devices with the help of two push-to-on switches. An up/down counter acts as a master-controller...
COMPUTERISED MORSE CODE GENERATOR/TRANSMITTER
The circuit given here can be used to send telegraphic messages via computer. The message data entered through the computer keyboard is converted to...
UPS FOR CORDLESS TELEPHONES
Cordless telephones are very popular nowadays. But they have a major drawback, i.e. they cannot be operated during power failure. Therefore usually another ordinary...
WATCH-DOG FOR TELEPHONES
Most of the telephone security devices available in market are simple but quite expensive. These devices provide blinking or beeping type line-tap misuse indications....
INTELLIGENT SWITCH
This intelligent switch circuit enables automatic, switching on of an emergency light system during darkness in the event of mains failure. The mains power...
LOW CURRENT, HIGH VOLTAGE POWER SUPPLY
A high voltage power supply is a very useful source which can be effectively used in many applications like biasing of gas-discharge tubes and...