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Simple Touch-Sensitive Switch    (New)

This touch-sensitive switch is built around NAND gate IC CD4011 and transistor BC547.

Auto Snooze for Digital Alarm Clocks    (New)

Alarm clocks are made to wake you up. However, it is quite bothersome to hear the alarm continuously until you get up and put it off. Also, you might fall asleep again. The snooze facility solves this problem to some extent by allowing you to turn the alarm off for a specific period of time by pressing a switch. But here again, you need to look for the snooze switch!

Solder Fumes Remover    (New)

During soldering, lead fumes are generated, which are toxic. The flux used for soldering also emits fumes, which again are highly toxic if inhaled in excess. So it is always better to remove these toxic fumes from the working area. The circuit described here removes these toxic fumes from the area automatically, when required, using a small exhaust fan.

Seven-Colour LED Lighting    (New)

Presented here is a simple circuit that uses six red, green and blue (RGB) LEDs to generate a running-light effect in seven colours-blue, green, red, cyan, yellow, magenta and white. The RGB LEDs have four pins, one for each colour and a common cathode. Different colours can be produced by mixing the primary colours (i.e., red, green and blue).

Voice Recorder and Playback System    (New)

There are several types of voice recorder and playback systems available in the market but most of them are expensive and their circuits are also very complex to assemble. Here is a simple circuit for recording and playback of voice messages. You can leave a voice message for your family or friends whenever you go out, which they can hear by pressing the play button.

Efficient LED Blinking for Embedded Systems   

Smart hardware design can simplify the embedded software and make it more reliable. Designers use blinking LED signals to indicate different status and for inbuilt testability. Making an LED array blink requires an individual software loop for each LED or an individual timer and specific software to serve it. This can be an issue in a system that uses low-level MCUs which provide limited resources.

Key Chain Light   

A key chain with a built-in white LED comes in handy to help you at your front door or search your valuables in the dark. The intensity of white LED is 4000 to 5600 mcd (millicandela) at forward voltage of 3.6V and forward current of 20 mA.

Flashing Headlight For Mobikes   

The dipper for a vehicles headlight changes the light from high beam to low beam or vice versa given a particular set of road conditions. The shifting of light from high to low beam reduces the dazzle for those approaching head-on towards the vehicle. But the dip beam (or low beam) sometimes fails to attract attention of the riders coming from opposite direction.

Electrolytic Capacitor Tester   

Using this electrolytic capacitor tester you can detect leaky and dead (open) electrolytic capacitors. It operates based on the time constant (T) of the capacitor when it is charged up to 63 percent of the applied voltage via a known resistor.

LED Torch   

LEDs are becoming increasingly popular in many lighting applications. White LEDs are now common in torches. Here is a simple and economical LED torch that operates off two 1.5V cells.

Intercom with Musical Ringtone   

Here is a low-cost two-way intercom circuit with musical ringtone that can be made using readily available components.

Fan On/Off Control by Light   

This circuit lets you turn on/off a fan by just directing torchlight or other light toward its light-dependent resistor (LDR). The circuit is powered from a 5V power supply.

Experimental Study of Switched-Capacitor Circuit   

In recent years switched-capacitor circuits have gained popularity due to their suitability in integrated circuits.

Window Charger   

Keep away intruders with this compact electrified window charger. The charger produces non-lethal shocks that are strong enough to threaten intruders.

Versatile Proximity Detector with Auto Reset   

Electrochemical processes taking place in our body generate complex sig-nals (hum) that are continuously being passed along the nerve fibres throughout the body. Any physical activity such as muscle movement increases hum.

DC-To-DC Converter   

Here is a low-cost circuit to convert 6V DC into 12V DC. It uses no transformer and is easy to construct with few components.

Over-Voltage Protector   

This circuit protects your television as well as other electrical appliances from over-voltage. It uses operational amplifier μA741 (IC1) as a comparator. The unregulated power supply is connected to resistor R3 and preset VR1 through resistor R2. Zener diode ZD1 provides reference voltage of 5.1V to the inverting input (pin 2) of IC1.

Visitors Counter   

Presented here is a simple counter that counts the number of visitors entering or exiting an auditorium or any other place where you have installed this circuit at the gates. On receiving an interrupt from light-dependent resistor (LDR) sensors, the circuit increments the count and shows it on a 7-segment display.

Noise-Level Alarm   

Noise is a serious environmental problem that affects us in our daily life. There is scientific evidence supporting that noise exposure can cause hearing loss, hypertension, heart disease, annoyance, sleep disturbance and decreased performance in schools. Sound-level indicators like the one presented here can help address this problem. This sound-level indicator monitors the sound level and indicates through an LED when the level is above the preset value.

Earth Fault Indicator   

In mains-powered equipment, exposed metal parts are connected to earth wire in order to prevent users from contact with high voltages if electrical insulation fails. Connections to ground through earth connection also limit the build-up of static electricity when handling electrostatic-sensitive devices. Earth in a mains electrical wiring system is a conductor that provides a low-impedance path to the earth to prevent hazardous voltages from appearing on equipment and hence the name.

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