Many of us have modular kitchen which have chimney to extract smoke out so that smell of smoke will not fill in kitchen and avoids the harmful effects of smoke on furniture and kitchen utensils. But sometimes it happens we forget to switch on the chimney which results in smoke in kitchen and sometimes we forget to off the chimney leading to the wastage of electricity and money. So to solve this problem we have described a circuit which will switch on the fan automatically when smoke reaches to point and off the fan automatically.You can also use this circuit while soldering because as we know solder fumes are not good for health so it will on the fan to extract the smoke present in room leaving smoke free area.

This is a simple shooting game comprising of an infrared pulse emitter and receiver.  There are 8 white leds and one green led which will light up periodically. The player has to shoot at the receiver when the green led lights up. This is a simple beginner’s project and can be used to make more complicated projects like “LASER TAG GAME”.  Infrared gun (transmitter) for this electronic game is built around IC1 timer (NE555) wired as an astable multivibrator with a centre frequency of about 35 kHz. The receiver circuit has 3 main ICs – 2 NE555s (one wired as an astable multivibrator and the other for monostable operation) and 1 CD4017B (decade counter). These circuits can be modified to make “LASER TAG GAME”. Read more to find out how IC555 is used in this circuit and how it works. 

The circuit presented here operates a relay for Fixed Timer Interval. So the device or machine connected with relay operates for same time. The device once switched ON, automatically switches OFF after Fixed (set) Time Interval when relay switches OFF. The Time Interval can be varied and it is displayed on 7 Segment Display. This kind of circuits can be used in many applications where it is required to operate any device or machine for Fixed Time Interval.

The 8-LED Flasher is built around Timer and Counter ICs. It Flashes 8 LEDs sequentially and the flashing speed can be controlled by a potentiometer. This can be used as a design pattern for decoration. But theoretically, it clears the Timer and Counter concepts in an easy way.The circuit comprises of various components like   555 Timer IC, Decade counter (CD4017), LEDs, Resistors, Capacitors, Wires & a 9V battery. The monolithic integrated circuit 555 timer can be used as square-wave generator, linear saw-tooth generator, pulse generator, time delay generator, etc. here we use it to generate square waveform i.e. it is used in the Astable Mode with a duty cycle of 66.6%.The 8 LEDs could be arranged in any pattern and thus be used as a decorative Light Toy in your living room. 

Children like to watch cartoons movies or any other their favourite show  on the television and do not pay attention on their studies even at the time of examination.  So to keep eye on children we have design a parental control device. When the children in your home hold the remote of the television to on the TV or want to change channel and press any button of the remote then a loud sound would be generated by the device. And these will let you know that your child has  tried to switch on the TV. The main advantage of these circuit is that you can easily do your work without any trouble as it produces loud noise so you can hear the noise while working in the kitchen or while sitting in the nearby room.

Controller is actually a combination of two circuits – driver circuit and Switching circuit. Driver is the actual circuit that drives DC motor and switching circuit decides how DC motor should be driven. So actually, switching circuit is the main circuit that controls the motor. Now there are two parameters of DC motor that can be controlled Speed and Direction.Changing the direction of DC motor is very simple just reverse the supply given to DC motor. For varying speed of motor you have to vary the applied DC voltage. One well known method widely used in industries is Pulse Width Modulated (PWM) speed control of DC motor also known as chopper control.

The 8-LED Flasher is built around Timer and Counter ICs. It Flashes 8 LEDs sequentially and the flashing speed can be controlled by a potentiometer. This can be used as a design pattern for decoration. But theoretically, it clears the Timer and Counter concepts in an easy way.The circuit comprises of various components like   555 Timer IC, Decade counter (CD4017), LEDs, Resistors, Capacitors, Wires & a 9V battery. The monolithic integrated circuit 555 timer can be used as square-wave generator, linear saw-tooth generator, pulse generator, time delay generator, etc. here we use it to generate square waveform i.e. it is used in the Astable Mode with a duty cycle of 66.6%.The 8 LEDs could be arranged in any pattern and thus be used as a decorative Light Toy in your living room.

This circuit responds to the change in light illumination in the form of varying frequency which can be observed through a flashing LED as output. The idea of [[wysiwyg_imageupload::]]this project is to use an LDR in place of a fixed value resistor which in turn generates a particular frequency. The generated frequency corresponds to the light conditions of the ambience.This concept finds popular application in motor speed control where the output is connected to motor driver circuit. Disco light is another interesting application of the idea where the lighting pattern keeps on changing. The circuit of this project uses NE555 to generate a continuous series of pulses in astable mode. The frequency of these pulses is obtained based on values of two resistors and a capacitor. Keep on reading to find out more information on the circuit and its working. 

The main aim of the Day and Night Indicator project is to help us to turn on the lights as the night falls automatically and as the dawn sets in the Day and Night Indicator automatically gets switches off the light and plays a musical morning wake up alarm. Another feature of the project is that at the time of no light in the room during night the night lamp gets turned on automatically. With the help of this circuit you are not required to switch on or off the lights in nights or in the morning.  

RPM counters are used to measure Speed of Motors (AC/DC) or any Rotating Object. They measures and indicates current Rotating Speed of Motor. They are very essential in applications like Speed Control of Motors and close Loop Control System. Such industrial RPM counters are very accurate made up of microcontroller or microprocessor. 

The circuit presented here transmits pulses wirelessly to long distance (more than 20 meter) using keychain LASER (readily available in market). A transmitter generates continuous pulses that are fed to LASER. LASER blinks at the rate of pulse frequency and emits light pulses. LDR on the receiver side, detects this light pulses and reproduces it at the output. So the same pulses that are generated at transmitter side can be received at receiver side to longer distance.To begin with the first thing that is required for this project is to prepare LASER. So let us start with how to prepare a LASER. LASER key-chains available in the market are like this. To prepare it for the project we need to take out its anode and cathode terminals to provide pulses. In order to remove button cells and keychain part from backside of the keychain. You will see one small spring, which is cathode terminal. Connect one wire with this as shown in the figure below.

ASK means Amplitude Shift Keying (also known as ON-OFF keying). It’s one of the Modulation Scheme used to transmit Digital Data using High Frequency carrier signal. It’s very simple and popular method. It transmits 1’s and 0’s of Digital Data by transmitting carrier or no carrier like ·         Bit 1 (logic high) is Transmitted with carrier frequency Fc·         Bit 0 (logic low) is Transmitted with no carrierMeans series of bits – bit stream is transmitted as carrier ON and carrier OFF. That’s why it is also known as ON-OFF keying. 

This project demonstrates how pulses can be transmitted from one place to another place wirelessly using light as medium. One LED is connected at the transmitter side that blinks at frequency of applied pulses. At the receiver side, Light Dependent Resistor (LDR) is used to receive light pulses. IC555 is used at both ends. At transmitter side it is used to generate continuous pulses with variable frequency output from 1 Hz to 10 Hz.  At receiver side it is used to generate same pulses as per the trigger input applied by LDR.   Note – for visual effect (demonstration) the pulse frequency is kept low. The frequency can be kept high in terms of KHz also. 

The circuit presented here rotates stepper motor and varies its RPM (speed). It does not use any micro controller (or micro processor) or any programmable digital device also it does not require any software program to generate sequence of pulses. It drives stepper motor using simple, easily available and commonly used components and ICs like IC555, decade counter, OR gate, current driver chip etc. That is why the name given simple stepper motor driver. 

The circuit presented here counts from 00 to 99 and displays it on two seven segment displays. It can work as free running counter in auto mode or it can count manually when button is pressed. In auto mode it gets continuous pulses and counts continuously at a rate of 1 Hz. That means the count is updated at every second or in other words counter displays time in seconds. This counting rate can be changed by changing pulse frequency. In manual mode, the count is incremented when push button is pressed manually. So it can be used to count up to 100 (from 0 to 99) as per manual requirement.The counter circuit is made up of decade counter cum display driver chip CD4026. The pulse circuit is build using IC555. The circuit can be used in many applications like object counter, frequency counter, RPM counter, stop watch timer, token count display and many others.