Digital Audio/Video Input Selector

Need to connect more than one audio-video (AV) source to your colour television? Don’t worry, here’s an AV input expander for your TV. It is inexpensive and easy to construct. The working...

Multiple Applications of High-Power LEDs

Nowadays, high-power light-emitting diodes (LEDs) LXHLMW1C are available in the market. These white LEDs contain indium-gallium-nitrogen (InGaN). The LEDs’ emitting capacity is 20 candela (Cd). We can use these LEDs for...

Pencell Charge Indicator

Small-size AA cells and button cells used in electronic devices providing a terminal voltage of 1.5V are normally rated at 500 mAh. As the cells discharge, their internal impedance increases to...

9-Line Telephone Sharer

This circuit is able to handle nine independent telephones (using a single telephone line pair) located at nine different locations, say, up to a distance of 100m from each other, for...

Audio Amplifier for Personal Stereo

In the output stages of most broadcast receivers and some amplifiers, there is a limit up to which maximum power can be developed without distortion. In the widely accepted output circuit,...

Solidstate Remote Control Switch

Here is a solidstate remote control switch which uses readily available electronic components. The control circuit comprises the transmitter and receiver sections. The range of the transmitter is around seven metres. The transmitter...

Stabilised Power Supply with Short-Circuit Indication

Here is an efficient 4-stage stabilised power supply unit for testing electronic circuits. It provides well regulated and stabilised output, which is essential for most electronic circuits to give proper results....

Digital Stop Watch

Here’s a digital stop watch built around timer IC LM555 and 4-digit counter IC with multiplexed 7-segment output drivers (MM74C926). IC MM74C926 consists of a 4-digit counter, an internal output latch, npn...

Under-/Over-Voltage Beep For Manual Stabiliser

Manual stabilisers are still popular because of their simple construction, low cost, and high reliability due to the absence of any relays while covering a wide range of mains AC voltages...

Watchman Watcher

Here is a circuit that can be used in offices, stores, warehouses, etc during night to check whether the watchman of your establishment is on duty. For operation, it uses an...