DIY 7MHz CW/AM QRP Transmitter Circuit
The circuit of a 7MHz C W / A M QRP transmitter described here can be used to transmit either CW or audio frequency...
Automatic Lamp Brightness Control Circuit
The circuit described here can be used for controlling a decorative lamp from zero intensity to maximum intensity in a specified time. Typical applications...
CLAP SWITCH
Here’s a clap switch free from false triggering. To turn on/off any appliance, you just have to clap twice. The circuit changes its output...
DIY Bi-Colour LED Dancing Light Circuit with 555 Timer
The circuit as shown in the figure employs 14 bi-colour (red and green) LEDs having three terminals each. Different dancing colour patterns are produced...
SONG NUMBER DISPLAY
Here’s a circuit to display the song number in an audio system for quick reference to songs. It also serves the purpose of an...
Build a DIY Electronic Lock System with Punched Cards and Relays
The circuit presented here can be used as a lock for important electronic/electrical appliances.
When card is inserted inside its mechanism, depending upon the position...
Teleremote Control
Here is a teleremote circuit which enables switching ‘on’ and ‘off’ of appliances through telephone lines. It can be used to switch appliances from...
SLEEP SWITCH CUM WAKE TIMER
Here is a sleep-switch circuit that can be easily converted into a wake-up timer. A dual-mode time setting makes the system versatile. The circuit...
PRECISION DIGITAL AC POWER CONTROLLER
Triacs and SCRs are extensively used in modern electronic power controllers—in which power is controlled by means of phase-angle variation of the conduction period....
Handy Zener Diode Tester
Here is a handy zener diode tester which tests zener diodes with breakdown voltages extending up to 120 volts. The main advantage of this...
SMART PHONE LIGHT
The circuit shown here is used to switch on a lamp when the telephone rings, provided that the ambient light is insufficient.
The circuit can...
CLAP REMOTE
An infra-red or wireless remote control has the disadvantage that the small, handy, remote (transmitter) is often misplaced. The sound operated switch has the...
Build a Crystal-Controlled 12 MHz AM Transmitter Without LC Tuning
The main feature of this transmitter is that it is free from the LC (inductor, capacitor) tuned circuit and operates on a fixed frequency...
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...
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...
Dual Priority Encoder Circuit Using
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...
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...